Serum 25-hydroxyvitamin D levels and bone mineral density in 16-20 years-old girls: lack of association

Association of serum 25-hydroxyvitamin D with bone health measured by calcaneal quantitative ultrasound: a large cross-sectional analysis in children and adolescents

Background: Vitamin D plays a crucial role in bone health; however, findings in children and adolescents remain inconsistent, and few studies have examined its impact on bone health measured by quantitative ultrasound (QUS). This study aims at assessing the relationship between serum vitamin D levels and bone health, as evaluated by QUS, across varying pubertal stages and genders. Methods: A baseline cross-sectional survey of an ongoing cohort study included 4682 children and adolescents aged 6 to 18 years from Shenzhen, China. Serum levels of 25-hydroxyvitamin D (25(OH)D), which is the sum of 25(OH)D2 and 25(OH)D3, were quantified using liquid chromatography-mass spectrometry. Bone health was measured through calcaneal QUS, utilizing the speed of sound (SOS) in the heel as a principal measure-a higher SOS indicating a denser bone structure. Generalized linear models were used to evaluate the association of serum 25(OH)D, 25(OH)D2, and 25(OH)D3 levels with the SOS. Results: Forty-one point-one percent of this population was vitamin D deficient (serum 25(OH)D < 20 ng ml-1), with only 11.1% being sufficient. In the fully adjusted model, we observed a significant positive association between increased serum 25(OH)D quartiles and SOS. Compared with the participants in the lowest quartiles of serum 25(OH)D, those in successive quartiles of 25(OH)D were 3.54 (95% CI: 0.81, 6.28) m s-1, 5.74 (95% CI: 2.87, 8.61) m s-1, and 8.83 (95% CI: 5.83, 11.84) m s-1, respectively (P for trend < 0.0001). The correlations observed for serum 25(OH)D2 and 25(OH)D3 with SOS were similar to those of serum 25(OH)D. Importantly, this association was primarily observed in post-pubertal children and adolescents but was absent in pre- and mid-pubertal participants (P for interaction = 0.0004). Conclusion: Elevated serum 25(OH)D levels were associated with better bone health, as measured through calcaneal QUS, in children and adolescents, particularly among those who had reached the post-pubertal stage. These findings highlight the crucial importance of maintaining sufficient vitamin D levels to support optimal bone health in this demographic.

Vitamin D status in adults and children in Transcarpathia, Ukraine in 2019

Background

Vitamin D deficiency is a global health problem, it is assessed by measuring serum 25-hydroxivitamin D (25(OH) D), nevertheless epidemiological data for many countries remains underreported.

Objectives

To study the prevalence of vitamin D deficiency throughout the calendar year in a large cohort recruited ina multiethnic Transcarpathian region of Ukraine.

Methods

In this retrospective study 25(OH) D serum concentration was measured during all 12 months of the year 2019 by electrochemoluminescent assay on the automatic analyzer Cobas e411 in 1823 subjects, including both children and adults (1551 females (85.03%) and 273 males (14.97%)).

Results

The mean 25(OH) D concentration in adults demonstrates significantly lower levels compared to children (22.67 ± 8.63 ng/ml vs. 26.00 ± 10.72 ng/ml respectively, p < 0.001). Adult women expressed significantly lower mean annual serum 25 (OH) D concentrations in comparison to men (22.29 ± 8.46 ng/ml vs. 25.75 ± 9.38 ng/ml respectively, p < 0.001). In contrast, children did not show a significant difference between sexes (girls 24.98 ± 10.38 ng/ml vs. boys 27.01 ± 11.01 ng/ml, p = 0.2003). In the winter months, 25(OH) D levels fell below 20 ng/ml in 51,74% of adult population of Thranscarpathia, and in 12.91%, − below 12 ng/ml.

Conclusions

The results of this study contradict the previously reported evaluations of the vitamin D levels in Ukraine which were assessed by measuring serum 25(OH) D. Specifically, only approximately half of the studied population is vitamin D deficient during winter season. This study features the most representative sample size in Ukraine to date.

25-Hydroxyvitamin D, Vitamin D Binding Protein, Bioavailable 25-Hydroxyvitamin D, and Body Composition in a Diverse Sample of Women Collegiate Indoor Athletes

Women athletes are at higher risk for bone diseases; yet, information on vitamin D status ((25(OH)D), vitamin D binding protein (VDBP), and bioavailable 25(OH)D is limited. Collegiate athletes (n = 36) from volleyball (WVB), basketball (WBB), and track and field (WTF) were measured for (25(OH)D), VDBP, and bioavailable 25(OH)D; body composition and bone mineral density (BMD); and skin pigmentation. Participants self-reported daily vitamin D intake and sun exposure. One-way analysis of variance analyzed mean differences in measures across sports. Linear regression examined relationships between 25(OH)D; VDBP; bioavailable 25(OH)D; and whole body, hip, and spine BMD. Participants' (mean ± SD, 19.4 ± 1.4 years, 172.75 ± 8.21 cm, 70.9 ± 13.2 kg, and 22.9 ± 4.1% body fat) overall mean 25(OH)D was 70.5 ± 32.25 nmol/L, and 28% of participants were deemed inadequate and 61% below thresholds identified as sufficient for athletes. Although WBB athletes consumed higher (p = 0.007) dietary vitamin D (760.9 ± 484.2 IU/d) than WVB (342.6 ± 257.8) and WTF (402.3 ± 376.4) athletes did, there were no differences across sport in serum 25(OH)D. WVB and WTF had higher bioavailable 25(OH)D than WBB. No relationships existed between vitamin D status and body composition. Vitamin D inadequacy was identified among 1/3 of women indoor sport athletes. Consistent monitoring of vitamin D status and diet are recommended to sustain athlete health and sport performance.

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.

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 adolescence: evidence-based dietary requirements and implications for public health policy

Vitamin D is a unique nutrient. First, it acts as a pro-hormone and secondly, the requirement for vitamin D can be met by both endogenous synthesis from sunlight and by dietary sources. This complicates the determination of dietary requirements for vitamin D, which along with the definition of optimal vitamin D status, have been highly controversial and much debated over recent years. Adolescents are a population group at high risk of low vitamin D status, which is concerning given the important role of vitamin D, and calcium, in promoting normal bone mineralisation and attainment of peak bone mass during this rapid growth phase. Dietary vitamin D recommendations are important from a public health perspective in helping to avoid deficiency and optimise vitamin D status for health. However limited experimental data from winter-based dose-response randomised trials in adolescents has hindered the development of evidence-based dietary requirements for vitamin D in this population group. This review will highlight how specifically designed randomised trials and the approach adopted for estimating such requirements can lead to improved recommendations. Such data indicate that vitamin D intakes of between 10 and about 30 µg/d may be required to avoid deficiency and ensure adequacy in adolescents, considerably greater than the current recommendations of 10-15 µg/d. Finally this review will consider the implications of this on public health policy, in terms of future refinements of vitamin D requirement recommendations and prioritisation of public health strategies to help prevent vitamin D deficiency.

