Diet & Disease: The Role of Fiber

Erin Simms, RD, CD, CNSD, Nutrition Services

Fiber has been known for many years as the "scrub brush" of the colon. Its effectiveness in the fight to prevent colon cancer, however, has recently come under critical review. Both the New England Journal of Medicine and The Lancet have published studies this year that refute earlier contentions that a diet high in fiber reduces colon cancer risk. So, in light of this new evidence, should you abandon fiber altogether? Certainly not. Despite this seemingly conflicting and confusing information, it is still the position of the American Cancer Society to encourage the consumption of fruits, vegetables, and whole grains in combination with a low fat diet to help decrease the overall incidence of cancers, diabetes, and heart disease.

How Does Fiber Help Reduce Risk of Disease?
Plant-based diets are high in fiber and are rich in vitamins, antioxidants, and phytochemicals that may inhibit free radicals (environmental and body toxins) from damaging tissues and leading to disease. High fiber foods containing insoluble fiber, a fiber not dissolved in water, can help maintain regular bowel movements that may reduce the risk of cancers by limiting the time potential carcinogens stay in the colon. These foods can also decrease the risk of diverticulosis, constipation, and hemorrhoids. Soluble fiber, the other form of fiber, can form a gel in the digestive system because it dissolves in water. Soluble fiber can help take cholesterol from the body, decreasing cholesterol levels and thus helping in the fight against heart disease. Including fiber in your diet has many health benefits.

What Types of Foods Contain Fiber, and How Much Do You Need to Eat Each Day?
Fiber is found in whole grains, nuts, seeds, fruits, and vegetables and contains a combination of soluble and insoluble forms. Insoluble fiber is found mostly in wheat and rye brans and in vegetables. Soluble fiber is found in higher amounts in oats, apples, beans, strawberries, and barley. The total amount of fiber you should consume is 20-35 grams per day, 5-9 grams of which should be soluble fiber.

If fiber isn’t already a significant part of your diet, remember to introduce these high-fiber foods slowly and drink plenty of fluids to help ease the gastrointestinal transition. To identify sources of fiber and increase your intake of high fiber foods, please refer to the table below.