Insufficient autumn vitamin D intake and low vitamin D status in 7-year-old Icelandic children

Influence of vitamin D supplementation on muscle strength and exercise capacity in Mongolian schoolchildren: a randomised controlled trial

Objective

To determine whether weekly oral vitamin D supplementation influences grip strength, explosive leg power, cardiorespiratory fitness or spirometric lung volumes in Mongolian schoolchildren.

Methods

Multicentre, randomised, double-blind, placebo-controlled clinical trial conducted in children aged 6-13 years at baseline attending 18 schools in Ulaanbaatar. The intervention was weekly oral doses of 14,000 IU vitamin D3 (n=4418) or placebo (n=4433) for 3 years. Outcome measures were grip strength, standing long jump distance and serum 25-hydroxyvitamin D (25[OH]D) concentrations (determined in all participants), peak oxygen uptake (VO2peak, determined in a subset of 632 participants using 20-metre multi-stage shuttle run tests) and spirometric outcomes (determined in a subset of 1,343 participants).

Results

99.8% of participants had serum 25(OH)D concentrations <75 nmol/L at baseline, and mean end-study 25(OH)D concentrations in children randomised to vitamin D vs. placebo were 77.4 vs. 26.7 nmol/L (mean difference 50.7 nmol/L, 95% CI, 49.7 to 51.4). However, vitamin D supplementation did not influence mean grip strength, standing long jump distance, VO2peak, spirometric lung volumes or peak expiratory flow rate, either overall or within sub-groups defined by sex, baseline 25(OH)D concentration <25 vs. ≥25 nmol/L or calcium intake <500 vs. ≥500 mg/day.

Conclusion

A 3-year course of weekly oral supplementation with 14,000 IU vitamin D3 elevated serum 25(OH)D concentrations in Mongolian schoolchildren with a high baseline prevalence of vitamin D deficiency. However, this intervention did not influence grip strength, explosive leg power, peak oxygen uptake or spirometric lung volumes, either overall or in sub-group analyses.

Vitamin D Determinants, Status, and Antioxidant/Anti-inflammatory-Related Effects in Cardiovascular Risk and Disease: Not the Last Word in the Controversy

Beyond its key role in calcium homeostasis, vitamin D has been found to significantly affect the cardiovascular (CV) system. In fact, low vitamin D levels have been associated with increased CV risk, as well as increased CV morbidity and mortality. The majority of effects of this molecule are related directly or indirectly to its antioxidative and anti-inflammatory properties. Generally, vitamin D insufficiency is considered for 25-hydroxyvitamin D (25(OH)D) levels between 21-29 ng/mL (corresponding to 52.5-72.5 nmol/L), deficiency as 25(OH)D levels less than 20 ng/mL (<50 nmol/L), and extreme deficiency as 25(OH)D less than 10 ng/mL (<25 nmol/L). However, the definition of an optimal vitamin D status, as defined by 25(OH)D, remains controversial for many extra-bone conditions, including CV disease. In this review, confounding factors affecting the 25(OH)D measurement and status will be discussed. In particular, available evidence on the mechanism and role of vitamin D in relation to CV risk and disease through its antioxidant effect will be reported, also facing the aspect regarding the debate on the minimum blood 25(OH)D level required to ensure optimal CV health.

Relationship between vitamin D and physical activity: systematic review and meta-analysis

Abstract Vitamin D plays an important role in immune function and inflammation and the physical activity demonstrate relationship near to syntheses of vitamin D, considering to necessary to factors immunologics, environmental and physical. We searched five databases through February 20, 2021. Two reviewers screened the studies, collected data, assessed the risk of bias, and ranked the evidence for each outcome across the studies, independently and in duplicate. The prespecified endpoints of interest were Cardiorespiratory Fitness; Sunlight Exposure; Body Mass Index (BMI). We only included data from peer-reviewed articles in our primary analyses. In our primary analysis, there was a positive trend between serum 25(OH)D <20 ng/ml and body mass index, this result should be interpreted with caution, considering confidence intervals (RR 1.10 95% CI 0.37 to 1.83. We identified 4 high quality evidence that vitamin D levels and high physical activity required a direct relationship considering (four trials with 2,253) ; RR 0. (RR 0.0; 95% CI -0.15 to 0.15) (RR 0.59; 95% CI 0.43 to 0.75. Although the evidence available so far, from observational studies of medium quality, can be seen as showing a trend towards an association between sufficient serum levels of 25(OH)D and physical activity, this relationship has been shown. have a stimulating effect on vitamin D synthesis, the relationship of low body mass index with sufficient vitamin D levels is not based on solid evidence. We await results from ongoing studies to determine this effectiveness.

