Effects of usual nutrient intake and vitamin D status on markers of bone turnover in Swiss adolescents

Vitamin D Status among 2-18-Year-Old Romanian Pediatric Patients: A Single-Center Study

An adequate vitamin D level is essential for optimal bone mass formation during growth. The present study aimed to assess (i) the sex-specific, age-specific, and potential seasonal (spring, summer, winter) influences on the pediatric circulating levels of 25-hydroxyvitamin D (25(OH)D); (ii) determine the frequency of pediatric patients with vitamin D deficiency (VDD) or insufficiency (VDI); and (iii) quantify the association between age category, sex, and season types and susceptibility to VDD and VDI, respectively. Laboratory data were collected on serum 25(OH)D levels in children aged between 2 and 18 years (n = 1674) who underwent blood sampling following admission to a university pediatric hospital in Cluj-Napoca (Romania) between January and June 2023. VDD (<20 ng/mL) was observed in 27% of pediatric patients. Among toddlers and preschoolers (2-5 years), VDD was 11%, while it was 33% among school-aged children (6-11 years) and 39% among adolescents (12-18 years). We found a significant difference in the frequencies of vitamin D status between females and males (p = 0.006). Also, we found significant associations of vitamin D status with age categories (p < 0.0001) and seasonal variations (p = 0.03). After adjusting for season of blood collection, the multinomial logistic regression model showed that children aged 6-11 years old (adjusted OR = 7, 95% CI: (4.9, 9.4)), children aged 12-18 years old (adjusted OR = 14, 95% CI: (9.3, 19.6)), and females (adjusted OR = 1.43, 95% CI: (1.10, 1.86)) were significantly associated with higher odds of VDD. In conclusion, the study revealed a significant difference in the frequency of VDD and VDI among pediatric patients older than six years, with a significant difference according to sex and season, being more pronounced among girls and during the winter and spring seasons.

Vitamin D in pediatric age: Current evidence, recommendations, and misunderstandings

In recent years vitamin D has been in the spotlight of many researchers for its possible role in various disorders, including autoimmune and infectious diseases. Even if vitamin D deficiency remains a major public health problem, its symptomatic manifestations are less and less common in clinical practice, and pediatric age represents a “gray area” where vitamin D supplementation is often administered in the absence of an effective evaluation of its status. Moreover, a poor knowledge about different definitions of “deficiency,” “insufficiency,” and similar terms is spread among clinicians, while guidelines are not univocal, especially after the first year of life. The aim of this brief opinion paper is to sum up recent evidence about vitamin D status and its supplementation in pediatrics, in order to better clarify a common definition of its deficiency. The aim of this opinion article is to raise awareness on this topic among clinicians and encourage a discussion on the real need for routine 25-hydroxycholecalciferol serum evaluation and its supplementation.

Bone health in adolescence

Adolescence is a fundamental period for the formation of the skeleton, because is the stage in which bones grow more in both size and strength, laying a solid foundation for the future health of the skeleton. Any condition interfering with optimal peak bone mass accrual can increase fracture risk later in life. Up to 80% of peak bone mass is genetically determined while the remaining 20% is modulated by environmental factors that, if deleterious, may result in low bone mineral density (BMD) and an increased risk of fracture. The preferred test to assess bone health is dual-energy x-ray absorptiometry (spine or total body less head) using Z scores instead of T scores, even though in short stature or growth delay, should be used the height Z-score. The correction of risk factors is the first treatment for low BMD in children and adolescents. It's necessary having a correct lifestyle for preserving bone health: a proper nutrition, an adequate physical weight-bearing activity and avoidance of alcohol intake and tobacco smoke. Bisphosphonates could be used in children who sustained osteoporotic fractures, impairing quality of life, when spontaneous recovery is low for the persistence of osteoporosis risk factors. This clinical review discusses factors affecting bone health during childhood and adolescence and deals with diagnosis and treatment of low bone mass or osteoporosis in this age group.

