By Kathryn Doyle
NEW YORK (Reuters Health) - 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 percent of U.S. 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 randomized 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 favorably 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.
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 behaviors with proven efficacy."
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 Euromonitor 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 said.
SOURCE: http://bit.ly/IZGqPC JAMA Internal Medicine, online December 16, 2013.