Virtually eliminating the amount of trans fatty acids in industrially produced food could avert between 72 000 (6% of the total) and 228 000 (19%) coronary heart events each year in the United States, a new US and Dutch review study concludes (N Engl J Med 354;1601-13). The amount of trans fats in packaged snack foods, bakery products, deep fried fast food, margarine, and packaged snacks such as tortilla chips increases consumers’ risk of cardiovascular disease, coronary heart disease, and sudden death from cardiac causes, say the researchers, from Brigham and Women’s Hospital and Harvard Medical School and the Harvard School of Public Health in Boston and Wageningen University in the Netherlands.
“The evidence and the magnitude of adverse health effects of trans fatty acids are in fact far stronger on average than those of food contaminants or pesticide residues, which have in some cases received considerable attention,” the report says.
Given that trans fats, which are formed from partially hydrogenated oils, have no intrinsic value to health above their energy content, consumption of them results in “considerable harm but no apparent benefit,” the study said.
Adverse effects are seen even at low levels of consumption, such as a person consuming only 1% to 3% of their overall energy from trans fats, says the study. “Thus complete or near-complete avoidance may be necessary to avoid adverse effects and would be prudent to minimise health risks,” it says.
In a letter to the editor in the same issue Danish researchers say they found the content of trans fatty acids in homogenised servings of french fries and chicken nuggets equivalent to the amount in a large serving from McDonald’s to vary from less than 1 g in Denmark and Germany to 10 g in New York (N Engl J Med 354;1650-2). Half of the 43 servings of fast food tested in 20 countries between November 2004 and September 2005 contained more than 5 g per serving, the daily intake associated with a 25% increase in the risk of ischaemic heart disease.
Trans fats—semi-solid fats used in commercial cooking and manufacturing processes and margarines—are attractive to the food industry because they have a long shelf life, remain stable during deep frying, and enhance the taste of baked goods and sweets.
The average amount of trans fats consumed in the US is 2% to 3% of the total energy intake, although the Department of Agriculture has recommended reducing the amount of industrially produced trans fatty acids in food products. Denmark has enacted legislation to eliminate them altogether, and Canada is considering similar legislation.
Naturally occurring trans fats in meat and dairy products from cows, sheep, and other ruminants are consumed in smaller amounts than artificial trans fats (about 0.5% of total energy intake). These trans fats are produced by the action of bacteria in the animals’ stomachs.
The report says that the study’s estimates of risk reduction from eliminating trans fats were “based on the replacement of trans fats with carbohydrates.”
“In practice, however,” it said, “trans fats … would most commonly be replaced with unhydrogenated (cis) unsaturated fats, which may have additional potential benefits as compared with carbohydrates.”