- NEW YORK - High intake of trans fatty acids - fats found
in many margarines - may be linked with elevated cholesterol, according
to results of a new study. But experts point out that the average US consumer
has no way of knowing which food products contain the highest amount of
these unhealthy fats.
- "Many scientists agree that the
amount of trans fatty acids should be stated on food labels," write
a group of experts led by Dr. Alberto Ascherio of the Harvard School of
Public Health in Boston, Massachusetts. Their comments and the study are
published in the June 24th issue of The New England Journal of Medicine.
- Most margarines are derived from vegetable
oils. These oils are 'hardened' by a process known as hydrogenation, which
makes them less likely to become rancid. But this process also raises their
trans fatty acid content. Studies have linked dietary trans fatty acids
to raised levels of blood fats linked to cardiovascular disease.
- In a study led by Dr. Alice Lichtenstein
of Tufts University in Boston, researchers supplied 36 men and women over
50 years of age with diets in which 30% of food energy was derived from
fats. Depending on the diet consumed, two thirds of this fat came from
either soybean oil, semiliquid ('squeeze-bottle') margarine, soft margarine,
shortening, stick margarine, or butter. The blood cholesterol level of
each subject was measured by researchers 35 days into the diet.
- The authors found that blood levels of
total and LDL ('bad') cholesterol "were lowest after subjects consumed
the soybean-oil and semiliquid-margarine diets." In fact, individuals
who consumed soybean oil saw their levels of total blood cholesterol fall
by 12% from pre-diet levels.
- In contrast, blood cholesterol levels
were highest in subjects placed on butter and stick-margarine diets, with
soft-margarine and shortening prompting more moderate (but still significant)
gains in cholesterol. Stick-margarine and butter also ranked first and
second, respectively, in lowering blood levels of HDL, the 'good' cholesterol
linked to a reduced risk of heart disease.
- "Our results suggest that both the
general public and patients with (high blood cholesterol) should be encouraged
to use vegetable oil in its natural state or after minimal hydrogenation,"
Lichtenstein and colleagues conclude.
- In their commentary, Ascherio and his
colleagues point out that the average US consumer derives just "25%
- 37% of daily trans fatty acid from hydrogenated vegetable oils... from
margarines," with the rest coming from "baked goods, fried fast
foods, and other prepared foods." The food industry could easily switch
over to the use of oils low in trans fatty acids, they say, but this switch
may need to be "encouraged by a change in federal regulations."
- The editorial writers note that "food
labels are not required to include the amount of trans fatty acids."
This includes fast foods, most of which are high in trans fatty acids.
- Nutritionist Dr. Chris Rosenbloom, a
spokesperson for the American Dietetic Association, said the study is important
because until now "we really haven't been sure what the effects of
trans fatty acids were on humans."
- In an interview with Reuters Health,
Rosenbloom advised that, in general, the harder the consistency of margarine
"the more trans fats it probably has." The best options, she
believes, "would be the liquid sprays or the squeezable kinds,"
or (better yet) "making your own blend with a liquid oil, something
like an olive oil that you might add some herbs to."
- Rosenbloom agrees with Ascherio's team
of experts that trans fatty acid content data should be included on food
nutrition labeling. As it stands now, she said, "a consumer who is
trying to monitor their cholesterol and monitor their food safety doesn't
know if they're getting trans fats by reading food labels."