DALLAS, April 1 - Eating fish regularly reduced the risk of heart
disease in
diabetic women by as much as 64 percent, according to study reported in
today's rapid access issue of Circulation: Journal of the American
Heart
Association.
"We found that women with type 2 diabetes who ate more fish had
significantly lower risk of coronary heart disease and total death than
those who rarely ate fish," says Frank B. Hu, M.D., lead author and
associate professor of nutrition and epidemiology at the Harvard School
of
Public Health in Boston. "Previous studies have found that fish
consumption
reduces risk of heart disease in a largely healthy population. This is
the
first study to look at the relationship among diabetic patients, who
have
very high risk of heart disease."
The American Heart Association recommends that adults, except pregnant
women, eat two servings of fish a week. For those with, or at high risk
of
cardiovascular disease (CVD), supplementing fish in the diet with fish
oil
capsules may be advisable in consultation with a physician.
Also known as fish oil, omega-3 fatty acids from fish have been shown
to
reduce the risk of irregular heartbeats that can lead to sudden death,
decrease blood triglyceride levels, improve the functions of blood
vessels
and reduce blood clot formation. These effects are particularly
important
for reducing risk for CVD among diabetics.
Even so, little data were available to confirm that diabetics who ate
fish
would receive the same benefits as people without diabetes who ate
fish, Hu
says. In addition, there was concern that fish oil might worsen control
of
blood sugar (glucose) among diabetic patients.
Hu and colleagues analyzed data from women with diabetes participating
in
the Nurses' Health Study, which was established in 1976 when 121,700
female
registered nurses completed a questionnaire about their medical history
and
lifestyle. Every two years, follow-up questionnaires have been mailed
to
update information on risk factors and any new health problems. The
current
study includes 5,103 women who reported physician-diagnosed type 2
diabetes
on any questionnaire from 1976-94. Women with a history of heart
disease,
stroke or cancer reported on the 1980 questionnaire (when diet was
first
assessed) or before were excluded.
The women were divided into five categories according to how often they
ate
fish: less than once a month, one to three times a month, once a week,
two
to four times a week, and five or more times a week.
Between 1980-96, the researchers documented 362 cases of heart disease
(141
heart-related deaths and 221 nonfatal heart attacks). There were 468
deaths
overall. Diabetic women who ate fish at least once a month were older,
slightly heavier, typically didn't smoke, tended to have hypertension
and
high cholesterol, and took multivitamin and vitamin E supplements.
Those who
ate more fish also ate more fruits and vegetables but ate less red and
processed meats.
Compared with diabetic women who seldom ate fish (less than once a
month),
the risk of developing heart disease was reduced on average by 30
percent in
those who ate fish one to three times a month, 40 percent for those who
ate
it once a week, 36 percent in those who ate fish two to four times a
week,
and 64 percent in those who ate fish five or more times a week. Higher
fish
consumption was also associated with a significantly lower death rate.
Hu says that the association between higher fish consumption in
diabetic
women and better heart health can also be extended to diabetic men
based on
similar findings in studies of healthier men and women.
"One limitation of this study is that it is not a randomized clinical
trial," Hu says. "Thus, the benefits we observed for fish may be due to
other dietary and lifestyle factors related to fish intake." Even so,
Hu
says their findings are solid because of their "careful adjustment for
many
important cardiovascular risk factors.
"Regular fish consumption should be considered as part of a healthy
diet for
diabetes management," Hu says. "For individual patients, at least two
servings of fish per week is recommended."
Fatty fish such as mackerel, lake trout, herring, sardines, albacore
tuna
and salmon are high in omega-3 fatty acids.
An accompanying editorial by Scott M. Grundy, M.D., director of the
Center
for Human Nutrition at the University of Texas Southwestern Medical
Center
at Dallas, provides a review of the current status of research on
omega-3
fatty acids in fish, plants and supplements.
Grundy says Hu's research supports previous prospective epidemiological
studies that found omega-3 fatty acids offer protection against CVD.
However, he urges that clinical trials of omega-3 fatty acids after a
heart
attack be conducted to determine if they can reduce coronary deaths in
the
short term.
Hu's co-authors are Eunyoung Cho, Sc.D.; Kathryn M. Rexrode, M.D.;
Christine
M. Albert, M.D.; and JoAnn E. Manson, M.D. The study was partly funded
by
the National Institutes of Health and the American Heart Association.
