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Constituents of Food and Its Functions! Carbohydrates: Carbohydrates are compounds which contain carbon, hydrogen and oxygen. Oxygen and hydrogen are present in carbohydrates in the same proportion as in water. They are the main sources of energy for human body. Carbohydrates are mainly distributed among plant food; exceptions like glycogen, lactose and ribose which are present in muscles or in liver, human milk and animal cells respectively. Classification of Carbohydrates: Carbohydrates are classified as: Monosaccharides — (Single sugar unit) ADVERTISEMENTS: Disaccharides — (Two sugar unit) Polysaccharide—(Many molecules of simple sugar units). Monosaccharides: These compounds cannot be hydrolyzed to simpler compounds. Based on the number of carbon atoms present in them, monosaccharide’s are grouped into triose (3-earbon), tetrose (4-carbon), pentose (5-carbon) and hexoses (6-carbon). Biose, triose and tetrose are not nutritionally significant. Pentose like ribose, xylose and arabinose are widely distributed in many roots and vegetables. ADVERTISEMENTS: Ribose is a part of riboflavin and DNA and RNA, body can synthesize it and it is not a dietary essential. Xylose and arabinose are not present in free state. Both of them are present in gums of various origins like wood gum, cherry gum, etc. In human nutrition only hexoses are of importance. Commonly found hexoses are aldose and ketose (containing aldehydes and ketones group). Glucose, Galactose, Fructose and Mannose have same formula (CHO). But they differ in the arrangement and are distinctive in their physical properties such as solubility and sweetness. (i) Glucose: It is also known as dextrose. Glucose is an aldose sugar. It is white, crystalline and easily soluble in water with sweet taste. Glucose is readily absorbed from the stomach. Glucose is also present in fruits and honey. ADVERTISEMENTS: Structure of Glucose: (ii) Fructose: Fructose is known as fruit sugar or levulose, it is a keto sugar. It is sweeter than glucose. It is also obtained by the hydrolysis of sucrose. ADVERTISEMENTS: (iii) Galactose: It is not found free in nature. Its only source being from hydrolysis of lactose. It also occurs in cerebrosides present in brain and nervous tissue. Hence, it is nutritionally important. (iv) Mannose: This does not occur free in nature. Mannose is a constituent of prosthetic polysaccharides of albumin, globulin and mucoids. Mannose on reduction gives mannitol. (v) Sugar Alcohols: The important sugar alcohols are Sorbitol, Mannitol and Dulcitol. D-Sorbitol is an alcohol made commercially from glucose by hydrogenation (which means the aldehyde (CHO) group is reduced to an alcohol group (OH). The rate of sorbitol absorption from the gut is slow as compared with glucose and does not increase the blood sugars. Hence, it is preferred for diabetics. Disaccharides: The disaccharides are formed by the condensation of two monosaccharide’s with the elimination of one molecule of water. The disaccharides of nutrition importance are: Sucrose Maltose iii. Lactose (i) Sucrose: Sucrose occurs in sugarcane and beet root. It is manufactured on a large scale from sugarcane or beet root. Sucrose is formed by the condensation of one molecule of glucose and one molecule of fructose. Sucrose is easily hydrolyzed to glucose and fructose either by dilute mineral acids or by the enzyme sucrase present in intestinal Juice. Sucrose+ HO (sucrose) Glucose + Fructose (ii) Maltose: Maltose is present in malt. It is formed in cereal grains during germination by the hydrolysis of starch. It is formed when starch present in the food is digested by salivary and pancreatic amylase. Maltose is also formed by the condensation of 2 glucose molecules. It is hydrolyzed to glucose by the enzyme Maltase. Maltose (maltase) Glucose + Glucose (iii) Lactose: It is the type of sugar present in milk of all mammals. Lactose is formed by condensation of one molecule of glucose and one molecule of galactose. Lactose is hydrolyzed to glucose and galactose by the enzyme Lactase present in intestinal juice. Lactose (lactase) Glucose + Galactose Polysaccharides: (i) Starch: These are complex compounds with relatively high molecular weight. Starch occurs widely in plant kingdom. Starch occurs in the form of granules which have characteristic shape when seen under microscope. Starch is a polysaccharide formed in nature by condensation of a large number of (4000-15,000) glucose molecules. When starch is cooked in moist heat the granules absorb water and swell and the wells of the cell are ruptured, thus permitting more ready access to the digestive enzymes. (ii) Dextrins: These are intermediate products in the hydrolysis of starch and consist of shorter chain of glucose units. Some dextrons are produced when flour is browned or bread is toasted. (iii) Glycogen: The so called “animal starch” is similar in structure to the amylopectin of starch but contains many more branched chains of glucose. It is rapidly synthesized from glucose in the liver and muscle. There are two types of glucose chains present: (1) Amylose consisting of long straight chains of glucose, (2) Amylopectin consists of short branched chain of glucose unit. Indigestible Polysaccharides: Indigestible polysaccharides include Cellulose. Hemicellulose, Pectin, Gum and Mucilages. Functions: Carbohydrates are the least expensive source of energy to the human body. Each gram of carbohydrates provides 4 Kcal of energy when oxidized. Glucose is primary source of energy for the nervous system and lungs. Protein sparing action: The body will use CHO preferentially as a source of energy when it is adequately supplied in diet thus sparing proteins for tissue building purposes. Regulation of fat metabolism: Some CHO is necessary in the diet so that the oxidation of fats can be processed normally. Role in gastrointestinal function: Lactose has several functions in the gastrointestinal fact. It promotes the growth of desirable bacteria, some of which are useful in the synthesis of B-Complex vitamins. Lactose also enhances the absorption of calcium. Dietary fibre: Though dietary fibre yields no nutrients to the body, but it aids in stimulation of peristaltic movement of gastrointestinal tract and gives bulk to the food we consume and also reduces the time during which the food wastes remain in the colon. Carbohydrates add flavour and variety to diet. Digestion: The purpose of carbohydrate digestion is to hydrolise the disaccharides and polysaccharides of the diet to their simplest forms. This is accomplished by the enzymes of the digestive Juices and yields the respective end products. Absorption: Most absorption of carbohydrates occurs in jejunum. The absorption of carbohydrates from the intestine is controlled by certain factors like condition of the Intestinal tract and muscle tone, endocrine glands, etc. Carbohydrate Metabolism: Glucose is quantitatively the most important carbohydrate available to the body whether it is by absorption from the diet or by synthesis within the body. Through the portal circulation the absorbed monosaccharide’s are carried to the liver. Here galactose and fructose are converted into glucose. The liver cells release some glucose into the blood stream and blood carries it to the tissues. In the tissues glucose is metabolized to release energy. Excess of glucose is polymerized in the liver into glycogen and stored in liver and muscles. This is again converted into glucose when energy is required. The carbohydrate metabolism involves a series of chemical reactions: Glycogen formation, break down of glycogen (catabolism) into glucose to supply energy, formation of glucose from Amino acids of protein and glycerol of fat and formation of fat from CHO are the main changes related to CHO metabolism. There are two phases of carbohydrate metabolism: Anaerobic and Aerobic phase. Anaerobic Phase of CHO Metabolism: The process of glycogen breakdown to glucose is known as glycolysis. This broken down glucose is converted into lactic acid. Glycolysis is also known as Embden. Meyerhof Pathway which takes place in the cytoplasmic matter of the cell. These reactions convert glycose to pyruvic acid for entering into the mitochondria. The reactions are catalyzed by the specific enzymes respectively. Aerobic Phase of CHO Metabolism: Aerobic phase of CHO metabolism involves Oxidation of lactic acid and pyruvic acid to Acetyl COA undergoes a series of chemical reactions where by carbon dioxide, water and COA are formed (Krebs cycle). Sources of Carbohydrates: There are three main sources of Carbohydrates: Starches: These are present in cereal, roots and tubers, e.g. cereals, pulses, tapioca, yam, colcassia potatoes, etc. Sugars Monosaccharide’s: Glucose, Fructose, Galactose. Disaccharides: Sucrose, Lactose, Maltose. Cellulose: This is the tough fibrous lining found in vegetables, fruits, cereals, etc. It is hard to digest and has no nutritive value. However, cellulose acts as roughage and prevents constipation. If the carbohydrate intake is the diet is inadequate. It leads to malnutrition and other metabolic disorders. Tissue protein and fats will be used up for energy purpose. If excess carbohydrate is taken, it will lead to obesity. Proteins: The word protein is derived from the Greek word “proteios” which means principal components of all living cells and are important in practically all aspects of cell structure and functions. Proteins contain Carbon, Hydrogen, Nitrogen and Sulphur and some also contain Phosphorus. Proteins are large molecules formed from the combination of large number of simpler substances known as Amino acids. Structure of amino acid can be represented as below: Different amino acids can be formed by varying the group of that is attached to Carbon containing the amino group. The R-group might contain straight or branched chain, an aromatic or heterocyclic ring structure or a sulphur group. There are 2 amino acids widely distributed in proteins. Proteins consist of chains of Amino acids joined to each other by the peptide linkage of the 21 Amino acids. There are 8 essential and 13 non-essential AA. Essential AA are those that cannot be synthesized in the body. Thus they can be attained from food alone. Non-essential amino acids are those that body can synthesize from an available source of nitrogen and carbon skeleton. Classification of Proteins: Simple proteins Conjugated proteins Derived proteins Simple Proteins: On hydrolysis by acid, alkali or enzymes yield only amino acids or their derivatives. Examples of this group are albumin and globulins found within all body cells, blood serum, keratin, collagen and elastin in supportive tissues of body, in hair and nails, globin in Hemoglobin and myoglobin, Zein of Corns, Gliadin and Glutenin in wheat, Legumin in peas and Lacto-albumin and Lacto-globulin in milk. Conjugated Proteins: These are composed of simple proteins combined with a non-proteinaceous substance. This group includes lipoproteins, the carrier needed for the transport of fats in blood; Nucleoprotein, the protein of cell nuclei; Phospho- proteins, such as casein milk and Ovovitellin in eggs; Metalloproteins, such as the enzymes that contain mineral elements. Mucoproteins found in connective tissues. Mucin and Gonadotropic hormones; Chromo-protein such as Haemoglobin and visual purple and flavoproteins which are enzymes that contain the vitamin D—Riboflavin. Derived Proteins: These are substances resulting from the decomposition of simple and conjugated proteins. These include rearrangement within the molecules without breaking the peptide bond such as that occurring with coagulation and also substances formed by hydrolysis of