Adults with higher blood and fat tissue levels of three fatty acids — which correlate with intake of high-fat dairy foods — were less likely to develop type 2 diabetes, in an epidemiologic study.
The researchers analyzed data from 16 pooled international cohorts with more than 60,000 people from the Fatty Acids and Outcomes Research Consortium (FORCE) project.
The participants had baseline measurements of three fatty acids — pentadecanoic acid (15-carbon saturated fatty acid, 15:0), heptadecanoic acid (17:0), and trans-palmitoleic acid (t16:1n7) — that reflect consumption of fat from dairy products such as milk and cheese.
During up to 20 years of follow-up, 23.8% of the participants developed type 2 diabetes. The people with the highest levels of all three fatty acids (highest quintile) had a 35% lower risk of developing type 2 diabetes during follow-up than people in the lowest quintile.
The study, by Fumiaki Imamura, PhD, University of Cambridge, United Kingdom, was published online October 10 in PLOS Medicine.
"Our results provide the most comprehensive global evidence to date about dairy fat biomarkers and their relationship with lower risk of type 2 diabetes," Imamura said in a statement by the UK Medical Research Council.
"We're aware that our biomarker work has limitations and requires further research on underlying mechanisms," he conceded, "but at the very least, the available evidence about dairy fat does not indicate any increased risk for the development of type 2 diabetes."
Senior author Dariush Mozaffarian, MD, Tufts University, Boston, Massachusetts, added: "While dairy foods are recommended as part of a healthy diet, US and international guidelines generally recommend low-fat or non-fat dairy due to concerns about adverse effects of higher calories or saturated fat."
These latest results, based on "measuring biomarkers of fatty acids consumed in dairy fat, suggest a need to re-examine the potential metabolic benefits of dairy fat or foods rich in dairy fat, such as cheese," he added.
What do these findings mean for clinicians and patients? Medscape Medical News asked Robert H. Eckel, MD, of the Division of Endocrinology, Metabolism and Diabetes, and Cardiology, and Director of the Lipid Clinic, at the University of Colorado, Aurora.
Should people switch to high-fat instead of low-fat dairy and eat more dairy?
"Epidemiology is epidemiology," he stressed in an email. "No changes in a heart-/diabetes-/cancer-healthy lifestyle are recommended until more science affirms this relationship" between high-fat dairy foods and lower risk of type 2 diabetes.
According to Eckel, "It’s not 'good foods' or 'bad foods', it's the overall diet. The Mediterranean and DASH diets are well studied" and recommended.
These Fatty Acids "At Least Partly Reflect Dairy Fat Consumption"
Prior studies have suggested that eating cheese or yogurt may be linked with a lower risk of incident type 2 diabetes, but research based on self-documented food intake may have recall bias, and dairy fat may be "hidden" in some foods and therefore not reported, Imamura and colleagues write.
However, previous work suggests that levels of 15:0, 17:0, and t16:1n7 may be a good surrogate for dietary intake of fat from dairy products, as levels of these fatty acids are increased when people report that they consume a lot of high-fat dairy products, and the levels decrease when people switch from high-fat to low-fat dairy products.
Thus, these two distinct fatty-acid classes (the odd-chain saturated fats 15:0 and 17:0; and the natural ruminant trans-fat t16:1n7) "at least partly reflect dairy fat consumption" from multiple dietary sources without relying on people's memory, according to the researchers.
They analyzed data from 16 prospective studies (seven in the United States, seven in Europe, one in Australia, and one in Taiwan). The 63,682 participants without known diabetes were middle-aged or older, with a mean baseline age of 49 to 76 years.
The researchers used gas chromatography to determine levels of 15:0, 17:0, and t16:1n7 in tissue samples and blood components. The relative concentrations of these three fatty acids were generally low (0.1% to 0.5 mol% of total fatty acids).
During an average follow-up of 9 years, 15,180 participants developed type 2 diabetes.
Higher concentrations of 15:0 and 17:0, t16:1n7, or all three, were associated with a lower incidence of type 2 diabetes.
Risk of Type 2 Diabetes, Top vs Bottom Quintile of Fatty Acid Levels
|Fatty Acid Type||HR (95%, CI)*|
|15:0||0.63 (0.52 - 0.76)|
|17:0||0.64 (0.47 - 0.87)|
|t16:1n7||0.83 (0.62 - 1.11)|
|All 3 types||0.65 (0.51 - 0.83)|
However, the study does have some limitations, the researchers acknowledge.
"Despite the several advantages of evaluating fatty acid biomarkers," they caution, "the results cannot distinguish between different types of dairy foods (eg, milk, cheese, yogurt, others), which could have differential effects."
Moreover, although these biomarkers reflect dairy fat consumption, their levels could be influenced by other factors, possibly unrelated to dairy intake.
Also, data from nonwhite populations were limited, so further research is needed among more diverse communities where other types of dairy products may be consumed with different food preparation methods.
Nevertheless, the study's "novel findings," Imamura and colleagues conclude, "support the need for additional clinical and molecular research to elucidate the potential effects of these fatty acids on glucose-insulin metabolism, and the potential role of selected dairy products for the prevention of type 2 diabetes."
Imamura and Mozaffarian have reported no relevant financial disclosures. Disclosures of the other authors are listed with the article.
PLOS Medicine. Published online October 10, 2018. Full Text
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Cite this: Dairy Fat May Protect Against Diabetes, Says Biomarker Study - Medscape - Oct 12, 2018.