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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 a type of carbohydrate found in plant foods. It is not digested or absorbed by the body. 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.

    Soluble fiber can interfere with the absorption of dietary fat and cholesterol. This can help lower low-density lipoprotein (LDL or “bad”) cholesterol levels in the blood. It can also help control blood sugar after a meal. Insoluble fiber can speed up the movement of food through the large intestine and relieve constipation.

    Studies suggest that fiber may help prevent colon cancer.

    Medically valid uses

    Some large studies have suggested that fiber in the diet, especially from whole grains, may lower colorectal cancer risk. Research in this area is still ongoing. 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:

    • Improve the taste and texture of food

    • Improve retention of water in foods

    • Prevent constipation

    • Bulk up some 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

    There may be benefits that have not yet been proven through research.

    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 people in the U.S. 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.

    Online Medical Reviewer: Cynthia Godsey
    Online Medical Reviewer: Diane Horowitz MD
    Online Medical Reviewer: Rita Sather RN
    Date Last Reviewed: 3/1/2019
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