Six (“6”) Crucial Functions of Dietary Fiber

Joseph R. Anticaglia MD
Medical Advisory Board

“Eat the vegetables on your plate, they’re good for you.”

I’ve heard this as a kid and maybe you have as well. Moms may not have known about the different kinds of fibers in vegetables, but they knew vegetables are a healthy part of the family’s diet.

Dietary fiber plays a vital role in digestion and good health. There are two main types of dietary fiber: soluble and insoluble.

Soluble Fiber

Some examples of fiber that dissolve in water (soluble fiber) are blueberries, lentils and oats. This fiber lowers the level of circulating cholesterol in the blood.

As the fiber passes through the intestines, it attracts water and becomes a gel-like substance. The fiber-gel combination attracts bile and interferes with the absorption of it in the intestines. Thereafter, the bile is excreted in the feces.

Cholesterol is an important component of bile – bile acids. Being a result of the combination/action noted, cholesterol is eliminated from the body. However, the liver needs to obtain more cholesterol to form bile acids needed for digestion. The liver grabs cholesterol from the blood and uses it to form more bile acids. Thus, as consequence, there is a lowering of the level of cholesterol in the blood.

Insoluble Fiber

As the name implies, insoluble fiber does not dissolve in water as it moves through the digestive tract. It is commonly called roughage, the fiber that the body cannot digest. It adds bulk to the stool, promotes regularity and works to prevent constipation. A few examples of this fiber are carrots, celery and green beans.

Fiber Choices

According to the Institute of Medicine, an adequate intake for total fiber per day is set at 38 grams for young men and 25 grams for young women. Most Americans need to boost their intake of dietary fiber, which can be found in most plant foods. Below is a variety of plant based dietary fiber food choices.

  • Beans, peas and other legumes
  • Fruits (blueberries, pears)
  • Nuts
  • Oats, Barley
  • Seeds
  • Vegetables (carrots, cauliflower, celery, green beans)
  • Whole wheat product

Benefits of Fiber

Weight Loss

High-fiber foods contribute to weight loss most likely because you need more time chewing food, plus they increase the sensation of fullness and consequently you cut down on overeating. Also, you feel satisfied for longer periods of time in between meals.

Lowers Cholesterol Levels (see above)

Soluble fiber lowers blood cholesterol and the risk of stroke and heart disease.

Blood Sugar

Studies report that high fiber intake, especially of soluble fiber, may lower the risk of type 2 diabetes and decreases the risk of developing insulin resistance. While eating a high carbohydrate meal, dietary fiber may slow the absorption of sugar, lessening the likelihood of spikes in your blood glucose level.

Normalizes Bowel Function

Many are familiar with the ability of fiber to normalize bowel movements. In addition, studies suggest that dietary insoluble fiber may lower your risk of diverticulitis, an inflammation of the intestine and reduce your risk of developing hemorrhoids.


Roughage (or insoluble dietary fiber) decreases the risk of colorectal cancer. Waste often contains carcinogens and the quicker it exits the digestive system the better you are. Roughage adds bulk to the GI system, shortening the time the waste remains in the colon.


Studies suggest that a healthy intake of dietary fiber makes you live longer.

Most Americans need to eat more fiber. When you have decided to introduce more fiber into your diet, it’s best to do so gradually and drink plenty of water. The literature may be confusing about fiber, but Moms had it right when they simply said: “Eat the vegetables on your plate. They’re good for you!”


U.S. Department of Agriculture, Nutrition Insight 36; The Food Supply and Dietary Fiber; Nov.2007

Klosterbuer, A et al; Benefits of Dietary Fiber in Clinical Nutrition; Nutr Clin Pract; Oct 26, 2011

Breneman CB, Tucker L; Dietary Fibre Consumption and Insulin Resistance; Br J Nutr; July 28, 2013 Anneleen Kuijsten, Dagfinn Aune et al; Dietary Fibre and Incidence of type 2 Diabetes; Diabetologia; July, 2015

Fuchs CS, Giovannucci EL, Colditz GA, et al. Dietary fiber and the risk of colorectal cancer and adenoma in women. N Engl J Med. 1999;

Shanshan Li et al; Dietary fiber intake and mortality among survivors of myocardial infarction. BMJ; April 29, 2014

This article is intended solely as a learning experience. Please consult your physician for diagnostic and treatment options.