Effect of 2-y n-3 long-chain polyunsaturated fatty acid supplementation on cognitive function in older people: a randomized, double-blind, controlled trial.

Randomized, double-blind, controlled trial in cognitively healthy adults aged 70–79 years recruited from 20 general practices in England and Wales. Participants were assigned to EPA+DHA supplementation or olive oil placebo and followed for 24 months; current daily fish-oil supplement users were excluded.

Two 650-mg dark-brown, vanilla-flavored soft-gel capsules were taken orally once daily for 24 months. The active capsules provided a total of 200 mg EPA and 500 mg DHA per day (EPA:DHA 20:50 ethyl ester); the comparator was olive oil placebo.

Two years of EPA+DHA supplementation did not improve cognitive function compared with placebo. For the primary CVLT outcome, the fish oil group changed by -0.02 6 4.7 versus 0.5 6 5.0 in placebo, with an unadjusted between-group difference of -0.5 (95% CI -1.2, 0.2; P = 0.14). Global cognitive function also showed no benefit (difference 0.03, 95% CI -0.05, 0.04; P = 0.77), and there were no significant differences for memory, processing, executive function, or global delay z scores. Cognitive performance remained stable in both groups over 24 months.

The study population was cognitively healthy and showed little decline in the placebo group, which limited the ability to detect a protective effect. The 24-month duration may have been too short to capture a cognitive benefit of omega-3 supplementation in this age group.