Vitamin D levels and busulphan kinetics in patients undergoing hematopoietic stem cell transplantation, a multicenter study

Vitamin D (Vit-D), an essential nutrient, interacts with different drugs including chemotherapeutic agents like busulphan, an alkylating agent used for conditioning prior to stem cell transplantation. The correlation between Vit-D plasma levels and busulphan clearance was investigated in an uncontrolled prospective study in patients and mice. Plasma 25(OH)D levels were measured and busulphan pharmacokinetics calculated in 81 patients. Adults received oral busulphan (n = 34) while children received busulphan orally (n = 19) or intravenously (n = 28). Patients received no Vit-D supplementation. To confirm our findings, pharmacokinetics after a single dose of busulphan (oral or intravenous) were evaluated in two groups of mice (n = 60) receiving high or standard-level Vit-D supplementation. Both busulphan clearance (P < 0.0001) and 25(OH)D levels (P = 0.0004) were significantly higher in adults compared to children. A significant negative correlation (P = 0.041) was found between busulphan clearance and 25(OH)D levels in children treated orally. No such correlation was observed in adults or in children receiving intravenous busulphan. In addition, no significant effect of Vit-D levels on busulphan pharmacokinetics in mice regardless of the administration route. In conclusion, 25(OH)D can affect oral busulphan pharmacokinetics in children and its level should be considered when personalizing oral busulphan treatment. Further studies are warranted to confirm the underlying mechanisms.

Establishment and Verification of Sex- and Age-Specific Serum Electrolyte Reference Intervals in Healthy Han Children in Changchun, Northeastern China

For lack of feasible interval values from population differences and potential analytical discrepancies, it is essential to ascertain potassium (K), sodium (Na), chlorine (Cl), calcium (Ca), and phosphorus (P) ions reference intervals within Chinese children to fill the gap. Healthy children (n = 1391, 2-<15 years old) were recruited from communities and schools to establish sex- and age-specific serum electrolyte reference intervals of Han children in Changchun, China. Levels of serum K, Na, Cl, Ca, and P were measured using a Hitachi 7600-210 automatic biochemical analyzer. Reference intervals were established according to Clinical and Laboratory Standards Institute EP28-A3c guidelines. Data from five representative hospitals located across Changchun were used to verify pediatric serum electrolyte reference intervals. Values were different from adult reference intervals in China. There were sex-specific differences in Na, Cl, Ca, and P reference intervals in 13-<14 children. Serum Na, Cl, and Ca reference intervals showed stable trends within early age groups but fluctuated in teens. Each serum electrolyte had ≤3 age-specific reference intervals. Five laboratories suggested reference intervals were applicable across Changchun.

Best Practices for Conducting Observational Research to Assess the Relation between Nutrition and Bone: An International Working Group Summary

Diet is a modifiable factor that can affect bone strength and integrity, and the risk of fractures. Currently, a hierarchy of scientific evidence contributes to our understanding of the role of diet on bone health and fracture risk. The strength of evidence is generally based on the type of study conducted, the quality of the methodology employed, the rigor and integrity of the data collected and analysis plan, and the transparency and completeness of the results. Randomized controlled trials (RCTs) are considered to be the gold standard from a clinical research paradigm, but there is a dearth of high-quality diet-related intervention trials with bone as the primary outcome, forcing the use of observational research to inform research and clinical practices. However, for observational research to be of the most utility, standardization and optimization of the study design, accurate and reliable measurement of key variables, and appropriate data analysis and data reporting are paramount. Although there have been recommendations made in relation to RCTs in the field of nutrition, no clear rubric exists for best practices in conducting observational research with regard to nutrition and bone health. Therefore, the purpose of this paper is to describe the best practices and considerations for designing, conducting, analyzing, interpreting, and reporting observational research specifically for understanding the role of nutrition in bone health, amassed by a global panel of scientific experts with strengths in bone, nutrition epidemiology, physical activity, public health, clinical and translational trials, and observational study methods. The global panel of scientific experts represents the leadership and selected participants from the 10th annual International Symposium for the Nutritional Aspects of Osteoporosis. The topics selected and best practices presented reflect expert opinion and areas of scientific expertise of the authors rather than a systematic or comprehensive literature review or professional reporting guidelines.

