Adverse interaction of low-calcium diet and low 25(OH)D levels on lumbar spine mineralization in late-pubertal girls

Factors Associated With Weight Loss After Laparoscopic Adjustable Gastric Banding in Adolescents With Severe Obesity

Childhood obesity is associated with many comorbidities. Bariatric surgery is known to be efficient for reducing weight in adolescents.

Objectives

The primary outcome was to identify somatic or psychosocial factors associated with success at 24 months after a laparoscopic adjustable gastric banding (LAGB) procedure in our cohort of adolescents with severe obesity. Secondary endpoints were to describe weight loss outcomes, comorbidity resolution, and complications.

Methods

We have retrospectively reviewed medical records of patients who had LAGB placed between 2007 and 2017. Factors associated with success at 24 months after LAGB were researched, with success being defined as positive percentage of excess weight loss (%EWL) at 24 months.

Results

Forty-two adolescents underwent a LAGB procedure, the mean %EWL was 34.1% at 24 months, with improvement in most comorbidities and without major complications. Having lost weight before surgery was associated with success, whereas a high body mass index at surgery was associated with a higher risk of failure. No other factor was found to be associated with success.

Conclusion

Comorbidities mostly improved 24 months after LAGB and no major complication occurred. Having lost weight before surgery was associated with a successful surgery, whereas a high body mass index at surgery increases the risk of failure.

A population based case-control study of association between dietary calcium intake and ulcerative colitis in adults

Limited data are available on the association of dietary calcium intake and ulcerative colitis (UC). We aimed to investigate the relation between dietary calcium intake and UC prevalence in Iranian adults. In this population-based case-control study, diagnosed patients with UC by gastroenterologists that were registered in the Iranian inflammatory bowel disease registry were included as cases. Age and sex-matched healthy controls were selected from Study on the Epidemiology of Psychological, Alimentary Health and Nutrition (SEPAHAN) dataset. Dietary calcium intakes of participants were examined through a validated food frequency questionnaire. We included 327 middle-aged participants (109 cases and 218 controls) in the analysis; 52.1% of them were females. After adjustments for potential confounders, individuals in the third tertile of dietary calcium intake had 92% lower odds of UC, compared to those in the first tertile (OR = 0.08, 95% CI 0.02-0.27). Our analysis based on recommended dietary allowances (RDAs) intake showed that dietary Ca intake deficiency was related to increased odds of UC (OR = 9.5, 95% CI 2.98-30.91). Stratified analysis by gender revealed that these associations were significant in both genders; although the results were stronger in the male population. A Significant decreasing trend was observed for odds of UC in tertiles of dietary calcium intakes, in both males and females. Higher dietary calcium intake was associated with lower UC prevalence in Iranian adults. Inadequate dietary calcium intake was also linked to elevated odds of UC. Further prospective investigations are needed to affirm these findings.

Acquisition of peak bone mass

Peak bone mass (PBM) is a key determinant of bone mass and fragility fractures later in life. The increase in bone mass during childhood and adolescence is mainly related to an increase in bone size rather to changes in volumetric bone density. Race, gender, and genetic factors are the main determinants of PBM achievement. Nevertheless, environmental factors such as physical activity, calcium and protein intakes, weight and age at menarche, are also playing an important role in bone mass accrual during growth. Therefore, optimization of calcium and protein intakes and weight-bearing physical activity during growth is an important strategy for optimal acquisition of PBM and bone strength and for contributing to prevent fractures later in life.

Pubertal Suppression, Bone Mass, and Body Composition in Youth With Gender Dysphoria

BACKGROUND AND OBJECTIVES

Puberty onset and development contribute substantially to adolescents' bone mass and body composition. Our objective with this study was to examine the effects of gonadotropin-releasing hormone agonists (GnRHa) on these puberty-induced changes among youth with gender dysphoria (GD).

METHODS

Medical records of the endocrine diversity clinic in an academic children's hospital were reviewed for youth with GD seen from January 2006 to April 2017 with at least 1 baseline dual-energy radiograph absorptiometry measurement.

