Dietary Fiber and its Health Benefits

Dietary fiber has been shown to lower cholesterol levels and prevent obesity, heart disease, diabetes and certain types of cancer.

dietary fiber

Fiber is found in plant foods, such as grains, vegetables, and fruits. There are two types: insoluble and soluble.

© Robyn Mackenzie |

The importance of fiber in the diet cannot be overemphasized. Dietary fiber—what we used to call “roughage” or “bulk”—can help prevent or alleviate chronic constipation, hemorrhoids, diverticulosis, IBS, and possibly colorectal cancer. There is some early evidence suggesting that a high-fiber diet may lessen or prevent food allergies, and dietary fiber also appears to have health benefits outside of the gastrointestinal tract—for example, it may help lower cholesterol levels, and prevent obesity, heart disease, diabetes, and certain types of cancer.

Fiber is found in plant foods, such as grains, vegetables, and fruits. There are two types: insoluble and soluble.

Insoluble fiber is not digested—instead, it adds bulk to the stool, enabling it to pass more rapidly through the digestive system. Sources of insoluble fiber include wheat bran, whole grains and wholegrain products, and the tough parts of fruits and vegetables that take longer to chew, like the skins of apples, cucumbers, and grapes.

Soluble fiber attracts water as it passes through the digestive system, resulting in soft stool that is easier to pass. Soluble fiber is found in beans, fruit, oats/oat bran, nuts, seeds, and many vegetables, including Brussels sprouts, sweet potatoes, and asparagus, among others. It also can be taken in capsule form as psyllium.

Introduce Dietary Fiber Slowly

If you’re planning to increase the amount of dietary fiber in your diet, it’s best to do so slowly. Soluble fiber has the potential to produce gas, so you may notice more gas or bloating when you suddenly increase your fiber intake. However, if you add fiber slowly over time, your gastrointestinal tract will adjust. In addition, as you increase fiber, it’s important to drink more fluids (water, soup, broth, juices). Try to drink eight glasses of liquid a day.

While the average American takes in only 15 grams (g) of fiber a day, the recommended intake is 25 g per day for women, and 38 g per day for men. If you consume less fiber than recommended, you’ll want to increase your daily fiber intake. You can do this by eating:

  • Two to three cups of vegetables per day
  • Two cups of fruit every day
  • Three servings of beans, lentils or peas every week
  • Whole-grain bread instead of white bread
  • Whole-grain cereals and bran cereal
  • Brown rice instead of white rice.

To learn more about ways to improve your digestion, purchase Digestive Diseases & Disorders from

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Matthew Solan

Matthew Solan has served as executive editor of Harvard Men's Health Watch since 2016. He was previously executive editor for UCLA Health's Healthy Years and was a regular contributor to … Read More

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