DHA supplementation improved both memory and reaction time in healthy young adults: a randomized controlled trial.

Randomized controlled trial in healthy adults aged 18 to 45 years with low habitual long-chain omega-3 intake in Auckland, New Zealand. In the DHA arm, 115 participants were randomized and 85 had baseline and end-of-study data available for analysis.

Participants in the active arm took DHA capsules orally once daily with a meal for 6 months. Each daily dose provided 1.16 g DHA and 0.17 g EPA in three 750-mg capsules, matched with identical placebo capsules in size and shape.

DHA supplementation improved memory performance and reaction time for memory, but it did not meaningfully improve attention or processing speed overall. Episodic memory showed a sex-by-treatment interaction (P = 0.01), with women improving more, and reaction time for episodic memory and working memory improved versus placebo (P = 0.02 and P = 0.001, respectively). APOE genotype did not change the overall cognitive response, although APOE3 sex-by-treatment interactions were seen for reaction time of working memory (P = 0.02) and attention (P = 0.005). Burping and unpleasant breath were more common with DHA (49% vs 22% and 39% vs 18%, both P < 0.001).

Single-site study with a moderate sample size and substantial attrition from randomization to complete baseline and end data in the DHA arm. Multiple subgroup analyses by sex and APOE increase the chance of chance findings, and the 6-month duration limits conclusions about long-term cognitive effects. Findings apply most directly to healthy young adults with low habitual DHA intake in New Zealand, and physical activity was not measured.