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Good fats are derived from natural plant fats and their unrefined, non-hydrogenated oils. We need a certain amount of these fats in our diet in order to live and thrive at optimal levels. It is imperative, however, that we consume the right type of fats and largely avoid the bad ones which can have negative consequences on our health over time. Both saturated and unsaturated fats, in proper proportions, are healthy to the body, especially when they are eaten in their raw state as opposed to heated or highly processed. Changing the types of fats you eat and consume on a regular basis can help to reduce the risk of many common health conditions as well as actually assist in protecting against cardiovascular disease rather than be the cause of it. Fat is a necessary substance for optimum brain function and the fats we eat have a strong influence on our mental faculties, from the time of our birth to our elderly years later in life. When healthy fats are digested they are broken down into fatty acids of varying lengths. These molecules help to nourish the brain and provide building blocks for its cell membranes like the myelin sheath, which insulates the brain's neuron fibers. Myelin, a white fatty material, serves to greatly increase the speed of signal transmission. Consequently, a loss of essential fatty acid concentrations in the brain have been shown in research to cause cognitive decline and impairment. The fats we eat are also needed to create special types of fat that incorporate into the casing around our cells. Every cell has a membrane and the membrane, like a "protective shield", is made mostly out of fat. Fatty foods affect the body in many ways and have a influential impact on hormonal activity. They are additionally an energy burning fuel source, required for the absorption of fat-soluble vitamins and help to keep our skin supple and soft. Adequate intake of these good fats and their oils, along with a health promoting diet and lifestyle, has been shown to reduced a number of health related problems including neurological conditions, high blood pressure, diabetes, obesity as well as depression and heart disease. Typically, depending on one's unique constitution, your total fat intake should be between 20-40% of your daily calories. This percentage is, of course, contingent on the amount of energy expended on any one given day. The higher fat percentages are specific for those who are highly physically active and tend to burn dietary fat as an energy source. Saturated fats are chains of carbon atoms that have no double bonds and are "saturated" with hydrogen atoms. These are oils and fats that are solid at room temperature. There are several types of saturated fatty acids, but the most common are stearic acid, lauric acid and palmitic acid. We need some saturated fats in our diet, but this is largely determined by the amount of physically activity conducted throughout the day as well as our unique body type and the kinds of foods we predominantly burn as energy. Generally speaking, total saturated fat should not be more than 10% of our daily caloric intake. Saturated fats are known to slow down the absorption of foods so you feel satiated for longer periods of time and are also important for assimilating the fat-soluble vitamins A, D, E and K. There are different classes of saturated fats, however, some being healthier choices over others. Good fats that are saturated have fewer carbon chains and are called "medium chain fatty acids." MCT's are easy to digest and have been linked to health benefits such as weight loss. They tend to be the most stable and are less affected by heat or light. Oils like cold pressed, virgin coconut oil and red palm oil are two good examples of this type of healthy saturated fat. Saturated fats that have longer chain fatty acids can have detrimental effects on the cardiovascular system when eaten in large quantities on a regular basis. These types of fats come from meat, eggs, and dairy products. When over-consumed, they are known to significantly raise blood cholesterol and cause numerous heart and health issues. Long chain saturated fats are beneficial only when eaten in moderation along with fibrous whole plant-based foods. Unsaturated fats have a double bond in their carbon chain and are liquid at room temperature. These fats are mainly sourced from plant fats and include both monounsaturated and polyunsaturated fat. Monounsaturated fats, also called MUFAs, are carbon chains that have one double bond present. These types of fats are seen as healthier fats to consume over saturated fat varieties. However, there are certain types of monounsaturated fats we would recommend consuming over others. They are found in abundance in raw plant fats and their oils, especially in the form of oleic acid. Some examples of healthy monounsaturated fats are olive oil, avocados, olives, nuts