Amidst nutrition messages that Americans should eat more bread, pasta and other grain products, research is showing more reasons than ever that whole grains are what we should be adding to our diets. Contrary to advice we often find in "health" magazines or stores, refined grains like white bread are not harmful to health, but they simply cannot provide us with the health benefits we get from eating whole wheat bread and other whole grains.

Higher dietary fiber content is the benefit most people associate with whole grains. A comprehensive review of diet and cancer research by the American Institute for Cancer Research notes that fiber might lower risk of not only colon and rectal cancer, but also possibly breast and pancreatic cancers. Dietary fiber reduces the concentration of cancer-causing substances in the colon and speeds passage of such substances through the body. Several studies have found that dietary fiber also influences estrogen metabolism within the body, which may explain the link with lower risk of breast cancer.

Dietary fiber also seems to be responsible for the slower digestion and absorption of the carbohydrates in whole grains compared to that in refined grains. Whole grains can be helpful in controlling blood sugar and insulin levels in people with diabetes, and a new study has suggested that including whole grains regularly may even help prevent diabetes.

Recently, researchers have also discovered that some undigested starch reaches the colon and, along with fiber, is fermented by bacteria, forming a substance called butyrate. Butyrate may offer additional protection against colon cancer by interfering with conversion of normal cells to cancer cells, and by promoting the death of cells that have become cancerous. Scientists say that whole grains tend to produce more butyrate than refined grains due to the additional fiber and starch that is more resistant to digestion.

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Another reason whole grains are more beneficial than refined products is because nutrients concentrated in the outer- and innermost parts of a grain are removed in the refining process, so whole grains are usually higher in vitamins E and B-6, as well as minerals such as selenium, zinc and magnesium. These are among the nutrients most commonly reported as below recommended levels in dietary surveys.

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Research on phytochemicals -- naturally-occurring substances in plant foods that may have important health benefits -- is providing even more reasons to choose whole-grain foods. Lignans, for example, are a type of "phytoestrogen" -- a plant substance similar enough to our body estrogen that it can bind to the same sites on cells, but so weak that it apparently cannot promote hormone-dependent cancers the way body estrogen can. Whole grains also contain a variety of phytochemical antioxidants that may help prevent cell damage that could otherwise promote cancer development and heart disease.

While some studies have not been able to clearly differentiate the benefits of fruits and vegetables from those of whole grains in a healthy high-fiber diet, all these apparent advantages of eating whole grains have scientists convinced of their importance. We need not choose whole-grain versions for all our bread, cereal and side dishes, but nutrition experts say that at least three or four servings each day should be whole grain. Just check the list of ingredients to find products that list a whole grain first.

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Karen Collins, M.S., R.D.,C.D.N.