Experts agree, dietary fiber is an important tool in fighting and preventing heart disease, colon cancer, diabetes and even obesity. Most experts agree that a key defining characteristic of dietary fiber is that it's derived from the edible parts of plants that are not broken down by human digestive enzymes, but the official definition is still up for debate. One complication in defining fiber is that fibers come in variety of forms, some soluble, some insoluble, some viscous, some fermentable and others not.

Like soluble fibers, viscous fibers lower serum cholesterol by reducing the absorption of dietary cholesterol. Soluble fiber may also reduce the amount of cholesterol manufactured by the liver. Viscous fibers help normalize blood glucose levels and increase insulin sensitivity, making them helpful in preventing and treating type 2 diabetes. Viscous fibers also slow food as it leaves the stomach, providing a full feeling and helping to prevent overeating and weight gain. Animal studies have also suggested some dietary fibers may help lower blood cholesterol levels. In addition, fermentable fibers help maintain healthy populations of friendly bacteria which enhance the immune system by preventing harmful bacteria from growing in the intestinal tract. Insoluble and non-fermentable fibers help maintain bowel regularity, decreasing the risk of colon cancer and hemorrhoids from straining and constipation.

The many forms of dietary fibers can be found among a spectrum of foods, from bran, oatmeal and whole grains, to legumes, root vegetables and cabbage, and even in fruits including apples, strawberries and citrus fruits, among others. Still, some of the best food sources of fiber include turnip greens, mustard greens, collard greens, navy beans, eggplant, raspberries and cinnamon. With the verdict still out on what is definitively a fiber, the simplest way to make sure you're getting all the vital fiber your body craves is to eat a healthy and balanced diet including a variety of these foods.

Resources

Fiber. The World's Healthiest Foods.
http://www.whfoods.com/genpage.php?tname=nutrient&dbid=59.

Marz, R. B. (1999). Medical nutrition from Marz: (a textbook in clinical nutrition). Portland, Or: Omni-Press.

Gaby, A. (2011). Nutritional medicine. Concord, N.H: Fritz Perlberg Publishing.

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