As part of a 12 step manifesto to better public health, the UK Faculty of Public Health and Royal Society for Public Health proposed that consumption of trans fatty acids (TFAs) should be virtually eliminated in the United Kingdom by next year.1 They noted that, “it has been proven that industrially-produced TFA can damage health,” “there is no known safe level of consumption,” and “banning TFA from foods is a relatively easy way to help protect the public.”1 Are these arguments sound?

TFAs are created when vegetable oils are partially hydrogenated to convert large numbers (typically 30-60%) of naturally occurring cis unsaturated double bonds into trans unsaturated double bonds. A high TFA content provides physical and chemical properties that are attractive to food manufacturers, including the creation of relatively inexpensive (compared with animal derived fats) solid or semi-solid fat. The process also destroys labile omega-3 acids (α-linolenic acid), and this reduces the propensity for fats to become rancid, increases shelf life, and optimises deep frying applications. Use of partially hydrogenated vegetable oils has increased since the 1950s because of these commercial advantages and since the 1960s because of public health recommendations to replace saturated fats (such as butter and lard) with alternatives.

Because mammals and most edible plants synthesise only cis double bonds, TFAs are rare in the natural …