Effect of Vitamin D Supplementation on Bone Turnover Markers in Children and Adolescents from North India

OBJECTIVES

Vitamin D is known to play an important role in bone mineral metabolism. Its deficiency may affect growth and status of bone markers in children. Hence, we undertook to study the status of bone markers in children with vitamin D deficiency (VDD) and impact of vitamin D3 supplementation on them.

MATERIALS AND METHODS

Total 468 out of 615 children and adolescents with VDD, who were given either of the three doses (600, 1000, and 2000) of vitamin D supplementation, were included in the study. These 468 children with pre- and postsupplementation preserved samples with available anthropometry, serum biochemistry, 25-hydroxy-vitamin D, and parathormone were evaluated for bone formation (procollagen type 1 amino-terminal propeptide [P1NP]) and resorption (β-cross laps [CTx]) markers.

RESULTS

The mean age and body mass index of these children were 11.3 ± 2.3 years (boys: 11.5 ± 2.4; girls: 12.2 ± 1.2 years; P = 0.03) and 18.1 ± 3.8 kg/m² (boys: 18.2 ± 3.9; girls: 17.6 ± 3.2 kg/m²; P = 0.208), respectively. There were 8.8% subjects with severe, 42.7% with moderate, and 48.5% with mild VDD. There was a significant decline in serum P1NP (from 691 ± 233 ng/ml to 640 ± 259 ng/ml, P < 0.001) and CTx (from 1.67 ± 0.53 ng/ml to 1.39 ± 0.51 ng/ml, P < 0.001) following supplementation. Though decline in serum P1NP and CTx levels was observed in both boys and girls, among all three supplementation groups and VDD categories, the effect was more marked in serum CTx than P1NP levels.

CONCLUSIONS

Vitamin D supplementation in VDD children resulted in decrease in both bone formation (P1NP) and resorption (CTx). The impact, however, was more marked on bone resorption than bone formation.

No improvement in vitamin D status in German infants and adolescents between 2009 and 2014 despite public recommendations to increase vitamin D intake in 2012

Purpose

Vitamin D is a key component for the growth and development of children and adolescents, influencing a multitude of functions. Worldwide epidemiological studies have shown that minimum vitamin D blood levels of ≥ 20.0 ng/ml, often defined as vitamin D sufficiency by international and national nutrition and pediatric organizations, are often not met in practice. In 2012 the D–A–CH (Germany, Austria, Switzerland) nutrition societies increased their vitamin D intake recommendations fourfold from 200 IU (5 µg) to 800 IU (20 µg) per day. The outcome of this study will contribute to answering the question as to whether the new recommendations for increased vitamin D intake improve the highly prevalent vitamin D deficiency status in German children and adolescents.

Methods

For this 6-year study (January 2009–December 2014) carried out in Mülheim an der Ruhr, Germany, healthy children and adolescents (n = 1929, age range 1–17 years, median age 11.0 years, 46.9% female) consulting a pediatric group practice (KIDS4.0) were recruited. Serum 25(OH)D determinations were performed using a competitive chemoluminescence immunoassay (CLIA, DiaSorin).

Results

The median serum vitamin D values for each year from 2009 to 2014 were 18.4, 13.0, 20.8, 16.4, 19.4 and 14.9 ng/ml. The summarized median 25(OH)D serum concentrations between the two time periods 2009–2012 and 2013–2014 after increasing recommendations for vitamin D intake did not show a significant difference (17.0 versus 16.8 ng/ml).

Conclusions

The increased D–A–CH recommendations for vitamin D intake had no influence on vitamin D levels in children and adolescents. The prevalence of vitamin D deficiency has not changed compared to previous studies.

Electronic supplementary material

The online version of this article (10.1007/s00394-018-1717-y) contains supplementary material, which is available to authorized users.

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 in adolescents: Are current recommendations enough?

