Modern diet may cause depression

Scientists have long maintained that a lack of omega-3 may contribute to depression, but the latest study suggests that an excess of omega-6 – the fatty acid which is more prevalent in the modern diets – may have more to do with it.

Natural sources of omega-3 include oily fish, canola and flaxseed oils, soybeans and nuts. But while these foods were more commonly eaten 50 years ago, these days consumers’ palates tend to favor foods that contain higher levels of omega-6, such as meat, eggs, poultry, cereals, breads, baked goods, vegetable oils, and margarine.

Previous studies into fatty acids and depression have measuring omega-3 levels in the blood of depressed humans, giving rise to the ‘phospholipid hypothesis’ which proposes that decreased omega-3 fatty acid intake, and hence decreased brain omega-3 fatty acid content, could be responsible for the disease.

Because of the high dietary variability of humans and the obvious inability to study their brains, Dr Pnina Green of Tel Aviv University and Dr Gal Yadid of Bar-Ilan University chose to test the theory by comparing the brains of normal and depressed rats.

Their findings, published in the June issue of the Journal of Lipid Research, took fatty-acid research surprising direction.

The two groups of rats were fed the same diet, but their brains showed marked differences in levels of omega-6 fatty acid levels. All regions of the depressed rats’ brains studied had significantly higher concentrations of arachidonic acid (ARA), a long-chain unsaturated metabolite of omega-6 fatty acid.

"The finding lends itself nicely to the theory that increased omega-3 fatty acid intake may shift the balance between the two fatty acid families in the brain, since it has been demonstrated in animal studies that increased omega-3 fatty acid intake may result in decreased brain arachidonic acid.” Green suggests that, in the future, depression may be controlled by shifting the balance between the two fatty acids – cutting back on omega-6 and increasing intake of omega-3 to bring levels back in line with those of our forebears.

According to the Depression and Bipolar Support Alliance, depression is the most common serious brain disease in the United States, affecting more than 23 million adults each year.

Steve - As previously discussed, we do not usually pay mention to animal studies, but we felt this was significant because for the first time a study focused on excessive omega-6 intake instead of lack of omega-3 intake.