proteins of smaller fraction. Properties of Protein: Amphoteric Nature: Like Amino acids, proteins are ampholites, i.e. they act as both acids and bases. For each protein there is pH at which positive and negative charges will be same and protein will not move in electric field. This is known as iso-electric point of protein. Solubility: Each protein has a definite and characteristic solubility in a solution of known salt concentration and pH, e.g. Albumins are soluble in water. Globulins are soluble in neutral sodium chloride solution but are almost insoluble in water. Some proteins like casein are soluble in alkaline pH. The differences in solubility are useful in the separation of proteins from a mixture. Colloidal Nature of Protein Solution: Proteins have large molecular weights and protein solution. They do not pass through semipermeable membranes. This property of proteins is of great physiological importance. Functions of Proteins: (a) Building Block: Proteins form the main solid matter of muscles, organs and endocrine glands. They are major constituents of matrix of bones and teeth, skin, nails and hair and blood cells and serum. The first need for amino acids is to supply the materials for the building and continuous replacement of cell proteins throughout life. (b) Regulatory Functions: The body proteins have highly specialized functions in the regulation of body processes. For e.g., haemoglobin, which is chief constituent of RBC carries oxygen to tissues; contractile proteins regulate muscle contraction. (c) Formation of Enzymes, Hormones and Other Secretions: Proteins supply raw materials for the body to synthesize enzymes like trypsin and pepsins hormones like insulin and thyroxine are protein in nature. Digestive juices also contain certain amount of protein in them. Antibodies which give resistance power to the body are in nature. They are known as Immune proteins (Immunoglobulin’s). Source of Energy: Protein is generally considered as building material of our body. But when diet contains insufficient amount of carbohydrates and fats, body uses up proteins for the energy purposes. Each gram of protein yields 4 Kcal of energy. (d) Acts as Binding Factor: Proteins like lipoproteins, transferrin, phosphoproteins are essential to our body for transporting many chemical substances. Digestion: The purpose of digestion is to hydrolise proteins to Amino acids so that they can be absorbed readily by the body. There is no protein breaking enzyme in saliva. So the digestion (hydrolysis) of protein begins in the stomach. The enzyme Pepsin secreted by gastric glands in the stomach breaks down protein to peptones and proteoses. In the case of milk, milk protein is first converted to casein by the enzyme called renin. Casein combines with calcium to form calcium casein-ate. Pepsin converts this to peptones. Stronger enzymes are needed to breakdown the peptide linkage. The stronger enzymes are found in pancreatic and intestinal juices. The pancreatic juice contains trypsin and chymo-trypsin. The final breakdown of all proteins fractions to amino acids is brought about by erpsin secreted by intestinal mucosa. Absorption: Amino acids are absorbed by the small intestine and thereby carried to the liver by portal vein. The amino acids reach the respective tissues where the required metabolism occurs. Metabolism: In tissues, amino acids undergo breakdown and synthesis. They are transaminised, deaminised or decarboxylated. The anabolic activities consist of formation of new cells or the repair and maintenance of existing ones and secretion of various substances. The liver is the key organ in the metabolism of liver. As amino acids are absorbed, the concentration in the portal circulation rises considerably. The liver rapidly removes the amino acids from the portal circulation for the synthesis of its own protein and for many of the specialised proteins such as lipoproteins, plasma, albumins, globulins and fibrinogen as well as non-protein nitrogenous substances such as creatinine. The liver is the principle organ for the synthesis of urea. Skeleton of Protein Metabolism: Sources: Plant sources: Cereal Grains, pulses, nuts, Legumes, etc. Animal sources: Meat, fish, poultry eggs, milk and milk products. Protein Deficiency: Deficiency of protein foods during growth period is known as kwashiorkor and marasmus. Protein calorie malnutrition is one of the largest nutritional problems in India. Salient Features of Kwashiorkor and Marasmus Treatment and Prevention of Protein Calorie Malnutrition (PCM): In developing countries breast feeding should be encouraged and it ensures adequate supply of nutrients and Antigens. Food stuffs that contain sufficient amounts of essential Amino acids should be provided. Improvement of sanitation and programme of immunization. Fluids with electrolytes of sodium and potassium which will maintain electrolyte balance. Fats: Fats are the most concentrated source of energy and supplies 9 Kcals of energy per gram of fat. They provide the body’s main reserve of energy and is essential for various functions. Like carbohydrates, fats are organic compounds composed of carbon, hydrogen and oxygen, but they differ from carbohydrates in that they contain much less oxygen and much greater proportions of carbon. Fat has one molecule of organic ester of glycerol and three molecules of fatty acids. Fats are insoluble in water and soluble in organic solvents like ether, benzene or chloroform. Their cooking property depends on the kind of fatty acid present in them. Lipids are heterogeneous group of compounds with same properties. Fat is the common household names given to lipids. Classification of Fats: Lipids are classified into: Simple lipids, Compound lipids, and Derived lipids. (a) Simple Lipids: These are esters of glycerol and fatty acid, glycerol is a 3 carbon alcohol with three hydroxyl groups each of can combine with fatty acid. Fatty acids are broadly divided into two main groups: Saturated acids Unsaturated fatty acids (containing one or two double bond). Saturated fatty acids: The formula for fatty acids is CHO where n is an even number of carbon atoms varying from 2 to 24. The common saturated fatty acids are palmatic. There is a single bond present in between the two Carbon atoms. Unsaturated fatty acids: An unsaturated fatty acid is one in which a hydrogen atom is missing from each of the 2 adjoining carbon atoms thus necessitating a double bond between the 2 carbon atoms. A mono unsaturated fatty acid has one double bond; oleic acid is widely distributed in food and body fats. A poly unsaturated fatty acid (PUFA) contains two or more double bonds; linoleic, linolenic and arachidonic acids are nutritionally important examples of this group. Unsaturated fatty acids can exist as geometric isomers. In this form the molecule folds back upon itself at each double bond. In the trans form the molecule extends to its maximum length. (b) Compound Lipids: These are esters of glycerol and fatty acids, with substitution of other components such as carbohydrate, phosphate and/ or nitrogen groupings, phospholipids such as lecithin and chephalin contain a phosphate and nitrogen, grouping replacing one of the fatty acids, i.e. the molecule. (c) Derived Lipids: These include fatty acids, alcohols (glycerol’s and sterols) carotenoids and the fat soluble vitamins A, D, E and K. Characteristics of Fat: The nature of fats, their hardness, melting point and flavour is determined by the length of carbon chain and the level of saturation of the fatty acids. A large number of fats exist in nature in different forms. Each food fat has distinctive flavour and hardness. Hardness: The hardness of fat is determined by its fatty acid composition. Saturated fatty acids containing fourteen carbon atoms or more are solids at room temperature. Food and body fats contain mixtures of short and long chain fatty acids and of saturated and unsaturated fatty acids. The unsaturated fats having only 1 double bond in fatty acid chain are termed as Mono unsaturated fatty acids. The fats that have a high proportion of fatty acids with two or more double bonds are referred to as Poly unsaturated fatty acids. Hydrogenation: In the presence of a catalyst such as nickel, the liquid fats can be changed into solid fats by hydrogenation. This consists of addition of Hydrogen at the double bonds of the carbon chain. When the oils are hydrogenated the fats formed are soft and plastic. Emulsification: Fats are capable of forming emulsions with liquids which means that the fat can be dispersed into minute globules which will increase the surface area thereby reducing the surface tension. Saponification: When fatty acids combine with a cation to form soap it is known as saponification. Rancidity: When fats are exposed to excess of atmospheric oxygen at room temperature, it results in change of odour and flavour, which is generally termed as rancidity. Effect of Heat: Excessive heating of fats leads to the breakdown of glycerol producing a pungent compound known as acrolin which is irritating to the gastrointestinal mucosa. Functions: The primary function of fat is to supply energy. 1 gram of fat provides 9 Kcal of energy which is twice more than that of carbohydrates and proteins. They provide taste to the food. The fats reduce gastric motility and remain in the stomach much longer and the onset of hunger is delayed, thus giving a good satiety value. Fats are the carriers of fat soluble vitamins, i.e. A. D, E and K. Fats are needed for the absorption of Vitamin A and its precursor carotene. The subcutaneous layer of fat acts as an effective insulator thus reducing the heat loss from the body in cold weather. It provides the diet with essential fatty acids as these cannot be synthesized in the body. Digestion, Absorption and Metabolism: The digestion of fats begins in small intestine. The fats are emulsified to form chyme. When the chyme enters duodenum, it stimulates the release of hormone enterogastrone. This hormone reduces the motility and stabilises the flow of chyme in order to correspond to the availability of pancreatic secretions. The presence of fat in duodenum also stimulates the intestinal wall to secrete cholecystokinin hormone which stimulates the contraction of gall bladder pouring bile into the small intestine after passing through common bile duct. Most of the absorption of fat occurs in jejunum. The blood is the means of transportation of lipids from one site to another and the liver is the specialised organ that controls lipid metabolism. It synthesises new lipids (Lipo-genesis) and catabolism of lipids (Lipolysis) is also taking place continuously. These reactions are catalyzed by specific enzymes under the control of nervous and hormonal mechanisms. Sources: Plant sources –> Ground nut oil, Coconut oil, gingely oil, Mustard oil Animal sources –> Lard, Butter, Ghee, Cream Most of the foodstuff contains some amount of fats in them which are termed as invisible fats. The above listed fats are visible fats. The invisible fats are believed to contribute significantly to the total fat and essential fatty acid content of the diet depending upon foodstuff present in diet. Diet containing nuts, oil seeds, soya bean, avocado pear (Butter fruit) and animal foods have higher amount of invisible fat. Vitamins: Vitamins are the discovery of the 20th century. Carbohydrates, proteins and fats were considered as nutrients essential for health. Vitamins are defined as organic compounds which are necessary for good health and vitality. Vitamins are required in minute quantities and their deficiency results in structural and functional disorders of various organs. Vitamins can be classified as: Fat Soluble Vitamins: Fat soluble vitamins are generally associated with fatty foods such as butter, ghee, cream, oils and fats of meat and fish. Fat soluble vitamins are stable to heat and are less likely to be lost during cooking and processing of foods. They are absorbed from the Intestine along with fats and lipids. (1) Vitamin A: Vitamin A is found in the form of Retinol and Carotene. Vitamin A in Its pure form is a pale yellow substance soluble in fat. It is unsaturated alcohol which is stored in the body as esters. Vitamin A is found in milk, meat, fish, etc. The vitamin is found in highest quantity in the liver. Plants do not contain vitamin A, but contain its precursor, the carotenoids which are converted to vitamin A after absorption by the ingesting animal. Carotenoids are orange and yellow pigments of fruits and vegetables. Vitamin A is expressed in terms of international units (IU). 