High Five For Fiber

By: Callie Pillsbury on Jan 21, 2019

The United States population consumes well below the recommended amounts of fiber (1). The 2015-2020 Dietary Guidelines has recognized dietary fiber as a nutrient of public health concern (2).

Fiber Definitions

There are different types of fiber on a food label. The most common seen are total fiber, dietary fiber, and functional fiber. Here's a break down of each term  to fully understand the different types of fiber.

  • Total fiber is the sum of dietary fiber and functional fiber
  • Dietary fiber is the indigestible portion of plant components. There are two different types of dietary fiber: soluble and insoluble. Soluble dietary fibers are found in legumes, apple pomace, and oats. Insoluble sources of fiber include whole grains, vegetables, and potatoes.
  • Functional fiber is an isolated and nondigestible type of carbohydrate that is beneficial to the human body. Examples of functional fibers are soluble corn fiber and polydextrose. These fibers can be found in beverages, frozen foods, salad dressings, and sauces (3).

Fiber is the only nutrient of public health concern that is not “essential.” An essential nutrient is one high_5_for_fiber-supporting_image-400x500.jpgthat is required for growth, maintenance, and reproduction. Fiber is not required for these functions; therefore, fiber is not an essential nutrient. A complete lack of fiber does not cause a state of deficiency, this means that individuals on low or zero fiber diets can still survive. Because fiber is not an essential nutrient, it does not have an EAR or RDA (4). Fiber does have an Adequate intake (AI), which is 14 grams per 1,000 calories. This converts to about 25 grams for women and 38 grams per day for men respectively.

Functions of Fiber

Satiety

Fiber promotes satiety and fullness. The specific type of fiber that contributes to fullness is soluble, or gel forming fibers. Soluble fibers absorb water. This uptake of water causes a sudden fullness sensation. Fiber also increase peptide YY, a hormone in the body that promotes the feeling of fullness. This helps with appetite control and limit daily food intake.

Cholesterol reducing

High cholesterol in the blood causes an increase in the “bad”, or LDL, type of cholesterol. An abundance of LDL cholesterol in the plasma causes plaque development and increases the risk for cardiovascular disease. Fiber has the potential to decrease cholesterol levels in the blood. Fiber binds to bile, which is then excreted  from the body. Because less bile is available to properly digest fat, more bile must be created. Cholesterol is then used to make more bile in the body. Cholesterol is converted to bile which means that less cholesterol is available in the blood.

Fermentation

The fermentation of fiber in the large intestine produces the short chain fatty acids acetate, propionate, and butyrate. This fermentation of short chain fatty acids promotes the healthy gut microbiota. Oat bran, inulin, and fructooligosaccharides are fibers that are highly fermentable. Specifically, fructooligosaccarides act as prebiotics and is a common functional food ingredient in many food products. Inulin is a fermentable fiber that promotes the formation of short chain fatty acids. This production of short chain fatty acids slightly decreases the pH of the large intestine. The lowering of the pH increases the absorption of the minerals calcium and magnesium (3).

Fiber Foods

The Dietary Guidelines encourages Americans to consume more high fiber foods (2). Examples high fiber foods are vegetables, fruits, legumes, and whole grains. In addition to fiber, these nutrient dense foods are high in many other vitamins and minerals. When fruits, vegetables, legumes, or whole grains are lacking in the diet, there are typically low fiber intakes. 

Food

Quantity

Fiber (grams)

Pinto Beans

½ cup

7.7 g

Oatmeal

1 cup

4 g

Raspberries

½ cup

4 g

Apple

1 medium

3.3 g

Whole Wheat Bread

1 slice

1.9 g

Cauliflower

½ cup

1.2 g 


References

1. King DE, Mainous AG, Lambourne CA. Trends in Dietary Fiber Intake in the United States, 1999-2008. Journal of the Academy of Nutrition and Dietetics. 2012;112(5):642-648. doi:10.1016/j.jand.2012.01.019

2. U.S. Department of Health and Human Services and U.S. Department of Agriculture. 2015 – 2020 Dietary Guidelines for Americans. 8th Edition. December 2015. Available at https://health.gov/dietaryguidelines/2015/guidelines/.

3. Stipanuk , M. H., & Caudill, M. A. (Eds.). (2013). Biochemical, Physiological and Molecular Aspects of Human Nutrition. St. Louis , MO : Elseiver Saunders Co.

4. Kohn, J. (2016, March 14). Is Dietary Fiber Considered an Essential Nutrient? Retrieved December 19, 2017, from https://www.eatrightpro.org/resource/news-center/nutrition-trends/foods-and-supplements/dietary-fiber