Whole-fat Dairy Consumption Associated with Lower Metabolic Risk Factors and Lower Incidence of Diabetes

Mozaffarian D, Cao H, King IB, et al. Trans-palmitoleic acid, Metabolic Risk Factors, and new-onset diabetes in U.S. adults: a cohort study. Ann Intern Med. 2010;143(12):790-799.

 

Prospective cohort study

 

Study conducted between 1992 and 2006 in 4 U.S. communities

 

3,736 adults in the Cardiovascular Health Study

 

Multivariate analyses

 

Anthrometric characteristics and levels of plasma phospholipid fatty acids, blood lipids, inflammatory markers, and glucose-insulin measured at baseline in 1992 and dietary habits measured 3 years earlier.

 

Whole-fat dairy consumption was most strongly associated with higher trans-palmitoleate levels, which in turn were associated with lower adiposity, higher high-density lipoprotein cholesterol levels (1.9% across quintiles; P=0.040), lower triglyceride levels (-19.0%; P<0.001), lower total cholesterol-HDL ratio (-4.7%; P<0.001), lower c-reactive protein levels (-13.8%; P=0.05) and lower insulin resistance (-16.7%, P<0.001). Higher levels of trans-palmitoleate was associated with substantially lower incidence of diabetes as well, with multivariate hazard ratio of 0.41 (95% CI, 0.27 to 0.64) and 0.38 (CI, 0.24 to 0.62) in the highest two quintiles versus the lowest (P for trend < 0.001).

 

Dairy fat is a complex fat, containing approximately 400 fatty acids,¹ including trans-palmitoleic acid. Human beings are not able to synthesize trans-palmitoleic acid, making it a blood marker for full-fat dairy consumption. Participants with the highest levels of trans-palmitoleic acid had a significantly lower risk of developing type 2 diabetes. Other recent studies have also shown health benefits from whole fat milk. A recent 9-year study demonstrated that higher dairy intake was associated with lower diastolic blood pressure, waist circumference, BMI gain, and triglycerides.² Another study in 2010 showed milk fat biomarkers through milk consumption lowered risk of first myocardial infarction, most significantly in women.³ The data in a study titled "Phytanic acid—an overlooked bioactive fatty acid in dairy fat?" suggest that phytanic acid, strongly correlated with red meat and dairy intake, may have preventative effects on metabolic dysfunctions.⁴ With this intriguing data, it may prove useful to consider that the 400 fatty acids in milk fat may serve important biological functions.

 

 

 

For years, saturated dietary fat has been maligned as the cause of a number of health conditions. As early as the 1950s, researcher Ancel Keys was instrumental in propagating the concept that eating a diet high in saturated fat increased mortality from heart disease. In his landmark Seven Countries Study, he highlighted data to support his theory, while ignoring statistics from 15 other countries. Shortly after his paper was published, the American Heart Association and the American government began recommending a diet low in saturated fats. Many in the medical community continue to purport that a healthy diet is a low-fat diet. Denmark, the producers of renowned Havarti cheese, are now contending with the world's first “fat tax,” a government-imposed tax on foods over 2.3% fat, a misguided effort to reduce the country's consumption of butter, cheese, and whole milk. Even today, the USDA's Food Pyramid emphatically discourages the consumption of full-fat dairy products, lumping the fat component in dairy into the “empty calories” category, shared also with refined sugar. The trans-palmitoleic acid study is one of many that have looked at the effect of dairy fat on health, with some interesting results.

 

Modern scientific method has a great interest and capacity for microscopic examination of whole foods. As with the case of skim milk, white flour, and processed breakfast cereals, dietary science has created a formidable industry out of refining whole foods to their simple carbohydrate base, then synthesizing vitamins and adding those deemed important back in. While reductionist science strives to understand compounds by looking at their elemental components, data continues to emerge that there are complexities to the interrelationships between constituents, accounting for their physiological benefits.^5,6,7 For those of our patients who tolerate dairy products, recommending full-fat dairy ensures the benefits from the full spectrum of fatty acids that whole milk contains. Obtaining high quality dairy from grass-fed cows further increases fatty acid content of the milk.⁸ We're continuing to collect data demonstrating that dairy products, consumed whole and unprocessed, have many important health benefits.