Vitamin D is essential for bone development during adolescence and low vitamin D status during this critical period of growth may impact bone mineralization, potentially reducing peak bone mass and consequently increasing the risk of osteoporosis in adulthood. Therefore, the high prevalence of vitamin D inadequacy and deficiency in adolescent populations is of great concern. However, there is currently a lack of consensus on the 25-hydroxyvitamin D [25(OH)D] concentration, the widely accepted biomarker of vitamin D status, that defines adequacy, and the vitamin D intake requirements to maintain various 25(OH)D thresholds are not well established. While the current intake recommendations of 10-15μg/day may be sufficient to prevent vitamin D deficiency (25(OH)D<25-30nmol/l), greater intakes may be needed to achieve the higher threshold levels proposed to represent adequacy (25(OH)D>50nmol/l). This review will address these concerns and consider if the current dietary recommendations for vitamin D in adolescents are sufficient.

Association between vitamin D status and serum parathyroid hormone concentration and calcaneal stiffness in Japanese adolescents: sex differences in susceptibility to vitamin D deficiency

There is currently insufficient information on serum 25-hydroxyvitamin D (25OHD) and parathyroid hormone (PTH) concentrations, and bone mineral status in healthy adolescents to allow reference values to be set. This study aimed to provide comparable data on vitamin D status in Japanese adolescents and to assess sex differences in susceptibility to vitamin D insufficiency. Serum 25OHD and PTH concentrations were measured in 1,380 healthy adolescents (aged 12-18 years). Subjects completed a questionnaire on exercise history, diet, and lifestyle factors. Calcaneal stiffness was evaluated by quantitative ultrasound. Serum 25OHD concentrations in boys and girls were 60.8 ± 18.3 and 52.8 ± 17.0 nmol/L, respectively. Approximately 30 % of boys and 47 % of girls had suboptimal 25OHD concentrations (<50 nmol/L). Serum PTH concentration was negatively correlated with serum 25OHD concentration in boys, but negatively correlated with calcium intake rather than serum 25OHD in girls. In contrast, the increment in calcaneal stiffness as a result of elevation of serum 25OHD was higher in girls than in boys. As vitamin D deficiency is common in Japanese adolescents, it was estimated that intakes of ≥12 and ≥14 μg/day vitamin D would be required to reach 25OHD concentrations of 50 nmol/L in boys and girls, respectively. Moreover, the results of the present study indicate that vitamin D deficiency has a greater association with calcaneal stiffness in girls than in boys.

Vitamin D deficiency in Europe: pandemic?

BACKGROUND

Vitamin D deficiency has been described as being pandemic, but serum 25-hydroxyvitamin D [25(OH)D] distribution data for the European Union are of very variable quality. The NIH-led international Vitamin D Standardization Program (VDSP) has developed protocols for standardizing existing 25(OH)D values from national health/nutrition surveys.

OBJECTIVE

This study applied VDSP protocols to serum 25(OH)D data from representative childhood/teenage and adult/older adult European populations, representing a sizable geographical footprint, to better quantify the prevalence of vitamin D deficiency in Europe.

DESIGN

The VDSP protocols were applied in 14 population studies [reanalysis of subsets of serum 25(OH)D in 11 studies and complete analysis of all samples from 3 studies that had not previously measured it] by using certified liquid chromatography-tandem mass spectrometry on biobanked sera. These data were combined with standardized serum 25(OH)D data from 4 previously standardized studies (for a total n= 55,844). Prevalence estimates of vitamin D deficiency [using various serum 25(OH)D thresholds] were generated on the basis of standardized 25(OH)D data.

RESULTS

An overall pooled estimate, irrespective of age group, ethnic mix, and latitude of study populations, showed that 13.0% of the 55,844 European individuals had serum 25(OH)D concentrations <30 nmol/L on average in the year, with 17.7% and 8.3% in those sampled during the extended winter (October-March) and summer (April-November) periods, respectively. According to an alternate suggested definition of vitamin D deficiency (<50 nmol/L), the prevalence was 40.4%. Dark-skinned ethnic subgroups had much higher (3- to 71-fold) prevalence of serum 25(OH)D <30 nmol/L than did white populations.

