Editors' note: The October issue of Functional Ingredients magazine includes an assessment of the overall market for omega-3s.

In a time of national and global recession, it perhaps shouldn't come as a surprise that the top-selling dietary supplement formulas in the past year have been those marketed for depression.

According to SPINS, sales in the combined natural and FDM channels (excluding Whole Foods and Wal-Mart) totalled $354.68 million during the 52 weeks ending May 15. This represents a 16.8% increase over the same year ago period.

Just what are the most promising anti-depressive nutrients to take? Since January 2010, more than a dozen studies have come out documenting the benefits of everything from vitamins D and B, to zinc, to red clover, to folate. Of course the old standby, St. Johns Wort, is still popular too.

But one of the most interesting new ideas in the treatment of depression became public on June 15, with the publication of the largest study ever conducted on the ability of omega-3s to treat major depression.

Published in the online Journal of Clinical Psychiatry, the study was a joint effort by Canadian researchers at four universities, involving patients at eight clinics.

From October 2005 to January 2009, 432 men and women with major unipolar depression were recruited to take part in this randomised, double-blind study. For eight weeks, half took three capsules per day of OM3 Emotional Balance, a fish oil supplement with 1050mg of EPA and 150mg of DHA. The other half took three identical capsules of a placebo consisting of sunflower oil, flavoured with a small quantity of fish oil.

The study included a high proportion of patients with complex and difficult-to-treat conditions, including patients resistant to conventional antidepressant treatments, and patients also suffering from an anxiety disorder.

The findings showed that for those patients who also had an anxiety disorder, the benefits to omega-3 supplementation were negligible. But for those without an accompanying anxiety disorder, there was a "clear benefit" in the supplement.

The supplement used in the study, OM3 Emotional Balance, has been sold in Europe since 2003, and been available in Canada since 2006, by Paris-based company isodisnatura. According to the company website, its fish oil is sourced from sardines and anchovies off the coasts of Peru; the company declined a request by FI to reveal who its fish-oil supplier is.