The question of whether supplements of omega-3 fatty acids can help memory and cognition has been a contentious one, with some studies showing a positive effect and others failing to find an effect. My own take on this issue is that, like so many other things, it all depends on what you’re working with. It seems unsurprising if only those who have a deficient diet, or greater demands on their system (e.g., because of stress or age), or greater needs (e.g., because of a lack of cognitive reserve) might benefit from supplementation. A new study is a case in point.
The study involved 362 3rd, 4th, and 5th year students (mostly aged 7-9) from 74 schools, all of whom were reading poorly (in the lowest third). Participants were given 600 mg/day DHA (from algal oil), or a taste/color matched corn/soybean oil placebo. This was given in three capsules throughout the day, for 16 weeks.
The study found no significant improvement in reading or working memory for the DHA group as a whole, and although parents did report fewer behavioral problems, this was not confirmed by teachers.
However, there was a significant effect on reading if only those in the worst-performing 20% are considered (224 children), and an even greater effect if only those in the worst-performing 10% (105 children) are considered.
There was no significant effects for working memory, but I observe that this seems to be due to the much greater variability between individuals in the worst-performing groups (with this particularly evident in the bottom-10% group). It seems likely that whether or not DHA supplementation improves working memory capacity, depends on the factors affecting an individual’s WMC. Interestingly, a U.K. study that looked at the effects of omega-3 supplements on reading found highly significant benefits for those with Developmental Coordination Disorder.
The researchers do say that they had originally intended to look only at the poorest 20%, but decided to extend it to the lowest third when their participant numbers failed to reach the desired threshold (over half of the participant pool declined to take part).
The other point, of course, and typically for this research, is that participants only took the supplements for four months. We cannot rule out greater effects, and to a broader range of individuals, if they were taken for longer. There is also the question of compliance — compliance for those given at school was about 75% on average, and parental compliance is unknown.
In summary, I would say this is affirmation that omega-3 oils can be helpful for some individuals, but it shouldn’t be assumed that it’s a magic bullet for all.
(2012). Docosahexaenoic Acid for Reading, Cognition and Behavior in Children Aged 7–9 Years: A Randomized, Controlled Trial (The DOLAB Study).
PLoS ONE. 7(9), e43909 - e43909.
Full text available at http://www.plosone.org/article/info:doi/10.1371/journal.pone.0043909
Richardson AJ, Montgomery P (2005) The Oxford-Durham study: a randomized, controlled trial of dietary supplementation with fatty acids in children with developmental coordination disorder. Pediatrics 115: 1360–1366.