RESULTS

At baseline, transgender females had lower lumbar spine (LS) and left total hip (LTH) areal bone mineral density (aBMD) and LS bone mineral apparent density (BMAD) z scores. Only 44.7% of transgender youth were vitamin D sufficient. Baseline vitamin D status was associated with LS, LTH aBMD, and LS BMAD z scores. Post-GnRHa assessments revealed a significant drop in LS and LTH aBMD z scores (transgender males and transgender females) without fractures and LS BMAD (transgender males), an increase in gynoid (fat percentage), and android (fat percentage) (transgender males and transgender females), and no changes in BMI z score.

CONCLUSIONS

GnRHa monotherapy negatively affected bone mineral density of youth with GD without evidence of fractures or changes in BMI z score. Transgender youth body fat redistribution (android versus gynoid) were in keeping with their affirmed gender. The majority of transgender youth had vitamin D insufficiency or deficiency with baseline status associated with bone mineral density. Vitamin D supplementation should be considered for all youth with GD.

Vitamin D Status Is Associated with Modifiable Lifestyle Factors in Pre-Adolescent Children Living in Urban Kuala Lumpur, Malaysia

Studies on vitamin D status and its determinants in growing children in countries with ample sunshine such as Malaysia have been limited. The aim of our study was to determine factors associated with serum 25(OH)D concentrations such as lifestyle, dietary intake, anthropometry, and body composition in 243 pre-adolescent Malaysian children from low-income families living in Kuala Lumpur. This cross-sectional study measured bone density and body composition using dual-energy X-ray absorptiometry (DXA), while serum 25(OH)D was measured using LC-MS/MS. Time spent outdoors, body surface area exposed to sunlight, dietary intake, and physical activity level were assessed using questionnaires. Multiple linear regression and stepwise analysis were performed to identify significant predictors for serum 25(OH)D. About 69.4% had 25(OH)D < 50 nmol/L, and 18.9% were vitamin-D-deficient with 25(OH)D < 30 nmol/L. Girls had a nine-fold higher prevalence of vitamin D deficiency than boys. Body surface area exposed to sunlight, Sun Index, and fat mass were significant predictors of 25(OH)D concentrations in this population. Modifiable lifestyle factors such as sun exposure and reducing obesity are important public health guidance to ensure optimal vitamin D status in these children.

Effects of milk powder intervention on bone mineral density and indicators related to bone metabolism in Chinese adolescents

The study is to determine the effects of milk powder on bone density and metabolism in healthy adolescents. Vitamin D and calcium supplements increased IGF-1 but did not affect bone mineralization or turnover. Higher vitamin D in combination with sufficient calcium supplementation in such populations requires attention.

INTRODUCTION

Both calcium and vitamin D play an important role in bone mineralization in adolescents.

METHODS

In this one and a half-year randomized controlled trial, 232 participants (aged 12-15 years) were randomly assigned to three intervention groups receiving milk powder fortified with vitamin D 400 IU plus calcium 300, or 600, or 900 mg [Ca3D (n = 54), Ca6D (n = 56), and Ca9D (n = 49)], or one control group maintaining habitual diet [control (n = 73)]. Bone turnover markers, serum intact PTH, 25(OH)D, and IGF-1 levels were measured at baseline and one and a half years, and bone mineral contents and bone areal mineral density were measured by Dual-energy X-ray absorptiometry (DXA) at baseline, one year, and one and a half years.

RESULTS

Baseline average serum 25(OH)D level and calcium intake were 29.4 nmol/L and 363.5 mg/day, respectively. There was a significant increase in bone turnover, total body, hip, lumbar spine bone mineral density (BMD), and total body BMC as well as slight fluctuations in 25(OH)D levels over one and a half years without between-group differences. Significantly decreased serum PTH level was only observed in the Ca6D group (31%, p < 0.0001), in which the intervention effect was also significant (p = 0.0029) compared with the control group. IGF-1 levels increased significantly in all intervention groups (18.5 to 22.8%, p < 0.05) but decreased in the control group (16.5%, p < 0.05), and the group by time interaction was also significant (p = 0.0029).