and seeds. We do not recommended heating or cooking with these types of fats or their derived oils as it denatures their molecular structure, turning their good fats into bad ones. In addition, we would largely avoid refined monounsaturated vegetable oils like soybean or canola oil. These oils involve a harsh extraction process that employs the use of the toxic solvent hexane to bleach and deodorize them. This is not the case with most olive oils, but it is best to use unrefined extra virgin monounsaturated oils whenever possible. Polyunsaturated fats, or PUFAs, are the essential fatty acids that have two or more double bonds in their carbon chain. They are also called omega fatty acids and include both omega-6 and omega-3. Omega fatty acids are the good fats that everyone needs to consume on a regular basis, but they are the most volatile to heat or oxidation, and thus damaging to the body when heated. Omega-6 acids (linoleic acid) need to be consumed in proper proportions to omega-3's (alpha-linolenic acid). The general standard for this is between a 4:1 or 1:1 ratio. This means than for the amount of omega-6 foods you consume, you would need to eat at least 1/4 of that amount in omega-3's. In a typical Western diet, high in refined vegetable oils, omega-6 is much higher than omega-3 at between an average 10:1 to 20:1 ratio. Omega-3 Fats It is very important that a health promoting diet include plenty of omega-3 fatty acid foods. ALA omega fatty acids are in green leafy vegetables, micro-algaes, raw fish, chia seeds, flaxseeds, hemp seeds, sacha inchi seeds, with small amounts available in seaweeds, walnuts and sprouts. Some of these foods can also be concentrated into oils for supplementation purposes. DHA and EPA, two essential fats needed for proper neurological functioning and inflammation control, are converted from ALA and can be consumed directly through algae and fish oil sources. Omega-6 Fats Omega-6's are especially concentrated in refined vegetable oils such as corn oil, cottonseed oil, sunflower oil, safflower oil, peanut oil and sesame oil. They are also found in abundance in grain-fed animal meat protein and dairy products. Avocados, olives as well as nuts and seeds also contain some degree of omega-6 content. Trans fats are the "ugly fats" you want to consume in minimal quantities or avoid all together. These types of fats have been altered by a process called hydrogenation to increase their shelf life, not your life! Trans fats are a source of harmful free radicals and proinflammatory compounds. They are known to raise LDL cholesterol and can significantly increase risk of heart disease and neurodegenerative conditions. These fats include hydrogenated or partially hydrogenated oils from plants like soy, sunflower, canola, cottonseed and corn. In addition, most of these foods are genetically modified and are largely void of any nutritional value. They are found in many packaged foods and fast foods and are the polar opposite of good fats the body needs and thrives on. Refined vegetable oils are nearly just as bad as hydrogenated trans fats. Most common vegetable oils sold, like safflower, canola, and corn, have gone through a refining process to increase oil stability for storage purposes. This strips away all nutrient content and deodorizes the oil at high temperatures of up to 500°F (260°C). "A lot of what's been marketed as "healthy" oils, like canola oil for example, lack color, flavor and nutrients. With the goal to increase shelf life, the fatty acids have been removed from these "plastic" oils and our livers are not designed to handle them." Body Ecology Cooking monounsaturated or polyunsaturated fats or oils denatures them and produces harmful free radicals. They become dense and clog the blood, lymph and digestive system. In addition, high heat prohibits them from being digested and eliminated properly, producing excess weight gain, as well as increased strain on the liver. Healthy saturated fats are the best oils to use for cooking purposes as they are more stable at high temperatures and are able to maintain their nutritional integrity to a large degree. If you are going to choose an oil to cook with, coconut oil and red palm oil are the best oils to use because they are the most stable at high temperatures. They are, however, more beneficial to the body when consumed in their unheated state. It is commonly believed that cholesterol is some kind of saturated fat because it is often categorized alongside saturate fat in conversation. Cholesterol, however, is a waxy fat-like sterol substance that naturally occurs in the human body. It is needed to make vitamin D and some hormones, build cell walls and create bile salts that help you digest fat. Dietary cholesterol is found mainly in animal foods, like meat, fish, eggs and dairy. These types of food sources can raise both LDL or HDL cholesterol levels. Cholesterol is virtually