October 2012

New reports fail to prove benefits from omega-3 supplements.

Two recent reports may cause you to have second thoughts about buying that bottle of fish-oil pills. Both published disappointing conclusions— one finding no difference between omega-3 supplements and placebo against cardiovascular disease, the other similarly negative for cognitive benefits. Unlike many of the previous studies linking fish-oil supplements to heart and brain benefits, these new reports were based on randomized clinical trials.

“There are strong data to indicate that people who consume fish are at lower risk of cardiovascular disease than people who do not consume fish,” says Alice H. Lichtenstein, DSc, director of Tufts’ HNRCA Cardiovascular Nutrition Laboratory. “This most recent trial indicates that merely adding fish oil to the diet, without changing other components, does not improve cardiovascular disease risk.”

The ORIGIN study, a large, randomized clinical trial, compared fish-oil pills with a placebo over more than six years in a range of outcomes primarily related to heart disease. Researchers tested 1,000 milligrams daily of the omega-3s DHA and EPA against a placebo in 12,536 patients with diabetes or prediabetes, average age 64.

Reporting their findings in the New England Journal of Medicine, Jackie Bosch, MSc, from McMaster University, and colleagues said that 9.1% of those in the omega-3 group died of cardiovascular causes, compared to 9.3% randomly assigned to placebo. Differences were similarly insignificant for all-cause mortality (15.1% versus 15.4%) and major vascular events (16.5% versus 16.3%). Indeed, on almost every outcome measure, there was little difference between those on the omega-3 supplements and those in the control group, including stroke, heart attack, death from arrhythmia, and heart-failure hospitalization. Other indicators, such as blood pressure and cholesterol levels, were also similar except for triglycerides, which were significantly lower in the fish-oil group.

Some previous trials have found a benefit from omega-3 supplementation. In 2000, the US Food and Drug Administration (FDA) approved a qualified health claim allowing EPA and DHA dietary supplements to boast of heart benefits. After a second review of the evidence, the FDA expanded that claim in 2004 to also cover foods high in EPA and DHA.

Bosch and colleagues speculated that the lack of an apparent benefit in their study could be because many patients were taking heart-protective medications, which could have masked any omega-3 effects.

Just days after the disappointing cardiovascular findings, a new review of the evidence for a protective benefit from omega-3s against mental decline reported no significant difference between fish-oil supplements and placebo. The analysis, for the prestigious Cochrane Review, looked at three high-quality clinical trials totaling 3,536 participants.

Some previous observational studies have suggested that omega-3s might protect against cognitive decline, and that possibility makes sense, since fatty acids play an important role in brain health. DHA is the most prominent fatty acid in the brain, especially in the neurons and synapses of the cerebral cortex—the “gray matter” responsible for memory, language and thinking.

But the new Cochrane Review, which looked instead at omega-3 supplementation in clinical trials, saw only tiny, statistically insignificant differences in performance on tests of memory, executive function and mental processing speed. One trial also used a test called the mini-mental status examination (MMSE), in which participants given omega-3s scored only 0.07 points apart from those on placebo. The trials used dosages of the omega-3s found in fish oil ranging from 400 to 700 milligrams and lasted from 6 to 40 months.

Lead author Emma Sydenham, MSc, of the London School of Hygiene and Tropical Medicine, says, “It’s important to understand the difference between observational research and randomized controlled trials. In observational studies, it’s really not possible to show cause and effect. It could be that people who eat fish or take fish-oil pills also have healthier lifestyles.”

Sydenham and colleagues could not find any randomized controlled trials of fish consumption and cognitive decline that met their standard of at least six months’ duration.

“Consumers should not be fooled into thinking that omega-3s necessarily improve cognitive health,” Sydenham adds. “It’s not a magic bullet.”

As for cardiovascular health, your best bet is to follow the recommendations of the American Heart Association and the latest Dietary Guidelines for Americans. Both advise consuming a variety of fish, preferably oily fish (such as salmon, tuna, mackerel, herring and trout), at least twice a week. Prepare fish by broiling, grilling or baking, not frying, and avoid breading and buttery sauces. Besides providing omega-3s, eating at least two weekly meals featuring fish replaces less-healthy entrées that may be high in saturated fat.

Says Tufts’ Lichtenstein, “The important point to focus on is it’s the whole diet and not just one component that can be put in a pill. I think current guidance to consume at least two fish meals per week, with the exception of battered and fried fish fillets, is still the best advice we can give people.”

TO LEARN MORE: New England Journal of Medicine, dx.doi.org/10.1056/NEJMoa1203859. Cochrane Database of Systematic Reviews dx.doi.org/10.1002/14651858.CD005379.pub3, www.cochranejournalclub.com/omega3-for-prevention-of-dementia-clinical.