CONCLUSIONS

Vitamin D deficiency is evident throughout the European population at prevalence rates that are concerning and that require action from a public health perspective. What direction these strategies take will depend on European policy but should aim to ensure vitamin D intakes that are protective against vitamin D deficiency in the majority of the European population.

Associations between serum 25-hydroxyvitamin D and bone turnover markers in a population based sample of German children

Severe vitamin D deficiency is known to cause rickets, however epidemiological studies and RCTs did not reveal conclusive associations for other parameters of bone health. In our study, we aimed to investigate the association between serum levels of 25(OH) vitamin D and bone turnover markers in a population-based sample of children. 25(OH)D, calcium (Ca), osteocalcin (OC), and β-Crosslaps (β-CTx) were measured in 2798 ten-year-old children from the German birth cohorts GINIplus and LISAplus. Linear regression was used to determine the association between bone turnover markers and 25(OH)D levels. 25(OH)D, OC, and β-CTx showed a clear seasonal variation. A 10 nmol/l increase in 25(OH)D was significantly associated with a 10.5 ng/l decrease (p < 0.001) in β-CTx after adjustment for design, sex, fasting status, time of blood drawn, BMI, growth rate, and detectable testosterone/estradiol. For OC alone no significant association with 25(OH)D was observed, whereas the β-CTx-to-OC ratio was inversely associated with 25(OH)D (−1.7% change, p < 0.001). When stratifying the analyses by serum calcium levels, associations were stronger in children with Ca levels below the median. This study in school-aged children showed a seasonal variation of 25(OH)D and the bone turnover markers OC and β-CTx. Furthermore a negative association between 25(OH)D and the bone resorption marker β-CTx was observed.

Vitamin D deficiency and its associated risk factors in children and adolescents in southern Iran

OBJECTIVES

To evaluate prevalence of vitamin D deficiency and its associated factors in southern Iranian children.

DESIGN

Cross-sectional study. Anthropometric and pubertal characteristics were assessed by a trained physician. Physical activity and sun exposure were evaluated using standard questionnaires. Body composition measurements were performed using dual-energy X-ray absorptiometry. Serum Ca, P alkaline phosphatase and 25-hydroxyvitamin D (25(OH)D) were assessed in all children. Statistical analysis was done using the statistical software package IBM SPSS Statistics 18·0.

SUBJECTS

Iranian children (n 477) aged 9-18 years.

SETTING

Fars Province, Iran, 2011.

RESULTS

Of the children, 81·3 % were 25(OH)D deficient. There was no significant difference in 25(OH)D concentration between boys and girls (P=0·3). 25(OH)D concentration was associated with BMI (r=-0·1, P=0·02), pubertal status (r=-0·08, P=0·04) and sun exposure (r=0·10, P=0·04). Fat mass index was associated with 25(OH)D concentration (r=-0·13, P=0·03), but not lean mass index (P=0·86). In multiple regression analysis with adjustment for confounding factors, age and puberty were found to be independently associated with 25(OH)D concentration (P=0·008 and P=0·006); there was a significant correlation between exercise and 25(OH)D concentration after adjustment for either BMI (P=0·01) or fat mass index (P=0·02).

CONCLUSIONS

25(OH)D deficiency is highly prevalent among children in the south of Iran. It is related to insufficient sun exposure, low physical activity, advancing age and pubertal stage. Measures should be taken to improve the health of southern Iranian children in this critical age group by preventing 25(OH)D deficiency.

The influence of puberty on vitamin D status in obese children and the possible relation between vitamin D deficiency and insulin resistance

BACKGROUND

Puberty can affect vitamin D levels.

OBJECTIVES

The goal of this study was to analyze the relation between vitamin D deficiency and puberty in obese Spanish children, along with the possible interrelation between vitamin D status and degree of insulin resistance.

