by Craig Weatherby
Chalk up another potential reason to enjoy milk products, thanks to research out of Harvard.
A growing body of evidence suggests that people whose diets contain relatively high proportions of milk products are less likely to develop insulin resistance… or diabetes, for which insulin resistance is the leading risk factor.
Fatty fish beats milk for vitamin D... hands down
It seems safe to assume that calcium and vitamin D are partly responsible for the anti-insulin-resistance and anti-diabetes effects of milk product.
If so, be aware that fatty fish like tuna and salmon contain far more vitamin D than milk does… 500 and 700 IU, respectively, vs. only 100 IU in an eight-ounce glass of milk.
And a half-can of traditional canned sockeye salmon with edible bones—about two ounces— provides 120mg of calcium, compared with about 290mg in an eight-ounce glass of milk and the 1000mg recommended for adults aged 19 to 50 years.
The same is true of people who have relatively high body levels of calcium and vitamin D—which often come from high milk-product intake.
A recent evidence review found that people reporting the highest dairy intakes—3 to 4 servings per day—were 29 percent less likely to develop insulin resistance, vs. those reporting only 0.9-1.7 servings per day (Tremblay A, Gilbert JA 2009).
Among the few clinical studies conducted to evaluate the effects of milk intake on the management or prevention of insulin resistance or diabetes, some have shown favorable effects on insulin resistance, blood pressure and weight… while others have not.
These varying findings may be due to differences among people with regard to the many other factors that could influence the degree to which someone’s milk-product intake affects their risk factors for insulin resistance or diabetes.
Overall, as the review authors concluded, “...the intake of low-fat dairy products… has been shown to contribute to a significant extent to the prevention of insulin resistance syndrome” (Tremblay A, Gilbert JA 2009).
And new findings from Harvard suggest another possible reason why milk would tend to deter diabetes.
Harvard team proposes a new anti-diabetes factor in milk
A team from the Harvard School of Public Health may have identified a fatty acid in milk that reduces the risk of type 2 diabetes.
The scientists examined data from a study that followed 3,736 adults from 1992 to 2006.
(Unlike many milk-related studies, this research was not paid for by the dairy industry, but instead by agencies within the National Institutes of Health.)
And the analysis showed that those with the highest blood levels of trans-palmitoleic acid—a monounsaturated fatty acid found primarily in milk products—were the least likely to have adult-onset (type II) diabetes.
Specifically, the one-fifth of participants with the highest trans-palmitoleic acid levels were 60 percent less likely to have developed diabetes, compared to the fifth who reported the lowest milk-products intake.
As lead author Dariush Mozaffarian, M.D., Dr.P.H., said, “This represents an almost three-fold difference in risk of developing diabetes among individuals with the highest blood levels of this fatty acid.”
Dr. Mozaffarian described the magnitude of the findings as “striking”, but added that the study should be followed up with more observational studies like this one, and controlled trials to confirm their initial conclusions.
The Harvard team noted that in animal experiments, the compound’s mirror image counterpart—called cis-palmitoleic acid—protects against diabetes.
And, they believe it’s possible that the “trans” version of cis-palmitoleic acid may mimic its beneficial effects with regard to insulin resistance and other diabetes risk factors.
Note: only the manmade trans omega-6 polyunsaturated fats in hydrogenated vegetable oils have been shown harmful to heart health, while the trans fats in milk appear harmless.
We hasten to add that fermented milk products like yogurt and buttermilk should be favored over regular milk products.
That’s because fermented milk products are easier to digest and offer “probiotic” cultures that can greatly benefit overall health.
Mozaffarian D, Cao H, King IB, Lemaitre RN, Song X, Siscovick DS, Hotamisligil GS. Trans-palmitoleic Acid, metabolic risk factors, and new-onset diabetes in u.s. Adults: a cohort study. Ann Intern Med. 2010 Dec 21;153(12):790-9
Tremblay A, Gilbert JA. Milk products, insulin resistance syndrome and type 2 diabetes.J Am Coll Nutr. 2009 Feb;28 Suppl 1:91S-102S. Review.