3 October 2011

(Reuters Health) – People with higher intakes of a fat found mainly in dairy products might have lower odds of developing diabetes, a new study suggests.

Looking at more than 3,700 U.S. adults, researchers found that those with higher blood levels of the fatty acid — known as trans-palmitoleic acid — were about 60 percent less likely to develop type 2 diabetes over the next 20 years than people with the lowest blood levels.

That would seem to run counter to longstanding recommendations to trade in whole milk and cheese for the skim varieties for the sake of health.

And experts caution that it’s indeed too soon to break out the full-fat dairy.

For one thing, whether the fatty acid itself deserves the credit for the lower diabetes risk is not clear. And then there’s the fact that full-fat dairy products are often high in calories, which could lead to weight gain — itself a risk factor for diabetes — and saturated fat, which could boost “bad” LDL cholesterol and contribute to heart disease.

“Dietary recommendations should not be changed based on any one study,” said lead researcher Dr. Dariush Mozaffarian, an associate professor at the Harvard School of Public Health in Boston.

But he said the findings are “exciting” and warrant further research — including, at some point, clinical trials in which people would be given supplements of trans-palmitoleic acid to see if the fat itself curbs diabetes risk.

The results, reported in the Annals of Internal Medicine, also point to a potential explanation for some previous research that showed dairy lovers to have a lower diabetes risk than people who consume little dairy.

Even if the benefit does not come from trans-palmitoleic acid specifically, Mozaffarian said, these findings bolster the case that dairy has some anti-diabetes property.

“I think this study confirms that there is something about dairy foods that’s responsible,” he said.

Mozaffarian said he feels confident, in part, because he and his colleagues were able to account for a range of diabetes risk factors among the study participants — including their age, weight, exercise habits and general diet. And those things did not explain the link between the dairy fat and lower diabetes risk.

Of more than 700 study participants with the highest blood levels of the fatty acid, 38 later developed diabetes. That compared with 94 cases among the 700-plus with the lowest levels of the dairy fat.

When the researchers adjusted for the other factors in their analysis, people with the top-20-percent blood levels of the fatty acid showed a 62 percent lower risk of diabetes than the group with bottom-20-percent fatty acid levels.

Trans-palmitoleic acid falls into the broad category of “trans-fat,” which has become notorious in recent years for its links to elevated LDL cholesterol and heart disease.

However, unlike the trans-fats in many processed foods, like cookies, crackers and chips, trans-palmitoleic acid is a natural fat. And so far, Mozaffarian said, research has not linked natural trans-fats in dairy and meat to an increased heart disease risk.

It may be that at least some natural trans-fats, like trans-palmitoleic acid, have health benefits, according to Mozaffarian. “I think we all have to start looking at dietary fats in a more nuanced way,” he said.

Animal research offers some hints as to why trans-palmitoleic acid might lower diabetes risk, he adds. A “sister” fat known as cis-palmitoleic acid — which is produced naturally in the body — has been shown to protect animals from developing diabetes when its production is revved up through genetic manipulation.

Cis-palmitoleic acid seems to suppress the liver’s overall production of fat and help muscles more efficiently use sugar from food, both effects that could help ward off diabetes.

It’s possible that trans-palmitoleic acid from dairy foods mimics its naturally occurring counterpart in the body, Mozaffarian said.

“This study is promising,” said Constance Brown-Riggs, a registered dietitian and certified diabetes educator based in Massapequa, New York. And given that an estimated 54 million Americans have “pre-diabetes,” she told Reuters Health, “the implications of the findings could really be far-reaching.”

Slightly impaired glucose processing, as evidenced by a fasting plasma glucose test result between 100 milligrams per deciliter and 125 mg/dL, is considered “pre-diabetes” according to the National Institute of Diabetes and Digestive and Kidney Diseases, and a sign of increased risk for progressing to full diabetes.

Regarding the current study, many questions remain, Brown-Riggs said, and for now, “We can’t translate this into any dietary recommendations today.”

Brown-Riggs, a spokesperson for the American Dietetic Association, also cautioned people against trying to find any one dietary “magic bullet” against diabetes.

While some studies have found that dairy lovers have a lower diabetes risk, there are also many studies linking the same benefit to the Mediterranean diet — typically low in dairy, but high in fats from olive oil and fish, and rich in high-fiber grains, vegetables and legumes.

“That just illustrates that there is more than one contributing factor to diabetes risk,” Brown-Riggs said.

“People often want to hook onto one thing and think that will be the magic bullet,” she noted. “At this point, the best defense we have against diabetes is maintaining a healthy weight, getting regular exercise and eating a balanced diet.”

This article was published in www.reuters.com on 22 December 2011.