non-existent in plant-based foods, which typically contain a cholesterol-like constituent called phytosterols, proven to be effective at actually lowering LDL cholesterol, the "bad cholesterol." This is our recommended list of health fats and oils that can be used to replace unhealthy, processed or refined fats in the diet. It is important to remember that consuming whole food fat sources are a better choice over large amounts of oil extracted concentrates. Coconut oil is the oil extracted from the fruit of the coconut palm species, Cocos nucifera, and contains medium-chain fatty acids that are easily digested and utilized as an energy burning fuel source, rather than stored as body fat. The oil is natural high in these good saturated fats (MCFAs) as well as lauric acid, which the body converts to monolaurin. Monolaurin is a natural antiviral agent helpful for eliminating parasites, viruses, bacteria, yeast and fungi. In addition to lauric acid the oil is also composed of other secondary saturated fatty acids, caprylic acid, capric acid and myristic acid. Coconut oil is one of the good fats under investigation as a dietary supplement for those with neurodegenerative diseases like Alzheimer's, serving as and alternative energy fuel for the brain. (Source) Consuming moderate amounts of the oil has also been shown to increase HDL "the good cholesterol" and improve thyroid function. It is one of the only oils we recommend for cooking, along with red palm oil, because it is very stable at medium-heat temperatures. The oil however is best used raw and unheated in blended drinks and recipes to preserve complete nutritional profile. The coconut oil we consume and promote as a good fat is organic, virgin, unrefined, non-GMO coconut oil derived from low-temp processed raw coconut meat. This is oil that has not been refined, hydrogenated, fractionated, deodorized or bleached. One tablespoon of coconut oil is 120-135 calories and approximately 14g total fat content with 13g saturated fat, 1g monounsaturated fat and 0.5g polyunsaturated fat. Olive oil is the oil extracted from the olive fruit or Olea europaea species. A popular oil consumed as part the Mediterranean diet, it is known to be a heart healthy monounsaturated fat high in oleic acid. Olive oil is also composed of palmitic acid, linoleic acid, stearic acid and small amounts of alpha-linolenic acid. Pure unprocessed olive oil is a source of antioxidant phenolic compounds such as flavonoids, lignans and pinoresinol. (Source) The best olive oil to use is raw unrefined extra virgin olive oil, which is typically a golden-green color. For highest nutritional benefits it is best not to heat the oil or use it for cooking purposed as it is highly volatile to oxidation. It is delicious drizzled over foods or added to raw unheated recipes. One tablespoon (14g) of olive oil contains 119 calories and has a total fat content of 13.50g with 1.9g saturated fat, 9.8g monounsaturated fat and 1.4g polyunsaturated fat. Red palm oil comes from palm fruit and is not the same thing as palm kernel oil or refined palm oil, which are both unhealthy oils to consume on a regular basis. Red palm oil is sourced from the African oil palm, or Elaeis guineensis species, and is composed of palmitic, stearic, oleic and linoleic acids. Similar to coconut oil, red palm is one of the few plant based saturated fats made up of "medium chain fatty acids." These are "good fats" to consume because they increase metabolism and are easily digested, providing an immediate energy source. Because these medium chain triglycerides can't be stored as body fat, they can be healthier oil alternatives for those needing to loose body weight. High quality, organic red palm oil is minimally processed using steam to extract the oil before it is expeller-pressed. The oil gets its super rich orange-red color from the presence of carotenes, the main ones of which are beta-carotene, alpha-carotene and lycopene. As a saturated fat, it is highly stable at high temperatures and a better choice for cooking than monounsaturated oils. One tablespoon of red palm oil is 130 calories and made up of 14g total fat content with 6g saturated fat, 6g monounsaturated fat and 1.5g polyunsaturated fat. One tablespoon is 240% of the daily value for vitamin A and 25% for vitamin E. Hemp seed oil is another type of good fat pressed from the seeds of the hemp plant, a tall seedy and fibrous Cannabis variety. As a highly nourishing oil, most are about 80% polyunsaturated fat and provide a balanced 3:1 ratio of omega-6 to omega-3 fatty acids. This ratio is known to be helpful for lowering the "bad" cholesterol and reducing inflammation in the body. Taken in capsule form or ingested as hemp oil, it can be used as a dietary supplement or as a nutty tasting condiment with foods. Consuming hemp oil is excellent for the hair and skin as it helps to nourish cell membranes and provides