By Keri Peterson, MD — Dietary fiber is an essential part of our diet and plays an important role fo...
Your Questions Answered
- What is dietary fiber?
Dietary fiber includes polysaccharides, oligosaccharides, lignin, and associated plant substances that are not digested by the body. Importantly, there is also a physiological basis for the definition of fiber where fiber is thought to promote beneficial effects including laxation, blood cholesterol reduction, and/or blood glucose attenuation. All types of fiber are needed every day for the body to function well.
- What is soluble fiber?
Soluble fiber is a type of fiber that readily dissolves in water. Some types of soluble fiber also provide viscosity and attract water to form a gel in the gastrointestinal tract. Other types of soluble fiber are not viscous but are fermented, which contributes different benefits.
- What is insoluble fiber?
Insoluble fiber is a type of fiber that does not readily dissolve in water. Most insoluble fiber provides bulking benefits but is minimally fermented. Other types of insoluble fiber (i.e., resistant starch) does not provide bulking but is fully fermented, contributing entirely different benefits.
- What is added fiber?
Added fiber is fiber that has been added to foods that do not usually contain it or to increase the fiber content in order to confer/increase health benefits.
- What is fermentable fiber?
Fermentable fiber is fiber that is resistant to digestion and absorption in the human small intestine but is broken down partially or completely by bacteria in the large intestine. Fermentable fibers are also call prebiotics.
- Where is fiber found?
Fiber is found naturally in fruit, vegetables, legumes, nuts, and whole grains. Fiber can also be found added to your favorite products.
- What is the recommended daily intake for fiber?
The Dietary Reference Intake (DRI) set by the Food and Nutrition Board of the Institute of Medicine is 21-29 grams/day for women and 30-38 grams/day for men. To find the exact recommended amount for your age group, go to the DRI table.
- What are the health benefits of fiber?
Fibers have numerous health benefits, more and more are being discovered every day. Fibers may reduce constipation and promote colon health; lower cholesterol, blood pressure, and the risk of cardiovascular disease; and improve blood sugar control after a meal and may aid in weight loss. Fibers can also help reduce diarrhea in some instances. Fibers that are fermented (prebiotics) provide energy for colonic cells, promote the growth of good bacteria in the GI tract, and trigger biochemical pathways that help with regularity, satiety, insulin sensitivity, and the immune system. It is important to consume a variety of fibers for their unique effects for maximized health.
- What products can help boost fiber intake?
Fruits, vegetables, legumes, nuts, and whole grains can all provide fiber. Additionally, foods with fiber added to them can help boost fiber intake.
- In what sort of foods and beverages do manufacturers include fiber?
Fiber is added to all kinds of your favorite foods like cereal, granola bars, yogurt, and bakery products.
- What happens to fiber in the body?
Dietary fiber is not digested in the small intestine, but reaches the large intestine. Some fibers provide bulking, which aid in regularity. Other types of fiber thicken the contents of the intestinal tract and help to reduce the absorption of cholesterol, glucose and other nutrients. Some fiber is fermented in the large intestine by the resident bacteria, which help to maintain colon health as well as contributing to health and wellness through the biological benefits of short-chain fatty acids (SCFAs).
- Will eating foods with added fiber provide the same benefits that eating foods with naturally occurring fiber will?
Yes! Many studies have demonstrated the same benefits from supplemental fiber like lower cholesterol and blood pressure, improved blood sugar control after meals, and assistance with weight loss. Because different types of fiber deliver different benefits, look for dietary fibers with evidence of the specific benefits you are looking for and, importantly, consume a variety of fibers.
- Will eating foods with fiber make me gassy?
It depends. Gas is a natural product of fermentation in the large intestine so the amount of gas produced will depend on the fiber’s fermentation characteristics. Most insoluble and viscous fiber won’t produce gas because they are not fermented. However, some people do experience flatulence when they suddenly eat more fermentable fiber than they are used to consuming. Some fibers are fermented more quickly and produce more gas than other types of fermentable fibers. If you are used to a high fiber diet, you likely won’t notice any difference when you eat foods with added fiber.
- What should I do if I experience flatulence after eating fiber?
Hang in there! It is normal to pass gas 20 to 30 times a day. With a diet rich in fermentable fiber, there may temporarily be an increase in gas, but eventually the body adapts. One tip to help reduce flatulence is to increase fiber intake slowly. Since fiber is so good for the body, the benefits definitely outweigh the gassiness!
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