CONCLUSIONS

Our study showed that in healthy adolescents with low vitamin D status and calcium intake, mild vitamin D and mild to modest calcium supplements increased IGF-1 but did not affect bone mineralization or turnover. Higher vitamin D in combination with sufficient calcium supplementation in such populations requires attention.

Vitamin D in children with growth hormone deficiency due to pituitary stalk interruption syndrome

Background

Recent studies have shown a relationship between vitamin D status and growth hormone (GH) and insulin-like growth factor 1 (IGF1). The objective of this study was to assess vitamin D status in children with GH deficiency due to pituitary stalk interruption syndrome (PSIS) and to investigate the relationship between 25-hydroxyvitamin D (25OHD) and 1,25-dihydroxyvitamin D (1,25 (OH) ₂D) serum levels and patient characteristics.

Methods

A retrospective single-center study of 25OHD and 1,25(OH)₂D serum concentrations in 50 children with PSIS at the initial evaluation before treatment.

Results

Mean concentrations of 33.2 ± 18.0 ng/mL for 25OHD and 74.5 ± 40.7 ng/L for 1,25(OH)₂D were measured. Additionally, 25OHD concentrations were significantly higher in boys than in girls (p = 0.04) and lower in the cold season than in the sunny season (p = 0.03). Significant positive correlations were observed between the GH peak and serum 1,25 (OH) ₂D concentrations (Rho = 0.35; p = 0.015) and the 1,25(OH)₂D/25OHD ratio (Rho = 0.29; p < 0.05). No correlation was found for other characteristics, including IGF1.

Conclusions

Vitamin D status in children with hypothalamic-pituitary deficiency due to PSIS was similar to that reported in national and European studies in healthy children. The positive significant correlations between the GH peak and the 1,25 (OH)₂D concentration as well as with the 1,25 (OH)₂D/25OHD ratio suggest that even in these patients who had severely impaired GH secretion and low IGF1 levels, an interplay between the GH/IGF1 axis and the vitamin D system still exists.

Does vitamin D supplementation improve bone density in vitamin D-deficient children? Protocol for an individual patient data meta-analysis

INTRODUCTION

Our previous study-level (aggregate data) meta-analysis suggested that vitamin D supplements may be beneficial for bone density specifically in children with vitamin D deficiency. However, the misclassification of vitamin D status inherent in study-level data means that the results are not definitive and cannot provide an accurate assessment of the size of any effect. Therefore, we propose to undertake an individual patient data (IPD) meta-analysis to determine whether the effect of vitamin D supplementation on bone density in children differs according to baseline vitamin D status, and to specifically estimate the effect of vitamin D in children who are vitamin D deficient.

METHODS AND ANALYSIS

This study has been designed to adhere to the Preferred Reporting Items for Systematic Review and Meta-Analyses of IPD statement. We will include randomised placebo-controlled trials of vitamin D supplementation reporting bone density outcomes at least 6 months after the study commenced in children and adolescents (aged <20 years) without coexistent medical conditions or treatments causing osteoporosis. We will update the search of the original review to cover the period 2009-2017, using the same methods as the original review. Fully anonymised data on all randomised patients will be requested. Outcomes will be femoral neck, total hip, lumbar spine and proximal and distal forearm bone mineral density, and total body bone mineral content. A two-stage IPD meta-analysis will be used to examine the effect of baseline serum 25-hydroxyvitamin D (25(OH)D) on treatment effect for each bone density outcome. Restricted maximum likelihood will be used to estimate the random-effects meta-analysis models, with 95% CI for summary effects. Heterogeneity will be assessed by I2 and potential publication bias (small-study effects) and availability bias by funnel plots, Egger's test and Peter's test.