antifungal, antibacterial and antiviral properties. It is also high in the antioxidants vitamin E and beta-carotene and also includes the rare gamma-linolenic acid (GLA) and stearidonic acid (SDA). All polyunsaturated oils are extremely volatile to heat and light and can easily go rancid. It is therefore imperative that they be kept refrigerated to preserve their nutrient content and essential fatty acid structure. They are only beneficial when consumed as raw unheated oils drizzled over salads, meals or raw recipes and should never be used for cooking or sautéing foods. All quality hemp seed oil is unrefined, cold pressed, always dark in color and preferably preserved in dark glass bottles. One tablespoon of the oil is 125 calories and made up of 12g total fat content with 1g saturated fat, 2g monounsaturated fat and 11g polyunsaturated fat. Flaxseed oil, or linseed oil, is a yellowish oil derived from the dried seeds of the flax plant species Linum usitatissimum. The oil was one of the first omega oils that was popularized in the health food movement in the 70's and 80's. Being a valuable source of omega-3 fatty acids, the seed extracted oil has been used extensively as a nutritional health supplement. As with all the omega-3 oils, flax is extremely sensitive to oxidation and must be kept refrigerated to preserve its nutritional quality and should always be consumed in its raw state and never heated. Besides alpha-linolenic acid, the oil also contains oleic acid, linoleic acid and smaller amounts of palmitic acid and stearic acid. In a study published in the Canadian Journal of Cardiology it states that "it is logical to predict that a rich source of ALA like flaxseed should have strong beneficial effects in the primary and secondary prevention of cardiovascular disease." Flaxseed oil, in experiments at the Gerson Institute, was shown to be the only oil that did not make cancerous tumors grow in size. One tablespoon of flaxseed oil is 119 calories and made up of 13.5g total fat content with 1.3g saturated fat, 2,7g monounsaturated fat and 8.9g polyunsaturated fat. The oil contains 7196mg omega-3 and 1715mg omega-6 fatty acids. Sacha inchi oil is sourced from a tropical seed-producing vine, Plukenetia volubilis, and is native to the Peruvian Amazon region. The oil is well-known for its higher amounts of omega-3 fatty acids that make up close to half of the total oil content. Concentrated in high amounts of tocopherols, consisting of both gamma-tocopherol and delta-tocopherol, it is a very nourishing food for the skin when consumed. The oil is also considerably sensitive to heat and light, being made up of mostly polyunsaturated fats and should be kept refrigerated to avoid rancidity. The best oil is unrefined, extra virgin and cold-pressed. It has a mild and nutty flavor and can be used on foods but should never be used for cooking purposes. One tablespoon of sacha inchi oil contains 124 calories and has a total fat content of 14g, with 1g saturated fat and 12g polyunsaturated fat. One tablespoon of oil contains 6.5g of omega-3 and 3.7g of omega-6. Olives are actually the fruit of the tree species Olea europaea and are a rich source of several phenolic compounds as well as vitamin E, vitamin A, iron and calcium. They are known for their high amounts of oleic fatty acid, a monounsaturated good fat to include in the diet. The olives we recommend consuming for highest nutritional content are naturally sun-ripened black olives, not green unripened varieties. Green olives are picked before they are actually ripe and then chemically treated with harsh substances to soften and remove their bitterness or astringent qualities. The best black olives are traditionally cured using natural methods that involve either sea salt brining and/or oil curing. According to Professor Arnold Ehret in his book the "Mucusless Diet Healing System", olives are an alkaline food source and powerful mucus-dissolvers when consumed. One ounce (or about 7 olives) contain 41 calories and 4g total fat with 0.5 saturated fat, 3g monounsaturated fat and 0.5 polyunsaturated fat. Because olives are usually high in salt content, they should be consumed in moderate amounts to avoid excess sodium intake. Coconuts come from the Cocos nucifera coconut palm species found all over the world in tropical climate locations. The white coconut flesh or meat on the inside of the hard shelled coconut is an energizing, nutritious, fatty food source and one of the best forms of raw, saturated good fat that you can eat. Consumed as fresh coconut meat, dried pieces or shredded flakes, coconut contains ingredients that nourish the skin and hair, regulate hormone production, support HDL "good" cholesterol levels and help to increase metabolic functions. Lauric acid, one of the main fatty acids in coconut, is useful for normalizing cholesterol by promoting LDL conversion to pregnenolone. The good fats in coconut meat additionally