St. John's Wort, several B vitamins and fish oil, particularly the omega-3 polyunsaturated fatty acid it contains, may be effective in alleviating the symptoms of depression, according to a review study conducted by Australian researchers. The study, carried out by researchers at the University of Sidney, analyzed literature on depression to determine how diet may influence mood, with 103 sources cited.

Dr. Diane Volker and Jade Ng write in the journal Nutrition and Dianetics that there is a great deal of epidemiological, experimental and circumstantial evidence that suggest omega-3 polyunsaturated fatty acid is protective against depression.

The study shows that the Inuit of Greenland, who eat a lot of cold-water fish, have almost non-existent rates of depression, although the researchers point out that social and environmental factors can contribute to the illness

Although the researchers say they found the most support for omega-3 fatty acids being effective in fighting depression, they also cite support for tryptophan, vitamins B6, B12, folate and S-adenosyl-L-methionine (SAMe).

The researchers also say that although St. John's Wort has not been shown to have anti-depressant effects in U.S. studies, European studies suggest that it does. They say the discrepancy may be due to the herb's interaction with other medications.