Recent research into the potential benefits
of fish oil has been largely disappointing. But sales of the supplements have
continued to rise, according to a new report. "About 10% of US adults use
fish oils, most in the belief that they help heart health," study author
Dr Andrew Grey, from the University of Auckland in New Zealand, said.
He and colleague Dr Mark Bolland looked at
the results of 18 randomised controlled trials – the gold standard in medical
research – and six analyses of past trials on fish oil published between 2005
and 2012. The studies compared the risk of heart disease, cancer, thinking and
memory problems and immune, digestive and respiratory conditions among people
who were randomly assigned to take fish oil or not.
The researchers also searched for news
reports generated by the studies within two weeks of publication. They ranked
how favourably the media covered each study on a scale from 1 (very negative
toward fish oil) to 5 (very positive).
Only two studies identified a benefit from
fish oil. But most media coverage of the studies was very positive, Grey and
Bolland wrote Monday in JAMA Internal Medicine.
No benefits for heart health
For example, the researchers rated media
coverage as 4 for two 2012 studies that found no benefits for heart disease or
stroke and were each heavily covered."It's clear fish oils don't improve
heart health," Grey told Reuters Health. "People can safely
discontinue fish oil supplements, and focus on pursuing health behaviours with
"Sales of fish oil supplements in the
U.S. rose from $425 million in 2007 to over $1 billion in 2012, according to
data from Euro-monitor International, a market intelligence firm. The
supplements can be bought over the counter for a couple dollars per month.
Omega-3 fatty acids, found in fish and fish
oil supplements, are considered to be important for a healthy diet. But they
don't appear to help prevent major health problems for most people.
The World Health Organization recommends
pregnant and nursing women consume at least 300 milligrams of omega-3s daily to
help boost their baby's brain development, and no studies included in the
report refute that recommendation.
Most people don't take the supplements
based on a doctor's recommendation, Grey said. So other factors, like
commercial efforts, may influence sales. "Under certain circumstances, the
pattern of use of some medicines or food additives tends to have a poor
relation with the evidence provided by clinical trials," Andrea Messori
told Reuters Health.
Messori, of Regional Health System in
Prato, Italy, authored a paper this year on fish oil and heart disease, which
found no benefit. He was not involved in the new report.
It's tough to figure out why evidence and
practice don't always align, he said.
Grey agreed that fish oil is not unique
among supplements. "Vitamin D is another supplement for which clinical
trial evidence of lack of efficacy has been accruing for some time, yet it
remains very widely used and very profitable for those who sell it," Grey