Vitamin D deficiency/insufficiency from childhood to adulthood: Insights from a sunny country

Vitamin D is known to be a key regulator of bone metabolism and is associated with muscle strength. Vitamin D deficiency is widely prevalent worldwide. In adults, vitamin D deficiency has been implicated in numerous health conditions including osteoporosis, cancer, diabetes, and autoimmune diseases. Considerable changes have occurred in lifestyles and childhood activities in the past years. Studies have shown that the children population is at high risks of vitamin D deficiency. The objective of this study was to learn about the extent of vitamin D deficiency in children worldwide and especially in sunny country like Israel. In this article we reviewed the extent and severity of vitamin D deficiency worldwide and especially in Israel, through a very comprehensive review of previous reports and research studies done during the last years. We found reports on vitamin D deficiency in children, which was associated with metabolic syndromes and obesity. It was more prevalent in children who spend less time on outdoor activities, in obese children, and in cases when there was imbalance between nutritional intakes and requirements. Vitamin D deficiency is common even in children living in sunny places like Israel. Health professionals should be aware of the fact that although vitamin D deficiency is prevalent in the elderly population, it is also common in children, and can be associated with different illnesses. We encourage supplementation of vitamin D to special populations (pregnant and lactating women, infants, and high risk groups). We also encourage implementation of international food fortification programs.

Determinants of vitamin D status in young adults: influence of lifestyle, sociodemographic and anthropometric factors

BACKGROUND

Very few studies have investigated the determinants of circulating 25-hydroxyvitamin D (25[OH]D) in young adults (18-25 years old) using a set of variables that include lifestyle, sociodemographic, and anthropometric data. Our aim was to investigate the association between these variables and vitamin D status in a sample of untreated young adults.

METHODS

A total of 738 young adults were enrolled in a (June cross-sectional study 2012 to May 2014) and were recruited from educational institutions in the Copenhagen area. For multivariate logistic regression subjects was categorized based on 25[OH]D in serum into; vitamin D sufficiency (S-25[OH]D > 50 nmol/L), vitamin D insufficiency (25 nmol/L ≤ S-25[OH]D ≤ 50 nmol/L), vitamin D deficiency (S-25[OH]D < 25 nmol/L). Information on lifestyle factors and education was obtained by self-reported questionnaires.

RESULTS

700 subjects with a valid measurement of S-25[OH]D and a completed questionnaire was analysed. 238 had vitamin D insufficiency, 135 had vitamin D deficiency of which 13 had severe vitamin D deficiency (S-25[OH]D < 12.5 nmol/L). The relative risk (RR) for vitamin D deficiency was highest for men 2.09 (1.52, 2.87); obese subjects 2.00 (1.27, 3.15); smokers 1.33 (1.02, 1.73); subjects who exercised 0-½ hours a week 1.88 (1.21, 2.94); and subjects who consumed fast food once a week 1.59 (1.05, 2.43). The relative risk was significantly lower for subjects who were studying for a Bachelor's degree (0.40 (0.23, 0.68). For vitamin D insufficiency, the highest RR was again for men 1.31 (1.06, 1.61); obese subjects 1.57 (1.17, 2.11); and subjects who exercised 0-½ hours a week 1.51 (1.11, 2.06).

CONCLUSION

In this study of young adults, vitamin D deficiency was highly prevalent. Modifiable factors such as smoking, maintenance of normal BMI, and physical activity are all potential targets for interventional trials to determine the causal order; such knowledge would be useful in improving S-25[OH]D in young adults. The small group with severe vitamin D deficiency warrants increased attention.

Building healthy bones throughout life: an evidence-informed strategy to prevent osteoporosis in Australia

Osteoporosis imposes a tremendous burden on Australia: 1.2 million Australians have osteoporosis and 6.3 million have osteopenia. In the 2007–08 financial year, 82 000 Australians suffered fragility fractures, of which > 17 000 were hip fractures. In the 2000–01 financial year, direct costs were estimated at $1.9 billion per year and an additional $5.6 billion on indirect costs. Osteoporosis was designated a National Health Priority Area in 2002; however, implementation of national plans has not yet matched the rhetoric in terms of urgency. Building healthy bones throughout life, the Osteoporosis Australia strategy to prevent osteoporosis throughout the life cycle, presents an evidence-informed set of recommendations for consumers, health care professionals and policymakers. The strategy was adopted by consensus at the Osteoporosis Australia Summit in Sydney, 20 October 2011. Primary objectives throughout the life cycle are: to maximise peak bone mass during childhood and adolescence to prevent premature bone loss and improve or maintain muscle mass, strength and functional capacity in healthy adults to prevent and treat osteoporosis in order to minimise the risk of suffering fragility fractures, and reduce falls risk, in older people. The recommendations focus on three affordable and important interventions — to ensure people have adequate calcium intake, vitamin D levels and appropriate physical activity throughout their lives. Recommendations relevant to all stages of life include: daily dietary calcium intakes should be consistent with Australian and New Zealand guidelines serum levels of vitamin D in the general population should be above 50nmol/L in winter or early spring for optimal bone health regular weight-bearing physical activity, muscle strengthening exercises and challenging balance/mobility activities should be conducted in a safe environment.

Vitamin D: An overview of vitamin D status and intake in Europe

In recent years, there have been reports suggesting a high prevalence of low vitamin D intakes and vitamin D deficiency or inadequate vitamin D status in Europe. Coupled with growing concern about the health risks associated with low vitamin D status, this has resulted in increased interest in the topic of vitamin D from healthcare professionals, the media and the public. Adequate vitamin D status has a key role in skeletal health. Prevention of the well-described vitamin D deficiency disorders of rickets and osteomalacia are clearly important, but there may also be an implication of low vitamin D status in bone loss, muscle weakness and falls and fragility fractures in older people, and these are highly significant public health issues in terms of morbidity, quality of life and costs to health services in Europe. Although there is no agreement on optimal plasma levels of vitamin D, it is apparent that blood 25-hydroxyvitamin D [25(OH)D] levels are often below recommended ranges for the general population and are particularly low in some subgroups of the population, such as those in institutions or who are housebound and non-Western immigrants. Reported estimates of vitamin D status within different European countries show large variation. However, comparison of studies across Europe is limited by their use of different methodologies. The prevalence of vitamin D deficiency [often defined as plasma 25(OH)D <25 nmol/l] may be more common in populations with a higher proportion of at-risk groups, and/or that have low consumption of foods rich in vitamin D (naturally rich or fortified) and low use of vitamin D supplements. The definition of an adequate or optimal vitamin D status is key in determining recommendations for a vitamin D intake that will enable satisfactory status to be maintained all year round, including the winter months. In most European countries, there seems to be a shortfall in achieving current vitamin D recommendations. An exception is Finland, where dietary survey data indicate that recent national policies that include fortification and supplementation, coupled with a high habitual intake of oil-rich fish, have resulted in an increase in vitamin D intakes, but this may not be a suitable strategy for all European populations. The ongoing standardisation of measurements in vitamin D research will facilitate a stronger evidence base on which policies can be determined. These policies may include promotion of dietary recommendations, food fortification, vitamin D supplementation and judicious sun exposure, but should take into account national, cultural and dietary habits. For European nations with supplementation policies, it is important that relevant parties ensure satisfactory uptake of these particularly in the most vulnerable groups of the population.

