There is little doubt that food can affect brain function. For example, caffeine can enhance mental energy and alertness, while a lull in blood sugar levels can have the reverse effect. Another important nutritional factor in mental functioning are the so-called omega-3 fats that are found most plentifully in “oily” varieties of fish such as salmon, mackerel, herring, trout and sardine. These fats have been associated with reduced risk of dementia as well as depression in ‘epidemiological’ studies.
However, epidemiological studies can only really tell us about the associations between things, and therefore are not particularly useful in terms of establishing whether one thing is causing the other. Epidemiological studies can’t tell us, therefore, that low omega-3 levels in the body and brain cause depression. Neither can they tell us, obviously, whether boosting omega-3 levels can have anti-depressant effects.
What is required here are so-called “intervention” studies, preferably of the “placebo controlled” type. Here, individuals are randomly assigned to take the treatment being tested (i.e. omega-3 fats) or placebo (inactive medication). A statistically significant difference in the effects of these two “treatments” in terms of, say, depressive symptoms provides strong evidence that omega-3 deficiency can cause depression and higher levels therefore can be genuinely antidepressant in action.
There is actually some evidence which suggests that omega-3 fats can indeed have antidepressant action. In a recent review from earlier this year, it turned out that of the two main forms of omega-3 fats in fish – EPA and DHA – only EPA appeared to have antidepressant action.
I was interested to read a recent study in which the potential antidepressant action of omega-3 fats was again assessed . In this study, the target treatment group were depressed women aged 66-95. Individuals in this group were treated with an omega-3 supplement or placebo for 8 weeks. The omega-3 supplement contained a total of 2.5 grams (2500 mg) of fat, 1.67 g of which was EPA, while the rest came in the form of DHA.
At the end of the study, compared to the women taking placebo, those taking the omega-3 supplement had significantly reduced symptoms of depression (as assessed by the “Geriatric Depression Scale”). Physical and mental functioning (as assessed by the “Short-Form 36-Item Health Survey”) was improved in this group too.
What we have here, therefore, is more good evidence that omega-3 supplementation has genuine antidepressant effects. And the effect was pretty quick, too.
Regular consumption of oily fish is one way to help ensure our bodies and brains are replete with omega-3 fats. However, if this is not an option, supplements are another option. Although some evidence to a degree pins the antidepressant effects of omega-3 to EPA specifically, I suggest a mix of EPA and DHA. That’s because there is some evidence linking DHA with benefits beyond depression, notably a reduced risk of dementia.
1. Rondanelli M, et al. Effect of omega-3 fatty acids supplementation on depression symptoms and on health-related quality of life in the treatment of elderly women with depression: a double-blind, placebo-controlled, randomized clinical trial J Am Coll Nutr 2010;29(1):55-64
There are quite a few studies reporting similar outcomes, See Garlands review,The British Journal of Psychiatry (2007) 190: 118-122. doi: 10.1192/bjp.bp.106.022707, and other articles by the same author. Also Hibbeln.
When one thinks of early human development, it is logical to assume that all societies grew up next to fresh water, and to be near the sea would also have been beneficial in terms of food supply, namely fish. I suspect these were easier to catch then Mammoths and other large quadropeds, but I could be wrong!