Diabetes Prevention: The Diet

Many people still believe that eating too much sugar causes diabetes. This misconception arises because diabetes is diagnosed by measuring blood sugar (glucose). But dietary sugar is only part of the picture. According to two recent Harvard studies, a diet rich in certain high-carbohydrate foods—those low in fiber and with a high glycemic index (see below)—increases the risk of Type 2 diabetes, at least in those predisposed to it.

One study tracked 65,000 female nurses (age 40 to 65); the other followed 43,000 male health professionals. Over the course of six years, a total of 1,438 developed diabetes. Men and women whose diet had a high glycemic index and low fiber content more than doubled their chance of developing diabetes. Foods that seemed to pose the greatest risk were white bread, white rice, potatoes, and sugary soft drinks. In contrast, whole-grain breads and cereals (rich in fiber and with a lower glycemic index) appeared to reduce the risk of diabetes. Fruits and vegetables didn't seem to have an effect, good or bad.

The researchers suggested that excessive amounts of carbohydrate-rich foods with a high glycemic index put pressure on the pancreas to produce more of the hormone insulin, which stimulates the body's cells to take in and store glucose. Over time, the body may become resistant to insulin. In such insulin-resistant people, the cells become less and less sensitive to insulin. This is characteristic of Type 2 diabetes. Of course, not everyone on such a low-fiber, high-starch diet develops diabetes. There seems to be a genetic predisposition to diabetes, which may be exacerbated by this kind of diet. Without these dietary factors, the men and women in these two studies might have developed diabetes later in life, or perhaps not at all.

Obesity is probably the leading risk factor for Type 2 diabetes. Family history of the disease, advancing age, and lack of exercise are other important factors.

Magnesium helps, too

The study also found that the mineral magnesium has a protective effect against diabetes. A few studies have suggested that this mineral improves insulin sensitivity. But since whole grains are rich in magnesium, it's hard to say whether the proposed benefit is due to something else in the grain (notably its fiber) or the mineral.
Bottom line: A diabetes-prevention diet, if there is one, is the same low-fat, high-fiber, semi-vegetarian diet that is known to lower the risk of heart disease and cancer. The Harvard studies simply underline the importance of choosing whole-grain products, as opposed to highly refined, low-fiber grain products such as white bread, in order to help control blood sugar. Such a diet helps in weight control. It also provides the vitamins, minerals, and other nutrients you need to help prevent chronic diseases, including, perhaps, diabetes.

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