LAUSR

Purpose Most children do not meet dietary guidelines for fish intake. Fish is the main source of EPA (20:5n-3), DHA (22:6n-3) and vitamin D, but may replace better iron sources such as meat. We investigated if intake of 300 g/week oily fish was achievable in children and how it affected their nutrient status. Additionally, we validated a fish food frequency questionnaire (FFQ) by correlations against EPA + DHA in red blood cells (RBC). Methods In a randomised 12-week trial, 199 children (8–9 years) received oily fish or poultry (control) to be eaten five times/week. We measured dietary intake and analysed fasting RBC EPA + DHA, serum 25-hydroxyvitamin D (25(OH)D), blood haemoglobin and plasma ferritin. Results 197 (99%) children completed the study. The median (25th–75th percentile) intake was 375 (325–426) and 400 (359–452) g/week oily fish and poultry, respectively. The fish group increased their intake of EPA + DHA by 749 (593–891) mg/day and vitamin D by 3.1 (1.6–3.8) µg/day. Endpoint RBC EPA + DHA was 2.3 (95% CI 1.9; 2.6) fatty acid %-point higher than the poultry group ( P  < 0.001). The fish group avoided the expected 25(OH)D winter decline ( P  < 0.001) and had 23%-point less vitamin D insufficiency (winter subgroup, n  = 82). Haemoglobin and ferritin decreased slightly in both groups ( P  < 0.05), but the number of children with low values did not change ( P  > 0.14). FFQ estimates moderately reflected habitual intake ( r  = 0.28–0.35) and sufficiently captured intervention-introduced changes in intake ( r  > 0.65). Conclusion Oily fish intake of 300 g/week was achievable and improved children’s EPA + DHA and 25(OH)D status, without markedly compromising iron status. These results justify public health initiatives focusing on children’s fish intake.