Monday June 16 6:14 PM EDT

-- The American Heart Association (AHA) says Americans need to double their average fiber intake if they hope to reap the heart-healthy benefits the nutrient can bring.

"By concentrating on... inexpensive foods a lot of us usually ignore or avoid -- like the lowly bean -- we could vastly improve our nutritional health and save money," says Dr. Linda Van Horn, a registered dietitian and member of the AHA's volunteer Nutrition Committee.

Van Horn published her "Statement for Healthcare Professionals" regarding the benefits of a high-fiber diet in the current issue of the journal Circulation.

The average American simply isn't consuming enough naturally-found fiber, Van Horn explains. "Current dietary fiber intakes among adults in the United States average about 15 grams (g), or half the recommended amount," she says. The AHA urge the consumption of between 25g to 30g of fiber per day, to help reduce the unhealthy amounts of dietary fat and cholesterol.

Studies suggest a real link between high-fiber diets and lowered cholesterol, which in turn helps reduce one's risk for heart disease. Van Horn points to one 1982 study, reported in the journal The Lancet, which found that study participants consuming the lowest amounts of dietary fiber "exhibited a four times higher rate of coronary heart disease" compared with those on high-fiber diets. Another study, this time a 12-year follow-up study of nearly 900 older men and women (published in 1987 in the American Journal of Epidemiology), revealed that just an extra 6 grams of fiber per day yielded a 25% reduction in risk of death from ischemic heart disease.

There are many theories as to just how fiber -- those parts of plants resistant to breakdown by digestive enzymes -- protects against heart disease. Van Horn says some types of fiber may work by "decreasing absorption of cholesterol or fatty acids" in the gastrointestinal tract. Or fiber may alter hormone levels in the blood which, in turn, affect the metabolism of fats.

However it works to protect health, Van Horn believes Americans need more fiber. Availability shouldn't be a problem -- oats, beans, barley, fruits, vegetables, and whole-wheat breads are all great sources of fiber. Of course, some foods (grains and beans) are richer in the nutrient than others (fruits and vegetables). And some sources contain more 'soluble' (water-retaining) fiber than 'insoluble' fiber. Van Horn points out that "both soluble and insoluble forms of fiber are important and appear to have different health properties."

Thinking about upping your fiber intake? Here's a sample of typical fiber sources, courtesy of the AHA:

• 1/2 cup cooked kidney or pinto beans contains 2 g soluble, 6.7 g insoluble fiber.

• 1/3 cup uncooked oatmeal - 1.3 g soluble, 2.8 g insoluble fiber.

• 1 ounce corn flakes - 0.1 g soluble, 0.3 g insoluble fiber.

• 1 slice whole-wheat bread - 0.4 g soluble, 2.1 g insoluble fiber.

• 1/2 cup cooked spinach - 0.5g soluble, 2.1 g insoluble fiber.

• 1 medium-sized apple - 1.2 g soluble, 3.6 g insoluble fiber.

• 1/2 medium grapefruit - 1.1 g soluble, 1.8 g insoluble fiber.

Van Horn says increasing fiber consumption is just part of a heart-healthy diet. "Fiber is not a substitute for a low-saturated fat, low-cholesterol diet, it's a complement to it." But she says upping fiber intake from natural sources (not supplements) can go a long way to healthier living.

SOURCE: Circulation (1997;95(12):2701-2704)