Any regular reader of my blog will know that there is strong evidence that consumption of omega3 fatty acids, particularly fish oil, is really important for proper brain function. A paper from this summer highlights the issue at hand (and is pertinent to 11/11 - Veteran's Day in the United States): Suicide Deaths of Active Duty US Military and Omega-3 Fatty Acid Status: A Case-Control Comparison.

This paper reports on an observational study, meaning we can only see correlations, not determine causation.  It is large for a suicide study (suicide is rare enough and multifactorial enough that finding statistical risk factors to make it easier to predict and prevent is actually pretty difficult). All told, 800 randomly selected suicide victims in the armed services between 2002-2008 were picked and compared to 800 matched controls. Cases were matched for time and theater of deployment, exposure to stress during deployment, report of mental health status, and demographics among other data points.  The paper says 99.1% of the controls had been deployed vs. only 61.9% of the suicides.

Fatty acid content of the blood of the participants were measured, and the lower the DHA (a type of fish oil) in the blood, the more likely the person was to have committed suicide. The relationship was linear and true of all octiles studied. There were only 70 women in the samples, and they tended to have higher DHA levels than the men, and lower suicides (among women, the omega 3 status to suicide relationship was not statistically significant as it was clearly so among the men). Men in the lowest DHA octile were 62% more likely to commit suicide than those in the highest octile.

Other fatty acids of interest - lower levels of stearic acid (a saturated fat found in chocolate! And steak!) were found to be associated with increased risk of suicide. My preliminary conclusion - eat more chocolate - though of course this data cannot prove causality, seems like a harmless intervention.  Also, I should probably tell you that stearic acid is almost immediately converted to oleic acid (a monounsaturated fat, the primary component of olive oil) in the body. Higher palmitoleic acid (a monounsaturated acid made from the saturated palmitic acid) levels also correlated with a lower level of suicide risk.

In this study, US military personnel were found to have, on average, a lower DHA level than average North American, Australian, Mediterranean, and Asian populations (unlike the medical students I wrote about yesterday, who had higher levels than the general population). In fact, among Chinese suicide attempters, nearly all of them had higher levels of omega 3 DHA than the highest octile of the US military personnel studied. And when both populations were studied together, the lowest DHA levels coincided with a 5-6 fold increased risk of suicide. For perspective, this risk increase coincides with the risk of undergoing severe stress under deployment (seeing wounded, killed, or dead comrades, for example) and the risk of suicide.

The observational nature of the study doesn't allow us to make too many solid conclusions, but it fits with other observational and controlled trials with regards to depression and makes physiologic and evolutionary sense.  Eat those marine omega3s and keep your 6:3 ratio minimal. The paper recommends 2 grams daily of marine omega 3s. Seems reasonable.

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Copyright Emily Deans, M.D.

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