People who increased their fish consumption to brighten their outlook on life may want to consider alternative strategies. A new review of published studies on the effects of long-chain omega-3 fats—the type found in fish oils—finds "little support" that they "improve depressed mood." However, that's no reason to give up eating fish. Their fats have been linked to a host of health benefits, mainly cardiovascular.
For more than a decade, there had been indications that fish oils might help people shed brooding dispositions (See Got Them Low-Fat, Polyunsaturated Blues). Katherine M. Appleton of Queen's University in Belfast, Ireland, and her colleagues at the University of Bristol identified 18 controlled clinical trials since 1999 that were designed to probe such apparent links—either as a primary or ancillary focus of the study.
Some studies had recruited only men, others only women. A number included both sexes, and one focused solely on children. The studies lasted from 1 to 6 months, and the number of people treated tended to be small. None included more than 452 volunteers, and most had just 11 to 80. Although one study administered fish, the rest dispensed as capsules of the long-chain fatty acids found in fish oil—types known as EPA and DHA.
The researchers note one major limitation of their new study: Assessing trends was made tougher by the fact that roughly a third of the trials lacked sufficient statistical data for outsiders to confirm the significance of any symptoms of depression.
After examining all of the studies closely and accounting for possible publication bias—findings from small studies that might have turned up indications of some positive effect—Appleton's group concludes that overall, "there is little evidence of a beneficial effect" of these fish fats on depression.
Reporting in the December 2006 American Journal of Clinical Nutrition, Appleton and her coworkers don't rule out that fish fats might be beneficial psychologically. Indeed, they report finding some evidence from a subset of the analyzed studies that fish oils might prove therapeutic. These particular studies had recruited only individuals diagnosed with severe depression.
However, to have the statistical power to confirm trends even in these populations would probably take at least 100 people in both the treatment and placebo arms of the trial. This criterion was met by only one of the 18 studies reviewed by the researchers. And this particular study focused not on patients with major depression but on those suffering from angina.
Katherine M. Appleton
School of Psychology
Queen's University, Belfast
18-30 Malone Road
Belfast BT9 5BP
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