Fiber: All You Need To Know
What is a balanced diet?
A balanced diet contains all the essential nutrients with a reasonable ratio of all the major food groups. The quantity of foods required to achieve a balanced diet may vary with age, gender, physiological status and physical activity. Our human system essentially requires macronutrients like carbohydrates, proteins and fats to avail and support the balanced diet. These macronutrients primarily support, promote and maintain overall well-being and good health. However, in addition to the macronutrients, a balanced diet may also include dietary fiber, antioxidants and phytochemicals.
What is dietary fiber? What does it do?
Fiber is classified under the category of carbohydrate which is considered to be an essential nutrient. Fiber is naturally present in plants and its functional derivatives are Cellulose, Resistant Dextrins, Hemicellulose, Oligosaccharides, Resistant Starch, Chitins, Pectins, Beta-Glucans and Lignin.
Generally, most of the carbohydrates are broken down into sugar molecules by various enzymatic hydrolysis in human system. However, dietary fibers are not completely broken down into sugar molecules in the small intestine as humans lack the necessary enzymes to break down the chemical bonds present in these fiber molecules. Undigested dietary fiber then passes through to the large intestine, where some of them are fermented by bacteria present in the gut. The by-products of this fermentation process are carbon dioxide, methane, hydrogen and short-chain fatty acids (SCFAs). Certain types of fiber may cause an increase in gas production which leads to bloating.
What are the types of fiber?
Fiber is classified as soluble fiber and insoluble fiber.
• Soluble fiber:
It is fiber which readily dissolves in liquids. Some types of soluble fiber are viscous and hydrophilic, and will form a gel-like substance in the gastrointestinal tract during the digestion process. The other non-viscous type of soluble fibers are fermented in the large intestine to provide several physiological benefits. Soluble fiber may increase the fecal stool bulk as well as soften it so that it slides easily through the large intestine, helping with constipation. Soluble fiber is present in apples, oranges, grapes, dry beans, lentils, peas, barley, oats and the likes thereof.
• Insoluble fiber:
It is the type of fiber which does not readily dissolve in liquids and remains relatively unchanged in the gastrointestinal tract during the digestion process. Insoluble fiber prevents constipation by adding bulk to fecal content in the large intestine. Generally, insoluble fiber is minimally fermented. Insoluble fiber is present in vegetables, whole grain products, whole wheat bread, bran, pasta, crackers, edible seeds, brown rice and the likes thereof.
How much fiber do I need each day?
The US Dietary Guidelines recommends a daily requirement of dietary fiber of 21g to 38g, depending on calorie requirements. Currently, dietary fiber intake among adults in the United States averages about 15g a day, which is only about half the recommended amount.
Where and how do we get fiber?
The dietary fibers of selected foods are provided below. The portion, intake, size of the food to be consumed is based on the individual characteristics and based on country-specific guidelines.
- Grains, Cereals & Millets:Maize or corn, Barley, Oats, Rice, Wholegrain Wheat and Ragi
- Legumes & pulses:Soy, Peas, kidney beans, Lentils, Green beans, Whole Greengram, Blackgram dhal and Bengal gram dhal.
- Nuts & Seeds:Almonds, Peanut, Cashew nut, Groundnut, Dates, Dry Coconut, Flaxseed & Sesame seed
- Vegetables:Green leaves, Spinach, Beetroot, Potato, Sweet Potato, Turnips, Bitter gourd, Fenugreek leaves, Broccoli, Ridge gourd, Snake gourd, Bottle gourd, Pumpkin yellow, Brinjal, Carrot, Onion
- Fruits:Pear, Kiwi, Banana, Strawberry, Mango, Orange, Apple, Guava
How fiber helps bowel regularity?
Fiber is complex carbohydrate which is not digested in the small intestine and generally comes from plant sources. It is found in a wide variety of foods. Based on the mechanisms, the three predominant forms of fiber includes bulking, viscosity, and fermentation.
1. Bulking
Fibers decrease the risk of constipation and gastrointestinal tract infection, specifically the disease or disorder associated with the colon. In the intestines or colon, fibers absorb water, which leads to the formation of bulk and promotes the regularity of normal intestinal functions. There is a wide variety of plant sources, cereals and legumes available to act as bulking agents. Specifically, wheat bran, cellulose and psyllium act as bulking fiber.