A systematic review of vitamin D status in populations worldwide

Vitamin D deficiency is associated with osteoporosis and is thought to increase the risk of cancer and CVD. Despite these numerous potential health effects, data on vitamin D status at the population level and within key subgroups are limited. The aims of the present study were to examine patterns of 25-hydroxyvitamin D (25(OH)D) levels worldwide and to assess differences by age, sex and region. In a systematic literature review using the Medline and EMBASE databases, we identified 195 studies conducted in forty-four countries involving more than 168 000 participants. Mean population-level 25(OH)D values varied considerably across the studies (range 4·9-136·2 nmol/l), with 37·3 % of the studies reporting mean values below 50 nmol/l. The highest 25(OH)D values were observed in North America. Although age-related differences were observed in the Asia/Pacific and Middle East/Africa regions, they were not observed elsewhere and sex-related differences were not observed in any region. Substantial heterogeneity between the studies precluded drawing conclusions on overall vitamin D status at the population level. Exploratory analyses, however, suggested that newborns and institutionalised elderly from several regions worldwide appeared to be at a generally higher risk of exhibiting lower 25(OH)D values. Substantial details on worldwide patterns of vitamin D status at the population level and within key subgroups are needed to inform public health policy development to reduce risk for potential health consequences of an inadequate vitamin D status.

Determinants of bone microarchitecture and mechanical properties in obese men

CONTEXT

Recent studies have suggested that obesity in men is associated with increased fracture risk. Obesity in men is also associated with dysregulation of the GH/IGF-I and gonadal steroid axes, important regulators of bone homeostasis.

OBJECTIVE

The aim of the study was to investigate body composition and endocrine determinants of bone microarchitecture and mechanical properties in obese men.

DESIGN AND SETTING

We conducted a cross-sectional study at a clinical research center.

PARTICIPANTS

Thirty-five obese men (mean age, 33.8 ± 6.4 yr; mean body mass index, 36.5 ± 5.8 kg/m(2)) participated in the study.

OUTCOME MEASURES

Distal radius microarchitecture and mechanical properties were measured by three-dimensional high-resolution peripheral quantitative computed tomography and microfinite element analysis; body composition by computed tomography; bone marrow fat by proton magnetic resonance spectroscopy; total and free estradiol and testosterone; IGF-I; peak glucagon-stimulated GH; 25-hydroxyvitamin D.

RESULTS

Men with high visceral adipose tissue (VAT) had impaired mechanical properties compared to men with low VAT (P < 0.05), despite comparable body mass index. VAT was inversely associated and thigh muscle was positively associated with mechanical properties (P < 0.05). Bone marrow fat was inversely associated with cortical parameters (P ≤ 0.02). Free estradiol was positively associated with total density (P = 0.05). Free testosterone was positively associated with trabecular thickness and inversely with trabecular number (P ≤ 0.05). Peak stimulated GH was positively associated with trabecular thickness, as was IGF-I with cortical area (P ≤ 0.04).

CONCLUSION

VAT and bone marrow fat are negative predictors and muscle mass is a positive predictor of microarchitecture and mechanical properties in obese men. Testosterone, estradiol, and GH are positive determinants of trabecular microarchitecture, and IGF-I is a positive determinant of cortical microarchitecture. This supports the notion that VAT is detrimental to bone and that decreased GH and testosterone, characteristic of male obesity, may exert deleterious effects on microarchitecture, whereas higher estradiol may be protective.

Efficacy of optimization of vitamin D in preventing osteoporosis and osteoporotic fractures: A systematic review

Increased intake or supplementation of vitamin D is often recommended for normal bone health; however, its preventive effect on osteoporosis has not been fully evaluated. The aim of this review is to gather evidence of the efficacy of the optimization of vitamin D nutrition in preventing osteoporosis and osteoporotic fractures. PubMed was used for searching the relevant literature using the MeSH terms "Bone Density (limited to "human", "female", and "English" literature)" or "Fractures (limited to "human", "age ≥45 years", and "English" literature)", and "Vitamin D". The searches yielded 19 randomized controlled trials (RCTs), nine cohort studies, 19 case-control studies, 19 cross-sectional studies, and one meta-analysis. We attempted to answer three questions: 1) does increased vitamin D intake prevent bone loss in peri- and postmenopausal women?, 2) does increased vitamin D intake prevent osteoporotic fractures in the elderly?, and 3) does increased vitamin D in take positively affect peak bone mass attainment in young women? The answer to questions 1 and 2 is that a vitamin D intake of 10-17.5 μg/day (400-700 IU/day) or more is effective in preventing bone loss in late postmenopausal women and an intake of 17.5-20 μg/day (700-800 IU/day) or more together with a calcium supplement reduces the risk of osteoporotic fractures. For question 3, some lines of evidence support the negative effect of low vitamin D nutrition on the attainment of peak bone mass in young women. Further studies are needed to clarify the effect of vitamin D in this age group.

A global representation of vitamin D status in healthy populations

PURPOSE

This paper visualizes the available data on vitamin D status on a global map, examines the existing heterogeneities in vitamin D status and identifies research gaps.

METHODS

A graphical illustration of global vitamin D status was developed based on a systematic review of the worldwide literature published between 1990 and 2011. Studies were eligible if they included samples of randomly selected males and females from the general population and assessed circulating 25-hydroxyvitamin D [25(OH)D] levels. Two different age categories were selected: children and adolescents (1-18 years) and adults (>18 years). Studies were chosen to represent a country based on a hierarchical set of criteria.

RESULTS

In total, 200 studies from 46 countries met the inclusion criteria, most coming from Europe. Forty-two of these studies (21 %) were classified as representative. In children, gaps in data were identified in large parts of Africa, Central and South America, Europe, and most of the Asia/Pacific region. In adults, there was lack of information in Central America, much of South America and Africa. Large regions were identified for which the mean 25(OH)D levels were below 50 nmol/L.

CONCLUSIONS

This study provides an overview of 25(OH)D levels around the globe. It reveals large gaps in information in children and adolescents and smaller but important gaps in adults. In view of the importance of vitamin D to musculoskeletal growth, development, and preservation, and of its potential importance in other tissues, we strongly encourage new research to clearly define 25(OH)D status around the world.

Determinants of bone mineral density in obese premenopausal women

Despite being a risk factor for cardiovascular disease and diabetes mellitus, obesity has been thought to protect against osteoporosis. However, recent studies have demonstrated a differential impact of specific fat compartments on bone mineral density (BMD) with visceral adipose tissue (VAT) having potential detrimental effects on BMD. Visceral obesity is also associated with dysregulation of the GH/IGF-1 axis, an important regulator of bone homeostasis. The purpose of our study was to evaluate the differential effects of abdominal fat depots and muscle, vitamin D, and hormonal determinants, including insulin-like growth factor-1 (IGF-1), testosterone, and estradiol, on trabecular BMD of the lumbar spine. We studied 68 healthy obese premenopausal women (mean BMI, 36.7±4.2 kg/m(2)). Quantitative computed tomography (QCT) was used to assess body composition and lumbar trabecular BMD. There was an inverse association between BMD and VAT, independent of age and BMI (p=0.003). IGF-1 correlated positively with BMD and negatively with VAT and, in stepwise multivariate regression modeling, was the strongest predictor of BMD and procollagen type 1 amino-terminal propeptide (P1NP). Thigh muscle cross sectional area (CSA) and thigh muscle density were also associated with BMD (p<0.05), but 25-hydroxyvitamin D [25(OH)D], testosterone, free testosterone, and estradiol levels were not. 25(OH)D was associated inversely with BMI, total, and subcutaneous abdominal adipose tissue (p<0.05). These findings support the hypothesis that VAT exerts detrimental effects, whereas muscle mass exerts positive effects on BMD in premenopausal obese women. Moreover, our findings suggest that IGF-1 may be a mediator of the deleterious effects of VAT on bone health through effects on bone formation.

