Prof. Dariush Mozaffarian and team explain that trans-palmitoleic acid may be behind recent studies which showed that dairy-rich diets are linked to a lower likelihood of developing diabetes type 2 and other metabolic problems.

Trans-palmitoleic acid is found in dairy fat, which goes against the advice of a significant number of health experts who tell people to avoid full-fat dairy produce.

The investigators gathered data on 3,736 individuals in the Cardiovascular Health Study. In this observational study, they had all been followed-up for 20 years for risk factors related to cardiovascular disease among older adults. They also measured blood glucose and insulin levels, as well as blood fatty acid levels, including trans-palmitoleic acid by using stored blood samples in 1992. The researchers wanted to find out how many of them went on to develop diabetes type 2.

They found that at baseline, healthier levels of blood cholesterol, insulin levels, insulin sensitivity, and inflammatory markers were linked to higher circulating levels of trans-palmitoleic acid, even after making adjustments for other risk factors.

They also found that people whose circulating levels of trans-palmitoleic acid were higher had a considerably lower chance of developing diabetes. Those in the top quintile of trans-palmitoleic acid levels had a 60% lower risk.

Mozaffarian said:

“This type of observational finding requires confirmation in additional observational studies and controlled trials, but the magnitude of this association is striking. This represents an almost three-fold difference in risk of developing diabetes among individuals with the highest blood levels of this fatty acid.”

Trans-palmitoleic acid should not be confused with industrially produced trans fats, found in partially hydrogenated vegetable oils and associated with cardiovascular disease.

Mozaffarian said:

“There has been no clear biologic explanation for the lower risk of diabetes seen with higher dairy consumption in prior studies. This is the first time that the relationship of trans-palmitoleic acid with diabetes risk has been evaluated. We wonder whether this naturally occurring trans fatty acid in dairy fats may partly mimic the normal biologic role of its cis counterpart, cis-palmitoleic acid, a fatty acid that is produced in the body. In animal experiments, cis-palmitoleic acid protects against diabetes.

Unfortunately, with modern diets, synthesis of cis-palmitoleic acid is now driven by high amounts of carbohydrate and calories in the diet, which might limit its normal protective function. We wonder whether trans-palmitoleic acid may be stepping in as a “pinch hitter” for at least some of the functions of cis-palmitoleic acid.”

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