1 I U = 0.3 ugms of retinol 1 I U = 0.6 ugms of carotene Rapid destruction of vitamin A occurs with exposure to high temperatures, in the presence of air. Functions of Vitamin A: It is essential for the building and growth of all cells, especially skeletal. Vitamin A is also needed for proper teeth structure. It is needed for the synthesis of glycoproteins and maintenance of cellular membranes. It is necessary for normal vision. Required for the formation of epithelial tissue. Vitamin A is essential to maintain normal reproductive function in males. Sources: (a) Animal sources: Important sources are liver, egg yolk, butter, cheese, whole milk and fish. (b) Plant sources: Contain Vitamin A is the form of their precursors which are present in fresh dark green leafy vegetables such as spinach, amaranth, fenugreek, etc. It is also present in orange and yellow colored fruits and vegetables such as carrot, papaya, pumpkin, mango, etc. (c) Fish liver oil: The richest natural source of Vitamin A is fish liver oil. One teaspoon of cod or shark liver oil supplies about 6000 IU of Vitamin A. Deficiency: Vitamin A deficiency is the most prevalent vitamin deficiency in developing countries, only next to protein calorie malnutrition. Vitamin A deficiency in human beings may be due to low intake of Vitamin A rich food or due to interference with absorption or storage of Vitamin A is the body. Night Blindness: Night blindness is one of the earliest signs of Vitamin A deficiency, where in a person is unable to see in dim light especially when they come into a dark room, after seeing bright light. As the condition advances it develops into xerophthalmia. The conjunctiva becomes dry and loses its lustre. The transparent appearance of the eye and its elasticity is lost. The eye becomes grey and opaque. If this condition persists the eye becomes infected and ulcerated. Advanced neglected xerophthalmia leads to degeneration of cornea and blindness. This condition is known as Keratomalacia. An inadequate supply of vitamin A may lead to definite changes in epithelial tissues throughout the body. Keratinization or a noticeable shrinking, hardening and progressive degeneration of the cells occurs which increases susceptibility lo severe infection. Prevention and Treatment: The Vitamin A deficiency can be corrected if sufficient amounts of carotene rich foods are included in the regular diet. Foods fortified with vitamin A can be supplemented in the diet to counteract vitamin A deficiency. Hypervitaminosis A: Excessive intakes of Vitamin A are toxic to both children and adults. Common symptoms of toxicity are hyper- irritability, drying, desquamation of the skin, loss of hair, headaches, enlargement of liver and spleen. (2) Vitamin D: Vitamin D is known as the sunlight vitamin as it is synthesized with the help of sunlight. It occurs in two major forms, but from nutritional point of view it occurs in two major forms. Vitamin D2—Ergocalciferol Vitamin D3—Cholecalciferol Vitamin D2 is formed when ergosterol found in plants is exposed to ultraviolet light. Vitamin D3 is the chief form occurring in animals and develops to 7-Dehydro cholecalciferol on exposure to ultraviolet light from sun. Vitamin D is measured in terms of international units. 1 IU = 0.025 ugms of pure crystalline Vitamin D. Functions: Vitamin D is required for the formation of healthy bones and teeth. It has direct action on the mineralization of the bones. It promotes the intestinal absorption and utilization of phosphorus and calcium. In DNA (Deoxyribose Nucleic Acid) to form active calcium binding protein. It maintains the concentration of calcium and phosphorus in blood. Sources: Sunlight — This is an important natural source of Vitamin D. 7-dehydro cholesterol which is normally present in the skin is converted to vitamin D3 by the action of ultraviolet rays of sunlight. Food rich in vitamin D are egg yolk, liver, fish and fish oils. Fish liver oils are the richest source of vitamin D. Vitamin D is not found in foods of vegetable origin. Vitamin D Deficiency: The deficiency of leads to inadequate absorption of calcium and phosphorus from the intestinal tract and faulty mineralization of bone and tooth structure. It also results in skeletal malformation. Vitamin D deficiency leads to: Rickets in children Osteomalacia in adults Rickets is common in children who do not have direct access to sunlight and who do not consume animal foods like egg, meat, fish etc., to meet their daily needs. Following are the characteristics of child suffering from rickets: Soft fragile bones leading to widening of the ends of long bones and bowing of legs. Enlargement of wrist, knee and ankle joints. Poorly developed muscles, lack of muscle tone, pot belly-being the result of weakness of the abdominal muscles, general weakness with delayed walking. Nervousness and restlessness Delayed softening of skull, delayed closure of fontanelles. Osteomalacia may occur when there is Interference with fat absorption and hence also retards Vitamin D absorption. Osteomalacia is seen among ladies, especially those who observe purdha system and do not expose themselves to natural light and in pregnant women. The following changes take place in Osteomalacia: Softening of the bones which may be so severe that bone of spine, thorax and pelvis bend into deformities. Pain of rheumatic type in bones of the legs and the lower part of the back. General weakness with difficulty in walking, especially difficulty in climbing. Spontaneous multiple fractures. Rickets and Osteomalacia can be treated with 1,000- 5,000 IU of Vitamin D orally for a month. Depending on the Improvement the dosage can be gradually decreased. Hypervitaminosis D: It occurs when excessive amount of Vitamin D is taken. The symptoms of toxicity are nausea, vomiting, diarrhoea, weight loss etc. As the toxicity increases, renal damage and calcification of the soft tissue such as heart, blood vessels, stomach, bronchi and kidney tubules occur. (3) Vitamin E: This vitamin is also known as tocopherol, the most common and active type being alpha-tocopherol. The vitamin prevents the oxidation of the unsaturated fatty acid and acts as an antioxidant. High temperatures and acids do not effects the stability of vitamin E. Decomposition of vitamin E occurs in the ultraviolet light. It is expressed in terms of international units. Vitamin E requires the presence of fats and bile salts for absorption into the intestinal wall. Functions: It acts as an antioxidant. It acts as a constituent of enzyme glutathione peroxides; selenium shares a role with Vitamin E in preventing destruction of lipids by oxidation. It helps in maintaining the stability and integrity of cell membranes. Deficiency: Vitamin E deficiency is not common among human beings as it is abundantly distributed in food. It is seen that premature babies with vitamin E deficiency showed impaired fat metabolism. If vitamin E deficiency is present in pregnant mothers, transfer of placental blood to foetus is poor may result in haemolytic anaemia. Sources: The principle sources of vitamin E in the diet are vegetable oils, hydrogenated fats from vegetable oils, whole grains and dark green leafy vegetables, nuts and legumes. Foods of animal origin are low in Vitamin E. (4) Vitamin K: Vitamin K consists of a number of related compounds known as Quinones. The important ones being: Vitamin K1-Phylloquinone Vitamin K2-Manaquinone This Vitamin requires bile for its absorption as it is a fat soluble vitamin. The two forms of Vitamin K occur naturally. Vitamin K1 [phylloquinone] is in green plants and K2 [Menaquinone] which is formed as a result of bacterial action in the intestinal tract. Functions: Vitamin K is very essential for the formation of prothrombin and other clotting proteins by the liver. Vitamin K is required for the synthesis or other proteins. It acts as co-factor for an enzyme in the liver Deficiency: Though dietary deficiency of vitamin K is not common, deficiency of Vitamin K is indicated by a tendency to bleed from skin. This deficiency may occur as a result of its deficient production in the gut. Deficiency of this vitamin among premature babies delays clotting of blood, seen in cases where intake was poor when the mother was pregnant. Sources: Green leafy vegetables like cabbage, cauliflower and pork liver. Cereals, fruits and other vegetables are poor sources of this vitamin. Water Soluble Vitamins: (1) B-Complex Vitamins: Vitamin B1 -Thiamine, B2-Riboflavin B6-Pyridoxine, B12 -Cyanocobalamine, Niacin, Folic acid. Pantothenic acid, Biotin, Choline. (a) Vitamin B1 [Thiamine]: This vitamin is widely distributed throughout the plant and animal kingdom. It is stable in its dry form. Cooking food is neutral or alkaline media. This vitamin gets destroyed. The vitamin is present in good amount in pulses and nuts, liver, meat, chicken, egg yolk and fish are also moderates sources of Thiamine. Thiamine is readily soluble in water and soluble in fat solvents. Extensive losses occur in cereals and pulses as a result of cooking or baking. It is also lost during processing of fruits, vegetables and meats. Functions: It combines with pyrophosphate to form Thiamine pyrophosphate which participates in intermediate metabolism of carbohydrates. It (Thiamine pyrophosphate) acts as a co-factor for a number of important enzymes in the body. Thiamine pyrophosphate is involved with the function of nerve cell membrane [influences the action of neurotransmitters]. Deficiency: Mild thiamine deficiency may result in fatigue, emotional instability, depression, irritability, retarded growth, loss of appetite and lethargy. Constipation is common among such people. Severe deficiency of thiamine causes beri-beri in human beings which leads to enlargement of the heart and breathlessness. In certain cases, when it is known as wet beri-beri, there is presence of oedema which masks the emaciation that is also present. Treatment: Beri Beri is a B-Complex deficiency disease patient’s make the greatest improvement when B-Complex concentrates are prescribed. Also a high protein and calorie diet is advised. (b) Vitamin B2 [Riboflavin]: It is a yellow colored pigment widely distributed in plant food and in small amounts in animal foods. Dried yeast is a rich source of this vitamin. It was named riboflavin because of the similarity of part of its structure to that of ribose sugar. This vitamin is stable in heat and to oxidizing agents and acids. Functions: It is the constituent of two co-enzymes: riboflavin monophosphate or flavin mononucleotide (FMN) and Flavin adenine Dinucleotide (FAD). [These enzymes are needed to complete the reactions during ATP formation]. It is a component of enzyme that catalyzes the oxidation of a number of purines. Riboflavin is absorbed from the upper part of small Intestine and is phosphorylated