No effect of 6-month supplementation with 300 mg/d docosahexaenoic acid on executive functions among healthy school-aged children: a randomized, double-blind, placebo-controlled trial

Docosahexaenoic acid (DHA) plays an essential role in brain, and its status is dependent on dietary intakes. School-aged children in rural China, who consume diets low in omega-3 polyunsaturated fatty acids, may benefit from DHA supplementation. Therefore, this trial was performed to examine the effect of 6-month DHA supplementation on executive functions (EFs) among healthy school-aged children in rural China. A randomized, double-blind, placebo-controlled trial was conducted among 106 primary school children aged 7–12 years in rural China. Participants were randomized to receive either 300 mg/d DHA or placebo for 6 months. EFs including working memory and cognitive flexibility were evaluated at baseline, at 3 months and at 6 months, using Digit Span Backwards and Wisconsin card sorting test, respectively. Socio-demographic data were collected at baseline, and erythrocyte membrane fatty acids and serum neurotransmitters were measured at baseline and after 6-month intervention. Ninety-four children (88.7%) completed the study according to the protocol. Changes in erythrocyte membrane fatty acids indicated good compliance of the participants. There was no significant intervention effect on serum neurotransmitters. In two-factor ANCOVA, both groups showed a significant improvement in the Digit Span Backwards and the Wisconsin card sorting test from baseline to endpoint. However, no significant intervention effect was found on any EF scores. Linear regression analysis suggested no significant association between changes in erythrocyte DHA level with changes in any EF scores. Supplementation with 300 mg/d DHA for 6 months had no benefit on EFs including working memory and cognitive flexibility among healthy school-aged children. This trial was registered at clinicaltrials.gov as NCT02308930 on December 5, 2014.