Fish oil, blueberries and cognitive improvement in the elderly
Based on existing evidence that eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA), as well as antocyanin (a flavonoid present in large amounts in blueberries), have beneficial effects on cognition, the authors of a recent study investigated the effect of long-term supplementation in 76 older subjects (aged 62-80) who reported mild cognitive problems (diagnosis of dementia and having taken medication for the problem were exclusion criteria for the study). To do this, they designed a double-blind, controlled, randomised trial with a 24-week intervention in which the subjects received fish oil, blueberry powder (made from freeze-dried blueberries), both or placebo daily. The fish oil capsules contained 400 mg of EPA and 200 mg of DHA; the participants had to take two with breakfast and two with dinner. The dose of blueberry powder was equivalent to one cup of cranberries a day. The placebo for the fish oil was corn oil, while the placebo for blueberry powder had a similar texture but a different nutritional profile (e.g. no fibre). The subjects had to avoid ingesting marine-origin food and antocyanin-rich fruits.
The results showed that fish oil consumption significantly increased the EPA + DHA composition of red blood cells. Antocyanins in urine did not differ in the three groups after supplementation, but glucosides increased only in the blueberry-supplemented groups. Both the fish oil-supplemented and blueberry-supplemented groups reported fewer cognitive symptoms, but the association of both supplements was unrelated to cognitive improvement, contrary to expectations. The authors consider that daily long-term supplementation with both treatments could have subverted the beneficial response.