Vitamin D status and PTH in young men: a cross-sectional study on associations with bone mineral density, body composition and glucose metabolism

OBJECTIVE

Although vitamin D and bone metabolism are closely related, few studies have addressed the effects of vitamin D status on bone in men at time of peak bone mass. The objectives of this study were to evaluate the prevalence of vitamin D inadequacy in a cross-sectional study in young men and the effects of vitamin D and parathyroid hormone (PTH) on bone mass, bone markers and metabolic function.

DESIGN AND PARTICIPANTS

The study population consisted of 783 men aged 20-29 years.

MEASUREMENTS

Bone mineral density (BMD) of the total hip, femoral neck and lumbar spine was measured. dual-energy X-ray absorptiometry was used to evaluate total body fat mass (BFAT). Visceral fat mass and abdominal subcutaneous fat mass (ViFM and ScFM) were assessed using magnetic resonance imaging. A radioimmunoassay was used to measure the level of 25-hydroxy vitamin D (25OHD).

RESULTS

The prevalence of vitamin deficiency (serum 25OHD < 50 nm) was 6·3% during summer and 43·6% during winter. Serum 25OHD was associated with BMD at all sites and inversely associated with bone-specific alkaline phosphatase and directly with carboxyterminal telopeptide of type-1-collagen. 25OHD and PTH were inversely associated with BFAT, whereas 25OHD also was inversely associated with body mass index, waist-hip ratio, ViFM and ScFM after adjustment for confounders. The associations were found only to be present in participants with insufficient levels of 25OHD. 25-Hydroxy vitamin D and PTH were inversely related to insulin resistance in vitamin-insufficient participants only. No associations between PTH or 25OHD and blood pressure were noted.

CONCLUSION

The study showed a high prevalence of 25OHD deficiency in young, northern European men, which was significantly associated with decreased BMD. PTH and 25OHD were found to be inversely related to the markers of insulin resistance.

Low vitamin D status has an adverse influence on bone mass, bone turnover, and muscle strength in Chinese adolescent girls

Our goal in this cross-sectional study was to investigate the influence of low-vitamin D status on bone mass, bone turnover, and muscle strength in 301 healthy Chinese adolescent girls. Blood plasma 25-hydroxyvitamin D [25(OH)D] was measured by RIA and plasma and urine biomarkers of bone turnover were measured. Bone mineral content (BMC) and density and bone area for the whole body and the distal and proximal forearm were measured by dual energy X-ray absorptiometry. When vitamin D deficiency was defined as a serum 25(OH)D concentration of < or =50 nmol/L and severe deficiency as <25 nmol/L, 57.8% of subjects were vitamin D deficient and 31.2% were severely deficient. Multivariate analysis shows that girls with adequate vitamin D status had higher size-adjusted BMC for the whole body (P < 0.001), distal forearm (P < 0.001), and proximal forearm (P < 0.01) than those with poorer vitamin D status after adjusting for body size, handgrip strength, physical activity, and dietary intakes of calcium and vitamin D. Similar results were also found for handgrip muscle strength. Participants with adequate vitamin D status had significantly lower concentrations of bone alkaline phosphatase in plasma and deoxypyridinoline:creatinine ratio in urine compared with those of the vitamin D-deficient girls. Adolescent girls with adequate vitamin D status had significantly higher bone mass and muscle strength compared with those with poor vitamin D status. This may be attributed in part to a lower rate of bone remodeling with adequate vitamin D status. These findings suggest that adequate vitamin D status during adolescence is important for optimizing bone mass, which may lead to higher peak bone mass at maturity. Poor vitamin D status also compromises forearm muscle strength.

Positive association between the course of vitamin D intake and bone mineral density at 36 years in men

INTRODUCTION

Studies on the association of vitamin D and bone mineral density (BMD) in adolescence and young adults have shown contrasting results. None of these studies have examined the course and baseline in vitamin D intake. The purpose of this study was to examine the association between baseline and the course of dietary vitamin D intake on the BMD.

METHODS

Vitamin D intake was assessed 3-8 times between the age of 13 and 36 years in 152 men and 168 women from the Amsterdam Growth and Health Longitudinal Study. The BMD of the femoral neck, lumbar spine, total hip and total body was measured at the age of 36 years with dual-energy X-ray absorptiometry. Linear regression analyses were used to determine the vitamin D intake pattern in time for each subject. The models provide a baseline, course and fluctuation of the vitamin D intake for each subject. These were used in separate regression analyses with the dependent variable BMD.

RESULTS

Mean baseline vitamin D was 6.86 (SD: 2.18) microg/day for men and 4.90 (1.19) microg/day for women. Mean course of vitamin D was -0.10 (0.12) microg/day/year and -0.05 (0.18) microg/day/year for men and women respectively. After adjustment for potential confounders and correcting for the other parameters of vitamin D intake, the associations between baseline vitamin D intake and BMD were significant in the total hip (0.018 g/cm(2) per -1 microg/day; 95% CI 0.001-0.035) and total body (0.015 per -1 microg/day; 0.001-0.029). The course of vitamin D intake was associated with BMD in the lumbar spine (0.50 g/cm(2) per -1 microg/day/year; 0.130-0.867), femoral neck (0.42 g/cm(2) per -1 microg/day/year; 0.10-0.743), total body (0.34 g/cm(2) per -1 microg/day/year; 0.09-0.59) and total hip (0.44 g/cm(2) per -1 microg/day/year; 0.11-0.77) in men. No significant associations were found in women.

CONCLUSION

In men, the level of vitamin D intake in adolescence and the course of vitamin D intake from adolescence into adulthood are positively related with BMD in adulthood. In women, however, no significant associations are found.

Vitamin D status and its relationship to body fat, final height, and peak bone mass in young women

CONTEXT

Vitamin D insufficiency has now reached epidemic proportions and has been linked to low bone mineral density, increased risk of fracture, and obesity in adults. However, this relationship has not been well characterized in young adults.

OBJECTIVE

The objective of the study was to examine the relationship between serum 25-hydroxyvitamin D (25OHD), anthropometric measures, body fat (BF), and bone structure at the time of peak bone mass.

DESIGN

This was a cross-sectional study. OUTCOME MEASURES AND SUBJECTS: Anthropometric measures, serum 25OHD radioimmunoassay values, and computed tomography and dual-energy x-ray absorptiometry values of BF and bone structure in 90 postpubertal females, aged 16-22 yr, residing in California were measured.

