Could a little trans fat found naturally in meat and dairy actually be protective?
Amid the stormy debate over dietary recommendations regarding saturated fats and carbohydrates, there’s been one area of calm and consensus. Nearly everyone seems to have agreed that trans fats have no place in the diet. The FDA’s recent move to ban trans fats received broad support.
But now a study is suggesting that some trans fats, especially naturally-occurring trans fats, may not be harmful, and might even be beneficial, at least in small doses.
German researchers assessed trans fatty acid (TFA) levels in 3,259 heart patients by measuring the fatty acid composition of erythrocyte membranes. Over 10 years of follow-up, total TFA concentrations were associated with a reduced risk of cardiovascular death (adjusted hazard ratio 0.82 for the intermediate versus lowest tertile, 95% confidence interval 0.68–1.00) and sudden cardiac death (adjusted HR 0.56 for intermediate vs lowest tertile, 95% CI 0.42–0.76).
The reduction in risk was “mainly driven” by naturally-occurring TFA, especially trans-palmitoleic acid, which is fairly specific for dairy products, Marcus Kleber, PhD, of Heidelberg University in Mannheim, Germany, and colleagues found.
There was no significant association in either direction for industrially-produced TFA, the researchers reported online in the European Heart Journal.
A very important caveat to the study is that overall TFA levels were much lower than in the United States. In the German subjects, TFA levels averaged less than 1% of the total fatty acid composition. The U.S. average is more than 2.6% of total fatty acids from trans fat.
Kleber said the researchers were “surprised to see that increases in the concentrations of industrially-produced TFAs were not followed by increased mortality, which stands in contrast to observations from the United States. The reason for this may be, that in our group of German patients, TFAs were in general much lower than those found in the United States, so that hardly anybody in the study reached concentrations common to people in the U.S.”
Experts Say Don’t Change Policy Yet
Alice Lichtenstein, DSc, of Tufts University in Boston, who has served on numerous guideline and expert panels, said that because the TFA levels were “very low in this cohort, they may not have had the breadth of intakes necessary to adequately test the hypothesis. On the basis of this study, there is no indication we should change the current recommendation to limit intake of TFA, as well as SFA [saturated fatty acid].”
James DiNicolantonio, PharmD, a researcher who has been scrutinizing nutrition policy, said that he “would not take this study as a green light to consume foods that contain some industrialized trans fat, as those ‘foods’ are processed and highly refined (unhealthy food so to speak). Industrialized trans fats lower the total cholesterol-to-HDL ratio, increase lipoprotein(a), triglycerides, thrombogenesis, atherosclerotic plaque, inflammatory markers, and the risk of coronary heart disease.”
But DiNicolantonio, of Saint Luke’s Mid America Heart Institute in Kansas City, Mo., did say that naturally-occurring TFAs may be healthful:
“Having a higher level of naturally-occurring trans fat in the blood being associated with a lower risk of sudden cardiac death makes complete sense. Ruminant trans fatty acids (rTFAs) being one example, which are derived from animals that chew regurgitated semi-digested food, such as goats, sheep, cows, deer, etc. In essence, fatty acids contained in dairy and meat contain ruminant trans fats. Vaccenic acid, a type of ruminant trans fat, has been found to inhibit atherosclerotic plaque formation. This may be why fats from meat or dairy may not be harmful, and in fact healthful.”
Arne Astrup, MD, DMSc, a researcher at the University of Copenhagen who was instrumental in putting in place a 2004 ban on TFAs in Denmark, agreed that the overall low level of industrially-produced TFAs in the study limit its significance.
Because the patients in the study already had heart disease, “it is very likely that they were instructed to reduce their intake of trans fat foods before the blood samples were taken,” Astrup said. He said he continues to support TFA bans.