Effects of oily fish intake on children’s nutrient status, cardiometabolic health, sleep and physical activity

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

  • Stine Vuholm
Background: The fish intake is low in most Western countries, especially among children, and thus few meet the dietary guidelines for fish intake. Fish is the main dietary source of n-3 long-chain polyunsaturated fatty acids (LCPUFA) and vitamin D, but may substitute meat which is a better iron source. Many children have an insufficient vitamin D status, especially during winter, but also iron deficiency is prevalent among European children, why there is a need for studies that evaluate how an increased fish intake affects children’s nutrient status. Intake of n-3 LCPUFA is recognized for having beneficial effects on several cardiometabolic risk markers mainly blood pressure and triacylglycerol. However, few trials have investigated if similar effects can be achieved by a fish intake in line with the dietary guidelines, and studies are lacking among children. Moreover, novel but very limited evidence has indicated that n-3 LCPUFA might affect sleep and physical activity but findings are inconclusive and there is a need for studies which apply objective assessment methods. Objectives: The overall objective of this PhD thesis was to investigate whether a high intake of oily fish affected health among healthy children, evaluated as the effects on nutrient status, cardiometabolic markers, sleep and physical activity. The secondary aim was to investigate if any of these effects were sex-specific. Design and methods: All papers included in this PhD thesis are based on data from the FiSK Junior, which was a randomized controlled trial where 199 healthy Danish 8-9-year-old children received either oily fish or poultry (control) to be eaten 5 times/week (~300 g/week) for 12±2 weeks. At baseline and endpoint examinations, we measured blood pressure, heart rate, and heart rate variability via 3-h continuous electrocardiograms and collected fasting blood samples which were analyzed for erythrocyte EPA (20:5n-3) + DHA (22:6n-3), serum 25-hydroxyvitamin D (25(OH)D), blood hemoglobin, plasma ferritin, serum triacylglycerol, LDL and HDL cholesterol and plasma glucose and insulin. Prior to the examinations, 4-day dietary intake was recorded and the children wore accelerometers on their waist for 7 consecutive days while their parents registered sleep times. Sleep and physical activity measures were extracted from the actograms. The co-primary outcomes of FiSK Junior were defined as diastolic blood pressure and serum triacylglycerol. Results: The fish group had a median (25th-75th percentile) fish intake of 375 (325-426) g/week which increased the children’s EPA+DHA and 25(OH)D status and improved their lipid profile by a dosedependent lowering in serum triacylglycerol and increase in HDL cholesterol. The iron status was slightlybut not markedly reduced compared to the poultry group while no effects were found on blood pressure,heart rate variability and glucose homeostasis. Furthermore, oily fish consumption appeared to improve sleepcompared to poultry reflected by shorter latency time to sleep onset and less weekly variability in sleepduration. Also, physical activity was modified in the fish group as sedentary spare time was dosedependently increased at the expense of light physical activity, while moderate-to-vigorous physical activity was increased during school hours. Several of the effects of oily fish intake indicated sex-specificity, as mainly the boys had a lowering in serum triacylglycerol and tended to have greater effects on physical activity compared to girls. On the other hand, the girls tended to reduce heart rate in response to oily fish intake and the sleep improvements appeared more pronounced in the girls than in the boys. Conclusion: The evidence enclosed in this PhD thesis supports that a high oily fish intake among children contributes to beneficial health effects. An increased intake of oily fish can be nutritionally justified among healthy children since n-3 LCPUFA and vitamin D status was increased while not markedly compromising iron status. The improvements in children’s lipid profile support that classical n-3 LCPUFA effects can be achieved by consumption of fish per se and even in healthy children. These changes potentially contribute to substantial health improvements at a population level. Additionally, a high oily fish intake possibly improves children’s sleep and modifies their physical activity pattern. However, these findings should mainly be considered as hypothesis-generating and need to be substantiated by more human randomized controlled trials. Likewise, the indicated sex-specific effects of oily fish should be investigated further, optimally in studies that are sufficiently powered for sex-stratified analyses. Nevertheless, the presented evidence altogether supports the dietary guidelines for fish intake and highlights the relevance for initiatives that aim for increasing the fish intake even among healthy children and with a priority for oily fish types which are rich in n-3 LCPUFA and vitamin D.
ForlagDepartment of Nutrition, Exercise and Sports, Faculty of Science, University of Copenhagen
Antal sider149
StatusUdgivet - 2020

ID: 240982688