How does eating fiber affect my health?

Fiber is a key reason that diets high in fruits, vegetables, and grains are good for you. People who eat a lot of fiber have significantly lower rates of aging. The person who eats at least 25 grams of fiber a day has a RealAge (physiologic age) as much as three years younger than that of the person who eats only 12 grams of fiber a day, the national average.

Fiber is found solely in plant foods and is largely indigestible, passing through the digestive tract intact. Therefore, it contains no calories but makes you feel full sooner and helps control overeating. Insoluble fiber does not readily dissolve in water and is not broken down by intestinal bacteria. This form of fiber can be found in many foods: grapefruit, oranges, grapes, raisins and dried fruit, okra, sweet potatoes, peas, zucchini, whole wheat bread, granola, papaya, and peaches. While this type of fiber is not as effective as soluble fiber at decreasing your Lousy low-density lipoprotein (LDL) cholesterol (bad cholesterol) levels, it still makes your RealAge younger. Soluble fiber does dissolve or swell in water. It helps regulate metabolism and digestion and stabilizes blood glucose levels by moderating the rate of nutrient absorption. Soluble fiber is found in grains such as oats, oatmeal, barley, and rye; legumes such as beans, peas, and lentils; and cereals such as Cheerios. Fiber, whether it's soluble or insoluble, slows the emptying of the stomach and first part of the intestine, making you feel fuller and less hungry four to eight hours later. Fiber in your breakfast will make you less likely to want a large afternoon snack.

In a study of forty-three participants at Northwestern University, a 10-gram increase in the daily intake of cereal fiber decreased the risk of heart attack by 29 percent (making a fifty-five-year-old's RealAge 1.9 years younger). It does not take much cereal to produce a definite effect: In the 2003 evaluation of the National Health and Nutrition Follow-Up Study, a 5-gram increase in cereal fiber-an easy addition to breakfast-reduced all-cause death rates by 12 percent. That alone makes your RealAge about 0.8 years younger. Individuals who eat less fiber also tend to have worse overall diets and to be more sedentary.

A high-fiber diet helps reduce the incidence of hemorrhoids, a condition that can be provoked by excess pressure on the bowel walls caused by the forced bowel movements that often accompany a low-fiber diet.