There is mounting evidence that milk can lower your risk of developing type 2 diabetes.

Men who drank 2 to 3 cups of low-fat or nonfat milk a day were found to be 20 percent less likely to develop type 2 diabetes in a study by researchers from Massachusetts General Hospital and the Harvard School of Public Health in Boston.

The study is the first to find a direct protective benefit for dairy against diabetes. But Harvard nutrition researcher Frank Hu, MD, PhD, says it is too soon to tell people at high risk for type 2 diabetes to eat more dairy.

"I don't think it is a good idea at this point to recommend high dairy consumption as a public health strategy to prevent diabetes," he says. "While this research is definitely intriguing, the public health implications are not yet clear."

More Servings, Lower Risk

About 18 million Americans have type 2 diabetes and 41 million more are considered to be at very high risk for developing the disease. Nine out of 10 cases of type 2 diabetes are believed to be caused by lifestyle factors such as being overweight, getting no exercise, and eating a poor diet.

The Harvard School of Public Health study included information obtained from more than 41,000 men participating in an ongoing nutrition and health investigation.

None of the men had diabetes when they enrolled in the study, but 1,243 cases were diagnosed during 12 years of follow-up.

"Each serving-per-day increase in total dairy intake was associated with a 9% lower risk for type 2 diabetes," researcher Hyon K. Choi, MD, notes in a news release.

The reduction in diabetes risk was limited to low-fat and nonfat dairy products, however. There was no decrease in men who drank whole milk.

The protection was seen even after accounting for known diabetes risk factors, such as body weight and exercise. Lifestyle differences between the men who drank milk and those who didn't could help explain the findings, says Hu.

"It is possible that people who drink a lot of nonfat milk or eat other low-fat dairy products would have healthier lifestyles overall," he says.

And though only men were included in the study, Hu says there is no reason to believe that the findings would not apply to women. The study is published in the May 9 issue of the journal Archives of Internal Medicine.

What About Dairy and Weight Loss?

In an editorial accompanying the study, nutrition researcher Janet C. King, PhD, of the Children's Hospital Oakland Research Institute wrote that the role of dairy foods in health remains complex and may vary from person to person.

Studies show that drinking milk helps people lose weight and protects against high blood pressure, heart disease, gout, and colorectal cancer.

But eating dairy foods has also been linked to an increased risk of prostate cancer. Several studies have also implicated cow's milk in the development of type 1 diabetes among genetically susceptible children, although this link has not been confirmed.

King says the evidence regarding dairy and weight loss is far from conclusive. She points out that the National Dairy Council's massive ad campaign promoting milk as a weight loss food is based on just two studies with fewer than 50 participants.

But Dairy Council spokesman Greg Miller, PhD, tells WebMD that a third trial supporting the link between dairy and weight loss was recently published in Europe, and several other clinical trials have been completed but have not yet been published.

Miller points out that that the government's dietary guidelines were recently changed to recommend that adults eat three servings of nonfat or low-fat dairy products a day instead of two. Although the government advisory committee noted that there was not enough evidence to prove that dairy foods help people lose weight, they did conclude that milk and milk-based products do not contribute to weight gain.

"That is a very important message, especially for young girls who might cut dairy out of their diets because of concerns about weight and body image," says Miller. "The best science we have supports the role of dairy foods in healthy diets.

By Salynn Boyles, reviewed by Michael W. Smith, MD

SOURCES: Choi, H. Archives of Internal Medicine, May 9, 2005; vol 165: pp 997-1003. Hyon K. Choi, MD, DrPH, department of medicine, Massachusetts General Hospital. Frank B. Hu, MD, PhD, assistant professor of nutrition and epidemiology, Harvard School of Public Health, Boston. Janet C. King, PhD, senior scientist, Children's Hospital Oakland Research Institute, Oakland, Calif. Greg Miller, PhD, senior vice president, nutrition and product innovation, National Dairy Council.