Why Is Too Much Fiber Bad for You?

A dietitian can help you figure out if you are getting the right amount of fiber.
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Although most people could benefit from adding more fiber to their diets, too much can backfire, causing the types of intestinal disturbances no one likes to talk about. The recommended daily amount of fiber for adults and older children is 20 to 35 grams each day. That includes both insoluble fiber, from whole-grain products such as wheat bran, and soluble fiber from oats, beans and psyllium supplements. Speak with a doctor or dietitian before you add more than the recommended amount of fiber to your diet or if you feel the recommended amount is too much for you.

Nutrient Loss

    A diet that is too high in insoluble fiber can cause food to move through your digestive tract so quickly that there is not enough time for minerals such as iron, zinc and calcium to be properly absorbed through your intestinal walls. Some high-fiber foods, such as whole grains, seeds and dried beans, also contain other substances that interfere with your body’s ability to efficiently absorb minerals. This does not mean you should avoid these foods. Instead, eat a wide variety of high-fiber foods.


    Too much fiber can be downright explosive, especially if you are older, have had gastrointestinal surgery or have a chronic medical condition, such as ulcerative colitis, or diverticulitis that flares up and causes loose stools or intestinal inflammation. If you have one of these conditions, your doctor may prescribe a low-fiber diet until diarrhea improves.

Bloating and Gas

    Eating too much fiber at once, or suddenly increasing the overall amount of fiber in your diet with food or supplements, can wreak havoc in your intestinal tract, causing abdominal bloating, gas and cramps. To prevent these painful side effects, gradually add more fiber to your diet over a period of several weeks to allow your digestive tract to adjust. Eat whole grains, fruits and vegetables and other foods that are rich in fiber throughout the day, at every meal and snack time, rather than concentrating large amounts of fiber in a single meal.


    Normally, a high-fiber diet helps moves things along, so to speak, not slow them down. However, since fiber absorbs a lot of water from your digestive tract in order to move food through your intestines, you must increase your fluids when you increase the amount of fiber in your diet. Otherwise, your stools will be dry and difficult to eliminate. To avoid this, the University of Arizona Cooperative Extension recommends drinking at least eight 8-ounce glasses of fluids a day.

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