support healthy thyroid gland functions which also plays a significant role in regulating cholesterol as well as maintaining ideal body weight. Fresh coconut meat provides a rich, flavorful texture in shakes, coconut kefir and a variety of desserts. Raw dried coconut can also be soaked and added to drinks or used in recipes. One ounce (28g) of fresh coconut meat contains 99 calories and 9g total fat with 8.3g saturated fat, 0.4g monounsaturated fat and 0.1g polyunsaturated fat. Avocados are a Mediterranean fruit tree species (P. americana) and probably one of the most common plant fats known around the world. Ripe avocados are made up of mostly monounsaturated fats and are sources of the antioxidants, vitamin C, vitamin E, xanthophyll carotenoids as well as pantothenic acid, vitamin K, choline, folate, Vit. B6 and other B vitamins. They are high in fiber, phytosterols and according to an article published in the journal of Food Science and Nutrition, "There are eight preliminary avocado cardiovascular health clinical studies that have consistently demonstrated positive heart healthy effects on blood lipids profiles." In a same article it also states that "The consumption of avocados with salads or salsa increases the bioavailability of carotenoids multi-fold." Avocados are high on our good fats list as a convenient raw food to add to meals, salads and raw soups. Containing both lutein and zeaxanthin, they are great for the eyes and also provide a nourishing food for the hair and skin. One ounce (28g) of ripe avocado contains 47 calories and 4.3g total fat with 0.6g saturated fat, 2.7g monounsaturated fat and 0.5g polyunsaturated fat. Nuts and seeds are a high energy dense fuel source, packed with concentrated protein, fatty acids, vitamins, minerals, fiber and other nutrients unique to the specific varieties. They are the perfect addition to a vegan, raw vegan or vegetarian diet, providing a quality alternative to many meat-based foods. The types of seeds and nuts we are referring to are raw shelled or unshelled assortments that have not been high heat steamed or fumigated with chemicals to "sanitize" them. These are also selections that have not been toasted, dry roasted or salted, but are minimally processed straight from the tree or plant from which they are derived. (For more information on how to identify and purchase raw nuts and seeds visit this page link.) The key to eating seeds and nuts is that "a little goes along way" as far as calories and nutrition. Some people can overeat nuts for they taste so good and are easy to snack on, but it is best to avoid the temptation. They are rich and tend to build up mucus and acidity in the body, especially if not properly balanced with other food selections. Nuts and seeds are easier to digest and assimilate when they have been soaked and strained (and sometimes sprouted) to remove phytates, lectins and other enzyme inhibitors that will impede their nutrient absorption. They can be soaked, processed and dehydrated into entrees that replicate traditionally served cooked foods such as: burgers, cheeses, milks, pizza and ice cream. Durians are an exotic tropical tree fruit native to Indonesia and Malaysia. The variety consumed and sold exclusively for export is the Durio zibethinus species. Often identified by their strong, sometimes off-putting sulfur smelling scent, durian's are a nutritious super fruit variety that provide beneficial nutrients to the skin and are known by aboriginal peoples as an aphrodisiac for increasing sexual libido. Being high in calories, they are especially energizing for intense physical activity and can help to foster weight gain, beneficial for depleted or emaciated individuals. The fruit's high thiamine, tryptophan and potassium content make it a desirable food for relaxing the nervous system, relieving anxiety and improving muscle tone. High in fiber, durian is helpful as a gentle laxative and, containing both carotenoids and vitamin C, additionally supports immune functions. This fruit is sweet and fatty with a custard like texture that to some palates tastes like vanilla pudding. Durians are not for everyone, most people love them or highly dislike them! Whole fresh durian can be purchased frozen at most Asian food markets if you don't happen to live in locations where they grow naturally. One cup serving (243g) of fresh durian fruit contains 357 calories and 13.5g total fat with 50-60% saturated fat content, along with amounts of monounsaturated fat and small concentrations of polyunsaturated fat. Precautions: Fat and oil consumption and nutritional requirements are unique for each individual and one's current state of health. They should be avoided in excessive amounts, but are beneficial when consumed in appropriate ratios within a health promoting diet and lifestyle.
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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.