Vitamin D-related genes and cardiometabolic markers in healthy children: a Mendelian randomisation study.

Observational studies show associations between low serum 25-hydroxyvitamin D (25(OH)D) and cardiometabolic risk markers. This Mendelian randomisation study examined associations between cardiometabolic markers in children and SNP in genes related to vitamin D metabolism (DHCR7; group-specific complement (GC); cytochrome P450 subfamily IIR1 (CYP2R1); and CYP24A1) and action (CYP27B1 and VDR). In 699 healthy 8-11-year-old children, we genotyped eleven SNP. We generated a genetic risk score based on SNP associated with low 25(OH)D and investigated associations between this and blood pressure, plasma lipids and insulin. Furthermore, we examined whether SNP related to vitamin D actions modified associations between 25(OH)D and the cardiometabolic markers. All GC and CYP2R1 SNP influenced serum 25(OH)D. A risk score based on four of the six SNP was associated with 3·4 (95 % CI 2·6, 4·2) mmol/l lower 25(OH)D per risk allele (P < 0·001), but was not associated with the cardiometabolic markers. However, interactions were indicated for the three VDR SNP (Pinteraction < 0·081) on associations between 25(OH)D and TAG, systolic blood pressure and insulin, which all decreased with increasing 25(OH)D only in major allele homozygotes (ß -0·02 (95 % CI -0·04, -0·01) mmol/l; ß -0·5 (95 % CI -0·9, -0·1) mmHg; and ß -0·5 (95 % CI -1·4, 0·3) pmol/l, respectively). In conclusion, genetic variation affected 25(OH)D substantially, but the genetic score was not associated with cardiometabolic markers in children. However, VDR polymorphisms modified associations with vitamin D, which warrants further investigation of VDR's role in the relationship between vitamin D and cardiometabolic risk.

Effects of vitamin D supplementation on cardiometabolic outcomes in children and adolescents: a systematic review and meta-analysis of randomized controlled trials.

PURPOSE: In observational studies, higher S-25-hydroxyvitamin D [S-25(OH)D] has been associated with a more favorable cardiometabolic profile in childhood, but results may be confounded. We examined effects of vitamin D supplementation on cardiometabolic outcomes in children and adolescents. METHODS: We systematically searched relevant databases for randomized controlled trials (RCTs) examining effects of vitamin D supplementation compared to placebo or a lower dose of vitamin D on blood glucose, insulin, homeostatic model assessment of insulin resistance (HOMA-IR), glycated hemoglobin, cholesterol [total, high-density, and low-density lipoprotein (LDL-C)], triglycerides, or blood pressure. We conducted random-effects meta-analyses of weighted mean differences in all participants and in subgroups of overweight/obese versus normal weight participants with or without baseline S-25(OH)D < 50 nmol/L. We also explored associations between responses in S-25(OH)D and outcomes by meta-regression. RESULTS: Fourteen RCTs with a total of 1088 participants aged 4-19 years were included. In the meta-analysis, vitamin D supplementation increased S-25(OH)D by 27 nmol/L [95% CI 16; 37] (P < 0.0001) and increased LDL-C by 0.11 mmol/L [0.02; 0.20] (P = 0.02) without any subgroup differences and a generally low to moderate heterogeneity. Vitamin D supplementation had no other effects. However, in the meta-regression analysis, HOMA-IR decreased by 0.51 points [- 0.97; - 0.04] per 10 nmol/L increase in the endpoint S-25(OH)D among overweight/obese participants (P = 0.04). CONCLUSIONS: These results do not support the use of vitamin D supplementation for improving cardiometabolic health in childhood. Indicated beneficial effects on insulin resistance in those with obesity could be investigated further, while unfavorable effects on LDL-C may be a concern.

Winter vitamin D3 supplementation does not increase muscle strength, but modulates the IGF-axis in young children.

