Most studies indicate that populations that consume high amounts of omega-3 essential fatty acids (EFAs)—mostly from fish—enjoy lower rates of depression.
To date, there have been only two clinical studies of the therapeutic value of omega-3s for depression. Unfortunately, they involved very different doses, and reached opposite conclusions.
However, the positive study employed much higher daily doses—6.6 grams of omega-3s, versus 2 grams in the negative study—and lasted two weeks longer (eight weeks versus six weeks).
While we await the results of planned clinical research designed to clarify the therapeutic value of omega-3s in depression, the reason for these mixed clinical results may lie in the excessive intake of omega-6 EFAs typical of diets in modern industrial countries.
The main sources of omega-6 essential fatty acids are vegetable oils—especially corn, cottonseed, soy, sunflower and safflower—found in most prepared and processed foods including margarine ( in which they are hydrogenated, which
destroys their nutritional value).
Omega-6 excess seen in sad rats... and average American diet
In a recent study published in the Journal of Lipid Research, researchers compared the brains of rats genetically “programmed” to experience chronic depression with brains of normal rats.
To their surprise, the scientists found that the chief distinction between the two lay in the brain levels of omega-6 fatty acids. They had expected that the depressed rats would have lower levels of omega-3 EFAs, but that was not the case.
Specifically, the brains of the depressed rats higher levels of arachidonic acid, a long-chain unsaturated fatty acid that the body makes from dietary omega-6 EFAs.
Lead researcher Dr. Pnina Green of Tel Aviv University noted that prior animal studies indicate that increased omega-3 fatty acid intake may reduce brain levels of arachidonic acid, which could account for the anti-depression effects of omega-3 fatty acids.
- Green P, Gispan-Herman I, Yadid G. Increased arachidonic acid concentration in the brain of Flinders Sensitive Line rats, an animal model of depression. J Lipid Res. 2005 Jun;46(6):1093-6. Epub 2005 Apr 1.
- Alessandri JM, Guesnet P, Vancassel S, Astorg P, Denis I, Langelier B, Aid S, Poumes-Ballihaut C, Champeil-Potokar G, Lavialle M. Polyunsaturated fatty acids in the central nervous system: evolution of concepts and nutritional implications throughout life. Reprod Nutr Dev. 2004 Nov-Dec;44(6):509-38.
- Horrocks LA, Farooqui AA. Docosahexaenoic acid in the diet: its importance in maintenance and restoration of neural membrane function. Prostaglandins Leukot Essent Fatty Acids. 2004 Apr;70(4):361-72. Review.