MELBOURNE, AUSTRALIA. Depression is becoming increasingly prevalent in Western society. Some researchers believe that part of the reason for this can be traced to major dietary changes which have taken place over the past century. During this time there has been a large increase in the intake of saturated fats and linoleic acid (LA)-rich vegetable oils at the expense of alpha-linolenic acid (ALA)-rich foods such as fish and wild game. It is estimated that the ratio between LA-type (n-6) polyunsaturated fatty acids (PUFAs) and ALA-type (n-3) PUFAs has risen from 1:1 to 10:1 or higher. Some researchers have postulated that the sharp rises in depression and other neurological disorders are closely related to the increased intake of LA-rich vegetable oils.
Now researchers at the Royal Melbourne Institute of Technology report that the severity of depression is indeed directly associated with the ratio of LA- to ALA-type PUFAs in red blood cells. Their study involved 20 moderately to severely depressed patients. The severity of depression was determined using the 21-item Hamilton depression rating scale and a second scale which omitted anxiety symptoms. All patients had blood samples drawn and analyzed for arachidonic acid (AA) - the major metabolite of linoleic acid, and EPA - the major metabolite of alpha-linolenic acid and the main constituent of fish oils. The researchers found a clear correlation between a high AA/EPA ratio and increased severity of depression. There was also a significant association between a low level of EPA in the red blood cells and increased severity of depression.
The researchers conclude that there is a definite relationship between high AA/EPA ratios and increased severity of depression, but are not certain whether the fatty acid imbalance causes depression or whether depression results in a high AA/EPA ratio. They suggest that further studies be done to determine the benefits of supplementation aimed at increasing tissue levels of EPA and thereby decreasing the AA/EPA ratio.
Adams, Peter B., et al. Arachidonic acid to eicosapentaenoic acid ratio in blood correlates positively with clinical symptoms of depression. Lipids, Vol. 31 (suppl), 1996, pp. S157-S61