RESULTS

Approximately 59% of subjects were 25OHD insufficient (<or=29 ng/ml), and 41% were sufficient (>or=30 ng/ml). Strong negative relationships were present between serum 25OHD and computed tomography measures of visceral and sc fat and dual-energy x-ray absorptiometry values of BF. In addition, weight, body mass, and imaging measures of adiposity at all sites were significantly lower in women with normal serum 25OHD concentrations than women with insufficient levels. In contrast, no relationship was observed between circulating 25OHD concentrations and measures of bone mineral density at any site. Unexpectedly, there was a positive correlation between 25OHD levels and height.

CONCLUSIONS

We found that vitamin D insufficiency is associated with increased BF and decreased height but not changes in peak bone mass.

Vitamin D status and its relationship with parathyroid hormone and bone mineral status in older adolescents

Osteoporosis is an important contributor to the global burden of disease, and in the UK alone results in one in three women and one in twelve men aged >50 years experiencing a fragility fracture. Optimising peak bone mass in early adulthood is thought to reduce osteoporosis risk by offsetting bone losses in later life. Ensuring sufficient vitamin D status (measured as 25-hydroxyvitamin D (25OHD) in plasma), among other factors, is believed to facilitate the achievement of optimum peak bone mass. Lower 25OHD is associated with a higher plasma concentration of parathyroid hormone (PTH). As PTH is associated with increased bone turnover and bone loss, maintenance of sufficient 25OHD is thought to have a protective effect on bone health. However, there is a lack of consensus internationally on what constitutes an optimum 25OHD concentration, and values between 30 and 80 nmol/l have been suggested. These values have been based on findings from various studies in adults in which PTH has been observed to plateau at a 25OHD concentration of >30 nmol/l; however, not all studies have found such a plateau. Although studies in younger adolescents (14–16 years) have shown an inverse relationship between PTH and 25OHD, the concentration of 25OHD required for achievement of optimum peak bone mass is unknown. The present review examines the evidence defining vitamin D insufficiency thresholds, and the relevance of such thresholds to adolescent bone health.

Geographical differences in vitamin D status, with particular reference to European countries

Vitamin D is produced endogenously when the skin is exposed to sunlight and can be obtained exogenously from a few natural food sources, from food fortification and from supplements. Generally, vitamin D intake is low ≤2–3 μg/d in Europe. Casual exposure to sunlight is thought to provide most of the vitamin D requirement of the human population. However, skin synthesis of vitamin D may not compensate for the low nutritional intake in Europe, even in countries with high supplies from food fortification and supplements. For assessment of vitamin D nutritional status the concentration of 25-hydroxyvitamin D (25(OH)D) in serum is considered to be an accurate integrative measure reflecting an individual's dietary intake and cutaneous production. A substantial percentage of the elderly and adolescents in Europe have a low concentration of 25(OH)D; in the elderly this percentage ranges from approximately 10 in the Nordic countries to approximately 40 in France. Low vitamin D status seems to be aggravated by disease and immobility, and by a low frequency of supplement use.

Vitamin D: a necessity for children and adolescents in Greece

Children and adolescents with the high bone turnover comprise a high risk population for vitamin D insufficiency. A sample of 178 clinically healthy children aged 3 to 18 years who came from public schools and lived in North West of Greece participated in the study. They were grouped into three age groups (I: 3-10, II: 11-14 and III: 15-18 years of age). Blood samples were taken during winter and summer months for determining calciotropic hormones, calcium, phosphate and biochemical markers of bone synthesis.A high percentage (47%) of the subjects aged 15-18 years was found to have 25OHD <10 ng/ml in winter but much less (13-14%) of the younger ages (13-14 years), while in the summer they were all >10 ng/ml. The prevalence was even higher in the girls of the older group accompanied by lower Pi concentrations again in winter (win:1.19+/-0.03, sum:1.93+/-0.03 mmol/l, p < 0.001). The 24,25(OH)(2)D levels were changing in parallel to 25OHD, but again in the older subjects, during winter, they were by 2/3 lower than the summer ones (0.73+/-0.10 vs. 2.41+/-0.20 ng/ml, p < 0.001). No significant differences were found between seasons and groups in the 1,25(OH)(2)D levels. The biochemical markers of bone synthesis, osteocalcin (OC) and total alkaline phosphatase (ALP), were found significantly lower in the girls of the older group both in winter and summer respectively. Even in a sunny country like Greece the adolescents living in an urban area are in high risk for vitamin D deficiency during winter. Supplementation with vitamin D of milk, of popular beverages and perhaps some foods would be of help.

Nutrition, mild hyperparathyroidism, and bone mineral density in young Japanese women

BACKGROUND

The adverse effects of poor nutrition on the bones of young Asian women have not been fully elucidated.

OBJECTIVE

The purpose of this study was to investigate possible associations of vitamin D nutrition, calcium intake, and other nutrients with bone metabolism and bone mass in young Japanese women.

DESIGN

The subjects were 108 female college students aged 19-25 y. Dietary nutrients were measured by using the duplicate sampling method on 3 weekdays. Serum 25-hydroxyvitamin D [25(OH)D], intact parathyroid hormone, and bone turnover markers were also measured. Bone mineral density (BMD) of the spine and femur was measured by dual-energy X-ray absorptiometry.

RESULTS

The proportions of the subjects with low 25(OH)D (< 30 nmol/L) and high intact parathyroid hormone (> or = 6.9 pmol/L) concentrations were 32.4% and 15.7%, respectively. Serum 25(OH)D concentrations (P = 0.0265) and calcium intake (P = 0.0103) were inversely associated with serum intact parathyroid hormone. In addition to weight and physical activity, the presence of mild hyperparathyroidism was associated with a low BMD of the lumbar spine (P = 0.0062) and the femoral neck (P = 0.0250), and a low calcium intake was associated with a low BMD of the femoral neck (P = 0.0044).

CONCLUSIONS

Low calcium intake (based on low BMD of the femoral neck only) and mild hyperparathyroidism (based on low BMD of both the femoral neck and lumbar spine), partly explained by low vitamin D nutrition and a low calcium intake, are important predictors of low BMD in young Japanese women. Effects of poor nutrition and mild hyperparathyroidism on bone peak bone mass in young women should be further investigated in longitudinal studies.

Physical activity in the post-pubertal period is associated with maintenance of pre-pubertal high bone density - a 5-year follow-up

OBJECTIVE

To evaluate the association between physical activity (PA) and skeletal growth in girls during adolescence.

DESIGN

A 5-year, observational, population-based study (Reykjavik, Iceland).

SUBJECTS

Seventy-eight Caucasian girls, mean age 13.4+/-1.0 (mean+/-SD) years at baseline.

METHODS

Bone mineral density (BMD, g/cm2) and bone width (cm) were measured in the forearm by single-photon absorptiometry at baseline and with dual-energy X-ray absorptiometry after 3 and 5 years, when lumbar spine, femoral neck (FN) and total body were also evaluated. Half of the physically active girls were compared with the other half of less active girls.

RESULTS

BMD in physically active girls was higher in the forearm at both baseline (P=0.001) and after 5 years (P=0.04) in comparison with less active girls. BMD was higher for the total body (P=0.0001), spine L2-L4 (P=0.02) and FN (P=0.002) in the active girls at age 18. The accrual of forearm BMD and bone width from age 13 to 18 was no different when comparing the two groups.

