A proposed amendment of the NYC Health Code aims to restrict NYC food service establishments (FSEs) from providing foods containing trans fatty acids (TFAs) that are produced by artificially hydrogenating vegetable oils. It is predicated on the assumption that doing so will significantly decrease the consumption of these fats by FSE patrons, and that this decreased consumption will have a discernable health benefit -- in particular a decrease in heart disease. It is the position of the American Council on Science and Health that the scientific data do not strongly support such a health benefit.
As of 2003, the FDA estimated that the average intake of TFAs by Americans contributed about 2.6% of total calories. Since that time, food manufacturers have been required to list TFAs on their food labels, and the amount of these fats in foods has been declining. Although some media reports attribute unique detrimental health effects to TFAs, in fact, the strongest evidence indicates that they are similar to saturated fats in their health effects -- that is, TFAs increase blood levels of LDL ("bad") cholesterol, which in turn are linked to an increased risk of heart disease.
There is some evidence -- by no means conclusive -- that TFAs also decrease the blood levels of HDL ("good") cholesterol. But the data suggesting that this is the case are not robust. Only at high levels of consumption have TFAs been seen to have such an effect -- not at the levels that are commonly consumed by Americans.
Because of these effects on blood lipids -- LDL increases and possible HDL decreases -- it is logical to assume that further decreasing the amounts of TFAs consumed will have an effect on the prevalence of deaths from heart disease. But there are no data demonstrating that the effect on blood lipids actually translates into an effect on heart disease -- all we have are widely varying estimates. Denmark has limited the amount of TFA allowed in their foods to <2% of total calories, but again we do not know if their replacement of TFAs with other fats has had a beneficial effect on the population's health -- and we may not know for a number of years.
To a great extent, any health effects of minimizing TFAs from our foods and diets will depend on the nature of their replacements. If they are replaced with highly saturated fats, which are known to also raise LDL cholesterol, the effect may not be beneficial. There are other proposed replacements, but again, we do not know the health effects of all of them. Let us not forget that the reason we now have as much TFA in our diets as we do is that twenty or so years ago food manufacturers and purveyors were encouraged to substitute them for more highly saturated animal fats -- because the latter were thought to pose a greater health risk. How do we know that (1) further reduction in TFAs will be beneficial or (2) their replacements will be any better in terms of blood lipid levels and heart health?
Although the proposed ban on the use of trans fats by New York City food establishments sounds like a health-promoting step, in fact the science to support such a move is not yet robust, and such a ban is, in our opinion, both coercive and premature.
Ruth Kava, Ph.D., R.D., is Director of Nutrition at the American Council on Science and Health (ACSH.org, HealthFactsAndFears.com).
See also: Testimony from ACSH's Dr. Elizabeth Whelan and ACSH's full-length report on Trans Fatty Acids and Heart Disease.