25-Hydroxyvitamin D and Cardiorespiratory Fitness in Prepubertal Overweight and Obese Children

Childhood obesity has become a major global health problem. Vitamin D deficiency and poor cardiorespiratory fitness are highly prevalent in children with overweight or obesity, but little is known about their relationships. In this study, we aimed to analyze the relationship between serum 25-hydroxyvitamin D (25(OH)D) and cardiorespiratory fitness parameters in prepubertal obese and overweight children. A cross-sectional design with a sample of 57 prepubertal children, aged 9–11 years, with overweight or obesity was used. The fasting concentration of 25(OH)D was analyzed with a chemiluminescent microparticle immunoassay. Fat and lean body masses were determined by using DXA. Maximal oxygen uptake (VO_2max) was measured with the maximal treadmill test. A total of 68.4% of the sample had sufficient levels of 25(OH)D. As expected, their cardiorespiratory fitness was poor compared with that of normal-weight children, but 60% of the group exceeded the median obesity-specific reference values. No differences were found between the sexes for relative VO_2max or 25(OH)D levels. Moreover, no correlations were found between 25(OH)D and body composition or cardiorespiratory parameters for sex or vitamin D groups. Vitamin D status seems not to be directly related to body composition or cardiorespiratory fitness in prepubertal overweight or obese children.

Serum 25-hydroxyvitamin D concentrations in 16-year-old Icelandic adolescent and its association with bone mineral density

OBJECTIVE

The aim of the study was to assess the potential association between serum 25-hydroxyvitamin D (25(OH)D) and whole-body bone mineral density (BMD) among 16-year-old adolescents and to study the prevalence of 25(OH)D insufficiency, defined as concentration under 50 nmol/l.

DESIGN

A cross-sectional study.

SETTING

Reykjavik, Iceland, latitude 64°08'N. Measurements took place in the Icelandic Heart Association's research lab during April-June 2015.

PARTICIPANTS

In total, 411 students in Reykjavik, Iceland, were invited to participate, 315 accepted the invitation (76·6 %) and 289 had valid data (mainly Caucasian).

RESULTS

25(OH)D < 50 nmol/l was observed in 70 % of girls and 66·7 % of boys. 25(OH)D ≥ 50 nmol/l was significantly associated with higher whole-body BMD after adjusting for the influence of sex, height, fat mass and lean mass. A linear relationship between 25(OH)D and whole-body BMD was significant for 25(OH)D < 50 nmol/l (n 199, P < 0·05) but NS for 25(OH)D ≥ 50 nmol/l (n 86, P = 0·48).

CONCLUSIONS

Our results are in line with some but not all previous studies on the relationship between BMD and 25(OH)D in adolescents. The observed difference in BMD between those with above v. below a 25(OH)D concentration of 50 nmol/l was of about a fifth of one SD, which may have a clinical relevance as one SD decrease in volumetric BMD has been associated with a 89 % increase in 2 years risk of fracture. Icelandic adolescents should be encouraged to increase their vitamin D intake as it is possible that their current intake is insufficient to achieve optimal peak bone mass.

