Effects of n-3 long-chain polyunsaturated fatty acids on neuropsychological function in children: Investigating effects of oily fish consumption on cognition, emotions, behavior and stress in healthy 8-9-year-old boys and girls

Publikation: Bog/antologi/afhandling/rapportPh.d.-afhandlingForskning

  • Marie Nygaard Teisen
Background: Long-chain n-3 polyunsaturated fatty acids (n-3 LCPUFA), especially docosahexanoic acid (22:6n-3, DHA), are accreted in the brain and likely play important roles in brain development and function. The accretion is substantial during early infancy and continues throughout childhood. However, randomized clinical trials (RCTs) in children show inconsistent effects of n-3 LCPUFA on neuropsychological functions such as cognition, emotions and behavior and no trials in children investigated effects on stress. Inconsistencies might arise from differences in the tests used and moreover, some studies indicate potential sex-specificity in the effects which could contribute to inconsistencies. Thus, assessment of overall patterns in the effects and potential sex differences might be important. Furthermore, only few of the studies investigated effects of fish per se, which likely resemble real life effects of fish consumption better than studies with n-3 LCPUFA supplements. 
Objective: The main objective of this thesis was to investigate effects of n-3 LCPUFA provided through oily fish on cognition, emotions and behavior in healthy children, and secondly to investigate the effects on stress. These effects were investigated with a focus on potential sex differences. To substantiate interpretation of effects on cognition, emotions and behavior, we investigated overall patterns in performance. 
Methods: The objectives were investigated in the FiSK Junior study, which was a two-arm parallel RCT in which 199 healthy Danish 8-9-year-old children were randomized to consume ~300 g/week oily fish or poultry (control) for 12±2 weeks. At baseline and endpoint, we assessed cognitive functions including attention, processing speed, executive functions, and memory, as well as emotions and behavior with a large test battery of tests and questionnaires. We used principal component analysis to explore overall patterns in cognitive performance as well as socioemotional traits (emotions and behavior) and the generated principal components were used as scores of overall function. We furthermore assessed the physiological response to cold-induced stress by measuring blood pressure, heart rate variability (HRV) and salivary cortisol and assessed general stress level by measuring cortisol released in the hair during the last ~3 months. Erythrocyte n-3 LCPUFA was used as biomarker for fish intake. 
Results: Fish intake dose-dependently improved the overall score of cognitive performance. This was driven by beneficial tendencies in several cognitive domains and by improvements in single measures of attention and cognitive flexibility. The fish intervention furthermore reduced a score of parent-rated socioemotional difficulties, mainly due to a reduction in emotional problems, and this was reflected in a tendency to reduction in the overall score of socioemotional problems. Some effects appeared to differ for boys and girls in the attention domain and the reduction in emotional problems was twice as strong in girls compared to boys. In contrast to the effects of the fish intervention, the analyses of baseline associations with erythrocyte n-3 LCPUFA indicated a positive association with processing speed and negative association with a single measure of attention, and no association with the overall cognitive performance score. Moreover, we observed no overall or gender-specific associations for the socioemotional scores. The fish intervention furthermore appeared to reduce stress responsiveness reflected by changes in HRV that indicated increased parasympathetic activity during the cold-induced stress and a tendency to improved endurance to the stress-stimulus. Interestingly, we observed a marked HRV response during recovery from the stress-stimulus with a sympathetic peak followed by a parasympathetic peak of which the latter appeared higher in the fish group. The effect on general stress tended to be modified by sex with a decrease in hair cortisol among boys but increase among girls in response to fish intake, although these effects were not significant.
Conclusion: Our findings suggested overall beneficial effects of oily fish on neuropsychological function in healthy children. Thus, our results substantiate the importance of n-3 LCPUFA for optimal brain function and recommendations of fish consumption in children. The effects of n-3 LCPUFA on specific cognitive domains remains inconclusive, possibly due to differences in the measured outcomes as we observed lack of correlation between measures supposed to reflect the same function, especially for the more complex cognitive domains. Thus, a deeper understanding of the functions underlying performance in different tests is needed. Likewise, there is a need for better characterization of a typical response to stress induced by various methods. This would be relevant to explore along with perceived stress in future studies. Furthermore, the indicated potential sex-specificity in effects of n-3 LCPUFA on some neuropsychological functions needs to be investigated in studies that are powered to perform sex-stratified analyses.
Udgivelses stedCopenhagen
ForlagDepartment of Nutrition, Exercise and Sports, Faculty of Science, University of Copenhagen
Antal sider175
StatusUdgivet - 2019

Bibliografisk note

CURIS 2019 NEXS 374

Note vedr. afhandling

Ph.d.-afhandlingen blev forsvaret den 13. marts 2020.

ID: 240795131