Omega-3 Intake and the Brain

Summarized by Robert W. Griffith, MD
May 8, 2006

Introduction

People are paying a lot of attention to omega-3 fatty acids these days. In particular, it's the ratio of omega-3 to omega-6 fatty acids that's often implicated as having protective effects against cancer, heart disease, Alzheimer's, diabetes, and other conditions. But there's another area of interest, which NIH scientists have been exploring in the last decade. It concerns the influence of omega-3 and omega-6 intake on the level of violence people express - as represented by the homicide rate. Here's a summary of a study reported in the medical journal Lipids in 2004.

What was done

The purpose of the study was to examine a possible association between homicide rates in different countries and their average consumption of seed oils - the dominant source of omega-6 linoleic acid. The countries involved were Argentina, Australia, Canada, UK, and USA.

Data on age-adjusted homicide mortality for the years 1961 to 2000 were obtained from the appropriate authorities in each country. The amount of linoleic acid consumed, expressed as percentage of total calories consumed, was calculated from WHO economic data for the same period for each country. Changes in the data examined, which reflected changes for the whole population of each country, were measured at different time points.

What was found

Greater consumption of linoleic acid correlated with higher rates of homicide for each country over time. Thus in the USA linoleic acid consumption ranged from a low of around 5% in 1961 up to a high of about 8.3% in 1998; the homicide rate for 1961 was around 4.5 per 100,000, and for 1998 about 9 per 100,000. In the UK, values in 1961 were 1.25% linoleic acid and 0.5 per 100,000 homicides, and in 2000 they were 4% linoleic acid and 1.4 per 100,000 homicides. Similar correlations were seen for the other 3 countries.

Combining the results from all countries and all time points led to an overall correlation of greater linoleic intake with a higher homicide rate that was highly significant over a 20-fold range.

What this means

The study investigators say that these results "suggest, but do not demonstrate, that increased availability of linoleic acid might be a causal factor contributing to the increased rates of homicide during the last half of the 20th century among these five countries". They point out that other, well-established factors would have to be measured and adjusted for in any future studies of this apparent association; however, they don't believe that the availability of firearms would be one of these so-called 'confounding' factors, based on published studies.

Another relevant study

A British study published in 2002 provides some corroboration for the role of omega-3 fatty acids in antisocial and violent behavior¹ Over 230 young prisoners were given nutritional supplements, including omega-3 and omega-6 fatty acids, or placebo, in a randomized fashion for 2 weeks. During this time the those receiving the supplement capsules committed 26% fewer offences than those taking the placebo capsules.

What these findings mean

There are already plenty of reasons for people to increase their omega-3 intake in an effort to bring their diet closer to that eaten by our ancestors (at least from the omega-3:omega-6 ratio viewpoint). The possible effects of more omega-3 and/or less omega-6 on mental heath represents another reason that may provide a little added motivation. So, to stay mellow, go fish!

Source

• Increasing homicide rates and linoleic acid consumption among five Western countries, 1961 - 2000. JR. Hibbeln, LR. Niemenen, WE.  Lands, Lipids, 2004, pp. 1207--1213

Footnotes
1. Influence of supplemental vitamins, minerals and essential fatty acids on antisocial behaviour of young adult prisoners. CB. Gesch, SM. Hammond, SE. Hampson,  et al., Brit J Psychiatr, 2002, vol. 181, pp. 22--28

Related Links
Omega-3s, the Heart-Healthy Fats
Fish May Reduce Prostate Cancer Risk
Essential fatty Acids
American Heart Association: Fish and Omega-3

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