ETHICS AND DISSEMINATION

Ethics approval will not be required as the data are to be used for the primary purpose for which they were collected and all original individual studies had ethics approval. Results of the IPD meta-analysis will be submitted for publication in a peer-reviewed journal.

PROSPERO REGISTRATION NUMBER

CRD42017068772.

There is no association between vitamin D status and characteristics of central precocious puberty in girls

Vitamin D deficiency has been associated with several pathologies in humans and has recently been linked to idiopathic central precocious puberty in girls. We evaluated this potential link in a retrospective study. Among 493 girls with idiopathic central precocious puberty previously described, we selected 145 girls for whom a plasma sample at the initial evaluation was available to determine the concentration of 25OHD and 1,25(OH)2D. We analyzed the correlation between different puberty characteristics (BMI, growth rate the year before the onset of puberty, bone age, LH and FSH peaks, LH/FSH peak ratio, and estradiol concentration) and the concentration of 25OHD and 1,25(OH)2D. The mean 25OHD serum concentration was 27.6±17.3 ng/mL. Eleven percent of the patients had a severe vitamin D deficiency, 18.6% had a moderate deficiency, 39.4% had an optimal vitamin D status, and 31% had a 25OHD concentration above 30 ng/mL. Season was the only factor that appeared to influence the 25OHD concentration. No correlation was found between 25OHD serum concentration and different puberty characteristics.

CONCLUSION

Overall, our patients had a satisfactory vitamin D status. We did not find any correlation between vitamin D status and the characteristics of central precocious puberty. Further studies are required to confirm this hypothesis. What is known: • Vitamin D status seems to affect gonadal hormones and fertility. • Vitamin D deficiency may contribute to earlier puberty and was associated with earlier menarche. What is new: • 25OHD of 145 girls with precocious puberty was similar to or higher than that of healthy French children or adolescents. • We did not find any correlation between vitamin D status and puberty characteristics.

A systematic review of vitamin D status in southern European countries

PURPOSE

Despite an acknowledged dearth of data on serum 25-hydroxyvitamin D (25(OH)D) concentrations from Southern European countries, inter-country comparison is hampered by inconsistent data reporting. The purpose of the current study was to conduct a systematic literature review of available data on serum 25(OH)D concentrations and estimate vitamin D status in Southern European and Eastern Mediterranean countries, both at a population level and within key population subgroups, stratified by age, sex, season and country.

METHODS

A systematic review of the literature was conducted to identify and retrieve scientific articles reporting data on serum 25(OH)D concentration and/or vitamin D status following standard procedures.

RESULTS

Data were extracted from 107 studies, stratified by sex and age group, representing 630,093 individuals. More than one-third of the studies reported mean 25(OH)D concentrations below 50 nmol/L and ~ 10% reported mean serum 25(OH)D concentrations below 25 nmol/L. Overall, females, neonates/ infants and adolescents had the higher prevalence of poor vitamin D status. As expected, there was considerable variability between studies. Specifically, mean 25(OH)D ranged from 6.0 (in Italian centenarians) to 158 nmol/L (in elderly Turkish men); the prevalence of serum 25(OH)D < 50 nmol/L ranged from 6.8 to 97.9% (in Italian neonates).

CONCLUSIONS

Contrary to expectations, there was a high prevalence of low vitamin D status in the Southern Europe and the Eastern Mediterranean regions, despite abundant sunshine. These data further emphasize the need for strategies, such as fortification of foods with vitamin D and/or vitamin D supplementation, which will be tailored to the needs of specific population groups with higher risk of insufficiency or deficiency, to efficiently tackle the pandemic of hypovitaminosis D in Europe.

Prevalence of vitamin D insufficiency among adolescents and its correlation with bone parameters using high-resolution peripheral quantitative computed tomography

Vitamin D deficiency and insufficiency are highly prevalent among adolescents in Hong Kong, which is a sub-tropical city with ample sunshine. Vitamin D level is significantly correlated with key bone density and bone quality parameters. Further interventional studies are warranted to define the role of vitamin D supplementation for improvement of bone health among adolescents.

