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.