PURPOSE: To explore whether muscle strength, the insulin-like growth factor axis (IGF-axis), height, and body composition were associated with serum 25-hydroxyvitamin D [25(OH)D] and affected by winter vitamin D supplementation in healthy children, and furthermore to explore potential sex differences. METHODS: We performed a double-blind, placebo-controlled, dose-response winter trial at 55ºN. A total of 117 children aged 4-8 years were randomly assigned to either placebo, 10, or 20 µg/day of vitamin D3 for 20 weeks. At baseline and endpoint, we measured muscle strength with handgrip dynamometer, fat mass index (FMI), fat free mass index (FFMI), height, plasma IGF-1, IGF-binding protein 3 (IGFBP-3), and serum 25(OH)D. RESULTS: At baseline, serum 25(OH)D was positively associated with muscle strength, FFMI, and IGFBP-3 in girls only (all p < 0.01). At endpoint, baseline-adjusted muscle strength, FMI and FFMI did not differ between intervention groups. However, baseline-adjusted IGF-1 and IGFBP-3 were higher after 20 µg/day compared to placebo (p = 0.043 and p = 0.006, respectively) and IGFBP-3 was also higher after 20 µg/day compared to 10 µg/day (p = 0.011). Children tended to be taller after 20 µg/day compared to placebo (p = 0.064). No sex interactions were seen at endpoint. CONCLUSIONS: Avoiding the winter-related decline in serum 25(OH)D may influence IGF-1 and IGFBP-3 in children. Larger trials are required to confirm these effects, and the long-term implication for linear growth.

Winter cholecalciferol supplementation at 55°N has little effect on markers of innate immune defense in healthy children aged 4-8 years: a secondary analysis from a randomized controlled trial.

PURPOSE: We explored the effect of winter cholecalciferol (vitamin D3) supplementation on innate immune markers in healthy Danish children (55°N). METHODS: In the double-blind, placebo-controlled trial, ODIN Junior, 119 healthy, white, 4-8 year-olds were randomized to 0 (placebo), 10 or 20 µg/day of vitamin D3 for 20 weeks (October-March). Cheek mucosal swabs, blood samples, and questionnaires on acute respiratory infections the previous month were collected at baseline and endpoint. Innate immune markers were measured as secondary outcomes including in vivo oral mucosal gene expression of calprotectin (S100A9), lipocalin-2 (LCN2), beta-defensin-4 (DEFB4), interleukin-8 (IL-8), viperin (RSAD2), and the cathelicidin-antimicrobial-peptide (CAMP); ex vivo whole-blood lipopolysaccharide (LPS)-induced cathelicidin, IL-8, and IL-6; and plasma cathelicidin, together with serum 25-hydroxyvitamin D [25(OH)D]. RESULTS: Serum 25(OH)D was 56.7 ± 12.3 nmol/L at baseline and 31.1 ± 7.5, 61.8 ± 10.6, and 75.8 ± 11.5 nmol/L at endpoint after placebo, 10 and 20 µg/day of vitamin D3 (P < 0.0001), respectively. A decreased oral mucosal S100A9 expression with placebo [- 18 (95% CI - 1; - 32)%] was marginally avoided with 20 µg/day [6 (- 13; 28)%] (P = 0.06). Likewise, a decreased LPS-induced IL-8 with placebo [- 438 (95% CI - 693; - 184) ng/L] was marginally avoided with 20 µg/day [- 109 (- 374; 157) ng/L] (P = 0.07). All other immune markers and respiratory infection episodes were unaffected by vitamin D3 supplementation (all P > 0.11). CONCLUSIONS: Winter vitamin D3 supplementation of 10 µg/day did not affect innate immune markers, whereas 20 µg/day tended to maintain the capacity to produce a few markers in healthy children.

Winter Cholecalciferol Supplementation at 51°N Has No Effect on Markers of Cardiometabolic Risk in Healthy Adolescents Aged 14-18 Years.

Background: Epidemiologic studies have supported inverse associations between low serum 25-hydroxyvitamin D [25(OH)D] and cardiometabolic risk markers, but few randomized trials have investigated the effect of vitamin D supplementation on these markers in adolescents. Objective: The objective of this study was to investigate the effect of winter-time cholecalciferol (vitamin D3) supplementation on cardiometabolic risk markers in white, healthy 14- to 18-y-old adolescents in the UK (51°N) as part of the ODIN Project. Methods: In a dose-response trial, 110 adolescents (mean ± SD age: 15.9 ± 1.4 y; 43% male; 81% normal weight) were randomly assigned to receive 0, 10 or 20 µg/d vitamin D3 for 20 wk (October-March). Cardiometabolic risk markers including BMI-for-age z score (BMIz), waist circumference, systolic and diastolic blood pressure, fasting plasma triglycerides, cholesterol (total, HDL, LDL, and total:HDL), and glucose were measured at baseline and endpoint as secondary outcomes, together with serum 25(OH)D. Intervention effects were evaluated in linear regression models as between-group differences at endpoint, adjusted for the baseline value of the outcome variable and additionally for age, sex, Tanner stage, BMIz, and baseline serum 25(OH)D. Results: Mean ± SD baseline serum 25(OH)D was 49.1 ± 12.3 nmol/L and differed between groups at endpoint with concentrations of 30.7 ± 8.6, 56.6 ± 12.4, and 63.9 ± 10.6 nmol/L in the 0, 10, and 20 µg/d groups, respectively (P ≤ 0.001). Vitamin D3 supplementation had no effect on any of the cardiometabolic risk markers (all P > 0.05), except for lower HDL (-0.12 mmol/L; 95% CI: -0.21, 0.04 mmol/L; P = 0.003) and total cholesterol (-0.21 mmol/L; 95% CI: -0.42, 0.00 mmol/L; P = 0.05) in the 20 µg/d than in the 10 µg/d group, which disappeared in the fully adjusted analysis (P = 0.27 and P = 0.30, respectively). Conclusions: Supplementation with vitamin D3 at 10 and 20 µg/d, which increased serum 25(OH)D concentrations during the winter-time, had no effect on markers of cardiometabolic risk in healthy 14- to 18-y-old adolescents. This trial was registered at clinicaltrials.gov as NCT02150122.

