DIETARY FIBER

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 fiber can provide other health benefits as well, such as 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 all parts of plant foods that 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. Therefore, it passes relatively intact through your stomach, small intestine, colon and out of your body. It might seem like fiber doesn't do much, but it has several important roles in maintaining health.

Fiber is commonly classified into two categories: those that don't dissolve in water (insoluble fiber) and those that do (soluble fiber

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 and many vegetables are good sources of insoluble fiber.

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.

The amount of each type of fiber 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:

N 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 also help to solidify the stool because it absorbs water and adds bulk to stool. For some, fiber may provide relief from irritable bowel syndrome.

Helps maintain bowel integrity and 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 blood 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. Epidemiologic studies have shown that increased fiber in the diet can reduce blood pressure and inflammation, which is also protective to heart health.

Helps control blood sugar levels. Fiber, particularly soluble fiber, can slow the absorption of sugar, which for people with diabetes can help improve blood sugar levels. A diet that includes insoluble fiber has been associated with a reduced risk of developing type 2 diabetes.

Aids in weight loss. High-fiber foods generally require more chewing time, which gives your body time to register when you're no longer hungry, so you're less likely to overeat. Also, a high-fiber diet tends to make a meal feel larger and linger longer, so you stay full for a greater amount of time. And high-fiber diets also tend to be less "energy dense," which means they have fewer calories for the same volume of food.

Uncertain effect on colorectal cancer. Evidence that dietary fiber reduces colorectal cancer is mixed — some studies show benefit, some show nothing and some suggest increased risk. If you're concerned about preventing colorectal cancer, adopt or stick with a colon cancer screening regimen. Regular testing for and removal of colon polyps can prevent colon cancer.