Salmon, rich in fats that may improve mood in mild depressives.

Salmon, rich in fats that may improve mood in mild depressives.(ELISABETH COLFEN)Overfed and overweight, it seems unlikely that most Americans would be deficient in fat. But there is one we are missing: omega-3 fatty acids, which are found in fish, flaxseed, and some nuts. It is thought that this deficiency may cause or worsen depression in some people.

Western diets have changed drastically over the past 150 years, during which the ratio of fats from fish and wild plants to those from animal and vegetable oil sources, especially in processed foods, has gone from 1:1 to 1:10. This switch has coincided with a sharp rise in the rates of depression in recent decades, suggesting that omega-3 supplementation could be one approach to treating depression and other mood disorders.

"By taking in more omega-3s, we're essentially re-equilibrating the ratio," says David Mischoulon, MD, a professor of psychiatry at Harvard Medical School.

Eating more fish helps SAD
Studies suggest that populations that eat more fish per capita, such as Japan (147 pounds a year) and Iceland (225 pounds a year), have unexpectedly low rates of seasonal affective disorder.

While researchers don't recommend omega-3s as a first-line treatment for anyone with major depression or bipolar disorder, emerging research suggests it may be effective for people with mild depression or as an adjuvant to medication. Omega-3 supplements affect the brain through a different mechanism than antidepressants, so adding them to an antidepressant regimen is "attacking the illness from a different front," according to Dr. Mischoulon.

The impact of omega-3s seems to vary by the type of depression. Studies of patients taking medication for major (or unipolar) depression have found that 1 to 2 grams a day of an omega-3 supplement led to a measurable reduction in symptoms. The benefits to patients with bipolar depression are less clear, however. While fish oil has been shown to prevent relapse and alleviate depressive symptoms in some bipolar patients, it appears to have no effect on the manic episodes associated with the condition.

Next Page: Omega-3s and postpartum depression [ pagebreak ]Omega-3s and postpartum depression
Though studies have yet to confirm it, one promising use of omega-3s may be the treatment of postpartum depression. Evidence shows that women who develop postpartum depression tend to have an omega-3 deficiency, and because pharmaceutical antidepressants can be harmful to the fetus and child (through breast-feeding), physicians are hopeful that omega-3s will prove to be an effective preventive treatment during pregnancy.

Much is still unknown about the link between omega-3 fatty acids and depression, but in the meantime, adding these fats to your diet can't hurt. (An important exception: people with certain blood conditions, especially those taking blood thinners.)

How to get omega-3s in your diet
The best way to get omega-3s is directly from the source (foods such as salmon, halibut, and walnuts), but fish-oil- and flaxseed-oil-based supplements are also available in both capsule and liquid form. Experts recommend taking anywhere from 0.5 to 2 grams a day, although the FDA warns that the daily intake of omega-3 fatty acids from all sources should not exceed 3 grams.

But people experiencing symptoms of depression shouldn't rely solely on omega-3s for relief. "This is still a relatively unproven treatment for mood disorders," says Dr. Mischoulon. "For general health purposes, people can proceed on their own with a supplement. But if you're looking to treat depression—even occasional depression—getting a psychiatric evaluation and proceeding under a physician's supervision is the most prudent way to go."