Trans Fats, Heart Risk: 'Strong' Link
Researchers Say Findings Justify Move to Reduce Trans Fat in U.S. Diet
March 26, 2007 -- New research offers some of the strongest evidence yet
linking artery-clogging trans fats to heart disease.
In a study of female nurses, women with the highest levels of trans fats in
red blood cells from stored samples had triple the risk of developing heart
disease compared with women with the lowest levels.
Higher trans fat levels were associated with elevated "bad" LDL
cholesterol and lower "good" HDL cholesterol. But the study's
researcher tells WebMD that this did not fully explain the impact of trans fats
on heart disease risk.
"We definitely believe that other mechanisms are involved, but we were
only able to look at cholesterol," says Frank B. Hu, MD, PhD, of the
Harvard School of Public Health.
"This research shows that trans fats are a very strong risk factor for
coronary heart disease, and it serves to justify current efforts to get trans
fats out of the American diet."
Banning Trans Fats
Those efforts include bans or considered bans on the use of trans fats in
restaurant food in major cities like New York, Philadelphia, and Chicago, and
pledges from a growing number of fast-food restaurant chains to make their
products trans-fat free.
Trans fats are formed when liquid vegetable oils are converted into solids
through a process called hydrogenation. Hydrogenated or partially-hydrogenated
oils are used to increase the shelf life of foods and to improve their
They are most often found in fried foods, vegetable shortenings, hard
margarine, and processed cookies, crackers, baked goods, and chips.
The newly published investigation included 32,826 women participating in the
larger Nurses' Health Study, an ongoing trial examining lifestyle and disease
risk in women followed since 1976. All of the women in the trans fat study
contributed blood samples between 1989 and 1990.
During six years of follow-up, 166 of the women developed coronary heart
disease. The researchers compared trans fat levels in the stored blood samples
of these women with samples from 327 women who did not develop heart
After adjusting for age, smoking status, and other known heart disease risk
factors, higher total trans fat levels in red blood cells were found to be
associated with an increased heart disease risk.
Women with the highest blood levels of trans fats were three times as likely
to develop coronary heart disease as women with the lowest levels.
Although the investigation included only women, Hu says there is no reason
to believe that the risk would be any different for men.
The study will be published in the April 10 issue of the American Heart
Association journal Circulation.
Good and Bad Fats
The American Heart Association (AHA) recommends limiting trans fats to no
more than 1% of total calories and saturated fats to less than 7% of total
Saturated fats are also bad because they increase total cholesterol levels
and bad LDL levels.
While there is some suggestion that trans fats are more dangerous than
saturated fats, AHA immediate past president Robert Eckel, MD, says both are
associated with an increased risk of heart disease.
The major sources of saturated fats in the diet are meat, poultry, whole-fat
dairy products, and butter. Some tropical oils such as palm and coconut oil are
also high in saturated fats.
Monounsaturated and polyunsaturated fats, such as those found in nuts, fish,
olive oil, and most other liquid vegetable oils, are better fat choices, Eckel
"Replacing trans fats with saturated fats would do little good," he
tells WebMD. "People should avoid trans fats whenever possible and they
should choose healthier fats."
Hu adds that the movement to eliminate or lower trans fat levels in the
foods Americans eat should have a positive impact at the population level.
"Eliminating the use of partially hydrogenated oils and other sources of
trans fats in the U.S. diet -- as long as saturated fat intake doesn't increase
-- will likely help reduce the burden of cardiovascular diseases," he