Vitamin D Status and Analysis of Specific Correlates in Preschool Children: A Cross-Sectional Study in Southern Croatia

Vitamin D deficiency is a globally important problem, particularly in children, but there is a lack of information regarding this deficiency in preschool children from southeastern Europe. This study aimed to establish the levels of 25-hydroxyvitamin D (25(OH)D) and associations of gender, time spent outdoors, physical activity (PA), and body mass index (as predictors) with the 25(OH)D level (outcome) in healthy preschool children. The participants were preschoolers (all 5⁻6 years of age) from southern Croatia. All the participants were tested during their mandatory medical examination 6⁻7 months prior to school enrollment. The PA was obtained using the preschool-age physical activity questionnaire (Pre-PAQ), which categorizes PA into five levels (from sedentary to vigorous PA). The prevalence of 25(OH)D deficiency was high: 58% of the children had 25(OH)D levels of <50 nmol/L (deficiency), and an additional 29% had an insufficient level of 25(OH)D (50⁻75 nmol/L). Boys had higher levels of 25(OH)D than girls. A multinomial regression using 25(OH)D categories as the outcome and a sufficient level (>75 nmol/L) as the reference value identified gender as the only significant predictor of 25(OH)D status, with boys being at lower risk for 25(OH)D deficiency than girls. These results showed a high prevalence of 25(OH)D deficiency in preschoolers from the southern part of Croatia, which is additionally alarming based on the geographical position of the studied region (42° N) and its high number of sunshine hours (>2600 h per year). Future studies examining other potential correlates of 25(OH)D in the region are warranted.

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 (n130), of whom 96% gave blood samples.

Results

Mean s-25(OH)D was 56·8 (sd12·5) 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)Dv. always/often (Pinteraction=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.

Increased vitamin D intake differentiated according to skin color is needed to meet requirements in young Swedish children during winter: a double-blind randomized clinical trial

Background: Dark skin and low exposure to sunlight increase the risk of vitamin D insufficiency in children.Objective: The aim of the study was to evaluate the amount of vitamin D needed to ascertain that most children >4 y of age attain sufficient serum 25-hydroxyvitamin D [S-25(OH)D; i.e., ≥50 nmol/L] during winter regardless of latitude and skin color.Design: In a longitudinal, double-blind, randomized, food-based intervention study, 5- to 7-y-old children from northern (63°N) and southern (55°N) Sweden with fair (n = 108) and dark (n = 98) skin were included. Children, stratified by skin color by using Fitzpatrick's definition, were randomly assigned to receive milk-based vitamin D₃ supplements that provided 2 (placebo), 10, or 25 μg/d during 3 winter months.Results: Mean daily vitamin D intake increased from 6 to 17 μg and 26 μg in the intervention groups supplemented with 10 and 25 μg, respectively. In the intention-to-treat analysis, 90.2% (95% CI: 81.1%, 99.3%) of fair-skinned children randomly assigned to supplementation of 10 μg/d attained sufficient concentrations, whereas 25 μg/d was needed in dark-skinned children to reach sufficiency in 95.1% (95% CI: 88.5%, 100%). In children adherent to the study product, 97% (95% CI: 91.3%, 100%) and 87.9% (95% CI: 76.8%, 99%) of fair- and dark-skinned children, respectively, achieved sufficient concentrations if supplemented with 10 μg/d. By using 95% prediction intervals for 30 and 50 nmol S-25(OH)D/L, intakes of 6 and 20 μg/d are required in fair-skinned children, whereas 14 and 28 μg/d are required in children with dark skin.Conclusion: Children with fair and dark skin require vitamin D intakes of 20 and 28 μg/d, respectively, to maintain S-25(OH)D ≥50 nmol/L, whereas intakes of 6 and 14 μg/d, respectively, are required to maintain concentrations ≥30 nmol/L during winter. This trial was registered at clinicaltrials.gov as NCT01741324.