METHODS

A cross-sectional study was carried out, in which clinical and biochemical data were gathered from 120 obese and 50 normal weight children between January 2011 and January 2013.

RESULTS

Mean vitamin D levels were 19.5 and 31.6 ng/mL in obese pubertal and obese prepubertal children, respectively. About 75% of the obese pubertal subjects and 46% of the obese prepubertal subjects had vitamin D deficiency. Vitamin D levels were significantly lower in pubescent subjects compared with pre-pubescent subjects in summer, fall, and winter. There was no apparent relation between vitamin D levels and homeostasis model assessment index for insulin resistence (expressed in standard deviation score for sex and Tanner stage) in either puberty or pre-puberty.

CONCLUSION

Puberty may be a risk factor for the vitamin D deficiency commonly found in the obese child population. This deficiency is not associated with higher insulin resistance in obese pubertal children compared with obese prepubertal children.

Vitamin D status and its relationship with metabolic syndrome risk factors among adolescent girls in Boukan, Iran

OBJECTIVE

To investigate vitamin D status and its association with components of the metabolic syndrome (MetS) in adolescent girls attending high school in Boukan, Iran during winter 2012.

DESIGN

A cross-sectional study.

SETTING

High schools of Boukan city, Iran.

SUBJECTS

A sample of 216 girls aged 14-17 years was selected by multistage random sampling from four districts of Boukan. Weight, height, waist circumference, blood pressure, daily energy intake, physical activity and serum 25-hydroxyvitamin D (25(OH)D), fasting blood glucose, TAG and HDL-cholesterol levels of all participants were evaluated. Serum 25(OH)D level <20 ng/ml was defined as vitamin D deficiency.

RESULTS

Mean serum 25(OH)D was 7.26 (sd 2.81) ng/ml and 96 % of the participants had vitamin D deficiency. According to age-modified definitions of the National Cholesterol Education Program Adult Treatment Panel III, MetS was diagnosed in 10.6% of the participants. In multivariable regression analysis after adjustment for BMI, energy intake and physical activity level, serum 25(OH)D was inversely associated with fasting blood glucose (β = -0.143, P = 0.04). No significant relationship was found between serum 25(OH)D and other components of MetS.

CONCLUSIONS

The high prevalence of vitamin D deficiency warrants national polices and interventions towards improving this major health problem among adolescent girls. Low 25(OH)D level was significantly associated with increased fasting blood glucose. Prospective studies are needed to determine the effects of vitamin D deficiency on the development of MetS and related metabolic diseases in adolescent girls.

Validation of a food-frequency questionnaire for the assessment of calcium intake in schoolchildren aged 9-10 years

Bone mass increases steadily until age 20-30 years, when peak bone mass (PBM) is acquired. Nutrition plays a critical role in achievement of the optimal genetically programmed PBM, with reduction in the risk of osteoporosis later in life. Intake of nutrients can be estimated through the use of various tools; typically, food-frequency questionnaires (FFQs) are used in epidemiologic studies. The aim of this study was to validate a 21-item, semiquantitative FFQ to assess important nutrient intakes for bone health in Italian schoolchildren 9-10 years of age. Relative validation was accomplished through comparison of the 7-days weighed food record (7D records) with an FFQ developed ad hoc, completed by a group of 75 Italian schoolchildren (36 females, 39 males). Agreement between the two methods was evaluated by Spearman's correlation test and Bland-Altman analysis applied on the data on intake of energy, macronutrients, and micronutrients. Particular attention was devoted to nutrients relevant for bone health. Good correlations between the two methods (FFQ and 7D records) were observed for all nutrients. In particular, mean dietary calcium intakes were 725.6 mg/day (95 % CI 683.2-768.1) from 7D records and 892.4 mg/day (95 % CI 844.6-940.2) from the FFQ. These results indicate that our FFQ for schoolchildren aged 9-10 years is highly acceptable as it is an accurate method that can be used in large-scale or epidemiological studies for the evaluation of nutrient intakes important for the prevention of osteoporosis in a similar population.