INTRODUCTION

The relationship between bone quality parameters and vitamin D (Vit-D) status remains undefined among adolescents. The aims of this study were to evaluate Vit-D status and its association with both bone density and bone quality parameters among adolescents.

METHODS

Three hundred thirty-three girls and 230 boys (12-16 years old) with normal health were recruited in summer and winter separately from local schools. Serum 25(OH) Vit-D level, bone density and quality parameters by Dual Energy X-ray Absorptiometry (DXA) and High-Resolution peripheral Quantitative Computed Tomography (HR-pQCT), dietary calcium intake, and physical activity level were assessed.

RESULTS

Sixty-four point seven percent and 11.4 % of subjects were insufficient [25 ≤ 25(OH)Vit-D ≤ 50 nmol/L] and deficient [25(OH)Vit-D < 25 nmol/L] in Vit-D, respectively. The mean level of serum 25(OH)Vit-D in summer was significantly higher than that in winter (44.7 ± 13.6 and 35.9 ± 12.6 nmol/L, respectively) without obvious gender difference. In girls, areal bone mineral density (aBMD) and bone mineral content (BMC) of bilateral femoral necks, cortical area, cortical thickness, total volumetric bone mineral density (vBMD), and trabecular thickness were significantly correlated with 25(OH)Vit-D levels. In boys, aBMD of bilateral femoral necks, BMC of the dominant femoral neck, cortical area, cortical thickness, total vBMD, trabecular vBMD, BV/TV, and trabecular separation were significantly correlated with 25(OH)Vit-D levels.

CONCLUSION

Vit-D insufficiency was highly prevalent among adolescents in Hong Kong with significant correlation between Vit-D levels and key bone density and bone quality parameters being detected in this study. Given that this is a cross-sectional study and causality relationship cannot be inferred, further interventional studies investigating the role of Vit-D supplementation on improving bone health among adolescents are warranted.

Calcium Intake, Major Dietary Sources and Bone Health Indicators in Iranian Primary School Children

Background:

Adequate calcium intake may have a crucial role with regards to prevention of many chronic diseases, including hypertension, hypercholesterolemia, different types of cancer, obesity and osteoporosis. In children, sufficient calcium intake is especially important to support the accelerated growth spurt during the preteen and teenage years and to increase bone mineral mass to lay the foundation for older age.

Objectives:

This study aimed to assess daily calcium intake in school-age children to ensure whether they fulfill the FGP dairy serving recommendations, the recommended levels of daily calcium intake and to assess the relationship between dietary calcium intake and major bone health indicators.

Patients and Methods:

A total of 501 Iranian school-age children were randomly selected. Calcium intake was assessed using a semi-quantitative food frequency questionnaire. Bone health indicators were also assessed.

Results:

Dairy products contributed to 69.3% of the total calcium intake of the children. Daily adequate intake of calcium was achieved by 17.8% of children. Only 29.8% met the Food guide pyramid recommendations for dairy intake. Dietary calcium intake was not significantly correlated with serum calcium and other selected biochemical indicators of bone health.

Conclusions:

The need for planning appropriate nutrition strategies for overcoming inadequate calcium intake in school age children in the city of Tehran is inevitable.

Vitamin D status of schoolchildren in Northern Algeria, seasonal variations and determinants of vitamin D deficiency

There are no published data on the vitamin D status of children living in North Africa. In 435 healthy Algerian children 5-15 years old, we found that vitamin D insufficiency (serum 25-hydroxyvitamin D (25OHD) <50 nmol/L) was frequent, especially in winter. Low vitamin D status was associated with increased parathyroid hormone (PTH) and leg deformation

INTRODUCTION

As there are no published data on the vitamin D status of children living in North Africa, we evaluated the 25OHD concentration of healthy Algerian children at the end of summer and at the end of winter. As secondary objectives, we studied the various determinants of vitamin D status and the PTH-25OHD relationship in these subjects.