Vitamin D status of Icelandic children and its influence on bone accrual

The importance of vitamin D for children's bone health has been well established, but the effects of less severe deficiency are not fully known. The main objective of this study was to assess the vitamin D status of Icelandic children at the age of 7, and again at 9 years of age, and the association of vitamin D status with bone mineral content and bone accrual over 2 years. We invited 321 children to participate in this study, and 267 (83 %) took part; 211 (79 %) underwent a DXA scan and 164 were again scanned 2 years later; 159 (60 %) vitamin D samples were measured and 119 (75 %) were measured again 2 years later. At age 7, 65 % of the children had vitamin D concentrations <50 nmol/l, and at age 9 this figure was 60 %. At age 7, 43 % of the children had insufficient amounts of vitamin D (37.5-50 nmol/l), and 22 % had a vitamin D deficiency (<37.5 nmol/l). In linear regression analysis, no association was found between vitamin D and bone mineral content. Furthermore, there was no significant difference in bone accrual over 2 years for the children with insufficient or deficient vitamin D at both ages, compared to those having more than 50 nmol/l at both time points. More than 60 % of Icelandic children have inadequate concentrations of vitamin D in serum repeatedly over a 2-year interval. However, vitamin D in the range did not have a significant effect on bone mineral content or accrual at ages 7 and 9.

Vitamin D Intake and Status in 6-Year-Old Icelandic Children Followed up from Infancy

High serum 25-hydroxyvitamin D (25(OH)D) levels have been observed in infants in Nordic countries, likely due to vitamin D supplement use. Internationally, little is known about tracking vitamin D status from infancy to childhood. Following up 1-year-old infants in our national longitudinal cohort, our aims were to study vitamin D intake and status in healthy 6-year-old Icelandic children (n = 139) and to track vitamin D status from one year of age. At six years, the mean 25(OH)D level was 56.5 nmol/L (SD 17.9) and 64% of children were vitamin D sufficient (25(OH)D ≥ 50 nmol/L). A logistic regression model adjusted for gender and breastfeeding showed that higher total vitamin D intake (Odds ratio (OR) = 1.27, 95% confidence interval (CI) = 1.08–1.49), blood samples collected in summer (OR = 8.88, 95% CI = 1.83–43.23) or autumn (OR = 5.64, 95% CI = 1.16–27.32) compared to winter/spring, and 25(OH)D at age one (OR = 1.02, 95% CI = 1.002–1.04) were independently associated with vitamin D sufficiency at age six. The correlation between 25(OH)D at age one and six was 0.34 (p = 0.003). Our findings suggest that vitamin D status in infancy, current vitamin D intake and season are predictors of vitamin D status in early school age children. Our finding of vitamin D status tracking from infancy to childhood provides motivation for further studies on tracking and its clinical significance.

Vitamin D intake and status in 12-month-old infants at 63-66° N

The objective was to assess the vitamin D status in healthy 12-month-old infants in relation to quantity and sources of dietary vitamin D, breastfeeding and seasons. Subjects were 76 12-month-old infants. Serum levels of 25-hydroxyvitamin D (25(OH)D) ≥ 50 nmol/L were considered indicative of vitamin D sufficiency and 25(OH)D < 27.5 nmol/L as being indicative of increased risk for rickets. Additionally, 25(OH)D > 125 nmol/L was considered possibly adversely high. Total vitamin D at 9-12 months (eight data collection days) included intake from diet and supplements. The mean ± SD of vitamin D intake was 8.8 ± 5.2 μg/day and serum 25(OH)D 98.1 ± 32.2 nmol/L (range 39.3-165.5). Ninety-two percent of infants were vitamin D sufficient and none at increased risk for rickets. The 26% infants using fortified products and supplements never/irregularly or in small amounts had lower 25(OH)D (76.8 ± 27.1 nmol/L) than the 22% using fortified products (100.0 ± 31.4 nmol/L), 18% using supplements (104.6 ± 37.0 nmol/L) and 33% using both (110.3 ± 26.6 nmol/L). Five of six infants with 25(OH)D < 50 nmol/L had no intake of supplements or fortified products from 0 to 12 months. Supplement use increased the odds of 25(OH)D > 125 nmol/L. Breastfeeding and season did not affect vitamin D status. The majority of infants were vitamin D sufficient. Our findings highlight the need for vitamin D supplements or fortified products all year round, regardless of breastfeeding.