CONCLUSIONS

Pre-pubertal PA is associated with high BMD at age 13 and continued PA is associated with maintenance of high BMD until age 18.

Bone mineral density and serum 25-hydroxyvitamin D level: is there any difference according to the dressing style of the female university students

Nutrition plays a role in the etiology of osteoporosis. Two of the most important nutrients for bone health are calcium and vitamin D. Plasma 25-hydroxyvitamin D [25-(OH)D] is the most sensitive clinical index of vitamin D status and has been found to be positively related to bone mineral density (BMD) in middle-aged and elderly women, and positive relations exist between the BMD of adult women and their calcium consumption throughout life. The aim of the present study was to determine relationships between BMD, serum vitamin D levels and dietary calcium intake of female young adult students who dressed in different styles. We studied two groups of volunteer female students (total = 67). Students in the first group dressed in a style that exposed the skin to sunlight, students in the second group wore dresses completely covering the skin except for the face and hands. Serum 25-(OH)D levels were measured by radioimmunoassay, BMDs were determined at the lumbar spine and femoral neck by dual-energy X-ray absorptiometry, and calcium intakes were estimated with a 3-day food recording questionnaire. The serum 25-(OH)D level was significantly lower in the second group. There was no significant difference in BMD between the two groups. The dietary calcium intake of the two groups were lower than the adequate intake of 1000 mg daily for this age. There was a correlation between the serum 25-(OH)D level and BMD at the femoral neck in the first group. Our results indicate that vitamin D and calcium requirements for normal bone mineral accrual in young adults may advance until a certain age, and the covered dressing style causes vitamin D insufficiency and most of the students were under risk for osteoporosis in later life.

Vitamin D and bone mineral density status of healthy schoolchildren in northern India

BACKGROUND

Current data on the prevalence of vitamin D deficiency in India are scarce.

OBJECTIVE

We assessed the calcium-vitamin D-parathyroid hormone axis in apparently healthy children from 2 different socioeconomic backgrounds in New Delhi, India.

DESIGN

Clinical evaluation for evidence of vitamin D deficiency was carried out in 5137 apparently healthy schoolchildren, aged 10-18 y, attending lower (LSES) and upper (USES) socioeconomic status schools. Serum calcium, inorganic phosphorus, alkaline phosphatase, 25-hydroxyvitamin D [25(OH)D], and immunoreactive parathyroid hormone were measured in 760 children randomly selected from the larger cohort. Bone mineral density of the forearm and the calcaneum was measured in 555 children by using peripheral dual-energy X-ray absorptiometry.

RESULTS

Clinical evidence of vitamin D deficiency was noted in 10.8% of the children. Children in the LSES group had a significantly (P < 0.01) lower 25(OH)D concentration (10.4 +/- 0.4 ng/mL) than did those in the USES group (13.7 +/- 0.4 ng/mL). Concentrations of 25(OH)D <9 ng/mL were seen in 35.7% of the children (42.3% in LSES; 27% in USES; P < 0.01). Boys had significantly (P = 0.004) higher 25(OH)D concentrations than did girls. There was a significant negative correlation between the mean serum immunoreactive parathyroid hormone and 25(OH) D concentrations (r = -0.202, P < 0.001). Mean forearm bone mineral density was significantly (P < 0.01) higher in the USES group than in the LSES group.

CONCLUSION

A high prevalence of clinical and biochemical hypovitaminosis D exists in apparently healthy schoolchildren in northern India.

Prévention de la carence en vitamine D chez l’enfant et l’adolescent. II. Validation d’un abaque décisionnel non invasif prenant en compte l’exposition solaire et les apports exogènes de vitamine D

OBJECTIVES

Rickets can still be observed among children and adolescents living in Europe, and a significant proportion of healthy children and adolescents presents serum 25-hydroxyvitamin D (25-(OH)D) values below the threshold indicating an insufficient vitamin D status. We have previously proposed detecting at risk individuals with a decision-making abacus based on questionnaires assessing calcium and vitamin D intakes and vitamin D production via sun exposure.

METHODS

We tested the validity of this detection by receiver operating characteristic (ROC) analysis, using, as the main outcome measure, the serum 25-(OH)D values measured at the time of questionnaires presentation. In addition, the original questionnaires have been simplified by limiting the items to those significantly associated with 25-(OH)D values. The study group included 116 children and adolescents aged 6 to 17 years, seen at the end of the winter, and randomized in 2 groups: "test", for the development of the tool (n =75), and "validation" (n =41).

RESULTS

The present analysis shows that the proposed decision-making abacus has a sufficient ability to detect children at risk of vitamin D deficiency (with 25-(OH)D values below 10 ng/ml): area under the curve 0.748/0.895, sensibility 0.71/0.83, and specificity 0.62/0.80, in the test and validation groups, respectively.

CONCLUSION

These questionnaire and abacus may offer a substantial help to detect children and adolescents at risk of vitamin D deficiency in both a private office or hospital environment.

Teenage girls and elderly women living in northern Europe have low winter vitamin D status

OBJECTIVE

To determine the vitamin D status (serum 25-hydroxyvitamin D; S-25OHD) in adolescent girls and elderly community-dwelling women living in four countries of northern Europe and to explain differences in S-25OHD concentrations between and within the countries.

DESIGN

A cross-sectional observational study conducted in a standardised way during February-March. S-25OHD was analysed by high-performance liquid chromatography. Vitamin D and calcium intake was calculated using a standardised food composition database.

SETTING

Denmark, Finland, Ireland, and Poland.

SUBJECTS

A total of 199 girls (mean (s.d.) age 12.6 (0.5) y) and 221 women (mean (s.d.) age 71.8 (1.4) y).

RESULTS

The median (inter quartiles) concentration of S-25OHD was 29.4 (20.3, 38.3) nmol/l for the girls and 40.7 (28.0, 54.2) nmol/l for the women. S-25OHD below 25 nmol/l was found in 37% of the girls and 17% of the women, and S-25OHD below 50 nmol/l was found in 92% of the girls and 37% of the women. Positive significant determinants for S-25OHD in girls were use of vitamin D supplements, and in women sun habits, dietary vitamin D intake, use of vitamin D and calcium supplements. Body mass index and smoking were negative determinants in women. For women predictors could explain the differences between countries (P(country) = 0.09, R(2) = 0.39), but for girls the difference remained significant even after including predictors (P(country) = 0.03, R(2) = 0.15).

CONCLUSION

Vitamin D status is low in northern Europe during winter. More than one-third of the adolescent girls have vitamin D status below 25 nmol/l and almost all are below 50 nmol/l. Two-thirds of the elderly community-dwelling women have vitamin D status below 50 nmol/l. Use of vitamin D supplements is a significant positive determinant for S-25OHD for both girls and women (P = 0.001).

SPONSORSHIP

The European Fifth Framework Programme (Contract No. QLK1-CT-2000-00623).

