Selenium linked to lower diabetes risk

The chances of developing type 2 diabetes were as much as 24 percent lower among people with a diet rich in selenium than among those who consumed little of the mineral in a large new U.S. study.

The findings, published in the journal Diabetes Care, are based on 7,000 male and female health care professionals followed for decades. But they add to a mixed bag of evidence on the protective effects of selenium, a known antioxidant, when it comes to diabetes.

"I wouldn't suggest, based on the findings from this study, that people start taking selenium supplements," said Dr. Dariush Mozaffarian, senior author of the new report, from the Harvard School of Public Health in Boston.

For one, he said, there are multiple different types of selenium, which may have different effects - and supplements contain only a single type.

Antioxidants are thought to offer some protection against chronic diseases, including diabetes, and selenium has become a popular supplement in recent years for that reason. The mineral is also found naturally in foods like bread, meat and nuts.

In some places, it occurs in high concentrations in soil, affecting the direct exposure of people who live nearby and the selenium content of foods grown in the region.

To look at the long-term effect of selenium exposure on diabetes risk in otherwise healthy people, Mozaffarian and his colleagues analyzed toenail clippings from the 1980s.

A little over 7,000 women and men participating in the long-term Nurses' Health Study and Health Professionals Follow-Up Study had contributed the samples between 1982 and 1987 and answered extensive questionnaires about their diets, lifestyles and illnesses over the next two decades.

None had diabetes or heart disease at the beginning of the study. And just over 10 percent developed Type 2 diabetes in subsequent years (a rate that is likely to be lower than in the general population, according to the researchers, since the study participants were all health professionals).

Though questionnaires about diet rely on memory, which can be faulty, the accumulation of selenium in toenails accurately reflects exposure to the mineral over about a year's time.

For both men and women, the researchers found the risk of developing diabetes was 24 percent lower among people with the highest levels of selenium in their toenails, compared to those with the lowest levels.

Still, they emphasized that the study reinforces the need for a healthy diet, while discouraging the use of supplements to get more selenium. If anything, said Mozaffarian, people should be choosing healthy foods like whole grains and fish, which are rich in the mineral.

The Institute of Medicine, an advisory panel to the U.S. government, recommends most adults get 55 micrograms of selenium each day. One bagel contains about 27 micrograms, for example, and one egg 15 micrograms.