in the intestinal wall. It is present in body tissues as co-enzymes or as flavoproteins. Deficiency: Its deficiency in human beings results in cracks at corner of the mouth [chelosis] swollen and reddened tongue [Glossitis] and scaly greasy dermatitis of the face, ears and other parts of the body. (c) Niacin or Nicotinic Acid: Niacin is also known as nicotinic acid or nicotinamide. It is a white crystalline compound soluble in water, stable to heat, light, acids and alkalies. In body niacin is converted into niacin-amide. Whole cereals, dried yeast, liver, ground nuts, legumes and fish are good sources. Milk, eggs and vegetables are fair sources of the vitamin. Functions: Like thiamine and riboflavin, niacin also takes part in the metabolism of carbohydrates, proteins and fats through enzymatic action. It takes part in tissue oxidation. It is essential for the normal functioning of the skin, gastrointestinal and nervous system. Deficiency: In mild deficiency, there is fatigue, loss of weight and loss of appetite. The severe deficiency leads to pellagra which is associated with 4D’s-Dermatitis, diarrhea, dementia and death. Tryptophan one of the essential amino acids is a precursor of Niacin so that a diet that contains liberal amounts of tryptophan will provide enough of niacin. (d) Vitamin B6 [Pyridoxine]: Vitamin B6 is otherwise known as Pyridoxine, pyrodoxal and pyridoxamine. This vitamin is widely distributed throughout the plant and animal kingdom. Vitamin V6 is soluble in water and distributed throughout plant and animal kingdom. The best sources are meat, especially liver, some vegetables and grains with bran. Functions: Pyridoxal phosphate is co-enzyme for a large number of enzymes involved with amino acid metabolism like decarboxylation and transamination. Deficiency: Vitamin B6 deficiency may result in epileptic form of convulsions, loss of weight and abdominal distress. Deprivation of this vitamin in adults may cause depression, confusion and convulsions. (e) Pantothenic Acid: Pantothenic acid is widely distributed in all foods particularly abundant in that of animal origin, whole grains and legumes. It occurs in small quantities in milk, fruits and vegetables. It gets decomposed by alkali or rise in temperature. Functions: It forms a complex compound co-enzyme A [CoA] and acyl carrier proteins and thus it takes part in the carbohydrate and fat aretabolism. It is necessary for the formation of Acetylcholine which is precursor of the ‘haem’ which is needed for the synthesis of haemoglobin. Deficiency disease of this Vitamin is rare. (f) Folic Acid: Folic acid is also known as folacin. Pure folic acid occurs as a bright yellow crystalline compound, slightly soluble in water. It is easily oxidised in an acid medium and is sensitive to light. Metabolism: About 25% of folacin in foods is in the free form and is readily absorbed. Flacin is stored principally in the liver. The active form is tetra hydrofolic acid. Ascorbic acid prevents the oxidation of this active form and thus maintains adequate level of folate for metabolic purposes. Functions: It is essential for the synthesis of DNA. It is needed together with Vitamin B12 for the formation of normal red blood cells in the bone marrow. It promotes protein synthesis. Sources: Folic acid is widely distributed in foods, liver, kidney, yeast and green leafy vegetables which are excellent sources. Vegetables, legumes, eggs, whole grain cereals and fruits are good sources. Deficiency: Folic acid deficiency results from inadequate dietary intakes. In the deficiency of this vitamin, the serum folate levels are reduced and changes take place in the production of red blood cells in the bone marrow. The anaemia that results from folic acid deficiency is characterised by the reduction in the number of red blood cells [Macrocytic Megaloblastic Anaemia]. (g) Vitamin B12 [Cyanocobalamin]: This is the most complex of the B-Vitamins. It has been named as cobalamin as it is found as a co-ordination complex with cobalt. It occurs in several forms known as cobalamin. Cyanocobalamln is the most stable form. There is little loss of Vitamin B12 in food by regular cooking procedures. Functions: In the bone marrow, the vitamin B12 co-enzyme participates in the synthesis of DNA. Vitamin B12 is required for the enzymes that accomplish the synthesis and transfer of single carbon units such as methyl group. For formation of mature RBCs. Deficiency: Vitamin B12 deficiency is a defect of absorption and rarely of dietary lack. Pernicious anaemia is a disease of genetic origin in which intrinsic factor is not produced and consequently Vitamin B12 is not absorbed. The characteristic symptoms include anorexia, dyspnoea, prolonged bleeding time, loss of weight, neurologic disturbances, etc. Sources: It is found in animal foods only. Like organ meats, muscle meats, fish, poultry, milk and eggs. (h) Biotin: Biotin is a relatively simple compound, a cyclic urea derivative which contains a sulphur group. It is very stable to heat, light and acids. In tissues and in foods, it is usually combined with proteins. Functions: Biotin is a co-enzyme of a number of enzymes that participate in carboxylation, decarboxylation and deamination reactions. Biotin is essential for the introduction of carbon dioxide in the formation of purines, these compounds being essential constituents of DNA and RNA. Deficiency: Biotin deficiency has been described in human beings when large amount of raw egg whites were fed in research trials. The substance known as Avidin in raw egg white is a glycoprotein that binds biotin and thereby prevents its absorption from the intestinal tract. Sources: Dried yeast, organ meats, rice polishings, soyabean are good sources of Biotin. (i) Choline: All living cells contain choline, principally in phospholipids which is essential for the structure and function of cell membranes and serum lipoproteins. Egg yolk is rich in choline but legumes, organ meats, milk, muscle meats and whole grain cereals are also good sources. Choline enhances the oxidation of fatty acids and cholesterol in blood and from the liver deposition and removal in adipose tissues. It is essential for the transfer of nerve Impulses. (2) Vitamin C: Ascorbic acid is an essential nutrient for man as he lacks the capacity to synthesise it like any other animal species, vitamin C is a water soluble vitamin. It is the most unstable of all vitamins, being rapidly destroyed by high temperature, oxidation, drying and storage. Ascorbic acid is a white crystalline substance readily soluble in water. Functions: One of the principal functions of ascorbic acid is the formation of collagen, an abundant protein that forms that intercellular substance in cartilage, bone matrices, dextrin and the muscular epithelium. Vitamin C is Important for wound healing and increases the ability to withstand the stress of injury and infection. Ascorbic acid also plays an important role in other hydroxylation reactions. Conversion of tryptophan to serotonin, an important neurotransmitter and vasoconstrictor, and formation of norepinephrine from tyrosine involves hydroxylation reactions which require ascorbic acid. Conversion of cholesterol to bile acids is another hydroxylation reaction that requires Vitamin C. Ascorbic acid is an important antioxidant and thus has a role in the protection of Vitamin A and E and the polyunsaturated fatty acids from excessive oxidation. Ascorbic acid enhances iron absorption by reducing ferric iron to ferrous iron across the intestinal mucosa. It may also bind with iron to form a complex which facilitates transfer of iron across the Intestinal mucosa. In the circulation ascorbic acid aids in there release of iron from transferring so that it can be incorporated into tissue ferretin. Sources: Fruits – All fresh fruits contain Vitamin C. Amla, the Indian gooseberry (Nellikayi) is one of the richest sources. Guava is another cheap source of Vitamin C. Vegetables – Vegetables especially green leafy vegetables are rich in Vitamin C. Roots and tubers are poor sources of Vitamin C. Sprouts also contain small amounts of Vitamin C. Animal food – Meat and milk contain very small amounts of vitamin C. Deficiency: Deficiency of Vitamin C results in a disease called scurvy. The deficiency of ascorbic acid leads to the defective formation of intercellular cement substances. Fleeting joint pains, irritability, retardation of growth in the infant, anaemia, dyspnoea poor wound healing and increased susceptibility to infections. Scurvy in children leads to pain, tenderness and swelling of the things and legs, infantile scurvy. The baby is pale and irritable and cries when handled. Loss of weight, fever, diarrhoea and vomiting are frequently present. Scurvy in adults results after several months of diet devoid of ascorbic acid. The symptoms include haemorrhagic spots on skin, swelling, infection and bleeding of gums, tenderness and anaemia. The teeth may become eventually loose and are lost early. Minerals: Minerals comprise a small fraction [4%] of our body weight. Most of the body weight is made up of carbon, hydrogen, nitrogen and oxygen which together form water in body tissues. Minerals are distributed in our body as Calcium 2%. Phosphorus 1%, remaining 1% is comprised of all other minerals, Magnesium, Zinc, Iron, Iodine, Copper, Selenium, Florien, Chromium, etc. The body contains about 24 minerals all of which must be provided by the food we eat. The minerals are needed for the following functions: As a constituent of bones and teeth e.g.: P & Mg. As soluble salts which are present in the body fluids and cell contents which provide stability which are essential for life, e.g.: Na, K, CI, and P. As constituent of body cells of soft tissues such as muscle liver, etc. e.g.: P. Some minerals are needed for specific functions, e.g.: (i) Iron for the formation of Hb, (ii) Sodine for the formation of thyroxine, (iii) Cobalt as the constituent of vitamin B12 (iv) Zinc as the constituent of an enzyme. Some other elements are essential for the activity of enzymes. A nutritional deficiency disease ultimately develops when inadequate amounts of essential nutrients are provided to the cells for their metabolic functions. Calcium: There is approximately 1200 gm of Ca in the adult body. 99% is combined as the salt that gives hardness to bones and teeth. The remaining 1% of Ca in the adults, that is about 10 to 12 gm, is distributed through extracellular and intracellular fluids. Functions: Gives hardness to the bones and teeth. Activates a number of enzymes including pancreatic lipase, adenosine triphosphatase and proteolytic enzymes. It is required for the synthesis of acetylcholine—a substance necessary for transmission of nerve impulse. It helps in increasing the permeability of cell membranes. Aids in the absorption of Vitamin B12 from the intestine. Regulates the contraction and the relaxation of muscles including the heart beat. Catalyses 2 steps in the clotting of blood. When tissue cells are injured the following reaction takes places: Cell Injury: Primary calcium deficiency is extremely rare. We need small quantity of calcium to replace the bone substance lost by daily wear and tear of skeletal tissue and there is scarely a diet which does not contain the required quantity of calcium except during pregnancy and lactation. Calcium deficiency may occur in pregnant or lactating women and in infants. During pregnancy normal calcium intake is no longer sufficient to maintain the calcium stores of the skeleton because large amount of calcium is diverted to the growing foetus. In most instances the calcium deficiency is not as much as it is a deficiency of Vitamin D which interacts with calcium