What is Dietary Fiber?

What is Dietary Fiber - Banana Walnut Oatmeal

Dietary fiber is part of plant foods your body can not completely digest (Wikipedia). “Most fiber-containing foods contain about one-third soluble and two-thirds insoluble fiber.” (The Journal of Nutrition) What’s the difference between soluble and insoluble fiber? Soluble fiber dissolves in water. However, insoluble fiber does not dissolve in water.

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Examples of foods with dietary fiber include oatmeal, bananas, and nuts.

Soluble Fiber

Soluble fiber is generally viscous (thick like syrup) and slows digestion. Fibrous carbohydrates have soluble fiber, which slows the rate of carbohydrate absorption. As a result, a high fiber diet may promote weight loss.

In 1997, the FDA authorized the health claims between soluble fiber from whole oats and a reduced risk of coronary heart disease. FDA concluded soluble fiber found in whole oats (beta-glucan) is primarily responsible for lowering blood cholesterol levels. (Federal Register) Consequently, the agency authorized the health claim: “Diets high in oat bran and oatmeal and low in saturated fat and cholesterol may reduce the risk of coronary heart disease.”

In 2020, Quaker Oats continues to advertise this FDA authorized health claim on its oatmeal packages: “As part of a heart-healthy diet, the soluble fiber in Oatmeal can help reduce cholesterol.”

Quaker Oats Oatmeal package

Resistant Starches

Resistant starch is a nonviscous soluble fiber. As a result of higher fluidity, resistant starch (bananas and beans) does not provide glycemic control nor lower blood cholesterol. Like the beta-glucans in whole oats, bananas ferment in the colon. Thus, bananas exert a “prebiotic effect” (OregonState.edu).

Dietary Fiber in Apples

Like most fibrous carbohydrates, apples contain soluble and insoluble fiber. Apples have soluble fiber called pectin in the fruit’s skin. Pectin is fermented in the colon and digested by bacteria. Furthermore, apples have insoluble fiber called cellulose found in the fruit’s cell walls. Cellulose is not digestible in humans.

How much Dietary Fiber per day?

Your recommended amount of dietary fiber depends on your gender and age. First, you need to look up in Appendix 2 your estimated calorie needs in the 2015 Dietary Guidelines. For example, a 50 year-old moderately active man needs about 2,400 calories per day. Then you can calculate your recommended dietary fiber using the adequate intake of fiber formula.

Dietary Fiber and Weight Loss

Forty-four randomized controlled trials have found the dietary fiber found in certain high-fiber foods improves satiety. Discover the fibrous carbohydrates that give you a feeling of fullness, and help you avoid overconsumption. Learn the fibrous foods that will satisfy your hunger and help you lose weight.


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