Got Milk? Trans Fatty Acid in Dairy Foods Linked to Reduced Diabetes Risk

December 21, 2010 (Boston, Massachusetts) — Circulating levels of trans-palmitoleic acid, a fatty acid derived from dairy food sources, are inversely associated with the risk of new-onset diabetes mellitus and metabolic risk factors [1]. The findings, according to researchers, open the possibility that yogurt, milk, and cheese might one day be recommended in attempts to lower the risk of developing atherogenic dyslipidemia, insulin resistance, and diabetes.

"In several recent observational studies, people who eat more dairy foods tended to have lower risks of insulin resistance and diabetes," lead investigator Dr Dariush Mozaffarian (Harvard School of Public Health, Boston, MA) told heartwire . "However, the mechanism for such potential protection is unknown. Trans-palmitoleic acid is a fatty acid relatively unique to dairy foods. We don't make it in our bodies, so consuming it is the only way for it to enter the bloodstream. This study provides evidence that people who have higher levels of blood trans-palmitoleic acid have a significantly lower risk of diabetes mellitus, as well as other metabolic risk markers."

The results of the study are published in the December 21, 2010 issue of the Annals of Internal Medicine.

From the Cardiovascular Health Study

To heartwire , Mozaffarian noted that other animal studies have suggested that circulating palmitoleic acid, which is derived from endogenous fat synthesis, might regulate and protect against insulin resistance. In the present study, the researchers wanted to determine whether an exogenous source of palmitoleate would also have a beneficial effect on metabolic risk factors, and to do so they measured circulating levels of trans-palmitoleic acid, a fatty acid derived from dairy sources that has not been linked with increased cardiovascular risk.

Using data from the Cardiovascular Health Study , they measured circulating trans-palmitoleic acid levels in 3736 adults from four US communities between 1992 and 2006. Trans-palmitoleic acid represented less 1% of the total fatty acids measured but was strongly correlated with biomarkers of dairy fat consumption.

Regarding markers of metabolic risk, trans-palmitoleic acid was associated with "slightly less" adiposity and independently associated with higher HDL-cholesterol levels, lower triglyceride levels, and a lower total-cholesterol/HDL-cholesterol ratio. In addition, trans-palmitoleic acid was also associated with less insulin resistance and a lower risk of new-onset diabetes mellitus. Regarding the risk of diabetes mellitus, there was nearly a threefold difference in risk when individuals with the highest levels of trans-palmitoleic acid were compared with those who had lower levels of trans-palmitoleic acid.

Incidence of Diabetes Mellitus by Quintiles of Plasma Trans-Palmitoleic Acid Level

Mozaffarian noted that it's too early to make recommendations regarding dairy consumption or changes to food policy but said the findings have the potential to be important given magnitude of benefit observed in this study. While he was cautious in interpreting the findings, he said that if interventional studies are performed and support the results from this trial, foods could be enriched with trans-palmitoleic acid, potentially lowering the risk of diabetes mellitus, insulin resistance, and other metabolic risk factors.

Milk: A Meta-Analysis

Another study published in the American Journal of Clinical Nutrition tackled the dairy question, with investigators, led by Dr Sabita Soedamah-Muthu (Wageningen University, the Netherlands), performing a meta-analysis of 17 prospective studies evaluating the association between milk and dairy consumption and risk of cardiovascular disease, stroke, and total mortality [2].

Overall, investigators observed a modest inverse association between milk intake and the risk of overall cardiovascular disease, with milk consumption associated with a 6% lower risk of cardiovascular disease. Milk intake was not associated with the risk of coronary heart disease or total mortality.

"Milk and dairy products cannot be recommended to benefit cardiovascular disease health outcomes on the basis of this dose-response meta-analysis," conclude the authors. "[The] intake of milk and dairy products does not seem to be harmful, but whether the association is truly inverse cannot be firmly concluded."

Trials of dairy consumption, although limited in number, also failed to show an association with coronary heart disease.

Mozaffarian's study was funded by grants from the National Heart, Lung, and Blood Institute and the National Institute of Diabetes and Digestive and Kidney Diseases. The Dutch study was funded by an unrestricted grant from the Dutch Dairy Association, but the sponsor was not involved in conduct of the trial or the writing of the manuscript.

Heartwire from Medscape © 2010  Medscape, LLC

Cite this: Got Milk? Trans Fatty Acid in Dairy Foods Linked to Reduced Diabetes Risk - Medscape - Dec 21, 2010.