Bone mineral density in children with familial Mediterranean fever

The aim of this study was to evaluate bone mineral content (BMC), serum and urinary bone turnover parameters in patients with familial Mediterranean fever (FMF), an autosomal recessive disease characterized by recurrent episodes of inflammation of serous membranes. Demographic characteristics and MEFV mutations were defined in 48 children diagnosed with FMF (23 F, 25 M; median age 7.0 years (3.0-10.0)). We evaluated the blood counts, acute-phase proteins and serum and urinary bone turnover parameters during attack-free periods. The BMC and BA (bone area) of vertebrae L1-L4 were measured by DEXA. Thirty-eight age-, sex- and ethnicity-matched healthy children constituted the control group. Mean L1-L4 BMC in Group I (patients with two mutations) and II (patients with no or single mutations) were 15.49+/-5.99 g and 15.68+/-4.89 g, respectively, both significantly lower than the mean L1-L4 BMC of control patients, which was 19.59+/-6.7 g (p<0.05). Mean L1-L4 BMD in Group I, Group II and the control group were 0.466+/-0.066 g/cm(2), 0.487+/-0.085 g/cm(2 )and 0.513+/-0.079 g/cm(2), respectively. Mean z-scores in Group I, Group II and the control group were -1.87+/-0.74, -1.55+/-0.92 and -1.39+/-0.84, respectively. Mean L1-L4 BMD and z-score of Group I were lower than in the control group (p<0.05). ESR and SAA (serum amyloid A) levels were higher in Group I patients: 28.3+/-14.5 mm/h and 350+/-62 mg/l in Group I; and 20.5+/-11.7 mm/h and 190+/-68 mg/l in Group II, respectively. In conclusion, FMF patients had lower BMC, BMD and z-scores than a control group. We suggest that decreased BMD, BMC and z-score in FMF patients may be secondary to subclinical inflammation.

Perspectives on osteoporosis in pediatric inflammatory bowel disease

Osteoporosis is now recognized as a problem in children with chronic illness. Decreased bone mineral density and increased risk of fracture have been reported in children with inflammatory bowel disease (IBD). Recent studies have led to a better understanding of the pathogenesis of bone loss. There are many risk factors for osteopenia and osteoporosis in children with IBD. Dual-energy x-ray absorptiometry remains the diagnostic procedure of choice for assessment of bone mineral density, but other modalities are being explored. Guidelines for diagnosis and treatment of osteoporosis in children have not been established. This article reviews the current understanding of osteopenia and osteoporosis in children with IBD.

Effect of the vitamin D3 analog ILX 23-7553 on apoptosis and sensitivity to fractionated radiation in breast tumor cells and normal human fibroblasts

PURPOSE

Previous work from this laboratory has demonstrated that the vitamin D(3) analogs EB 1089 and ILX 23-7553 enhance the response of breast tumor cells to ionizing radiation and promote radiation-induced apoptotic cell death. The current studies were designed to more closely simulate clinical radiotherapy in the treatment of breast cancer by examining the utility of ILX 23-7553 as an adjunct to fractionated ionizing radiation. The potential toxicity to normal tissue of the combination of ILX 23-7553 and fractionated radiation was assessed in a model of BJ human fibroblasts in culture.

METHODS

MCF-7 cells and human fibroblasts were treated with fractionated radiation alone (5x2 Gy over 3 days), ILX 23-7553 alone (50 n M) or ILX 23-7553 followed by 5x2 Gy. Viable cell numbers were determined by trypan blue exclusion and apoptosis by the TUNEL assay. A statistical model of additivity was utilized to assess the nature of the interaction between ILX 23-7553 and fractionated radiation.

RESULTS

Radiation and ILX 23-7553 each alone reduced viable cell numbers by 72+/-3.1% and 62+/-4.8%, respectively. Pretreatment with ILX 23-7553 followed by 5x2 Gy reduced viable cell numbers by 93.2+/-0.7%. The interaction between ILX 23-7553 and fractionated radiation appeared to be additive despite the fact that the combination of ILX 23-7553 and fractionated radiation also promoted a twofold increase in apoptotic cell death. ILX 23-7553 failed to enhance the response to radiation or to promote apoptosis in BJ human foreskin fibroblasts.

CONCLUSIONS

ILX 23-7553 enhanced the antiproliferative and apoptotic effects of fractionated ionizing radiation in MCF-7 breast cancer cells. These effects appeared to be selective in that similar responses were not observed in a model of normal human fibroblasts. Vitamin D(3) analogs such as ILX 23-7553 may prove to have utility in combination with conventional radiotherapy of breast cancer as well as other malignancies which are sensitive to vitamin D(3).

Serum 25-hydroxyvitamin D status of adolescents and adults in two seasonal subpopulations from NHANES III

Subclinical vitamin D deficiency may be common in certain subgroups in the U.S., but to date vitamin D data from other groups in the population have not been available. We used serum 25-hydroxyvitamin D (25-OHD) data from 18,875 individuals examined in the Third National Health and Nutrition Examination Survey (NHANES III 1988-1994) to assess the vitamin D status of selected groups of the noninstitutionalized U.S. adolescent and adult population. Serum 25-OHD levels were measured by a radioimmunoassay kit (DiaSorin, Inc., Stillwater, MN; normal range 22.5-94 nmol/L). Because physical exams are performed in mobile vans in NHANES, data could not be collected in northern latitudes during the winter; instead data were collected in northern latitudes during summer and in southern latitudes in winter. To address this season-latitude aspect of the NHANES design, we stratified the sample into two seasonal subpopulations (winter/lower latitude and summer/higher latitude) before examining vitamin D status. Less than 1% of the winter/lower latitude subpopulation had vitamin D deficiency (25-OHD <17.5 nmol/L). However, the prevalence of vitamin D insufficiency in this group ranged from 1%-5% with 25-OHD <25 nmol/L to 25%-57% with 25-OHD <62.5 nmol/L, even though the median latitude for this subsample (32 degrees N) was considerably lower than the latitude at which vitamin D is not synthesized during winter months (approximately 42 degrees N). With the exception of elderly women, prevalence rates of vitamin D insufficiency were lower in the summer/higher latitude subpopulation (<1%-3% with 25-OHD <25 nmol/L to 21%-49% with 25-OHD <62.5 nmol/L). Mean 25-OHD levels were highest in non-Hispanic whites, intermediate in Mexican Americans, and lowest in non-Hispanic blacks. Our findings suggest that vitamin D deficiency is unlikely in the two seasonal subpopulations of noninstitutionalized adolescents and adults that can be validly assessed in NHANES III. However, vitamin D insufficiency is more common in these two seasonal subpopulations. Of particular interest is that insufficiency occurred fairly frequently in younger individuals, especially in the winter/lower latitude subsample. Our findings support continued monitoring of this vitamin in the U.S. population.

Current concepts in pediatric bone disease

It is widely believed that osteoporosis prevention may be best accomplished during childhood and adolescence, when bones are growing rapidly and are most sensitive to environmental influences, such as diet and physical activity. For children with chronic diseases, a variety of factors may influence normal bone mineralization, including altered growth, delayed maturation, inflammation, malabsorption, reduced physical activity, glucocorticoid exposure, and poor dietary intake. In healthy children, maintaining adequate levels of calcium intake, serum vitamin D, and weightbearing physical activity may be sufficient to prevent osteoporosis later in life. Far less is known about effective prevention and treatment of poor bone mineralization in children with chronic illness, such as CF or CD. Osteoporosis prevention and intervention measures during childhood are limited by the paucity of reference data on bone mineralization. Although it is widely recognized that puberty, skeletal maturation, and body size influence BMC and bone density, no reference data for bone mineralization are scaled to these important measures. In children with chronic disease with delayed growth and maturation, the creation of such reference data is of paramount importance. In addition, the dynamic changes that occur during growth and maturation in the structural characteristics of trabecular and cortical bone and the development of the bone-muscle unit may influence current and future fracture risk. Further research is needed to characterize these changes and their use in the assessment of bone health and fracture risk in children. Only then can the impact of treatment strategies be appreciated fully.