Winter Cholecalciferol Supplementation at 55°N Has No Effect on Markers of Cardiometabolic Risk in Healthy Children Aged 4-8 Years.

Background: Low serum 25-hydroxyvitamin D [25(OH)D] has been associated with unfavorable cardiometabolic risk profiles in many observational studies in children, but very few randomized controlled trials have investigated this. Objective: We explored the effect of winter-time cholecalciferol (vitamin D3) supplementation on cardiometabolic risk markers in young, white, 4- to 8-y-old healthy Danish children (55°N) as part of the pan-European ODIN project. Methods: In the ODIN Junior double-blind, placebo-controlled, dose-response trial, 119 children (mean ± SD age: 6.7 ± 1.5 y; 36% male; 82% normal weight) were randomly allocated to 0, 10 or 20 µg/d of vitamin D3 for 20 wk (October-March). Cardiometabolic risk markers including BMI-for-age z score (BMIz), waist circumference, systolic and diastolic blood pressure, serum triglycerides and cholesterol (total, LDL, HDL, and total:HDL), plasma glucose and insulin, and whole-blood glycated hemoglobin were measured at baseline and endpoint as secondary outcomes together with serum 25(OH)D. Intervention effects were evaluated in linear regression models as between-group differences at endpoint adjusted for baseline value of the outcome, and additionally for age, sex, baseline serum 25(OH)D, BMIz, time since breakfast, and breakfast content. Results: Mean ± SD serum 25(OH)D was 56.7 ± 12.3 nmol/L at baseline and differed between groups at endpoint with concentrations of 31.1 ± 7.5, 61.8 ± 10.6, and 75.8 ± 11.5 nmol/L in the 0-, 10-, and 20 µg/d groups, respectively (P < 0.0001). Vitamin D3 supplementation had no effect on any of the cardiometabolic risk markers in analyses adjusted for baseline value of the outcome (all P ≥ 0.05), and additional covariate adjustment did not change the results notably. Conclusions: Preventing the winter decline in serum 25(OH)D with daily vitamin D3 supplementation of 10 or 20 µg had no cardiometabolic effects in healthy 4- to 8-y-old Danish children. This trial was registered at www.clinicaltrials.gov as NCT02145195.

Sun behaviour and physical activity associated with autumn vitamin D status in 4-8-year-old Danish children.

OBJECTIVE: To explore determinants of serum 25-hydroxyvitamin D (s-25(OH)D) during autumn in young, Caucasian children not consuming vitamin D-fortified foods or supplements, and explore differences in sun behaviours between pre-school and school children. DESIGN: In September-October, s-25(OH)D was measured by LC-MS/MS; physical activity, sun behaviours and vitamin D intake were assessed with questionnaires. SETTING: Baseline data from the ODIN Junior trial at 55°N. SUBJECTS: Children aged 4-8 years (n 130), of whom 96% gave blood samples. RESULTS: Mean s-25(OH)D was 56·8 (sd 12·5) nmol/l and positively associated with fat-free mass index (P=0·014). Children being active 6-7 h/week had 5·6 (95% CI 1·1, 10·0) nmol/l higher s-25(OH)D than less active children (P=0·014). Children seeking shade sometimes or rarely/never had 7·0 (95% CI 1·2, 12·9; P=0·018) and 7·2 (95% CI 0·8, 13·6; P=0·028) nmol/l higher s-25(OH)D, respectively, than children always/often seeking shade. Pre-school children had more sun-safe behaviour than school children in terms of use of a hat, sunscreen and sunscreen sun protection factor (P<0·05). In school but not pre-school children, using a hat rarely/never was associated with 12·1 (95% CI 2·5, 21·7; P=0·014) nmol/l higher s-25(OH)D v. always/often (P interaction=0·019). Vitamin D intake was not associated with s-25(OH)D (P=0·241). CONCLUSIONS: Physical activity and sun behaviours are associated with s-25(OH)D in young children. Identifying factors influencing autumn s-25(OH)D is relevant to optimize levels before sun exposure diminishes. Strategies to reduce risk of inadequacy should consider risk of skin cancer and sunburn, and could include fortification and/or vitamin D supplementation.