2. Viscosity
Viscous fibers decrease the absorption of lipoproteins, other forms of cholesterol and nutrients by thickening the contents of gastrointestinal tract. These actions may slow down the movement of essential and non-essential nutrients into the gastrointestinal tract walls. Other advantages also include: reducing or lowering the cholesterol levels in the blood and decreasing the glycemic response or blood sugar levels. The viscosity of the fiber is directly proportional to the effectiveness in reducing absorption. There is also a wide variety of plant sources available which act as bulking agents. Specifically, beta-glucan, guar gum and psyllium acts as viscous fiber.
3. Fermentation
It is reported that trillions of bacteria live in the healthy human gastrointestinal tract, which in turn play a vital role in human health and well-being. Dietary fibers play a vital role in feeding the gut microbiota and microflora, which is crucial for the health of the gut. The bacteria present in the colon interact with fibers through a process of fermentation and produce the short chain fatty acids (SCFAs). These SCFAs have multiple beneficial effects in maintaining the health and integrity of the colon and the gut system. It increases the bowel regularity by peristalsis movement. The SCFAs also trigger various biochemical pathways which are assumed to provide a wide range of health benefits. They also play a vital role in the absorption of essential minerals such as calcium and magnesium.
Benefits of consuming fiber
Nature provides the support for humans to obtain dietary fibers in the form of fruits, vegetables, whole grains, and legumes which supports for normal well-being. Dietary fibers are indicated for supporting the gut/digestive system. Consuming fibers also have enormous benefits for other body systems. For one, consumption of fibers also help develop the immunity in the gut, produces beneficial probiotics and aids in reducing excess amount of cholesterol and other toxins from the human system. Evidence also points to increasing fiber intake being associated with decreasing risks of common disorders such as cardiovascular disease, cancer, diabetes / control of blood sugar, skin health and weight management/obesity.
Below are few reported and emerging evidence which supports potential benefits of dietary fibers in humans:
Reduced Constipation/ Improved Regularity:
Fibers help to reduce constipation by adding bulk to the stool. It is proven that, feces bulkiness allows faster elimination, which aids in improving bowel regularity and easy-to-pass stools.
Improved Digestive Health:
Fibers enhances and promotes the healthy gastrointestinal and digestive system. The short-chain fatty acids (SCFAs) produced in the gut by the fermentation of fibers by the gut microbiota also promotes colonic health which in turn facilitates the digestive health.
Reduced Cholesterol Levels:
Intake of fibers also showed improvements in cholesterol and lipids levels in the body. It is reported that viscous fibers may reduce the absorption of cholesterol. Various studies have also reported lowered risk of developing heart diseases by consuming high amounts of dietary fibers.
Blood sugar control / Reduced Blood Glucose Levels:
Viscous fibers may help to slow the breakdown of carbohydrates and limit the absorption of sugar, helping with blood sugar control. It is reported that viscosity of a fiber is related to the reduction in postprandial blood glucose.
Increased Insulin Sensitivity:
The short-chain fatty acids (SCFAs) produced by the fermentation of fibers alters the production of hormones related to insulin sensitivity.
Increased Mineral Absorption:
It is reported that fibers may improve absorption of minerals such as calcium, which in turn is able to lead to improvements in bone mineral density in adults.
Increased Immune Support:
The short-chain fatty acids (SCFAs) produced by the fermentation of fibers have also been shown to influence immune functions, together with the diversity of the gut microbiota.
Obesity/Weight Management:
Fibers may contribute to weight management and to maintaining a healthy weight. The short-chain fatty acids (SCFAs) produced by the fermentation of fibers alters lipid and carbohydrate metabolism, which in turn affects weight loss.
Skin health:
Fibers may clean yeast and/or fungus out of the human system which prevents acne or rashes.
Diverticulitis:
Fibers may reduce the risk of inflammation of polyps in the gastrointestinal intestine.
Hemorrhoids / Irritable bowel syndrome:
Increased consumption of fibers may lower the risk of hemorrhoids. Fibers may also provide relief from the several symptoms of irritable bowel syndrome (IBS), including abdominal pain, constipation and diarrhea.
FiberFacts. Mechanisms of Dietary Fiber. Available on: https://www.fiberfacts.org/mechanisms-of-dietary-fiber/
Dhingra D, Michael M, Rajput H, Patil RT. Dietary fibre in foods: a review. J Food Sci Technol. 2012;49(3):255-266. Available on: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3614039/