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Docosahexaenoic acid supplementation increases prefrontal cortex activation during sustained attention in healthy boys: a placebo-controlled, dose-ranging, functional magnetic resonance imaging study

McNamara RK, Able J, Jandacek R, Rider T, Tso P, Eliassen JC, Alfieri D, Weber W, Jarvis K, DelBello MP, Strakowski SM, Adler CM. (2010) Am J Clin Nutr.  91(4) 1060-7. doi: 10.3945/ajcn.2009.28549. Epub 2010 Feb 3. 

Web URL: View this and related abstracts via PubMed here

Abstract:

Background: Emerging evidence suggests that docosahexaenoic acid (DHA, 22:6n23), the principal omega-3 (n-3) fatty acid in brain gray matter, positively regulates cortical metabolic function and cognitive development. However, the effects of DHA supplementation on functional cortical activity in human subjects are unknown.

Objective: The objective was to determine the effects of DHA supplementation on functional cortical activity during sustained attention in human subjects. Design: Healthy boys aged 8–10 y (n = 33) were randomly assigned to receive placebo or 1 of 2 doses of DHA (400 or 1200 mg/d) for 8 wk. Relative changes in cortical activation patterns during sustained attention at baseline and endpoint were determined by functional magnetic resonance imaging.

Results: At 8 wk, erythrocyte membrane DHA composition increased significantly from baseline in subjects who received lowdose (by 47%) or high-dose (by 70%) DHA but not in those who received placebo (211%).

During sustained attention, both DHA dose groups had significantly greater changes from baseline in activation of the dorsolateral prefrontal cortex than did the placebo group, and the low-dose and high-dose DHA groups had greater decreases in the occipital cortex and cerebellar cortex, respectively.

Relative to low-dose DHA, high-dose DHA resulted in greater decreases in activation of bilateral cerebellum.

The erythrocyte DHA composition was positively correlated with dorsolateral prefrontal cortex activation and was inversely correlated with reaction time, at baseline and endpoint.

Conclusion:
Dietary DHA intake and associated elevations in erythrocyte DHA composition are associated with alterations in functional activity in cortical attention networks during sustained attention in healthy boys.

This trial was registered at clinicaltrials.gov as NCT00662142.
Am J Clin Nutr doi: 10.3945/ajcn.2009.28549.

FAB RESEARCH COMMENT:

This study found that omega-3 DHA, given to healthy boys for 8 weeks, led to signficant and dose-related increases in brain activation compared to placebo while they performed a task involving sustained attention. 

Following DHA consumption, activation increased in particular frontal lobe regions (the dorsolateral pre-frontal cortex, or DLPFC) that are already implicated in attentional and other cognitive functions, particularly 'executive' functions such as working memory, impulse control and planning ahead.

These functions are typically impaired in children with ADHD - so these findings add further support to the proposal that an increased intake of omega-3 DHA might be of benefit to some people with difficulties in these areas.  However - that proposal was NOT directly tested in this study.

It is therefore unfortunate that much of the media coverage of this research became yet abother 'miracle pill' story - as exemplified by this Guardian / Observer article (which was then duly and appropriately criticised elsewhere).
Both before and after supplementation, the researchers also found that higher blood DHA concentrations were associated with higher DLPFC activation, and with quicker reaction times.