Recent studies may have put the kibosh on three common health claims made for fish oil (omega-3) supplements:
1. No, for preventing age-related cognitive decline.
It has been proposed that “fish is brain food” and that its omega-3 fats, in particular, can help maintain brain health, but clinical trials testing this with fish oil supplements have produced inconsistent (mostly disappointing) results.
The latest study, in the American Journal of Clinical Nutrition, gave 390 cognitively healthy Australians (ages 65 to 90) capsules containing either omega-3s (2,300 milligrams a day, the amount in about 4ounces of salmon) or olive oil (the control group). After 18 months, cognitive testing found that treatment with omega-3s did not help participants maintain or improve cognitive performance.
In fact, the omega-3 group had slightly worse performance in some tests than the control group.
2. No, for treating dry eyes.
Over the years, some doctors and even the American Academy of Ophthalmology have recommended fatty fish or omega-3 supplements for dry eyes based largely on observational studies linking high dietary intake of omega-3 fats to reduced risk, small clinical trials on the supplements, and theories about how omega-3s might ease symptoms (for instance, by reducing inflammation).
But a well-designed, NIH-funded clinical trial in the New England Journal of Medicine called this into question. It involved 349 people with moderate to severe dry eyes not responding to other treatments, half of whom took 3,000 milligrams of omega-3 capsules a day, half a placebo (olive oil capsules).
After a year, the two groups did not differ significantly in terms of various eye-related signs and symptoms. In fact, both groups had improvements, suggesting that, as in other clinical trials of treatments for dry eyes, “the placebo effect was substantial,” the researchers noted, and that in some people the condition simply gets better over time.
3. No, for preventing cardiovascular events in people with prior coronary heart disease (such as a heart attack) or strokes.
An analysis in JAMA Cardiology focused on 10 large clinical trials, which tested 400 to 2,500 milligrams of omega-3s a day in high-risk people for an average of four years, and found that the supplements did not reduce the risk of another cardiovascular event.