Plain language summary
The consumption of omega-3 rich oily fish is associated with good health and is included as a recommendation in dietary guidelines in many countries. In this randomised controlled trial, 415 Norwegian children were assigned to eat either a fish meal, a meat meal or take a fish oil supplement 3 times a week for 12 weeks, to see if this affected their blood status of fatty acids, Vitamin D and iron, and their urinary status of iodine. In addition, the study measured the effects of the trial intervention on attention performance (visual attention, processing speed and accuracy). The study found that participants were deficient in fatty acids, vitamin D, iron and iodine at baseline. After the intervention, the omega-3 status increased most in the fish oil supplement group, followed by the fish group and lastly the meat group. It was noted that there was a low compliance rate in the fish meal group which many account for the difference between the fish oil supplement and fish meal groups in change in omega-3 status. Vitamin D, iron and iodine increased in all groups, however no differences were noted between the groups, and there were no effects of the changed nutritional markers on attention performance. The authors note that a healthy dietary pattern and intake of oily fish was positively associated with attention performance at baseline.
Abstract
BACKGROUND Adolescence involves changes in dietary habits that may induce imbalances in the intake of different nutrients. Fish is an important dietary source of omega-3 (n-3) long-chain polyunsaturated fatty acids (LCPUFAs), vitamin D, several minerals and high-quality protein. By using secondary outcomes and exploratory analyses, the aims of this paper were to evaluate if nutritional biomarkers (red blood cell fatty acids, serum (s)-25(OH)D, s-ferritin and urinary iodine concentration (UIC)) were altered during a dietary intervention, and if they mediated previously reported changes in attention performance. In addition, to examine the status of the biomarkers and explore associations between dietary pattern, biomarkers and attention performance cross-sectionally at baseline. METHODS The Fish Intervention Studies-TEENS (FINS-TEENS) was a three-armed intervention trial, including adolescents from eight secondary schools (n = 415; age: 14-15y) in Bergen, Norway. Participants were individually randomized to receive either fish meals, meat meals or n-3 LCPUFA supplements, three times a week for a total of 12 weeks. Blood and urine samples were collected pre and post intervention and attention performance was assessed with the d2 test of attention. Analyses of covariance (ANCOVA) assessed differences between groups in changes of biomarkers and linear mixed models were applied in analyses of attention performance and biomarkers. The trial is registered in ClinicalTrials.gov (NCT02350322). RESULTS At baseline, the mean omega-3 index was 5.8 ± 1.3% and deficient status were identified for s-25(OH)D (54%), s-ferritin (10%) and UIC (40%). The intervention resulted in an increase in DHA and the omega-3 index which was larger in the supplement group compared to the fish and meat group (P < 0.01), and in the fish group compared to the meat group (P < 0.01). No differences between the groups were observed for changes in 25(OH)D, s-ferritin or UIC. None of the biomarkers mediated performance in the d2 test. The intake of fatty fish and a healthy dietary pattern was associated with scores in processing speed at baseline. CONCLUSIONS These results show that Norwegian adolescents have insufficient status of important nutrients, which may be improved with fatty fish consumption or n-3 LCPUFA supplements. However, nutritional status was not associated with scores in the d2 test of attention.
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