A new review suggests that increased consumption of fish oils rich in omega-3 long-chain polyunsaturated fatty acids (omega-3 PUFA) shows no benefit among cognitively healthy older people.

Researchers at the London School of Hygiene and Tropical Medicine (United Kingdom) conducted a meta-study involving three trials of omega-3 supplementation in which 3,536 participants--over 60 years of age and cognitively healthy at the start of the study--were randomized to receive extra omega-3 PUFA in their diet or a placebo (such as olive oil). The main outcome measures were new cases of dementia diagnosed during the study period, cognitive decline, side effects, and adherence to the intervention.

The results showed that in two studies, involving 3,221 participants, there was no difference between the omega-3 PUFA and placebo group in mini-mental state examination score at final follow-up. In two studies, involving 1,043 participants, other tests of cognitive function such as word learning, digit span, and verbal fluency showed no beneficial effect of omega-3 PUFA supplementation. Participants in both the intervention and control groups experienced little or no cognitive decline during the studies.
In all three studies, mild gastrointestinal symptoms were the most common side effects, and were reported with equal frequency in treatment and placebo groups. Adherence to the supplementation protocol was high in all trials with on average over 90% of supplements being apparently consumed by trial participants. The study was published online on June 6, 2012, in the Cochrane Database of Systematic Reviews.

“All three studies included in this review were of high methodological quality, and so the findings are unlikely to be due to chance or bias,” concluded lead author Emma Sydenham, MSc, and colleagues. “While cognitive benefits were not demonstrated in this review, consumption of two servings of fish each week, with one being an oily fish such as salmon or sardines, is widely recommended for overall health benefits.”

Oily fish such as salmon, mackerel, herring, and sardines are a rich source of omega-3 PUFA, which are essential for brain development.

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