and is required for good development and maintenance of bones and teeth. Iron: The amount of iron in the body of an adult male is about 50 mg/kg or a total of 3.5 gm. In women, it is about 35 mg/ kg or total of 2.3 gm. All body cells contain some iron; approximately 75% of the iron is in haemoglobin 5% is present in myoglobin in cellular constituents including the containing enzymes and 20% is stored as ferritin and haemosiderin by the liver, spleen and bone marrow. Unhealthy human beings the iron reserve is 1000 mg but in menstruating women in the plasma bound to a B-globulin, transferring also known as siderophilin. Functions: Haemoglobin is the principle component of the RBC and accounts for most of the iron in the body. It acts as a carrier of O2 from lungs to tissues and indirectly aids in the return of CO2 to the lungs. Myoglobin is an iron protein complex in the muscle which stores some oxygen for immediate use of the cell. Enzymes such as catalase, cytochromes in hydrogen iron transport, xanthene part of the molecules. Iron is required as co-factor for other enzymes [aconitase]. Absorption: The amount of iron absorbed from the intestinal tract in governed by: The body’s is need for iron The condition existing in the intestinal lumen. Food mixture that is fed. Iron is absorbed into the mucosal cells as: (i) Non-heme iron from energetic salts in foods, and (ii) As heme iron. The absorption of iron is meticulously regulated by the intestinal mucosa according to the body needs. Utilization: Most of the iron utilized by the body is needed by the bone marrow to make Hb and new RBC. The life of a RBC is about 120 days. It is then destroyed, the Hb broken down and stored in the reticuloendothelial system and then the iron liberated. For this reason 1/20th of the total Hb of the body has to be replaced daily in the bone marrow. Storage: Iron combines with a protein to form a complex compound known as ferritin which is chiefly stored in the liver, spleen and bone marrow. Any excess iron which cannot be stored as ferritin is stored in the liver in the form of haemosiderin. Iron stored in this form cannot be utilized by the body. Food contains inhibitors [such as Phytates, Phosphates and Polyphenols] and promote [such as ascorbic acid and sucrinic acid] iron absorption. Iron Deficiency Anaemia: The clinical features are the result of diminished oxygen carrying power of the blood due to low haemoglobin contents [3 to 9 gm /100 ml blood]. Symptoms General fatigue, breathlessness on exertion, giddiness. In severe cases there may be oedema of the ankles, the appetite is poor and growth and development in children is retarded due to low food intake. Fortification: Several countries like Sweden, UK and USA have programs in operation for the fortification of Bread. In India salt was first recognised as a vehicle for iron fortification right from 1975 [Narasinga Rao and Vijaya Sarathy]. The causes for iron deficiency in Indian population: Inadequate availability of Fe from the diet. Increased blood loss. Increased iron requirements. Phosphorus: An adult human body contains about 400 to 700 mg of phosphorus as phosphates. A greater part is present in the bone and teeth and the rest in other tissues. Phosphorus is present in the body as inorganic salt of phosphorus acid or in combination with organic acids. Functions: Phosphorus is necessary for the foundation of bone and teeth. It is necessary for the formation of phospholipids lecithin and cephalin which are integral parts of cell structure and also act as intermediates in fat transport and metabolism. It is essential for carbohydrate metabolism as phosphorylation of Glycogen requires inorganic phosphates and phosphoric esters. It is a constituent of certain co-enzymes concerned in the oxidation of carbohydrates, fats and proteins. It is an essential constituent of nucleic acid and nucleoproteins which are integral parts of cell wall nuclei. Metabolism: Most of the phosphorus in food is In organic combinations that split by intestinal phosphatase enzyme to free the phosphate. The phosphorus is absorbed as inorganic salt. Deficiency: The phosphorus present in milk and animal foods is available to a greater extent than that present in cereals and pulses. A person absorbs most of the ingested phosphorus. The phosphorus deficiency occurs with that of Calcium. Magnesium: Functions: Magnesium is essential for all living cells. In plants magnesium is present in chlorophyll. It is required as a co-factor for oxidative phosphorylation. It is involved with protein synthesis. Magnesium along with calcium, sodium and potassium is needed for the maintenance of balance in extracellular fluid for the transmission of nerve impulse and the consequent muscle contraction. It is found in certain enzymes, e.g. Co carboxylase which decarboxylates pyruvic acid. Metabolism: Magnesium is absorbed by active transport and competes with calcium for carrier sites. Thus a high intake of either calcium or magnesium interferes with the absorption of the other. Usually the excess magnesium intake will be lost in the stools. Deficiency: The magnesium deficiency is not very easy to diagnose but it can be seen during chronic alcoholism, cirrhosis of liver malabsorption syndromes, kwashiorkor, severe vomiting, etc. Sodium: The adult human body contains about 100 gms of sodium ions. About half this quantity is found in extracellular fluid and the remaining half in the tissue cells and bones. Sodium in the form of sodium chloride [NaCI] is ingested directly through food. Function of Sodium: Regulation of acid base balance in the body. Regulation of osmotic pressure of plasma tissue fluids thus protecting the body against excess fluid loss. It plays an important role in the absorption of monosaccharide’s and amino acids from the small intestine. It plays an important role in circulating blood and maintaining heart beat. Metabolism: Most of the sodium in the diet is in the form of inorganic salts principally sodium chloride. The absorption of sodium from the gastrointestinal tract is rapid and practically complete. The loss of Sodium in perspiration depends upon the concentration and total volume of sweat. A person absorbs sodium almost completely in the proximal small intestine. It is person consumes excess of sodium, it is excreted in the urine and it is not stored in the body. Sodium Imbalance: When sodium excretion is reduced water accumulates as excess extracellular fluid, a condition known as oedema. The acid base balance is also disrupted. Cardiac and renal failures are also the principal causes of reduced sodium excretion. Hyponatremia: In this condition the serum sodium level is low. Severe hyponatremia is caused due to: Severe dehydration Decrease in blood volume Low blood pressure Circulatory failure. Hypernatremia: In this condition the plasma sodium level will be higher than normal. This condition occurs due to: Hyperactivity of Adrenal cortex. Prolonged treatment with cortisone. ACTH and sex hormone. The symptoms of hypernatremia are: Increased retention of water Increased volume of blood Increased blood pressure. Sources: Foods of animal origin contain more sodium than those of plant origin. Potassium: Potassium is present in the intracellular fluids of the body. It is an important constituent of cells and is present in small amounts in the intracellular fluid. 90% of the potassium present in our body is present in the cells of various tissues and RBCs. Functions: It acts as main cation in the cells and plays an important role in the regulation of acid base balance in the cell. It is an essential constituent of extracellular fluid though, the level is small, and it influences the activity of muscles. It is essential for growth and building of tissues. It is essential for synthesis of glycogen. Every glycogen synthesis is accompanied by the retention of potassium. During muscular contractions, potassium is lost from the muscle in extracellular fluid and during the recovery phase potassium ions are withdrawn from the muscle cell from the extracellular fluid. A person absorbs potassium almost completely from the gastrointestinal tract. Excess of potassium is excreted in the urine. It is not stored in the body. A person can become depleted of sodium, potassium and chlorine more rapidly, especially during increased losses due to vomiting, diarrhea and extreme sweating. Hypokalemia: This condition occurs due to deficient intake of potassium or during excessive loss of potassium through gastrointestinal tract due to persistent vomiting or diarrhea. Hyperkalemia: When the serum potassium level is high this condition is known as hyperkalemia. This occurs due to diminished urine volume, excessive intake of potassium salts, during kidney disorders. Cardiac and central nervous system are affected by this condition. Iodine: About 1/3rd of iodine in the adult body is found in the thyroid gland where it is stored in the form of thyroglobulin. Functions: The only known function of iodine is as a constituent of the thyroid hormones, thyroxine and triodothyroxine. Tyrosine, one of the amino acid, incorporates four atoms of iodine to form thyroxine. The thyroid hormone regulates the rate of oxidation within the cell and in doing so Influences the physical and mental growth. The functioning of nervous and muscular tissue, circulatory activity and the metabolism of all nutrients. Metabolism: Iodine is ingested in foods as inorganic iodides and as organic compounds. In the digestive tract iodine is split from organic compounds and is rapidly absorbed as inorganic iodide. The degree of absorption is dependent upon the level of circulating thyroid hormone. Thyroid activity is controlled by the thyroid stimulating hormone (TSH) secreted by the anterior lobe of the pituitary. Handling of Iodine by the Body: Iodine is transported by the circulation as free iodine and protein bound Iodine (PBI).PBI is sensitive to the changes in the level of thyroid activity. It rises during pregnancy and with hypertrophy of the gland and falls with hypo-function of the gland. When thyroid hormone is utilized for cellular oxidation, it is released into the circulation. About 1/3rd of the released iodine is again incorporated into thyroid hormone and the remainder is excreted in the urine. Deficiency: Deficiency of iodine leads to goitre. When goitre occurs in significant number of people in a defined geographic area it is known as endemic goitre. Lack of iodine leads to increase in the size and number of epithelial cells in the thyroid glands and thus an enlargement of the gland. This condition is known as goiter. The basal metabolism remains normal, the deficiency is more prevalent in females than in males and is more frequent during adolescence and pregnancy. Cretinism occurs in infants when the pregnant woman is severely depleted and she cannot supply iodine for the development of foetus. Cretinism is characterised by a low basal metabolism, muscular flabbiness and weakness, dry skin, enlarged tongue, thick lip, arrest of skeletal development and severe mental retardation. Prophylaxis: The best way to supplement iodine is either by common salt, bread or water or any other medium. In India, in the Himalayan region where goiter is more prevalent, a supplement of one gram KI (potassium iodide) is added to 10 kg of common salt which is adequate to provide 1 mg of Potassium iodide in 10 gm of daily salt intake. Zinc: About 2-3 gm of zinc is present in the adult body. It is distributed widely in all tissues but not evenly. High concentrations are found in the eye, especially the iris and retina in the liver, bone, prostrate and prostatic secretion and in the hair. In the blood about 85% of the zinc is