Fish oil supplements did not prevent heart problems in
people who hadn't had a heart attack yet, in a large long-term study from
Italy. The study - a gold-standard randomized, controlled trial - tested the
effect of omega-3 fatty acids, which are found in oily fish such as tuna or
Patients in the study had risk factors for heart disease,
such as high blood pressure, high cholesterol, a history of smoking or narrowed
arteries. But patients who had a heart attack in the past weren't allowed to
Five years after the study began, 11.7% of the 6 244
patients taking a capsule containing one gram of fish oil daily had died or
been hospitalized for heart problems, compared to 11.9% for the 6 269
volunteers who instead received one gram of olive oil every day as a placebo.
Omega-3 good for
heart attack survivors
The result, reported in the New England Journal of Medicine, is in sharp contrast to other research suggesting that omega-3
fatty acids can help those who have survived a heart attack or suffer from
For people who haven't had a heart attack, though, the new
findings "provide no evidence of the usefulness of (omega)-3 fatty acids
for preventing cardiovascular death or disease," according to the research
team, led by Dr Maria Carla Roncaglioni of the Mario Negri Institute for
Pharmacological Research in Milan.
She said that the finding argues
against the use of fish oil supplements, at least among Italians, who are
already exposed to the Mediterranean diet. "There is no reason to
prescribe fish oil supplementation unless they have a heart attack," she
Reduction in hospital
The researchers did see a reduction in hospital admissions
for heart failure and a preventive effect in women, but "both may be due
to chance, although they are consistent with two findings from other
studies," the researchers said.
Alice Lichtenstein, from Tufts University in Boston and a
spokeswoman for the American Heart Association, told Reuters Health the
findings from the new study are further evidence that, in general, "just
giving a supplement on top of a non-heart-healthy lifestyle doesn't seem to
"We thought vitamin E pills were going to be the answer
and that turned out to be wrong. We though beta carotene as an antioxidant was
going to reduce cardiovascular disease . . . and that pill didn't work,"
she said in a telephone interview. "It's the whole package, not just
popping one pill." The patients in the Italian study were treated by 860
general practitioners throughout the country. Their average age when they
enrolled in the study was 64 years old.
Researchers looked at
Originally, the researchers had thought the main goal of
their study would be to see how many people died or had a heart attack or
stroke. But those events turned out to be less common than expected, probably
because the patients "were rather intensively exposed to recommended
preventive treatment (including healthy lifestyle habits) by their family
physicians," Roncaglioni said.
Thus, the goal of the study was modified to count anyone who
died or was admitted to the hospital for a heart-related cause. Certain factors
did seem to improve slightly more in the fish oil recipients, such as levels of
fat and "good" cholesterol in the blood.
But other measures such as "bad" cholesterol,
blood pressure and blood sugar remained similar in the fish oil and olive oil
groups, and there was no difference in the proportion of patients in the two
groups who needed heart medications. Roughly two of every 100 patients died of
heart disease, regardless of which group they were in.
10 of every 100
And roughly 10 of every 100 patients in each group needed to
be hospitalised for a heart-related problem. By the end of the study, 18% had
stopped taking their fish oil and 19% had stopped taking their olive oil. When
those volunteers were excluded from the study, there was still no significant
difference between the groups in the risk of death or hospitalization for heart
The rates of gastrointestinal side effects, cancer and
bleeding were comparable in the two groups. The US Food and Drug Administration
says olive oil has heart benefits of its own. Is it possible that using olive
oil as the placebo in this study skewed the results by protecting the placebo
group to some extent? Roncaglioni doesn't think so.
She said giving olive oil as a placebo probably did not
bring down the overall rate of heart problems in that group because "one
gram of olive oil corresponds to only 1/30th of the mean amount consumed in the
Mediterranean diet," which would make it of very small benefit.