Socio-economic differences in cardiometabolic risk markers are mediated by diet and body fatness in 8- to 11-year-old Danish children: a cross-sectional study.

OBJECTIVE: To explore whether socio-economic differences exist in cardiometabolic risk markers in children and whether lifestyle-related factors potentially mediate these differences. DESIGN: Cross-sectional study including measurements of fasting blood lipids, glucose, homeostasis model assessment of insulin resistance (HOMA-IR), blood pressure and heart rate. Potential mediators examined were fat mass index (FMI); intakes of fruit, vegetables, dietary fibre and added sugar; whole-blood n-3 long-chain PUFA (LCPUFA) as a biomarker of fish intake; and physical activity and sedentary time. SETTING: Nine primary schools in Denmark. SUBJECTS: Children aged 8-11 years (n 715). RESULTS: Children of parents with the shortest compared with longest education had higher TAG by 0·12 (95 % CI 0·04, 0·21) mmol/l and HOMA-IR by 0·36 (0·10, 0·62), whereas children of parents with a vocational education had higher total cholesterol by 0·14 (0·02, 0·27) mmol/l and LDL cholesterol by 0·14 (0·03, 0·25) mmol/l compared with children of parents with the longest education; all P<0·05. FMI explained 25 % of the difference in TAG, 64 % of the difference in HOMA-IR and 21-29 % of the differences in cholesterols. FMI and whole-blood n-3 LCPUFA combined explained 42 % of the difference in TAG, whereas FMI, whole-blood n-3 LCPUFA and dietary fibre explained 89 % of the difference in HOMA-IR. CONCLUSIONS: Socio-economic differences were present in blood lipids and insulin resistance among 8- to 11-year-olds and were mediated by body fatness, whole-blood n-3 LCPUFA and dietary fibre. These lifestyle factors may be targets in public initiatives to reduce socio-economic differences. Confirmation in longitudinal studies and trials is warranted.

Mediation analysis for logistic regression with interactions: Application of a surrogate marker in ophthalmology.

Mediation analysis is often based on fitting two models, one including and another excluding a potential mediator, and subsequently quantify the mediated effects by combining parameter estimates from these two models. Standard errors of such derived parameters may be approximated using the delta method. For a study evaluating a treatment effect on visual acuity, a binary outcome, we demonstrate how mediation analysis may conveniently be carried out by means of marginally fitted logistic regression models in combination with the delta method. Several metrics of mediation are estimated and results are compared to findings using existing methods.

Probiotics and Child Care Absence Due to Infections: A Randomized Controlled Trial.

OBJECTIVES: The risk of infections is higher in children attending child care compared with children cared for at home. This study examined the effect of a combination of probiotics on absence from child care because of respiratory and gastrointestinal infections in healthy infants aged 8 to 14 months at the time of enrollment in child care. METHODS: The ProbiComp study was a randomized, double-blind, placebo-controlled study. A total of 290 infants were randomly allocated to receive a placebo or a combination of Bifidobacterium animalis subsp lactis and Lactobacillus rhamnosus in a dose of 109 colony-forming units of each daily for a 6-month intervention period. Absence from child care, occurrence of infant symptoms of illness, and doctor visits were registered by the parents using daily and weekly Web-based questionnaires. RESULTS: Median absence from child care was 11 days (interquartile range: 6-16). Intention-to-treat analysis showed no difference between the probiotics and placebo groups (P = .19). Additionally, there was no difference in any of the secondary outcomes between groups; the number of children with doctor-diagnosed upper or lower respiratory tract infections, the number of doctor visits, antibiotic treatments, occurrence and duration of diarrhea, and days with common cold symptoms, fever, vomiting, or caregivers' absence from work. CONCLUSIONS: A daily administration of a combination of B animalis subsp lactis and L rhamnosus for 6 months did not reduce the number of days absent from child care in healthy infants at the time of enrollment in child care.