in the RBC. However, leucocytes contain about 25 times as much Zinc as in each RBC. Functions: Zinc is essential for all living organisms. Its numerous functions include the following: As an Integral part of at least 20 enzymes that belong to a large group known as metalloenzymes. Among these are: Carbonic anhydrase is an essential for the transport of CO2 to the lungs as Haemoglobin is to the transport of O2. Lactic dehydrogenase for inter-conversion of pyruvate to lactic acid in the glycolytic pathway. Alkaline phosphates required in bone metabolism. Carboxy peptidase and amino peptidase bring about removal of the terminal carboxyl amino groups in the digestion of proteins. Alcohol dehydrogenase in the liver which oxidises not only ethanol as well as other primary and secondary alcohols including methanol and ethyl glycol. Thus it acts as a major detoxifying mechanism. As a co-factor in the synthesis of DNA and RNA. It is especially important in cellular systems that undergo rapid turnover, as in the GI tract including the taste buds. Thus, zinc plays a role in the sensory system that controls food intake. The mobilization of Vitamin A from the liver to maintain normal concentration in the blood circulation. Large intakes of calcium. Vitamin D and phytate interact with absorption. Deficiency: A clinical syndrome characterised by small stature, hypogonadism, mild anaemia and low plasma zinc occurs in older children and adolescents, in poor peasant committee in Iran and elsewhere in Middle East where the staple diet is unleavened bread. Suppressed taste and odour acuity is a consequence of Zinc deficiency. Hypogeusia—is a decrease in taste acuity. Dysgeusia—unpleasant, perorated and obnoxious taste. Hyposmia—is decrease in odour acuity. Dysosmia—a disagreeable odour sensation. Copper: The body of the human adult contains about 100 to 150 mg of Copper. Traces of topper are found in the liver, brain, heart, and kidney. In the foetus and at birth, the copper content in these organs is several times higher and decreases during the first year. Functions: The copper containing Ceruloplasmin has a role in the transport of iron in the transferring for haemoglobin synthesis. Thus, metabolic deficiency of copper can result in anaemia and other diverse functions. Requirement of copper is for taste sensitivity. Melanine pigment sheath, maturation of collagen, elastin formation, phospholipid synthesis, bone development and haemoglobin formation as a constituent of number of enzymes. Copper containing proteins such as hepatocuprin and erythrocuprin helps protect against the toxic effects of Oxygen. Copper is a constituent of the elastic connective tissue protein elastin. Deficiency: Anaemia due to copper deficiency has not been found, but Infants especially those who are premature may develop copper deficiency which usually presents as chronic diarrhoea, plasma copper concentrations are low and later leads to anaemia. Copper deficiency is also associated with protein energy malnutrition. Fluorine: Fluorine occurs normally in the body primarily as calcium salts which brings about striking reduction in tooth decay because the tooth enamel is made more resistant to the action of acids produced in the mouth by bacteria. Fluoride is involved with the maintenance of bone structure. The fluoride salts of calcium are less readily lost from bone during immobilization or following the menopause: Metabolism: Fluorides are absorbed readily from the gastrointestinal tract. They replace the hydroxyl groups in calcium phosphorus salts of bones and teeth to form fluoroapatite. Most of the fluoride ingested is excreted in the urine. Sources: Fluoride occurs in soil, water supplies, plants and animals and is a normal constituent of the diet. The amount present in direct correlation with the fluoride concentration in water and soils. Effects of Excess: Chronic dental fluorosis results when the concentration of fluoride in drinking water is in excess of 2.0 parts per million. The teeth becomes mottled (tooth enamel becomes dull and englazed with some pitting). At higher concentrations of fluoride some dark brown stains appear. Although aesthetically undesirable, such teeth are surprisingly due to dental caries. Skeletal fluorosis – Large excess of fluorine 20 to 80 mg daily for several years leads to bone fluorosis with symptoms resembling arthritis. There is increased density and hyper-calcification of the bone and spine, pelvis and limbs. Sulphur: Sulphur accounts for about 0.25% of the body weight. All living matters contain proteins and all proteins contain some sulphur. This element therefore contains amino acid. Sulphur is a constituent of thiamine and Biotin-B-Complex Vitamins, connective tissue, skin, nails, and hair are rich in sulphur. Functions: Sulphur is structurally important constituent of Mucopolysaccharides. Sulpholipids are abundant in tissues of liver, kidney and the salivary glands and the white matter of the brain. Other important sulphur containing compounds are insulin and heparin, an anticoagulant. Sources: The sulphur content of foods depends upon the concentrated of methionine and cystine. Cereals and pulses contain good amount of sulphur. Other Trace Elements: Nickel, Manganese, Molybdenum, Selenium, Chromium and Cobalt are an integral constituent of enzymes or as activators. A diet that is adequate in other nutrients and that does not contain a high proportion of refined foods is considered to satisfy the needs for these trace elements. Dietary deficiency is not likely in human beings. An excess of one element may lead to toxicity. Water: Water is the largest constituent of the body. The body’s need for water is second only to that for oxygen. One can live without food for weeks but death is likely to follow, deprivation of water for more than a few days. A 10% loss of body water is a serious hazard and, death is likely to follow a 20% loss. Water makes up 50% to 70% of the weight of the human body, lean individuals have a higher percentage of body water than do obese individuals. Water is present inside the cells of tissues [intracellular] and outside the tissue cell [extracellular). Water and electrolytes are essential constituents of cellular functions and to regulate the excretion through kidney, lungs and skin. The excretion of water through skin and kidneys changes according to the climatic conditions. In dry climate one sweats a lot and in cold weather one passes urine more often. Water is a simple compound containing two parts of hydrogen with one of oxygen. Good drinking water has no odour and is pleasant to taste. Water may contain traces of calcium, sodium, magnesium and iron depending upon the soil from which it is obtained. Soft water contains small amounts of minerals and lathers easily. Hard water contains higher proportion of calcium salts and does not lather easily. Functions: Water is a structural component of all cells. Water helps in maintaining osmotic pressure (The pressure created when fluid flows from lower concentration to higher concentration) between the extracellular and intracellular fluids. Water is the medium of all body fluids including digestive Juices, lymph, blood, urine and perspiration. Water is a solvent for the products of digestion holding them in solution and permitting them to pass through the walls of intestinal tract into blood stream. Water regulates the body temperature by taking up the heat produced in cellular reactions and distributing it throughout the body. Water is essential as a body lubricant. The saliva that makes the swallowing of food; the mucous secretions of gastrointestinal, respiratory and genitourinary tract; the fluids that bathe the joints, etc are all constituted of water. Sources: The Ingestion of water and beverages The moisture or water present in food The water resulting from oxidation of food stuff, e.g. the oxidation of glucose, fatty acids and amino acids yields water. Acid Base Balance: The acid base balance indicates the regulation of hydrogen Ion concentration (pH) of fluids. From various metabolic processes there is continuous production of acids which also have to be eliminated. Lung and kidneys are the major agents in carrying out this function in our body. When there exists an imbalance of acid and base in the body. It could either lead to acidosis or alkalosis. Acidosis is the condition in which the pH (Hydrogen Ion concentration is Increased or there is excessive loss of base. Alkalosis is the condition in which the pH is decreased or there is excessive increase in the base. The pH of blood plasma is maintained within very narrow limits of 7.35 to 7.45. Sources: Fruit and vegetables containing high percentage of moisture in them like, cucumber, watermelon, ashgourd, tomatoes, orange, sweet lime, lemon, grapes, pomegranate, pineapple, cashew fruit, khol khol, cho-cho, marrow, bottle gourd, brinjal, bitter gourd, etc.
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Prof. Dr Midhat Jašić Tehnološki fakultet, Tuzla E-mail: jasic_midhat@yahoo.com E-mail: midhat.jasic@untz.ba Lipidi nisu samo masti i ulja. Lipidi obuhvataju širok spektar molekula raznovrsne hemijske strukture i biološkog porijekla uključujući: masne kiseline, triacilglicerole , voskove, fosfolipide, sfingolipide, holesterole i druge steroide. Različiti kriteriji se mogu uzimati pri podjeli i klasifikaciji lipida. To može biti: porijeklo, hemijski sastav, uloga u organizmu, nivo složenosti, nutritivni zahtjevi i utjecaj na zdravlje. Prema porijeklu lipidi se dijele na biljne i životinjske. Prema hemijskom sastavu (mogućnosti osapunjenja) dijele se na osapunjive i neosapunjive. Osapunjivi lipidi u molekuli sadrže ostatak bar jedne masne kiseline, koja se pri alkalnoj hidrolizi oslobađa u vidu alkalne soli, odnosno sapuna. U ovu grupu spadaju: neutralne masti (triacilgliceroli), fosfogliceridi, sfingolipidi i voskovi. Neosapunjivi lipidi se često zovu zajedničkim imenom i izoprenoidi, a obuhvataju: steroide (steroli, žučne kiseline i steroidni hormoni) i terpene. Prema ulozi koju obavljaju u organizmu postoje lipidi kao depoi energije, strukturni lipidi (fosfolipidi, voskovi, steroidi) i regulatorni lipidi (polni hormoni i hormoni korteksa nadbubrežnih žlijezda). Prema nivou složenosti hemijske strukture lipide možemo podijeliti na jednostavne, konjugirane, derivirane i ostale lipide. Jednostavni lipidi su neutralne masti (triacilgliceroli i poligliceridi) i voskovi. U konjugirane lipide spadaju: - fosfolipidi (sadrže fosfatnu skupinu i molekulu masti) - cerebrozidi (sadrže ugljikohidrat i molekulu masti) - sulfolipidi (sadrže sulfatnu grupu) U derivirane lipide spadaju: - masne kiseline - masni alkoholi - masni aldehidi - masni ugljikohidrati - vitamini A, D, E, K U ostale vrste lipida spadaju - sapuni - pigmenti i boje - oksidativni polimeri - termalni polimeri - lipoproteini Lipidi u hrani imaju jedinstvena fizička i hemijska svojstva. Njihov sastav, kristalna struktura, temperatura topljenja, sposobnost asociranja (vezivanja) molekula vode i drugih nelipidnih molekula su od velikog značaja za funkcionalna svojstva većine namirnica. Svojstvo lipida je stvaranje micela i dvosloja u kontaktu sa vodom. Lipidi s jednim bočnim lancem stvaraju micele dok lipidi s dva bočna lanca stvaraju dvosloje. Lipidi se u svim živim ćelijama javljaju kao strukturna komponenta. Neki su linearne alifatske molekule, dok drugi imaju prstenastu strukturu. Neki su aromatski, dok drugi nisu. Neki lipidi imaju djelimično polarni karakter, dok su drugi nepolarni. Općenito, njihova izvorna struktura je nepolarna ili hidrofobna, što znači da ne postoji dobra intereakcija sa polarnim otapalima kao što je voda. Neke grupe lipida mogu imati dio strukture koji je