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Is "healthy trans fat" an oxymoron? Maybe not. Although we've learned to opt for zero trans fats and search labels for deadly hydrogenated oils, there may be an exception to the no trans fats rule. Researchers at the Harvard School of Public Health have identified a naturally occurring trans fat in dairy that may substantially reduce the risk of type 2 diabetes.
For many years, studies have shown an association between eating dairy products and lower diabetes risk. But how dairy protects against diabetes remained a mystery. The answer may lie in dairy's fat.
Trans-palmitoleic acid is a fatty acid found in milk, cheese, yogurt, and butter. It's not produced by the body. It only comes from your diet.
Palmitoleic acid, or trans-palmitoleate, is found almost exclusively in naturally-occurring dairy and meat trans fats. Unlike trans fat found in hydrogenated vegetable oils, it has not been linked to higher heart disease risk. In fact, palmitoleic acid is heart healthy. It also has anti-microbial properties and is a key compound in cell communication.
In a study published in The American Journal of Clinical Nutrition Harvard researchers analyzed data from the Multi-Ethnic Study of Atherosclerosis (MESA), a prospective cohort study designed to investigate risk factors associated with cardiovascular disease in the U.S.
In 2000-2002, they recruited 6,814 adults aged 45-84 years from six regions of the country. They measured circulating blood levels of trans-palmitoleate.
At the end of 5 years participants with the highest levels of trans-palmitoleate had 6.4% higher LDL cholesterol. But their triglycerides were 19% lower, their fasting insulin levels were 9% lower, and their systolic blood pressure was 2.4 Hg lower.
Compared to those with the lowest level of the fat, those with the highest levels had half the risk of developing diabetes.
The results confirmed an earlier Harvard study reported in the Annals of Internal Medicine. In that study, researchers examined 3,736 participants in the National Heart, Lung, and Blood Institute-funded Cardiovascular Health Study. They had been followed for 20 years to evaluate risk factors for cardiovascular diseases in older adults.
At the beginning of that study, higher levels of trans-palmitoleic acid were associated with healthier levels of blood cholesterol, inflammatory markers, insulin levels, and insulin sensitivity.
During follow-up, participants with the highest levels of trans-palmitoleic acid had a 60% lower risk of developing diabetes.
When the researchers combined the data from the two studies they found that each .05% increase in trans-palmitoleate in the blood levels was associated with a 34% lower risk of diabetes.
The authors called for additional observational studies and controlled trials, noting the magnitude of the association between trans-palmitoleic acid and reduced diabetes risk was striking. They noted that this trans fat seems to have an extremely strong protective effect, stronger than other things known to be beneficial against diabetes.
In the meantime, enjoy full-fat milk, cheese, and yogurt, preferably from grassfed animals. And you can add reducing diabetes risk to the 10 other healthy reasons to eat real butter.
But continue to avoid artificial trans fats from hydrogenated and partially hydrogenated oils.