• By Cynthia Weiss

Mayo Clinic Q and A: Increasing fiber intake for constipation relief

August 10, 2021
a close-up overhead view of a bowl of oatmeal with almonds, blueberries and cranberries sprinkled on top

DEAR MAYO CLINIC: I experience constipation almost weekly, and eating bran flakes every day isn’t helping. Are fiber supplements safe to use regularly and long term? Is there anything else I can do? I’m a 53-year-old woman and otherwise in excellent health.

ANSWER: When consumed at recommended levels, dietary fiber is widely recognized to have health benefits, including relief of constipation. Adult women 50 and younger should consume at least 25 grams of fiber a day. Women 51 and older should have at least 21 grams a day. Adult men need at least 38 grams of fiber a day if they are younger than 50 and at least 30 grams of fiber a day if they are 51 and older. Ninety percent of the U.S. population consumes far below those recommendations, averaging only 15 grams of daily fiber.

Fiber-rich foods include fruits, vegetables, whole grains and legumes. Many cereals, such as bran flakes, are good sources of fiber. Although fiber supplements can fill the daily fiber gap, they usually have only one type of fiber, rather than a variety of fibers and micronutrients, and they may not provide all the health benefits associated with fiber in food. Therefore, boost your fiber intake in your diet first by eating a wide variety of high-fiber foods.

If you still can’t get enough fiber to meet the daily recommendation, consider using a supplement. But keep in mind, not all fibers provide laxative effects. Some, unfortunately, can even cause constipation.

Fibers can be classified as soluble versus insoluble, fermentable versus unfermentable and coarse versus fine. In general, fermentable fibers may increase flatulence, with no effect in providing relief of constipation. Finely ground wheat bran and solid/fermented wheat dextran have been shown to worsen constipation. Coarse wheat and psylium can increase stool water content and fecal mass, and can be used to alleviate constipation.

Before taking a fiber supplement, ask your health care provider or pharmacist to review your medications. Fiber supplements can decrease the absorption of certain medications, including drugs that treat thyroid disorders, depression, diabetes, high cholesterol, seizures and various heart ailments. Even common medications, such as aspirin, ibuprofen and penicillin, can be affected by an increase in fiber. You may take your medications one hour before or two hours after eating fiber to minimize the interaction.

Some fiber supplements may not be appropriate for people with certain medical conditions. For example, if you have celiac disease, you may need to stay away from fiber products derived from wheat. If you have diabetes, you may need to use a flavorless formula to avoid extra sugar. Consult your health care provider for guidance about the appropriate fiber supplement.

Go slow as you begin fiber therapy. Fiber supplements may cause abdominal bloating, cramping and flatulence, especially if you start at a high dose. Begin with a low dose, gradually increasing the amount of fiber. Don’t add more than 50 grams of fiber in a supplement per day, as that may affect how your body absorbs nutrients. Your health care provider can help you determine what’s right for you.

Drinking plenty of water and exercising regularly can ease constipation, too. You also may want to consider nonfiber products, such as stool softeners, stimulant medications that cause your intestines to contract, enemas or suppositories.

If increasing fiber doesn’t improve your symptoms, see your health care provider. Constipation can be a symptom of various underlying medical disorders, such as pelvic floor muscle dysfunction, slow gastrointestinal motility, anatomical abnormalities or endocrine dysfunction, that may require different treatment. — Dr. Yan Bi, Gastroenterology, Mayo Clinic, Jacksonville, Florida

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