polaran ili hidrofilni i pokazuje dobru tendenciju da se združe sa polarnim otapalom kao što je voda. Općenito ova pojava ih čini amfolitnim molekulama (posjeduju oba svojstva hidrofilno i hidrofobno). U slučaju holesterola hidrofilna komponenta je – OH grupa (hidroksil ili alkohol). U slučaju fosfolipida polarne grupe su veće i više polarizirane. Ključni pojmovi - Lipidi nisu samo ulja i masti. - Lipidi su jedinjenja različitog sastava po pravilu nerastvorljiva u vodi, a rastvorljiva u organskim rastvaračima. - Lipidi obuhvataju širok spektar molekula raznovrsne hemijske strukture, uključujući: masne kiseline, triacilglicerole, voskove, fosfolipide, sfingolipide, sterole i druge spojeve. - Postoje i složeni lipidi konjugirani sa proteinima kao što su lipoproteini (HDL, LDL i VLDL). - Lipidi se mogu klasificirati po različitim kriterijima kao što su: porijeklo, hemijski sastav, uloga u organizmu, nivo složenosti, nutritivni zahtjevi i utjecaj na zdravlje. - Lipidi su osnovna komponenta bioloških membrana i utiču na: Propustljivos membrana,prenos nervnih impulsa,stvaraju kontakte među ćelijama,čine energetske rezerve,štite organizam od mehaničkih povredaformiraju termoizolacioni sloj - Hrana bogata lipidima je meso, mlijeko, jaja, leguminoze, uljarice i jezgrasto voće. Masti i ulja – triacilgliceroli Triacilgliceroli (triacilgliceroli, masti ili neutralne masti) su esteri trohidroksilnog alkohola i monokarboksilnih masnih kiselina. Molekula masti i ulja se sastoji od tri molekula masnih kiselina, koje su vezane za jedan molekul trihidroksilnog alkohola glicerola. Masti koje sadrže nezasićene masne kiseline (sa dvostrukim vezama između ugljenikovih atoma) zapravo su ulja, karakterističnija za biljke nego za životinje. Molekule masti kao izvor energije deponuju se u masnim (adipoznim) ćelijama, koje sadrže mnoge lipidne kapljice. U sastav masti ulaze masne kiseline sa 4-26 ugljenikovih atoma i to samo masne kiseline sa parnim brojem C atoma. U sastavu većine masti dominiraju masne kiseline sa 16-18 atoma ugljenika u lancu (palmitinska, stearinska i oleinska). Kao trovalentni alkohol glicerol može graditi monoestere, diestere i triestere, koji se nazivaju monoacilgliceroli, diacilgliceroli odnosno triacilgliceroli. Triacilgliceroli koji u sva tri položaja sadrže istu vrstu masne kiseline nazivaju se jednostavnim triacilglicerolima. Triacilglicerol koji sadrži tri palmitinske kiseline naziva se tripalmitoilglicerol ili tripalmitin, onaj koji sadrži tri stearinske kiseline tristearilglicerol ili tristearin. Masti se u organizmu nalaze kao protoplazmatične masti (u određenoj količini) i kao rezervne masti (u neodređenoj količini). Većina triacilglicerola koji su prisutni u prirodi su mješoviti i sadrže dvije ili više različitih masnih kiselina. Osnovna struktura masne kiseline je lanac ugljičnih atoma u kojoj je karboksilna grupa (-COOH) na jednoj strani i metilna grupa (-CH3) na drugoj strani. Masne kiseline koje nisu vezane sa drugim komponentama ponekad se zovu „slobodne“ masne kiseline. Neke slobodne masne kiseline imaju vlastite ukuse. Buterna kiselina, na primjer, daje maslacu njegov okus. Kaprolna, kaprilna i kapronska kiselina, dobile su naziv od grčke riječi capra (koza) i imaju neugodan miris te doprinose jakom neugodnom mirisu pokvarene hrane. Zavisno od broja vodonikovih atoma koji su vezani na slobodne valencije ugljenika u molekuli kiseline razlikuju se tri tipa masnih kiselina: zasićene, mononezasićene i polinezasićene. Masne kiseline se razlikuju u dužini lanca. Masne kiseline su podjeljene na kratko-lančane (manje od 6 ugljika), srednje-lančane (6 do 10 ugljika), i dugo-lančane (12 ili više ugljika). Što je kraći ugljični lanac to je masnoća u više tekućem obliku (snižava se njeno talište). Dužina lanca masnih kiselina opredeljuje puteve njihove apsorpcije u probavnom traktu. Ako su lanci između ugljičnih atoma u masnoj kiselini povezani jednostrukim vezama (C-C) te masna kiselina pripada zasićenim masnim kiselinama. Vodikovi atomi potpuno ispunjavaju sva slobodna mjesta. Ovaj tip masnih kiselina dominira u mastima koje su čvrste na sobnoj temperaturi (masti životinjskog porijekla). Na primjer, stearinska kiselina sa 18-ugljičnih atoma je zasićena masna kiselina. Nalazi se u čokoladi i mesu. Ako je jedna ili više veza između ugljikovih atoma povezana dvostrukim vezama (C=C) masna kiselina pripada nezasićenim masnim kiselinama. Masna kiselina s jednom dvostrukom vezom je mononezasićena masna kiselina, sa dvije ili više dvostrukih veza zove se polinezasićena masna kiselina. Mononezasićene masne kiseline imaju takav hemijski sastav koji im omogućuje vezivanje još dva atoma vodika u molekuli masne kiseline. Ako se u molekuli nalazi dosta nezasićenih kiselina to su onda ulja, koja su na sobnoj temperaturi tečna (maslinovo ulje, sojino, suncokretovo, ulje uljane repice). Međutim neke masti se često nazivaju uljima iako su u krutom stanju na sobnoj temperaturi, kakav je slučaj sa palminim uljem. Oleinska kiselina sa 18-ugljičnih atoma je mononezasićena masna kiselina. Zastupljena je u maslinovom ulju. Maslinovo ulje je tečno na sobnoj temperaturi, a hlađenjem se može stvrdnuti. Polinezasićena linolna kiselina je masna kiselina sojinog ulja koja je manje tečna na sobnoj temperaturi. Ukoliko su kiselinski ostaci duži, utoliko raste i tačka topljenja. Ako su kiseline nezasićene, tačka topljenja opada sa brojem dvostrukih veza. Životinjske masti su uglavnom na sobnoj temperaturi čvrste izuzev životinjskih ulja riba sjevernih mora . Polinezasićene masne kiseline imaju više „slobodnih“ mjesta na atomima ugljika na koje mogu vezati atome vodika. Najpoznatija od tih masnih kiselina je linolna masna kiselina koja ulazi u sastav brojnih biljnih ulja poput suncokretovog, kukuruznog i sezamovog. Veliki izvor polinezasićenih masnih kiselina su ribe, a naročito plava riba. Najčešće masne kiseline Masne kiseline u sastavu triacilglicerola se prikazuju skraćenim brojčanim izrazima. Prvi predstavlja broj atoma ugljenika a drugi broj dvostrukih veza. Tako na primjer 12:0, 18:1 i 18:3 predstavljaju laurinsku, oleinsku i linolensku kiselinu. Reakcije nezasićenih masnih kiselina podliježu reakcijama adicije-hidrogenizacije, te tako nastaju zasićene masne kiseline. Biljna ulja se hidrogenizacijom pretvaraju u krute biljne masnoće i margarin. Transmasne kiseline su nezasićene masne kiseline koje sadrže trans dvostruku vezu između atoma ugljika koja tvori lanac molekule manje svinut u odnosu na masne kiseline s cis dvostrukom vezom. Masovnija konzumacija ulja, dovela su do razvoja mnogobrojnih tehnoloških postupaka uključujući zagrijavanje i tiještenje na visokim temperaturama, dekolorizaciju, dezodoriranje itd. Razvijani su tehnološki procesi proizvodnje hidrogeniziranih masti i margarina u kojem se procesom hidrogenacije molekule vodika “dodaju“ molekuli nezasićene masne kiseline. Ovi hemijski procesi mijenjaju prirodnu CIS strukturu masnih kiselina u TRANS koja je neprirodna i ljudski organizam je ne može iskoristiti. Trebalo je nekoliko desetljeća da bude potvrđeno da se i ovim procesom prirodni CIS oblici masnih kiselina prevode u neprirodne, i čak po zdravlje rizične TRANS masne kiseline. Takva “trans“ svojstva se najčešće pojavljuju industrijskom preradom, postupkom koji se naziva hidrogenizacija biljnih ulja . Pretjerano konzumiranje trans masnih kiselina dovodi do ozbiljnih zdravstvenih poremećaja i zato u naprednim zemljama odgovorne institucije određuju postotak trans masti u prehrambenim namirnicama. Trans masne kiseline i hidrogenirana ulja doprinose opadanju imuniteta, gojaznosti, pojavi šećerne bolesti, holesterola, razvoju krvožilnih bolesti, bolesti prostate, smanjenju izlučivanja testosterona i sperme, pa čak i povećanoj učestalosti poroda djece sa niskom porođajnom težinom. Vrste masnih kiselina i njihovi izvori Esencijalne masne kiseline. Ljudsko tijelo ne raspolaže enzimom koji razlaže dvostruke veze masnih lanaca većih od 10 ugljikovih atoma. Masne kiseline sa više dvostrukih veza (linolna, linolenska i arahidonska) ubrajaju se u esencijalne sastojke hrane, jer se ne mogu sintetizovati u organizmu. Esencijalne masne kiseline Linolna kiselina ima prvu dvostruku vezu između 6. i 7. ugljenikova atoma, zbog čega se naziva omega 6-masnom kiselinom, a linoleinska kiselina ima dvostruku vezu između 3. i 4. ugljenikovog atoma i ubraja se u omega 3-masne kiseline. Prisutne su u sjemenkama i sjemenim uljima. Esencijalne masne kiseline su ključne u metabolizmu i presudne su za dobro zdravlje. Sudjeluju u funkcioniranju živčanog tkiva, mrežnice i mozga. Ključne su za kognitivnu funkciju mozga, memoriranje, vizualno razlikovanje itd. Omega-3 masne su kiseline ključne za stanične membrane – ako ih nema dovoljno u opskrbi, trpe sve stanice, a time tkiva i organi. Od vremena kada je utvrđeno da Eskimi, koji konzumiraju isključivo meso i masnoću, ne obolijevaju od srčanog udara jer ih štite upravo masne kiseline popularno nazvane omega-3. Do danas, stručna literatura o njihovim ljekovitim učincima popela se na nekoliko hiljada naslova i svakim se danom povećava. Omega-3 masne kiseline redovito dodaju umjetnoj hrani za dojenčad jer ih u uobičajenim namirnicama (osim morskih plodova) nema. Kada je u pitanju riba ili riblje ulje, za procjenu kvalitete potrebno je u analizama gledati na dvije ključne omega-3 masne kiseline: EPA-C 20:5 (eikosapentenska) i DHA-C 22:6 (dokosaheksanoinska) masne kiseline. Treća je esencijalna ALA – C 18:3 (alfa-linolna). Premda spada u omega-3 skupinu, ima je u ulju lanenog sjemena, a ne u ribljem ulju (osim u tragovima). Pod omega-3 masnim kiselinama podrazumijevamo zbroj EPA i DHA masnih kiselina. Ova vrsta masti vrlo lako podliježe reakcijama oksidacije, zbog čega se pakuje u tamnu ambalažu nepropusnu za sunce. U njih se prilikom pakovanja dodaju antioksidansi. Nedostak esencijalni masnih kiselina izaziva gubitak vode, dermatoze i perifernu neuropatiju. Potreban – preporučeni denvni unos je 15 do 20 % od ukupno unesene energije, odnosno 15 g /dan kod djece i 50 g / dan kod odraslih. Posljednjih nekoliko godina pažnju fiziologa i farmaceuta zaokuplja gama-linolenska kiselina jer djeluje kao preteča u nastanku tvari koje zovemo prostaglandini-2. To su specijalni hemijski „glasnici“ koje koriste sva tkiva u organizmu. Preko njih može se odrediti biološka dob pojedinog organizma, a neophodni su za sve životne funkcije. Fizikalno hemijska svojstva. Masne kiseline se već na sobnoj temperaturi mijenjaju putem oksidacije. Pri tome se molekule masnih kiselina razlažu na ugljikovodike, ketone, aldehide, te u manjoj mjeri na epokside i alkohole. Teški metali i u malim količinama ubrzavaju oksidaciju (čime pokazuju stupanj zagađenja). Masnoće i ulja se zbog toga često tretiraju sa antioksidansima. Gliceridi reaguju kao estri, a posebno je važna reakcija hidrolize, pri čemu se izdvaja glicerol i masne kiseline. Hidroliza se može vršiti enzimski ili dejstvom kiselina ili baza. Za triacilglicerole je karakteričan jodni, kiselinski broj i saponifikacioni broj. Na stepen degradacije ukazuju slobodne masne kiseline, peroksidni broj i anisidin vrijednost. Jodni broj predstavlja količinu joda u gramima koja se veže na 100 g masti. Jod se veže na dvostruke veze masne kiseline te iz njega dobijamo uvid u stepen nezasićenosti masti. Jodni broj svinjske masti je 46-66, a maslinovog ulja oko 85. Saponifikacioni broj predstavlja miligrame KOH potrebne za osapunjenje 1 g masti (mg KOH/g masti). Zavisi o sastavu masnih kiselina, te masti koje sadrže masne kiseline niže molekularne mase imaju viši saponifikacioni broj i obratno. Kiselinski broj ili broj neutralizacije je mjerilo stupnja hidrolize. Definira se kao broj miligrama KOH koji je potreban za neutralizaciju slobodnih masnih kiselina