Fish is sometimes described as ‘brain food’ – why? Well, at least part of the explanation may rest in the fact the certain types of fish are rich in so-called omega-3 fats that appear to have benefits for the brain. There is some evidence, for instance, which suggests that omega-3 fats can normalise brain function and protect against certain mental disorders including psychotic illness (see here for more about this) and depression.
There are two principle omega-3 fats found in fish: eicospentaenoic acid (EPA) and docosahexaenoic acid (DHA). Recently, scientists have attempted to unpick which, if any, of these two major fats gets the nod in terms of antidepressant action. Researchers based in Cambridge recently reviewed 28 placebo-controlled studies (the gold standard of studies for determining if a treatment works of not) in which omega-3 fats were used in the treatment of depression [1].
Some of the findings from this review include the facts that, generally speaking, omega-3 supplements were more effective when:
• treating major depression and bipolar depression over milder forms of depression
• the omega-3 supplements were used as an adjunct to other treatments rather than being the sole treatment
• the omega-3 was used to treat depression, rather than prevent it
Additionally, a major focus of this study was whether which, if any, of EPA or DHA appears to have the most potential as an antidepressant.
The results of this analysis showed that when EPA was the sole or main omega-3 fat used there was evidence of significant anti-depressant action. The same, however, was not true for DHA: in studies where DHA was the sole or main omega-3 supplement, no significant antidepressant action was found.
The authors of this review call for larger, well-designed studies of sufficient length to be performed, but at this stage the results suggest that if it’s mood enhancement we’re looking for, EPA gives more bang for our buck.
References:
1. Martins JG, et al. EPA but not DHA appears to be responsible for the efficacy of omega-3 long chain polyunsaturated fatty acid supplementation in depression: evidence from a meta-analysis of randomized controlled trials. J Am Coll Nutr 2009;28(5):525-42
I have sen it postulated that humans are poor converters of DHA which explains why EPA is significantly more beneficial than DHA.
It is also why the EFSA (European Food Safety Authority) stance on functional benefits of foods has been so contentious. Manufacturers are permitted to claim ‘high in omega 3′ when actually the product is high in DHA and not so functionally beneficial as a consumer might perceive. Furthermore, such claims are often on products that are largely derivatives of vegetable oils (margarine, mayonnaise etc.) that can be high in certain omega-6 fats. Certain omega-6 fatty acids can be physiologically competitive of omega-3 and can be pro-inflammatory.
Link here to the response of scientists to EFSA.
Dr. Briffa,
I try to avoid supplements where possible.
I eat fish and seafood, mainly mackerel and sardines almost every day. I am assuming that this is adequate consumption of EPA omega 3′s, combined with reduceing omega 6 in my diet.
How much fish do we need to consume to ensure good EPA intake?
Bill,
We actually convert EPA to DHA, so poor conversion wouldn’t explain this finding. Frankly, I’m surprised by it since most of the evidence suggests that DHA is more important than EPA.
Well, glad I reviewed the abstract, because this is nothing short of an editorial masquerading as a meta-analysis.
“RESULTS: Two hundred forty-one studies were identified, of which 28 met the above inclusion criteria and were therefore included in the subsequent meta-analysis.”
Oh hi, we used 11.6% of the available literature to prove our point.
The following is taken from: Fat Intake and CNS Functioning: Ageing and Disease – Michael A Crawford, Richard P. Bazinet, Andrew J. Sinclair. Published online: September 15, 2009 – Annals of Nutrition and Metabolism:
‘The brain contains very low levels of EPA compared with DHA (Crawford et al, 1976) yet of all the studies conducted, those using EPA have shown the most consistent benefits. It is possible that EPA exerts some of its effects in mood disorders by improving blood flow and therefore supplying the brain with nutrients such as glucose. This EPA effect could be mediated by the endothelial cells in the extensive blood vessel architecture of the brain’.
However, the paper goes on to say ‘the studies which support this distinction between EPA and DHA are few and there are problems with the design, mainly related to the duration, dose and fatty acid control’.
The Global Forum for Health predicts that by 2020 mental ill health will be in top three health burdens worldwide. And it does seem to be a wake up call that we must stop trashing our ocean environment – the health of which is essential for all life. These long chain omega 3 essential fatty acids EPA and DHA are to be found most abundantly preformed in the marine food chain and would seem very important to both physical and mental wellbeing. Restoring healthy rivers, estuaries, and coastlines and marine productivity (A recent study suggests that the decline in UK fish stocks is more severe than thought) perhaps needs to be given urgent consideration by government to reduce costs to the National Health Service and future costs to the health of our children.
Chris K rightly states that EPA is converted to DHA rather than the other way round. To get to EPA and DHA, starting with alpha-linolenic acid, a 16 carbon chain (found in plants), the human body (or the fish, or any other animal) adds carbon atoms to the chain, two by two. EPA (20 carbons) gets converted into eicosanoids, notably the series 3 prostaglandins, which are anti-inflammatory. The brain uses DHA (the longest chain EFA at 22 carbons) as an important component in the cell membrane. This fact seems to explain antidepressant action as something to do with relieving or preventing inflammation rather than improving cell function, which is interesting.
I’m not a particular fan of supplements but after two years of bi-polar and a dozen kinds of drugs I finally out of desperation tried a supplement from Canada for bi-polar, and the bi-polar symptoms went away. I have no way of knowing if the supplement was responsible (emPowerPlus from truehope.com) or if it went away on it’s own, though there’s some research on the website from the University of Calgary that it works for many people though not everyone. I have now been mercifully free of depression and mania for five years, though I have to say I miss the mania a little. I took fish oil the whole two years that I had the depression and mania, but it didn’t seem to help in my case.