Dietary fiber: Essential for a healthy dietBy Mayo Clinic Staff
Eat more fiber. You've probably heard it before. But do you know why fiber is so good for your health?
Dietary fiber — found mainly in fruits, vegetables, whole grains and legumes — is probably best known for its ability to prevent or relieve constipation. But foods containing fiber can provide other health benefits as well, such as helping to maintain a healthy weight and lowering your risk of diabetes and heart disease.
Selecting tasty foods that provide fiber isn't difficult. Find out how much dietary fiber you need, the foods that contain it, and how to add them to meals and snacks.
What is dietary fiber?
Dietary fiber, also known as roughage or bulk, includes the parts of plant foods your body can't digest or absorb. Unlike other food components, such as fats, proteins or carbohydrates — which your body breaks down and absorbs — fiber isn't digested by your body. Instead, it passes relatively intact through your stomach, small intestine and colon and out of your body.
Fiber is commonly classified as soluble, which dissolves in water, or insoluble, which doesn't dissolve.
- Soluble fiber. This type of fiber dissolves in water to form a gel-like material. It can help lower blood cholesterol and glucose levels. Soluble fiber is found in oats, peas, beans, apples, citrus fruits, carrots, barley and psyllium.
- Insoluble fiber. This type of fiber promotes the movement of material through your digestive system and increases stool bulk, so it can be of benefit to those who struggle with constipation or irregular stools. Whole-wheat flour, wheat bran, nuts, beans and vegetables, such as cauliflower, green beans and potatoes, are good sources of insoluble fiber.
Most plant-based foods, such as oatmeal and beans, contain both soluble and insoluble fiber. However, the amount of each type varies in different plant foods. To receive the greatest health benefit, eat a wide variety of high-fiber foods.
Benefits of a high-fiber diet
A high-fiber diet has many benefits, which include:
- Normalizes bowel movements. Dietary fiber increases the weight and size of your stool and softens it. A bulky stool is easier to pass, decreasing your chance of constipation. If you have loose, watery stools, fiber may help to solidify the stool because it absorbs water and adds bulk to stool.
- Helps maintain bowel health. A high-fiber diet may lower your risk of developing hemorrhoids and small pouches in your colon (diverticular disease). Some fiber is fermented in the colon. Researchers are looking at how this may play a role in preventing diseases of the colon.
- Lowers cholesterol levels. Soluble fiber found in beans, oats, flaxseed and oat bran may help lower total blood cholesterol levels by lowering low-density lipoprotein, or "bad," cholesterol levels. Studies also have shown that high-fiber foods may have other heart-health benefits, such as reducing blood pressure and inflammation.
- Helps control blood sugar levels. In people with diabetes, fiber — particularly soluble fiber — can slow the absorption of sugar and help improve blood sugar levels. A healthy diet that includes insoluble fiber may also reduce the risk of developing type 2 diabetes.
- Aids in achieving healthy weight. High-fiber foods tend to be more filling than low-fiber foods, so you're likely to eat less and stay satisfied longer. And high-fiber foods tend to take longer to eat and to be less "energy dense," which means they have fewer calories for the same volume of food.
Another benefit attributed to dietary fiber is prevention of colorectal cancer. However, the evidence that fiber reduces colorectal cancer is mixed.
How much fiber do you need?
The Institute of Medicine, which provides science-based advice on matters of medicine and health, gives the following daily fiber recommendations for adults:
Sept. 22, 2015
See more In-depth
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- Dietary, functional and total fiber. Institute of Medicine. http://www.nap.edu/openbook.php?record_id=10490&page=339. Accessed Aug. 30, 2015.
- Colditz GA. Healthy diet in adults. http://www.uptodate.com/home. Accessed Aug. 30, 2015.
- Position of the American Dietetic Association: Health implications of dietary fiber. Journal of the American Dietetic Association. 2008;108:1716.
- Whole grains and fiber. American Heart Association. http://www.heart.org/HEARTORG/GettingHealthy/NutritionCenter/HealthyDietGoals/Whole-Grains-and-Fiber_UCM_303249_Article.jsp. Accessed Aug. 30. 2015.
- Duyff RL. Carbs: Sugar, starches, fiber. In: American Dietetic Association Complete Food and Nutrition Guide. 4th ed. Hoboken, N.J.: John Wiley & Sons; 2012.
- Zeratsky KA (expert opinion). Mayo Clinic, Rochester, Minn. Sept. 10, 2015.