Scientific studies have linked a low dietary intake of omega 3 fatty acids and dieting with growing rates of depression in the United States. Depression affects more than 19 million Americans over the age of 18 every year. Furthermore, the incidence of major depression has been increasing while the age of onset has decreased. Interestingly, the risk of developing depression has increased at a rate similar to the rise in consumption of omega 6 fatty acids (vegetable seed oils) and relative to the decrease in omega 3 fatty acids (fish, walnuts, flaxseed.) Many nutritionists feel that this is a direct result of the increased consumption of processed foods among Americans.
Omega 3 As An Antidepressant
The association of omega 3 fatty acids as an antidepressant stems from a handful of epidemiological studies, which established that rates of depression among different countries were directly related to fish consumption. Hibbeln et al. published in the Lancet Journal a strong relationship of fish consumption with lower rates of depression in countries such as Japan, Korea, and Taiwan. He has also reported that high fish consuming nations have the lowest rate of post-partum depression.
A more recent study by Nemets et al, studies the effects of the omega 3 fatty acid, EPA (eicosapentaenoic acid) in twenty people with recurrent depression. These individuals received either a fish oil capsule or a sugar pill in addition to antidepressant medication. As soon as two weeks into the study, there was an improved sense of well being and sleeping patterns in the EPA group. By four weeks into the study, 6 of the ten individuals taking the EPA had a significant reduction in the symptoms of depression as compared to only one of the ten taking the sugar pill. The study concluded that the fatty acid EPA may boost the antidepressant effect of the medication in depressed individuals.
Low Fat Diets And Depression
A separate but related issue involves the consequences of dieting, in particular, dieting with a low fat diet and or by caloric restriction alone. It is conceivable that dieting provokes stress, anxiety, and even depression. However, recent studies conclude that these feelings may also be related to the actual amount and type of fat consumed and that a low fat diet (approximately 25 percent of total caloric intake from fat) does indeed promote the symptoms of depression. Dieting and weight cycling decrease serotonin levels by decreasing the blood levels of the amino acid precursor, tryptophan. Dieting also results in alterations or depletion of total membrane essential fatty acids. Omega 3 fatty acids were one of the groups to be depleted. These changes in the membrane distribution of fatty acids alter the balance of saturated, monounsaturated, omega 3 and omega 6 levels, potentially leading to a neurochemical imbalance conducive to depression. These compositional changes in membrane properties directly influence the activity of the neurotransmitter serotonin.
© Connie Guttersen, RD PhD 2003
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