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Other name(s):

b-glucan, cellulose, chitosan, gellan, guar gum, gum, hemicellulose, konjac mannan, lignin, mucilage pectin

General description

Fiber is present to some degree in almost all plant species. It’s also made by marine life, insects, yeasts, fungi, bacteria, and a host of other organisms. Fiber is often referred to as soluble or insoluble. This depends on whether it dissolves in water. Food sources include bran, whole grains, vegetables, fruits, and seaweed.

Studies suggest that fiber may help prevent colon cancer. It may also help treat diabetes and control high blood pressure.

Medically valid uses

Fiber has been shown in many studies to help prevent colon cancer. Many studies have shown that people and cultures whose diet is made up largely of fruits and vegetables have a lower rate of colon cancer. This is compared to those whose diet contains large amounts of meat and animal fats.

Fiber is also used to do the following:

  • Improve the taste and texture of food

  • Improve retention of water in foods

  • Prevent constipation

  • Provide body in liquid medicines

Fiber is also used as a no calorie or low-calorie meat expander in foods, such as hamburger. It’s also used as a low-calorie fat substitute. Fiber can also be used as a surgical dressing for wounds.

Unsubstantiated claims

Please note that this section reports on claims that have not yet been substantiated through scientific studies.

Fiber may help treat diverticulosis and diabetes. It may also help treat high cholesterol and high blood pressure.

Dosing format

The Adequate Intake (AI) for total fiber in foods is shown below:


Grams (g) of fiber per day

Children ages 1–3 years

19 g

Children ages 4–8 years

25 g

Males 9–13 years

31 g

Females 9–13 years

26 g

Males 14–18 years

38 g

Females 14–18 years

26 g

Males 19–50 years

38 g

Females 19–50 years

25 g

Males 50 years and older

30 g

Females 50 years and older

21 g

Pregnant women

28 g

Lactating women

29 g

Many Americans don’t get enough fiber in their diet. When adding more fiber to your diet, increase it slowly over time. Make sure to drink plenty of water. This can reduce the risk of gastrointestinal issues.

Side effects, toxicity, and interactions

Some fibers can cause diarrhea. Others can cause constipation.

There are no known food or medicine interactions linked with fiber.