Effects of oily fish intake on cardiovascular risk markers, cognitive function, and behavior in school-aged children: study protocol for a randomized controlled trial.

BACKGROUND: Most children in Western populations do not meet recommendations for fish consumption. Oily fish is an important source of n-3 long-chain polyunsaturated fatty acids (LCPUFA), which reduce blood pressure and plasma triacylglycerol in adults and may affect cognitive development and behavior. However, to our knowledge, the potential effects of oily fish on cardiometabolic health, cognitive function, and behavior in children have not been investigated. The aim of the FiSK Junior study is to investigate the effects of oily fish consumption on cardiovascular risk markers, cognitive function, and behavior in healthy children. METHODS/DESIGN: We are conducting a randomized controlled trial with 8- to 9-year-old Danish children, comparing the effect of consuming 300 g/week of oily fish with poultry (control) for 12 weeks between August 2016 and June 2017. The primary outcomes are blood pressure and fasting plasma triacylglycerol, which will be measured at baseline and endpoint. In addition, we will assess erythrocyte fatty acid composition (compliance), heart rate, plasma cholesterol, markers of glucose homeostasis, growth and body composition, dietary intake, and physical activity and sleep. We will also examine effects on cognitive function (attention, memory, and executive functions) by using standardized tests, behavior and emotions by administering parent-rated questionnaires and child interviews, and we will measure physiological stress response and cortisol levels. We need 150 children to complete the trial to detect a between-groups difference of 2.7 mmHg in diastolic blood pressure and 0.13 mmol/L in plasma triacylglycerol; thus, we aim to recruit 200 children. All outcomes will be analyzed in completer analysis supplemented with sensitivity analyses for the primary outcomes, and attention will be given to potential sex and genotype specificity. DISCUSSION: The results of the FiSK Junior study are expected to fill important gaps in the current knowledge about the importance of dietary fish and n-3 LCPUFA for children's health and development, and may be used when setting dietary recommendations. TRIAL REGISTRATION: ClinicalTrials.gov identifier: NCT02809508 . Registered on 22 June 2016.

Estimation of the dietary requirement for vitamin D in white children aged 4-8 y: a randomized, controlled, dose-response trial.

BACKGROUND: Children in northern latitudes are at high risk of vitamin D deficiency during winter because of negligible dermal vitamin D3 production. However, to our knowledge, the dietary requirement for maintaining the nutritional adequacy of vitamin D in young children has not been investigated. OBJECTIVE: We aimed to establish the distribution of vitamin D intakes required to maintain winter serum 25-hydroxyvitamin D [25(OH)D] concentrations above the proposed cutoffs (25, 30, 40, and 50 nmol/L) in white Danish children aged 4-8 y living at 55°N. DESIGN: In a double-blind, randomized, controlled trial 119 children (mean age: 6.7 y) were assigned to 0 (placebo), 10, or 20 µg vitamin D3/d supplementation for 20 wk. We measured anthropometry, dietary vitamin D, and serum 25(OH)D with liquid chromatography-tandem mass spectrometry at baseline and endpoint. RESULTS: The mean ± SD baseline serum 25(OH)D was 56.7 ± 12.3 nmol/L (range: 28.7-101.4 nmol/L). Serum 25(OH)D increased by a mean ± SE of 4.9 ± 1.3 and 17.7 ± 1.8 nmol/L in the groups receiving 10 and 20 µg vitamin D3/d, respectively, and decreased by 24.1 ± 1.2 nmol/L in the placebo group (P < 0.001). A nonlinear model of serum 25(OH)D as a function of total vitamin D intake (diet and supplements) was fit to the data. The estimated vitamin D intakes required to maintain winter serum 25(OH)D >30 (avoiding deficiency) and >50 nmol/L (ensuring adequacy) in 97.5% of participants were 8.3 and 19.5 µg/d, respectively, and 4.4 µg/d was required to maintain serum 25(OH)D >40 nmol/L in 50% of participants. CONCLUSIONS: Vitamin D intakes between 8 and 20 µg/d are required by white 4- to 8-y-olds during winter in northern latitudes to maintain serum 25(OH)D >30-50 nmol/L depending on chosen serum 25(OH)D threshold. This trial was registered at clinicaltrials.gov as NCT02145195.