METHODS

Four hundred thirty-five children 5-15 years old were examined and had a blood sample in September 2010. Of them, 408 were sampled again in March 2011.

RESULTS

Median 25OHD concentration in the whole group was 71.4 nmol/L in September and 52.9 nmol/L in March. In September, 58.4, 29.9, and 8.1% had a 25OHD concentration below 75, 50, and 30 nmol/L respectively. In March, these percentages increased to 65.2, 41.4, and 17.4% for the 75, 50, and 30 nmol/L threshold, respectively. In multivariate analysis, older age, darker skin phototype, low daily vitamin D and calcium intake, poor socioeconomic status, and short daily sun exposure remained significantly associated with a 25OHD <50 nmol/L at both visits. In 72 (16.6%) children, genu varum/valgum was present. Compared to the 363 children without leg deformation, they presented more frequently with the risk factors of vitamin D insufficiency. They also had lower 25OHD concentrations and higher PTH and tALP. Serum PTH and 25OHD concentrations were negatively and significantly correlated (r = -0.43; p < 0.001) without a 25OHD threshold above which PTH does not decrease anymore.

CONCLUSION

Despite a sunny environment, vitamin D insufficiency is frequent in healthy Algerian children.

Dietary calcium intake in patients with inflammatory bowel disease

BACKGROUND & AIMS

Osteopenia and increased risk for fractures in IBD result from several factors.

AIM OF THE STUDY

To investigate the dietary intake of calcium in IBD patients.

METHODS

A 22-item quantitative validated frequency food questionnaire was used for quantifying dietary calcium in relation to gender and age, in 187 IBD patients, 420 normal- and 276 diseased controls.

STATISTICAL ANALYSIS

Mann-Whitney, chi-square- and T-tests.

RESULTS

The mean calcium intake was 991.0 ± 536.0 (105.8% Recommended Daily Allowances) and 867.6 ± 562.7 SD mg/day (93.8% RDA) in healthy and diseased controls, and 837.8 ± 482.0 SD mg/day (92.7% RDA) in IBD, P<0.001. Calcium intake was high in celiac disease (1165.7 ± 798.8 SD mg/day, 120% RDA), and non-significantly lower in ulcerative colitis than in Crohn's disease (798.7 ± 544.1 SD mg/day vs 881.9 ± 433.0). CD and UC females, but not males, had a mean calcium intake well under RDA. In all study groups the intake was lower in patients believing that consumption of lactose-containing food induced symptoms, versus those who did not (105.8% vs 114.3% RDA in normal controls; 100.4% vs 87.6% RDA in IBD).

CONCLUSIONS

Diet in IBD patients contained significantly less calcium than in healthy controls. Gender and age, more than diagnosis, are central in determining inadequate calcium intake, more so in IBD. Self-reported lactose intolerance, leading to dietary restrictions, is the single major determinant of low calcium intake. Inadequate calcium intake is present in one third of IBD patients and represents a reversible risk factor for osteoporosis, suggesting the need for tailored nutritional advice in IBD.

Calcium intake in health maintenance - a systematic review

Background

Calcium (Ca) is an essential nutrient for the human body. Despite lively research, there is uncertainty about Ca requirements in terms of desirable health outcomes including an upper intake level above which the potential for harm increases.

Objectives

The aim was to conduct a review to update requirements and desirable or harmful health effects of Ca on the current scientific evidence.

Methods

We searched Medline and Swemed from January 2000 to December 2011 and included all systematic reviews that reported Ca supplementation or usual Ca intake on health outcomes. Meta-analyses, randomized clinical trials and cohort studies were included in the second search between May 2009 and March 2011 and an additional search covering studies till the end of 2011. This review concentrated on studies reporting independent effects of Ca, although a few recent trials report sole effects of Ca on health outcomes, most trials use Ca in combination with vitamin D vs. placebo.

