In the world of nutrition there seems to be no shortage of complexity and confusion. But I've found that simple and straightforward solutions are often strikingly successful. In no area is this more true than the remarkable power of whole grains.

Over the years, countless clients of mine have struggled with various gastrointestinal complaints such as constipation or irritable bowel syndrome. Many have come to me after trying costly medications, usually with little relief.

In most cases, symptoms disappeared once they began increasing their fiber intake by eating adequate amounts of whole-grain foods. Some of my clients even teasingly call these foods their wonder drug.

But while it's true that whole grains are valuable for their fiber content, their benefits are much more vast. Whole grains play a profound role in health. A growing body of research shows whole grains -- wheat, oats, rice, rye and corn, for example, may help keep body weight down and prevent diabetes, heart disease and some cancers.

The importance of whole grains in health came to light in the 19th century, when refining grains became popular -- and its negative consequences were learned. In Asia, chickens were cured of symptoms of a human illness called beriberi, characterized by muscle wasting and nerve degeneration, when they were fed the discarded part of polished white rice. It was later found that the parts discarded during the refining process contain the essential nutrient, thiamin (a B vitamin) necessary to prevent beriberi.

In 1975, researchers Dennis Burkitt and Hugh Trowell published a book of scientific observations comparing the diet of Africans eating their native whole grains versus North Americans and British eating their diet of highly refined carbohydrates. The researchers described for the first time the role that whole, unrefined foods play in reducing coronary heart disease, diabetes and cancer. Since then, numerous other research studies have chronicled the effects of whole grains on human health.

A whole grain has three parts: bran, germ and endosperm. The bran and germ contain fiber, Vitamin E, B vitamins (thiamin, niacin, riboflavin and pantothenic acid) minerals (calcium, magnesium, potassium, phosphorous, sodium, selenium and iron), protein, essential oils, antioxidants and phytochemicals (plant substances that may protect health). The endosperm contains mostly starch with a little protein and very few nutrients. When a grain is refined, turning whole wheat flour into white flour or brown rice into white rice, only the nutrient-poor endosperm is left. The riches found in the bran and germ are lost.

Food manufacturers attempt to make up for the loss in nutrients by enriching refined grains (those found in breads, pasta, rice and cereals, for instance) with some essential nutrients, such as B vitamins and iron.

But overwhelming scientific evidence has found major health differences in people who eat more whole grains compared with people who eat refined grains, proving enrichment doesn't make up for the difference:

* Whole grains are our major source of fiber. The grain's outer layer (the bran) keeps us regular and helps prevent hemorrhoids, diverticulitis, and reduces risk for ulcerative colitis (Crohn's disease).

* Whole-grain intake is strongly correlated with reduced cardiovascular disease. This is partly explained by the soluble fiber in grains (oats, rye and barley have the highest levels), which is associated with cholesterol lowering. But other substances in grains, such as antioxidants like Vitamin E, also play a role.

* People who eat more whole grains also have lower body weights, according to epidemiological research. This is attributed to the fiber, which promotes feelings of fullness in foods that are generally low in calories.

* Many studies have shown a strong link between whole-grain intake and reduced incidence of type II diabetes. This may be partly because the fiber in whole grains slows down stomach emptying, causing a lower rise in blood glucose and insulin. Also, whole grains contain nutrients such as Vitamin E and magnesium, which may help improve insulin sensitivity.

* This research is less consistent, but whole grains may also help prevent cancers, especially of the intestinal tract and maybe even breast cancer. Several theories have been put forth explaining the mechanisms. For one, the fiber speeds intestinal transit, which reduces exposure to potential carcinogens. Also, antioxidants enter the circulation through colon cells, providing long-term antioxidant protection through the entire digestive tract, according to Joanne Slavin, a professor in the department of food science and nutrition at the University of Minnesota in St. Paul. Ninety percent of a grain's antioxidants aren't released until they get to the colon, the last stage of digestion, where they may provide maximum protection against cancer.

Interestingly, grains are still a mystery to researchers. They are so complex and full of a multitude of different compounds, scientists are largely unsure of what components of the grain are responsible for the benefits.

"We're not sure if the benefits are from the fiber or the phytochemicals," says Simin Liu, assistant professor of medicine and epidemiology at Harvard. "In my opinion, it's the thousands of phytochemicals in whole grains which produce most of the benefits."

To prove his point, Liu points to a four-year National Cancer Institute-funded study of high-fiber cereals in which wheat bran was added in the processing as opposed to naturally occurring in a whole grain. Researchers were surprised to find the high-bran diet did not prevent colon polyps, often a precursor to cancer.

"The data doesn't support the claim that added bran fiber or fiber supplements make a positive difference in colon cancer, which is why I like to use the term 'whole grain foods' instead of fiber. The data only point to whole foods," says Liu.

But while whole grains provide this wide array of health benefits, most Americans don't take advantage of them.

"American adults eat six to seven servings of refined grains but only one serving of whole grains a day, with children eating less than one serving -- well below U.S. Dietary Guideline recommendations of at least three servings," says Slavin.

While science continues its search for the answers, I recommend you switch from refined-grain products to whole-grain products. Instead of white bread or crackers, choose whole wheat, whole rye or whole grain breads and crackers. Instead of white pasta or white rice, choose whole wheat pasta or brown rice or cereals made with whole oats or whole corn. Try unusual grains such as bulgur (cracked whole wheat), whole wheat couscous or exotic grain-like substances such as quinoa and amaranth.

But looking for whole-grain foods in your supermarket can be challenging. Many "whole wheat" or "multi-grain" breads, for instance, are made predominantly of white flour, even though the label may say "wheat flour." Be sure the first ingredient on the nutrition label of your pasta, cereal, crackers or bread is a "whole" grain such as whole wheat, whole oats or whole rye. Also look for a whole-grain product containing three or four grams of fiber per one ounce (28 grams) or per 80- to 100-calorie serving. That signifies that the grain is likely in its most natural state.

Katherine Tallmadge is a Washington nutritionist and author of "Diet Simple" (Lifeline Press, 2004). Send e-mails to her at