WEDNESDAY, May 22 (HealthDay News) -- Fish oil supplements could
help reduce the risk for type 2 diabetes, new research
The supplements, also known as omega-3 fatty acids, increase
levels of a hormone called adiponectin that's linked to insulin
sensitivity, Harvard researchers found. Higher levels of this
hormone in the bloodstream have also been linked to a lower risk
for heart disease.
"While prior animal studies found fish oil increased circulating
adiponectin, whether similar effects apply in humans is not
established," the study's lead author, Jason Wu, from the Harvard
School of Public Health, said in a news release from the Endocrine
For their study, the researchers conducted a "meta-analysis" of
14 clinical trials. A meta-analysis reviews existing research and
attempts to find a consistent pattern. In this case, the studies
that were reviewed were all randomized, placebo-controlled trials,
which is considered the gold standard in research.
"By reviewing evidence from existing randomized clinical trials,
we found that fish oil supplementation caused modest increases in
adiponectin in the blood of humans," Wu explained.
Overall, the new study looked at 682 people who took fish oil
supplements, and 641 who were given placebos such as sunflower or
Among the people treated with fish oil, adiponectin levels
increased by 0.37 micrograms per milliliter of blood. This hormone
plays a beneficial role in processes that affect metabolism, such
as blood sugar regulation and inflammation.
Because the effects of fish oil varied significantly in the
studies analyzed, the researchers suggested that omega-3 fatty
acids could have a stronger effect in certain groups of people. The
investigators concluded that more research is needed to determine
which people would benefit most from fish oil supplements.
"Although higher levels of adiponectin in the bloodstream have
been linked to lower risk of diabetes and coronary heart disease,
whether fish oil influences glucose [blood sugar] metabolism and
development of type 2 diabetes remains unclear," Wu said.
"However, results from our study suggest that higher intake of
fish oil may moderately increase blood level of adiponectin, and
these results support potential benefits of fish oil consumption on
glucose control and fat cell metabolism," he added.
But the association does not prove a cause-and-effect
relationship between fish oil supplementation and decreased
Roughly 37 percent of adults and 31 percent of children in the
United States take fish oil supplements, according to a 2007 survey
by the National Institutes of Health's National Center for
Complementary and Alternative Medicine.
The study is scheduled for publication in the
Journal of Clinical Endocrinology & Metabolism. It was
supported by grants from the National Institutes of Health's
National Heart, Lung, and Blood Institute.
The U.S. National Library of Medicine has more about
fish oil supplements.