Results

In total, we reviewed 38 studies addressing the effects of Ca on bone, pregnancy-related outcomes, cancers, cardiovascular outcomes, obesity, and mortality. There was a lot of heterogeneity in the study protocols, which made it difficult to draw any strong conclusions. According to the literature, high Ca intake seems to have a small positive effect on bone mineral content (BMC) or bone mineral density (BMD) in children and postmenopausal women. We did not find any consistent evidence on the effects of Ca on bone health in premenopausal women or men. Also, the evidence that Ca supplementation reduces fracture incidence is scarce and inconsistent. Maternal diet may influence the peak bone mass of offspring but more studies are required. There was no overall effect of Ca intake on cancers. Ca was associated with a decreased risk of breast cancer and a slightly increased risk of prostate cancer in two of the three studies. No associations were found with other cancers. We found no consistent association between cardiovascular outcomes and Ca intake except for blood pressure. A small decrease of 2–4 mmHg in systolic blood pressure was found in pregnant and in hypertensive subjects with Ca supplementation. Reviewed studies did not show consistent evidence relating Ca intake to either mortality or obesity.

Conclusion

Based on this evidence, there is no need to change the Nordic recommendations for Ca intake. However, due to heterogeneity in the studies it is difficult to interpret the results and provide single summary statement.

Vitamin D and bone health in childhood and adolescence

Vitamin D plays a key role in bone metabolism. The link between vitamin D deficiency and rickets is well understood. However, subclinical vitamin D deficiency may also be detrimental to bone health in childhood. Its effects on bone mineralization have the potential to result in lower peak bone mass being attained, which could in turn contribute to increased fracture risk in both childhood and older adult life. As vitamin D deficiency is common globally, any detrimental effects of vitamin D deficiency on bone health are likely to have substantial public health implications. This review describes the current literature relevant to vitamin D and bone health in childhood and adolescence, with a particular emphasis on evaluating the emerging evidence for the impact of subclinical vitamin D deficiency on bone health and the effectiveness of vitamin D supplementation. The evidence suggests that subclinical vitamin D deficiency does affect bone acquisition, potentially beginning in utero and extending into adolescence. However, the effectiveness of vitamin D supplementation for improving bone health in situations of subclinical deficiency remains unclear, particularly in early life where there are few trials with bone density outcomes. The available evidence suggests that benefits are likely to be greatest in or even restricted to children with serum 25-hydroxyvitamin D levels at least below 50 nmol/L and possibly even lower than this. Trials of sufficient duration in deficient pregnant mothers, infants, and children are urgently required to address critical evidence gaps.

Maternal vitamin D status and calcium intake interact to affect fetal skeletal growth in utero in pregnant adolescents

BACKGROUND

Maternal calcium intake and vitamin D status may affect fetal bone development.

OBJECTIVE

This study was designed to examine relations between maternal calcium intake, 25-hydroxyvitamin D [25(OH)D] status, and fetal bone growth across pregnancy.

DESIGN

This was a prospective longitudinal design. Maternal 25(OH)D, parathyroid hormone, and 1,25-dihydroxyvitamin D [1,25(OH)(2)D] were determined at midgestation (∼26 wk) and at delivery in 171 adolescents (≤ 18 y). Dietary recalls and fetal sonograms were performed up to 3 times across gestation, and fetal femur and humerus z scores were generated.

RESULTS

Fetal femur and humerus z scores and neonatal birth length were significantly greater (P < 0.03) in adolescents consuming ≥ 1050 mg than in those consuming <1050 mg Ca/d. Maternal 25(OH)D > 50 nmol/L was significantly positively associated with fetal femur and humerus z scores (P < 0.01). When maternal smoking, height, race, weight gain, and gestational age were controlled for, these relations remained significant. Interactions between calcium intake and 25(OH)D were evident. Calcium intake was associated with fetal femur z scores and birth length only when maternal 25(OH)D was ≤ 50 nmol/L (P < 0.05). Similarly, maternal 25(OH)D was associated with fetal femur and humerus z scores only when maternal calcium intake was <1050 mg/d (P < 0.03).

