Press Releases

1999 Releases

Harvard review of evidence verifies that eating trans fats increases risk of heart disease

For immediate release: June 23, 1999 

Boston, MA--Over the course of the last decade, numerous studies have examined the relationship between the consumption of trans fatty acids found in partially hydrogenated oils and coronary heart disease (CHD). A comprehensive review of the scientific evidence confirms that eating trans fatty acids increases the risk of CHD.

The review, published in the June 24, 1999, New England Journal of Medicine, is authored by researchers at the Harvard School of Public Health and the Wageningen Centre for Food Sciences in the Netherlands.

Lead author, Alberto Ascherio, said "Coronary heart disease kills 500,000 Americans each year. According to our estimations, if trans fats were replaced by unsaturated vegetable oils, we would expect to see at least 30,000 fewer persons die prematurely from CHD each year."

Trans fatty acids are found in most margarines, in many commercially baked goods, and in the fats used for deep-frying in many restaurants. The commercial advantages trans fats hold over unsaturated vegetable oils are that they are solid at room temperature, they can remain on the shelf for a longer time before becoming rancid, and they allow for deep-frying at higher temperatures.

"Because of concerns that trans fatty acids increase risk of CHD," said Ascherio. "The Food and Drug Administration is considering new regulations for nutrition labels that will require manufacturers to report the amount of trans fatty acids."

Under current guidelines, a consumer who is trying to be heart-healthy might choose a product that is labeled as being low in cholesterol and saturated fat, but which is high in harmful trans fats.

The researchers reviewed more than 25 metabolic and epidemiologic studies. The metabolic studies showed that trans fats have a two-pronged harmful effect on blood cholesterol levels: trans fats increase low-density lipoprotein cholesterol (LDL--"bad cholesterol") and decrease high-density lipoprotein cholesterol (HDL--"good cholesterol").

The epidemiologic studies tracked people's eating habits and examined occurance of CHD later in their lives. These studies found a link between consumption of trans fats and CHD that was higher than expected from the results of the metabolic studies. "We don't fully understand all of the ways that trans fats increase risk of CHD," said Ascherio, "but it seems clear that they do increase risk."

Ascherio and colleagues urge the food industry to replace the partially hydrogenated fats used in foods and in food preparation with unhydrogenated oils: "Such a change would substantially reduce the risk of coronary heart disease at a modest cost."

Alberto Ascherio is an associate professor of nutrition and epidemiology at the Harvard School of Public Health.

See also:Trans Fatty Acids and Coronary Heart Disease, The New England Journal of Medicine -- June 24, 1999 -- Vol. 340, No. 25.

For further information, please contact:

Robin Herman
Harvard School of Public Health
Office of Communications
677 Huntington Avenue
Boston, MA 02115
Phone: 617-432-4752
Email: rherman@hsph.harvard.edu