Oily fish improves cognitive, socioemotional functions in children

Oily fish intake leads to better cognitive functions, particularly attention and cognitive flexibility, and fewer socioemotional problems in children, a study has shown.

“[O]ur findings support a dose-dependent beneficial effect of oily fish consumption on cognitive performance in healthy children and indicate improvements in attention, cognitive flexibility, and socioemotional problems,” the researchers said.

A total of 199 healthy children aged 8–9 years were randomized to receive ∼300 g/wk oily fish or poultry (control) for 12±2 wk. Attention, memory, processing speed, executive functions, behaviour, and emotions were assessed at baseline and endpoint using a large battery of tests and questionnaires. The researchers also analysed erythrocyte fatty acid composition.

Of the participants, 197 (99 percent) completed the trial. Children in the fish group consumed 375 g/wk oily fish, which was 2.3-percent (95 percent confidence interval [CI], 1.9–2.6) higher in erythrocyte n–3 long-chain polyunsaturated fatty acids (LCPUFA) than the control group. [Am J Clin Nutr 2020;112:74-83]

The overall cognitive performance improved by 0.17 points (95 percent CI, –0.01 to 0.35) in children who consumed fish compared with poultry, and this was supported by n–3 LCPUFA dose dependency. Such improvement was primarily driven by fewer errors (–1.9, 95 percent CI, –3.4 to –0.3) in an attention task and improved cognitive flexibility measured as faster reaction time (–51 ms, 95 percent CI, –94 to –7) in a complex relative to a simple task (mixing cost).

Oily fish consumption further reduced parent-rated Strength and Difficulties Questionnaire total difficulties by –0.89 points (95 percent CI, –1.60 to –0.18), driven by a –0.61-point (95 percent CI, –1.11 to –0.16) decrease in internalizing problems that was indicated in tendency to a reduction in the overall socioemotional problems score of –0.13 points (95 percent CI, –0.26 to 0.01).

Of note, overall effects were not significantly different in boys and girls.

“These results substantiate the importance of n–3 LCPUFAs for optimal brain function and recommendations of fish intake in children,” the researchers said. “Although a few sex-specific differences were indicated in attention and socioemotional measures, most effects were comparable in boys and girls.”

Dose dependency with n–3 LCPUFAs substantiated the indicated favourable effect of fish on the overall cognitive performance score. This supports a previously observed positive association between whole-blood EPA + DHA and overall school performance in response to a fish-rich school meal intervention, and a dose-dependent effect of oily fish on total cognitive score in preschool children. [BMC Med 2018;16:41; Br J Nutr 2015;114:1623-1637]

“However, n–3 LCPUFA supplementation trials that have used overall measures of cognitive performance in children have not shown any effects, possibly due to use of low doses of n–3 LCPUFAs (∼100 mg/d) or effects of whole fish that go beyond n–3 LCPUFAs,” the researchers said. [Am J Clin Nutr 2009;89:1766-1775; Am J Clin Nutr 2007;86:1082-1093]

“Future sufficiently powered studies are needed to understand the effects of fish consumption on specific cognitive and socioemotional domains and the potential influence of sex,” they added.