The idea that modern diets might affect our brains and thus our behaviour is at once shocking and, as Bernard Gesch, a senior research fellow at Oxford University says, "bleeding obvious".

Gesch points out that the brain is a "metabolic powerhouse, which despite being only 2% of our body mass consumes about 20% of available energy" and 12% of the heart's output to supply it with nutrients. These nutrients are classed as essential for the normal functioning of the brain; in other words there are likely to be consequences if we don't get them in our diet.

This week I wrote about new research by Joseph Hibbeln and colleagues at the US government's National Institutes of Health near Washington. They have been investigating the effects of omega-3 fatty acid deficiency on violent alcoholics. Together with an earlier study by Gesch, which gave multivitamin, mineral and essential fatty acid supplements to young offenders at Aylesbury high security prison, the research suggests that violent behaviour may be attributable at least in part to nutritional deficiencies.

Hibbeln believes that the radical changes in the modern diet have altered the very architecture and functioning of the brain. His theory is that the main mechanism involved here is the flood of omega-6s in the industrialised diet washing out omega-3s since they compete for the same metabolic pathways.

In the paper version of yesterday's Guardian we reproduced a graph showing the correlation between the rise in murder rates in the UK and the increase in consumption of omega-6s from vegetable oils mainly in processed foods. Someone wrote to our letters page to say our use of this graph was "sensationalist". Well the implications are certainly sensational, but I don't think our use of it was. We didn't have room to reproduce figures for other countries but you can look at some of them and Hibbeln's detailed discussion of what they might mean in his paper in the journal Lipids.

My colleague Ben Goldacre has been critical of media coverage of fish oil supplements in his Bad Science column recently. He is particularly scathing about Durham LEA's project to give them to mainstream schoolchildren without the scientific evidence to justify its claims that they may help improve their learning. I agree with him on the Durham experiment but he also queries my coverage of the Cotswold community school where boys with severe behavioural difficulties have been treated with fish oils. You can see the correspondence on this on his Bad Science site and my response, which will be posted on that blog once some technical glitches have been overcome.