Biomarkers and Fatty Fish Intake: A Randomized Controlled Trial in Norwegian Preschool Children

Biomarkers such as omega-3 (n–3) PUFAs, urinary iodine concentration (UIC), 1-methylhistidine (1-MH), and trimethylamine N-oxide (TMAO) have been associated with fish intake in observational studies, but data from children in randomized controlled trials are limited. The objective of this exploratory analysis was to investigate the effects of fatty fish intake compared with meat intake on various biomarkers in preschool children. We randomly allocated (1:1) 232 children, aged 4 to 6 y, from 13 kindergartens. The children received lunch meals of either fatty fish (herring/mackerel) or meat (chicken/lamb/beef) 3 times a week for 16 wk. We analyzed 86 biomarkers in plasma (n = 207), serum (n = 195), RBCs (n = 211), urine (n = 200), and hair samples (n = 210). We measured the effects of the intervention on the normalized biomarker concentrations in linear mixed-effect regression models taking the clustering within the kindergartens into account. The results are presented as standardized effect sizes. We found significant effects of the intervention on the following biomarkers: RBC EPA (20:5n–3), 0.61 (95% CI: 0.36, 0.86); DHA (22:6n–3), 0.43 (95% CI: 0.21, 0.66); total n–3 PUFAs, 0.41 (95% CI: 0.20, 0.64); n–3/n–6 ratio, 0.48 (95% CI: 0.24, 0.71); adrenic acid (22:4n–6, −0.65 (95% CI: −0.91, −0.40), arachidonic acid (20:4n–6), −0.54 (95% CI: −0.79, −0.28); total n–6 PUFAs, −0.31 (95% CI: −0.56, −0.06); UIC, 0.32 (95% CI: 0.052, 0.59); hair mercury, 0.83 (95% CI: 0.05, 1.05); and plasma 1-MH, −0.35 (95% CI: −0.61, −0.094). Of the 86 biomarkers, the strongest effect of fatty fish intake was on n–3 PUFAs, UIC, hair mercury, and plasma 1-MH. We observed no or limited effects on biomarkers related to micronutrient status, inflammation, or essential amino acid, choline oxidation, and tryptophan pathways. The trial was registered at clinicaltrials.gov (NCT02331667).