“Fish oil delivers few benefits, study finds,” reported ABCNews.com in April 2012.
The news was a meta-analysis by Korean scientists of 14 trials conducted on more than 20,000 people that showed that fish oil was no better than a placebo at preventing a second heart attack, stroke, or other cardiovascular event. The meta-analysis came on the heels of other disappointing studies.
“The Korean meta-analysis looked at only placebo-controlled trials, which excluded the large-scale GISSI and JELIS trials,” notes JoAnn Manson, chief of preventive medicine at Brigham and Women’s Hospital in Boston, who co-wrote an editorial that accompanied the meta-analysis.
Most advice to take fish oil relies heavily on GISSI (Gruppo Italiano per lo Studio della Sopravvivenza nell’Infarto Miocardico) and JELIS (Japan EPA Lipid Intervention Study) because they were so large.
“But even when the meta-analysis included those trials, it didn’t see clear evidence for a benefit,” adds Manson. Why?
“One reason is that the more recent trials in the meta-analysis were small and short duration,” she explains. “Many were only one to two years, which is too short to see benefits for atherosclerosis.”
Another reason: “The management of people with a history of heart attack, stroke, or other cardiovascular events has improved tremendously in the past couple of decades,” Manson notes.
“Many of these people are on high-dose statins, aspirin and other anti-platelet medications, ACE inhibitors, and other medications.”
So taking fish oil with those drugs doesn’t add much. “The medications are working through similar pathways as fish oil—decreasing lipids, clotting, and inflammation,” says Manson. “So it’s possible that the improved treatment of heart disease is obscuring the benefits of omega-3s.”
It’s also harder to see a difference between the placebo and fish-oil takers because both have fewer heart attacks than they used to.
But fish oil may help people who have not had a heart attack.
“Omega-3s may still have a benefit for a population that’s not high risk where the use of statins and aspirin and other anti-platelet medications is relatively infrequent,” says Manson.
Her Vitamin D and Omega-3 Trial (VITAL) is testing 1,000 mg a day of the two major fish oil omega-3s, EPA and DHA, on men aged 50 and older and women aged 55 and older with no history of heart disease or stroke.
“In VITAL, fewer than half of the participants are using statins or aspirin,” notes Manson. In contrast, roughly 80 percent of people who have had a heart attack are taking statins, and nearly all use aspirin.
The study will look at far more than heart disease.
“We now have 14 ancillary studies,” says Manson. “In addition to looking at cancer and cardiovascular disease—the trial’s main goal—we’ll be looking at diabetes, memory loss, depression, atrial fibrillation, cardiac function, bone health, fractures, falls, knee pain, asthma, and autoimmune conditions like thyroid disease, rheumatoid arthritis, and lupus.”
What to do until the results are out, which is likely to be 2017?
“Go ahead and eat two or more servings of fish a week,” suggests Manson. “Not only has fish intake been linked to a reduced risk of cardiovascular disease in many populations, it often replaces less healthy sources of protein in the diet such as red meat.”
But fish oil capsules? “The jury is still out,” says Manson. “The early evidence was promising for secondary prevention, but now with better treatments, there may be only a small incremental benefit. But it’s still appropriate to treat very high triglyceride levels” with fish oil capsules.
For people who haven’t had a heart attack, it may be a completely different story. “We’re still holding out hope that omega-3s will have benefits for preventing first cardiovascular events,” says Manson.
The Bottom Line: Eat fish at least twice a week. For people who have already had a heart attack or stroke and are on medication, taking fish oil may not help. For others, the jury is still out.
Sources: Arch. Intern. Med. 172: 686, 2012. N. Engl. J. Med. 2012. DOI:10.1056/NEJMoa1203859. N. Engl. J. Med. 363: 2015, 2010. Arch. Intern. Med. 172: 694, 2012. Lancet 354: 447, 1999. Lancet 369: 1090, 2007.