u 1 g masti ili za neutralizaciju 1 g masnih kiselina. Kiselost ili aciditet masti često se izražava i kao procenat slobodnih masnih kiselina. Što je veći % slobodnih masnih kiselina (SMK) ulje je lošije i procesi degradacije su većeg intenziteta i redovito su obrnuto proporcionalni sa sadržajem svih ostalih sastojaka koji čine kvalitetu (aromatski spojevi, vitamini, polifenoli i drugi) a time i njegovu prehrambenu vrijednost. Povećanje sadržaja slobodnih masnih kiselina, kao i peroksida u triacilglicerolima praćeno je pojavom neugodnog okusa i mirisa. Peroksidni broj označava nivo primarne oksidacije masnih kiselina i on pokazuje količinu hidroperoksida kao primarnih proizvoda autooksidacije i izražava se u miliekvivalentima O2/kg. Peroksidni broj je u uskoj vezi s načinom čuvanja ulja. Oksidacija masti je jedna od osnovnih reakcija koja utječe na zdravstvenu ispravnost triacilglicerola jer su produkti reakcije oksidacije štetni po zdravlje potrošača. Ključni pojmovi - Triacilgliceroli su najčešće zastupljeni lipidi u prehrani. - Triacilgliceroli su estri glicerola i masnih kiselina. - Svojstva triacilglicerola određuju masne kiseline koje mogu biti nezasićene i zasićene, kratkolančane, srednjelančane i dugolančane, u cis i trans obliku. - Triacilgliceroli su u krutom stanju na sobnoj temperaturi ako ih grade zasićene masne kiseline, a u slučaju kad ih grade nezasićene onda su tečni-ulja. - Neke masne kiseline su esencijalne kao što je linolna, linolenska i arahidonska . - Linolna kiselina ima prvu dvostruku vezu između 6. i 7. ugljenikovog atoma, zbog čega se naziva omega 6-masnom kiselinom, a linoleinska kiselina ima dvostruku vezu između 3. i 4. ugljenikovog atoma i ubraja se u omega 3-masne kiseline. - Ljudsko tijelo ne raspolaže enzimom koji razlaže dvostruke veze masnih lanaca većih od 10 ugljikovih atoma. Fosfolipidi Fosfolipidi su glavne strukturne komponente ćelijskih membrana. Slično mastima, sastoje se od masnih kiselina i glicerola. Međutim, treća masna kiselina je zamijenjena fosfatnom grupom koja posjeduje negativna naelektrisanja, za koju je obično vezana još neka polarna grupa. Predstavnici fofolipida su: lecitin, cefalin i drugi. Lecitini i cefalini površinski su aktivna biološka sredstva jer imaju hidrofilni polarni kraj i hidrofobnu komponentu. Sojino ulje sadrži oko 3,5% fosfatida , te ovo ulje služi kao izvor njihovog dobijanja. Prehrambena industrija koristi lecitin kao emulgator pri miješanju dva sastojka koji se prirodno ne miješaju kao što su ulje i voda. Njegova hranjiva vrijednost ovisi o sadržaju kolina i esencijalnih masnih kiselina, odnosno o namirnici u kojoj se nalazi. Lecitin se nalazi u jajima, soji, mlijeku, čokoladi, vafel proizvodima, majonezi kao i žvakaćoj gumi te brojnim drugim prehrambenim proizvodima. Sva nerafinirana ulja sjemenki sadrže veći ili manji postotak lecitina. Djeluje kao izvrstan emulgator masti. Lecitin je strukturni dio membrane stanice i staničnih organela. Jedan je od tri glavna emulgatora u prirodi, uz sfingomijelin i cefalin. Neophodan je za detoksikacijsku ulogu jetre. Konstitucija fosfolipida važna je u biološkim sistemima. Fosfatna grupa kod fosfolipida čini hidrofilnu glavu molekule, za razliku od hidrofobnih repova masnih kiselina. Zahvaljujući ovakvoj strukturi, fosfolipidi su amfipatične molekule, koje spontano u vodi obrazuju dvoslojni film u kome su glave orijentisane prema spolja – prema vodi, a repovi prema unutra, što predstavlja osnovu strukture ćelijskih membrana. Fosfolipidi su najobilniji u žumanjcima jaja, jetri, soji i kikirikiju. Ljudsko tijelo je u stanju sintetizirati fosfolipide. Sfingolipidi Sfingolipidi su vrsta fosfolipida bez glicerola, ali su po strukturi i djelovanju srodni fosfolipidima. To su složeni lipidi kod kojih je na primarnu OH- grupu na C1 sfingozina u dijelu molekule esterski vezan fosfoholin ili fosfoetanolamin. Od masnih kiselina u sfingomijelinima najčešće su prisutne palmitinska, stearinska, lignocerinska kiselina, kao zasićene masne kiseline i nervonska kiselina. Ključni pojmovi - Fosfolipidi su komponente hrane, a imaju značajnu funkciju u ljudskom oragnizmu. - Najznačajniji fosfolipid u hrani je lecitin. - Fosfolipidi su najobilniji u žumanjcima jaja, jetri, soji i kikirikiju. - Ljudsko tijelo je u stanju sintetizirati fosfolipide. Voskovi Voskovi su takođe jedan od oblika strukturnih lipida. Voskovi su estri viših masnih kiselina i viših alkohola sa 20 do 70 C atoma u molekulu. Oni formiraju zaštitni sloj na koži, krznu, perju, lišću i plodovima viših biljaka i na egzoskeletu mnogih insekata. Prirodni voskovi (pčelinji vosak, mast iz kitove glave, biljni voskovi) smjese su različitih tvari. Glavni sastojak je ester dugolančanih jednovalentnih alkohola s višim masnim kiselinama. Iz pčelinjeg voska izoliran je miricin, ester palmitinske kiseline s miricilnim alkoholom, C30H61OH. Iz glave kita je izoliran cetilpalmitat, CH3-(CH2)14-CO-O-C16H33. Uz te estere nalazimo u voskovima nerazgranate ugljikovodonike, estere sterola, slobodne masne kiseline i hidroksi masne kiseline. Kod biljaka su 80% svih lipida voskovi koji stvaraju zaštitni sloj na površini biljke i štite je od isparavanja vode. Prirodni vosak (pčelinji, lanolin) pored estara sadrži i malu količinu slobodnih masnih kiselina, nekih alkohola i ugljovodinika, sa 20-35 C atoma u molekulu. Lipidi izoprenoidnog porijekla Lipidi izoprenoidnog porijekla mogu se svrstati u sljedeće grupe: - steroidi čija struktura potiče od od triterpena (C5H8) 6 a to su: holesterol, sterolni derivati (esteri, glikozidi), vitamin D, žučne kiseline, steroidni hormoni - karotenoidi kao što je provitamin A - izoprenoidni vitamini kao što su vitamini E i K Steroidi. Holesterol pripada grupi jedinjenja poznatih kao steroidi. To je steroid životinjskog porijekla. Steroidi se po strukturi razlikuju od drugih lipida, ali su svrstani u ovu grupu zato što su nerastvorljivi u vodi. Svi steroidi imaju četiri povezana prstena sastavljena od ugljenika, a neki od njih kao holesterol, imaju ugljovodonični lanac. Holesterol je steroidni alkohol koji u položaju 3-beta A prstena steroidnog skeleta sadrži hidroksilnu skupinu, a na C17 atomu razgranati alifatični lanac od 8 C atoma. Holesterol je od osnovnog značaja za život. Tijelo odraslog čovjeka sadrži oko 150 gr holesterola. Prehrambeni holesterol je holesterol koji je prisutan u hrani koju jedemo. Nalazi se u hrani animalnog porijekla uključujući jaja, maslac, mlijeko, kajmak, džigerica i bubrezi. Nema ga u hrani biljnog porijekla. Holesterol u krvi indikator je u uspostavljanju medicinskih dijagnoza. Holesterol je prisutan u svim ćelijskim membranama, sem u bakterijskim. Oko 25% suhe težine membrana crvenih krvnih zrnaca čini holesterol. Također obezbjeđuje osnovnu shemu za sinteze mnogih hormona – polni steroidi, kao što su estradiol i testosteron, steroidni hormoni kore nadbubrežne žlijezde, npr. kortizol, kao i prethodnik vitamina D (7-dehidroholesterol). Holesterol je također ključni prethodnik žučnih kiselina i stoga je od vitalnog značaja za probavu masnoća. Glavna je komponenta mijelinskog omotača nervnih vlakana. U starijih ljudi holesterol formira masne naslage u unutrašnjosti krvnih sudova što smanjuje njihovu elastičnost, zatvara ih i dovodi do povećanog krvnog pritiska te srčanog i moždanog udara. Karotenoidi. Osnovnu strukturu karotenoida čine kovalentno povezane izoprenske jedinice. Razlikujemo dvije strukturne grupe karotenoida: karoteni i ksantofili. Karotenoidi su topivi u uljima i organskim otapalima, a boja im varira od žute preko narančaste do crvene što podrazumijeva da se nalaze u narančastom, žutom, crvenom i zelenom voću i povrću. Danas poznajemo oko 600 karotenoida. Najpoznatiji karotenoidi su beta karoten, likopen i lutein. Struktura provitamina A potiče od tetraterpena (C5 H8)8. Beta-karoten je snažan izvor vitamina A, u koji ga ovisno o potrebi pretvara naš organizam. Ukoliko ne dođe do pretvorbe karotenoida u vitamin A, oni se ugrađuju u hilomikrone te dolaze u jetru. U cirkulaciji se nalaze vezani za lipoproteine. U karotenoide spadaju: - narančasti karoten (mrkva, kukuruz, marelica, breskva, agrumi, bundeva), - crveni likopen (rajčica, lubenica, marelica), - žuto-narančasti ksantofil (kukuruz, breskva, paprika, bundeva), - žuto-narančasti krocetin (šafran). Izoprenoidni vitamini su vitamini E i K. Većina namirnica koje sadrže višestruko nezasićene masne kiseline sadrže i vitamin E. Ključni pojmovi - Voskovi su estri viših masnih kiselina i viših alkohola sa 20 do 70 C atoma u molekulu. - Holesterol je lipid steroidne strukture i integralni je dio životinjskih tkiva (jaja, meso, neke ribe, punomasno mlijeko itd.). - Nema ga u biljnim ćelijama. - Holesterol ima mnogo funkcija u organizmu, neophodan je za sintezu polnih hormona i žučnih kiselina koje učestvuju u varenju hrane. Lipoproteini Lipoproteini su kompleksi-čestice masnih spojeva i proteina. Konkretnije, lipoprotein je kompleks holesterola, triacilglicerola i fosfolipida s proteinima. Lipidna komponenta lipoproteina sadrži četiri tipa molekula, u različitom omjeru u različitim razredima lipoproteina. Svi lipoproteini imaju u svom sastavu fosfolipide, kolesterol, esterificirani kolesterol i triacilglicerole. Poznavajući svojstva ovih kategorija lipida može se pouzdano sačiniti opći model lipoproteina. Fosfolipidi, zbog svojstva amfipatičnosti (jedan kraj molekule je polaran, a drugi nepolaran) zajedno s proteinima čine vanjsku ovojnicu lipoproteina. Polarne glave fosfolipida su izložene vodenom mediju, a nepolarni krajevi okrenuti prema unutrašnjosti. Esterificirani holesterol i triacilgliceroli su velike nepolarne molekule i smještene su u sredini čestica. Holesterol je blago polaran, pa može biti i na površini i u unutrašnjosti čestice. Glavna uloga lipoproteina je transport lipida u organizmu. Lipoproteini se dijele prema sastavu, veličini i gustoći na 4 kategorija u kojima redom opada udio masti, a raste udio proteina. To su: - hilomikroni - VLDL lipoproteini - LDL lipoproteini - HDL lipoproteini Najveće lipoproteinske čestice, ujedno i čestice najmanje gustoće nazivamo hilomikronima (CM) u kojima se nalazi najviše triacilglicerola uz manje količine fosfolipida, kolesterola i apoproteina. Služe za transport triacilglicerola unesenih hranom. Nešto manje čestice nazivamo lipoproteinima vrlo male gustoće, najčešće poznate pod akronimom VLDL (od engleskog Very Low Density Lipoprotein) i oni služe za transport endogenih triacilglicerola u organizmu. Postoje i lipoproteini srednje gustoće (Intermediate Density Lipoproteins) poznati po kratici IDL, formiraju se katabolizmom VLDL i prekursori su za tvorbu LDL. Još manje i gušće čestice su lipoproteini male gustoće (LDL – Low Density Lipoprotein) koji služe kao glavni transporteri holesterola do perifernih stanica. Najgušće i najmanje čestice su lipoproteini velike gustoće, HDL (od engl. High Density Lipoprotein). Sadrže najviše proteina od svih navedenih kategorija, služe također za transport kolesterola ali od stanica u jetru. Glikolipidi Glikolipidi su složeni lipidi konjugirani sa ugljičnim hidratima, a ugljikohidratna komponenta je najčešće D-galaktoza. Bitni su za funkciju bioloških membrana. Nalaze se u mozgu i krvi. Glikolipidi su izgrađeni od sfingozina, ostatka masnih kiselina (acila) i šećera vezanog na primarnu hidroksilnu skupinu sfingozina Ključni pojmovi - Lipoproteini su konjugati proteina i lipida. - Od namirnica, jaja su posebno bogata lipoproteinima. - U ljudskom organizmu imaju značajnu ulogu u transportu nutrijenata. - Za razliku od HDL-a, LDL je lipoprotein štetan po zdravlje, jer povišene vrijednosti LDL u cirkulaciji dovode do stvaranja plaka u krvnim sudovima. Literatura Spisak korišćene literature možete naći u Literatura – Hemija hrane.