High Fiber Diet & Fat Absorption

Most Americans eat far less dietary fiber than the minimum amounts called for in government nutritional recommendations. Also known as roughage or bulk, fiber includes those portions of plant-based foods that are indigestible. Dietary fiber offers a host of health benefits, not the least of which is its effect on the amount of fat and cholesterol the body absorbs during the digestive process.

Significance

Since the body can neither digest nor absorb fiber, it's not unusual that people question its role in human nutrition. Its primary benefit, according to MayoClinic.com, is the normalization of bowel function. This helps to prevent constipation, but also keeps this important section of the digestive tract in good working order and helps to prevent irritable bowel syndrome, a collection of digestive ills that afflicts large numbers of Americans, and colon cancer.

Soluble or Insoluble

Dietary fiber falls into two categories: soluble and insoluble. The former, found in apples, barley, beans, carrots, citrus fruits, oats and peas, dissolves in water, forming a gel-like substance. This substance slows the rate at which the body digests and absorbs glucose, according to AskDrSears.com. Insoluble fiber, that which comes from the outer coverings of whole grains, plant leaves, skins and peels, absorbs water, adding to its bulk and keeping the intestinal tract clear as it passes through.

Fiber and Fat

Dietary fiber appears to slow and, in some cases, inhibit, the absorption of fat, according to "Fight Back With Food," published by Reader's Digest. This phenomenon allows dieters to feel full more quickly and thus curtail their overall fat intake. Fiber also works in other ways to reduce the intake of fats and other calorie-laden macronutrients. It slows the rate of digestion of carbohydrates, avoiding the spike in blood sugar levels that is almost always followed by cravings for foods that will replicate that sugar rush. "Fight Back With Food" cites a study in which volunteers eating high-fiber diets consumed an average of 130 fewer calories daily.

Fiber Needs and Sources

According to MayoClinic.com, the Institute of Medicine, part of the National Academies of Science, recommends a daily intake of 38 g and 25 g, respectively, for men and women who are 50 or younger. Daily fiber needs drop to 30 g and 21 g, respectively, for men and women who are 51 or older. Good sources of dietary fiber include whole grains and whole-grain products; fruits and vegetables; nuts and seeds; and beans, peas and other legumes.

Effect on Fat-Soluble Vitamins

Gene A. Spiller, author of the "CRC Handbook of Dietary Fiber in Human Nutrition," warns that fiber's tendency to increase fecal fat excretion suggests that a diet high in fiber could interfere with the absorption of fat-soluble vitamins, such as vitamin E. People supplementing with fat-soluble vitamins should probably take such supplements well before or after consuming high-fiber meals.