CONCLUSIONS

Optimal calcium intake and adequate maternal vitamin D status are both needed to maximize fetal bone growth. Interactions between these nutrients were evident when either calcium or vitamin D status was limited. Improving maternal calcium intake and/or vitamin D status during pregnancy may have a positive effect on fetal skeletal development in pregnant adolescents.

Vitamin D: still a topical matter in children and adolescents. A position paper by the Committee on Nutrition of the French Society of Paediatrics

The aims of the present position paper by the Committee on Nutrition of the French Society of Paediatrics were to summarize the recently published data on vitamin D in infants, children and adolescents, i.e., on metabolism, physiological effects, and requirements and to make recommendations on supplementation after careful review of the evidence. Scientific evidence indicates that calcium and vitamin D play key roles in bone health. The current evidence, limited to observational studies, however, does not support other benefits for vitamin D. More targeted research should continue, especially interventional studies. In the absence of any underlying risk of vitamin D deficiency, the recommendations are as follows: pregnant women: a single dose of 80,000 to 100,000 IU at the beginning of the 7th month of pregnancy; breastfed infants: 1000 to 1200 IU/day; children less than 18 months of age, receiving milk supplemented with vitamin D: an additional daily dose of 600 to 800 IU; children less than 18 months of age receiving milk not supplemented with vitamin D: daily dose of 1000 to 1200 IU; children from 18 months to 5 years of age: 2 doses of 80,000 to 100,000 IU every winter (November and February). In the presence of an underlying risk of vitamin D deficiency (dark skin; lack of exposure of the skin to ultraviolet B [UVB] radiation from sunshine in summer; skin disease responsible for decreased exposure of the skin to UVB radiation from sunshine in summer; wearing skin-covering clothes in summer; intestinal malabsorption or maldigestion; cholestasis; renal insufficiency; nephrotic syndrome; drugs [rifampicin; antiepileptic treatment: phenobarbital, phenytoin]; obesity; vegan diet), it may be justified to start vitamin D supplementation in winter in children 5 to 10 years of age as well as to maintain supplementation of vitamin D every 3 months all year long in children 1 to 10 years of age and in adolescents. In some pathological conditions, doses of vitamin D can be increased. If necessary, the determination of 25(OH) vitamin D serum concentration will help determine the level of vitamin D supplementation.

Daily supplementation with 25 μg cholecalciferol does not increase calcium absorption or skeletal retention in adolescent girls with low serum 25-hydroxyvitamin D

In healthy adolescents, cross-sectional studies show either no or negative relationships between serum 25-hydroxyvitamin D [25(OH)D] and calcium (Ca) absorption. Using a 2-period metabolic balance study, the effect of vitamin D supplementation on Ca absorption and retention in adolescent girls was investigated. Eleven girls aged 12-14 y with a mean entry serum 25(OH)D of 35.1 nmol/L consumed a controlled intake (providing 5 μg vitamin D and 1117 mg Ca/d) for two 3-wk metabolic balance periods separated by a 1-wk washout period. Sunlight exposure was minimized by sunscreen with a sun protection factor ≥ 15. After the first metabolic balance period, participants received 25 μg/d cholecalciferol supplementation for 4 wk. Fractional Ca absorption was measured in each metabolic balance period using a stable Ca isotope method. All urine and fecal samples were collected and analyzed to measure net Ca absorption and Ca retention. Paired t tests and correlations were used to analyze the data. Daily supplementation with 25 μg vitamin D resulted in a mean increase in serum 25(OH)D of 13.3 nmol/L (P < 0.01) but a decrease in fractional Ca absorption of 8.3% (P < 0.05) and no significant change in fasting serum 1,25-dihydroxyvitamin D, parathyroid hormone, net Ca absorption, or Ca skeletal retention. In pubertal girls with vitamin D status considered insufficient in adults, vitamin D supplementation of 25 μg/d for 4 wk did not improve fractional Ca absorption, net Ca absorption, or Ca retention.