A recent study in the British Journal of Nutrition (Rogers, Appleton et al. 2008) throws doubt on the value of fish oil supplementation as a treatment for depression. The authors stated " ... while a majority of previous trials have focused on individuals with severe depression in clinical settings and have mostly administered high amounts of n-3 LCPUFA (n-3 long-chain, poly-unsaturated fatty acids), the present trial was concerned with investigating possible benefits in mild to moderate depression of an intake of n-3 LCPUFA that many in the general population might attain by appropriate changes in diet, supplement use or both." Participants were given fish oil supplements containing 630mg of EPA (eicosapentaenoic acid) and 850mg DHA (docosahexaenoic acid) or a placebo containing olive oil. Three months' intervention appeared to produce no worthwhile benefit.

These negative results are well worth contrasting with a recent careful review of fish oils and depression (Sontrop and Campbell 2006). The authors looked at a number of different facets of the fish oil/depression relationship. When considering seven double-blind randomized controlled trials of omega-3 PUFA supplementation for depression sufferers, they wrote "There are a few important differences between the four positive trials and the three null trials. First, participants in the positive trials received antidepressant or mood stabilizing medications concurrently to treatment with EPA and/or DHA, whereas participants in two of the three null trials did not. This is a very important difference and also makes it impossible to discern whether treatment with EPA and/or DHA exhibited effects independent of antidepressant treatment or acted as an adjuvant. The second important difference is that each of the positive trials administered a minimum EPA dose of 1 g/day, alone, or in combination with DHA . This is in contrast to the null trials, which administered DHA alone or low dose EPA (0.6 g/day) in combination with DHA. Future research should further refine dosage efficacy and examine whether treatment with EPA alone or the combination of EPA and DHA is more effective."

The take away messages, for now, seem to be that fish oil supplementation for depression should use at least 1 gm per day of EPA (and any associated DHA) and that supplementation may work best when taking standard antidepressants as well. I'll look at the many other benefits of eating fish/taking supplements and at safety issues soon in another post.

Rogers, P. J., K. M. Appleton, et al. (2008). "No effect of n-3 long-chain polyunsaturated fatty acid (EPA and DHA) supplementation on depressed mood and cognitive function: a randomised controlled trial." Br J Nutr 99(2): 421-31. [PubMed]
Sontrop, J. and M. K. Campbell (2006). "Omega-3 polyunsaturated fatty acids and depression: a review of the evidence and a methodological critique." Prev Med 42(1): 4-13. [PubMed]