Vitamin D depletion following burn injury in children: a possible factor in post-burn osteopenia

BACKGROUND

Children burned > 40% total body surface area (TBSA) have chronically low bone mineral density (BMD) and increased risk for fractures and adult-onset osteoporosis. Because they are advised to avoid sunlight to prevent burn scar hyperpigmentation, we hypothesized that they develop vitamin D depletion, which could contribute to post-burn osteopenia.

METHODS

We studied 24 children, ages 5-20 years, burned > or = 40% TBSA 7.1 +/- 3.8 (SD) years, range 1.9-13.3 years, previously (n = 12) and 2.0 +/- 0.2, range 1.4-2.1 years, previously (n = 12), of which half received recombinant human growth hormone during the first post-burn year. We measured lumbar spine BMD, serum 25-hydroxyvitamin D (25(OH)D), 1,25-dihydroxyvitamin D (1,25(OH)2D), intact PTH (iPTH), and osteocalcin.

RESULTS

Serum 25(OH)D was low in 10/11 patients and 1,25(OH)2D was low in 5/11 at 7 years post-burn. Serum 25(OH)D was low in 10/12, while 1,25(OH)2D was low in 0/12 at 2 years; osteocalcin was low in 9/12 in the 7-year group; iPTH levels were in the lowest quartile in 5/12 patients at 7 years and 10/12 patients at 2 years. Serum 25(OH)D levels correlated with BMD z-scores, r = 0.53, p < 0.05, and inversely with iPTH levels, r = -0.66, p < 0.05, in the 7-year group.

CONCLUSION

Burned children have low circulating levels of 25(OH)D which correlated with BMD z-scores, suggesting that post-burn vitamin D depletion may play a role in the chronically low bone density observed in these children.

Vitamin D status and bone mineral density of veiled and unveiled Turkish women

The aim of the study is to compare vitamin D status and bone mineral density (BMD) in veiled and unveiled healthy Turkish women of reproductive age. Thirty young to middle-aged volunteer veiled women and 30 age-matched control subjects with western clothing habits were enrolled in the study. The two groups had similar dietary habits, body mass index (BMI) distribution, and gestational history. Physical and laboratory examinations were performed to rule out any disease that could affect bone metabolism. Serum 25-hydroxyvitamin D (25-OHD) levels were measured, and BMD of the spine and hip were investigated by dual energy x-ray absorptiometry (DEXA). The mean age of dressing the veil was 15.7 +/- 6.13 years, and 66.7% of the veiled women claimed that they were not ever exposed to direct sunlight, as they were leading an indoor life. Compared with the control group, veiled women were less educated and physically less active (p < 0.001 and p < 0.05, respectively). 25-OHD levels were positively correlated with exposure to sunlight and negatively correlated with the duration of being veiled. None of the veiled women had vitamin D insufficiency, but their mean 25-OHD concentration (33.1 +/- 16 ng/ml) was significantly lower than that of controls (53.9 +/- 27.3 ng/ml) (p < or = 0.001), and serum alkaline phosphatase (ALP) levels were higher (p < 0.01). Differences in the absolute BMD values at the spine and hip were not statistically significant, but the mean Z value at the lumbar spine was significantly lower in the veiled subjects (p < 0.05). Veiled women have low 25-OHD status, and vitamin D supplementation should strictly be advised to these women for the prevention of osteomalacia and osteoporosis.

The genetics of osteoporosis: vitamin D receptor gene polymorphisms and circulating osteocalcin in healthy Irish adults

BACKGROUND

A relationship between bone turnover and the vitamin D receptor (VDR) genotype is reported in Australian subjects of UK-Irish descent. There is conflicting evidence of linkage between the VDR genotype and differences in bone mineral density. No such study has been carried out on a resident Irish population.

AIMS

This study examined the relationship between serum osteocalcin (a marker of bone turnover) and VDR genotype in Irish adults.

METHODS

One hundred and eighteen healthy Irish adults aged between 19 and 67 were recruited and had two fasting blood samples taken. One sample was analysed for osteocalcin by enzyme immunoassay. The other was used to isolate genomic DNA and determine VDR genotype.

RESULTS

Tt was the most prevalent VDR genotype (53%) and tt (15%) the least prevalent in this group of healthy Irish adults. The tt VDR genotype was associated with significantly higher levels of serum osteocalcin (29% and 40%) than the Tt or TT VDR genotypes.

CONCLUSIONS

These findings suggest that healthy Irish adults with the tt VDR genotype have higher rates of bone turnover than those with Tt or TTVDR genotypes. They may have a higher risk of low bone mineral density and osteoporosis in later life.

Bone loss in adolescents using Depo-Provera

ISSUES AND PURPOSE

Contraceptive methods that decrease bone density in a population already deficient in calcium are a rising concern in women's health.

CONCLUSIONS

Use of Depo-Provera (DMPA) significantly decreases bone mass density (BMD) in normal adolescents up to the age of 21. DMPA is often used in adolescents with disabilities who may already be at high risk for osteoporosis. The effects are likely to be similar to that in able-bodied adolescents, but research is limited.

PRACTICE IMPLICATIONS

Through early identification of risk factors in able-bodied and disabled adolescents, primary care providers considering the use of DMPA in adolescents can optimize BMD by providing adequate nutritional assessment, counseling on nutritional sources of calcium, calcium supplementation, guidance on exercise, and alcohol and smoking prevention or cessation.

Lean mass and physical activity as predictors of bone mineral density in 16-20-year old women

OBJECTIVE

The aim of the study was to quantify the inter-relationship between bone mineral density and physical activity, muscle strength, and body mass composition in a group of healthy 16-20-year-old women.

DESIGN

A cross-sectional study.

SETTING

Reykjavik area.

SUBJECTS

Two-hundred and fifty-four Icelandic Caucasian women aged 16, 18 and 20 years, randomly selected from the registry of Reykjavik.

MAIN OUTCOME MEASURES

Bone mineral content (BMC) and density (BMD) in lumbar spine, hip, distal forearm and total skeleton and lean mass and fat mass were measured with dual energy X-ray absorptiometry (DEXA) and compared with grip strength measured with a dynamometer and physical activity as assessed by a questionnaire.

RESULTS

The lean mass had the strongest correlation with BMC and BMD, stronger than weight, height and fat mass, both in univariate analysis (r = 0.41-0.77; P<0.001) and in linear regression analysis. The total skeletal BMD was logarithmically higher by hours of exercise per week (P<0.001)). About 30% of variability in total skeletal BMD in this age group can be predicted by lean mass and physical exercise.

CONCLUSIONS

Modifiable factors, such as exercise and adequate muscle seem to be significant predictors of the attainment of peak bone mass in women.