Vitamin D in the healthy European paediatric population

In recent years, reports suggesting a resurgence of vitamin D deficiency in the Western world, combined with various proposed health benefits for vitamin D supplementation, have resulted in increased interest from health care professionals, the media, and the public. The aim of this position paper is to summarise the published data on vitamin D intake and prevalence of vitamin D deficiency in the healthy European paediatric population, to discuss the health benefits of vitamin D and to provide recommendations for the prevention of vitamin D deficiency in this population. Vitamin D plays a key role in calcium and phosphate metabolism and is essential for bone health. There is insufficient evidence from interventional studies to support vitamin D supplementation for other health benefits in infants, children, and adolescents. The pragmatic use of a serum concentration >50 nmol/L to indicate sufficiency and a serum concentration <25 nmol/L to indicate severe deficiency is recommended. Vitamin D deficiency occurs commonly among healthy European infants, children, and adolescents, especially in certain risk groups, including breast-fed infants, not adhering to the present recommendation for vitamin D supplementation, children and adolescents with dark skin living in northern countries, children and adolescents without adequate sun exposure, and obese children. Infants should receive an oral supplementation of 400 IU/day of vitamin D. The implementation should be promoted and supervised by paediatricians and other health care professionals. Healthy children and adolescents should be encouraged to follow a healthy lifestyle associated with a normal body mass index, including a varied diet with vitamin D-containing foods (fish, eggs, dairy products) and adequate outdoor activities with associated sun exposure. For children in risk groups identified above, an oral supplementation of vitamin D must be considered beyond 1 year of age. National authorities should adopt policies aimed at improving vitamin D status using measures such as dietary recommendations, food fortification, vitamin D supplementation, and judicious sun exposure, depending on local circumstances.

Prevalence of vitamin D insufficiency in Swiss teenagers with appendicular fractures: a prospective study of 100 cases

BACKGROUND

The significance of subclinical vitamin D deficiency in the pathogenesis of fractures in children and adolescents currently remains unclear.

OBJECTIVE

We aimed to determine the prevalence of vitamin D insufficiency and its effect on bone mineral density (BMD) and bone mineral content (BMC) values in a collective of Swiss Caucasian children with a first episode of appendicular fracture.

DESIGN AND METHODS

One hundred teenagers with a first episode of appendicular fracture [50 upper limb fractures (group 1) and 50 lower limb fractures (group 2)] and 50 healthy controls (group 3) were recruited into a cross-sectional study. The BMC and BMD values were measured by dual-energy X-ray absorptiometry, and serum 25 hydroxyvitamin D [25(OH)D] was assessed by electrochemiluminescence immunoassays.

RESULTS

From the 100 injured teenagers in the study, 12 % had deficient vitamin D levels (<20 ng/mL; <50 nmol/L) and 36 % had insufficient levels (≥20 <30 ng/mL; ≥50 <78 nmol/L), whereas 6 and 34 % of healthy controls were, respectively, vitamin D deficient and insufficient. There were no significant differences for serum 25(OH)D levels, L2-L4 BMD Z-score, and L2-L4 BMC Z-score variables (p = 0.216) between the three groups nor for the calcaneal BMD Z-score variables (p = 0.278) between healthy controls and lower limb fracture victims. Investigations on the influences of serum 25(OH)D on BMD and BMC showed no correlation between serum 25(OH)D and L2-L4 BMD Z-scores (r = -0.15; p = 0.135), whereas low but significant inverse correlations were, surprisingly, detected between serum 25(OH)D and calcaneal BMD Z-scores (r = -0.21; p = 0.034) and between serum 25(OH)D and L2-L4 BMC Z-scores (r = -0.22; p = 0.029).

CONCLUSIONS

A significant proportion of Swiss Caucasian teenagers were vitamin D insufficient, independent of limb fracture status, in our study. However, this study failed to show an influence of low vitamin D status on BMD and/or BMC of the lumbar spine and heel.

Bone turnover is not influenced by serum 25-hydroxyvitamin D in pubertal healthy black and white children

Low serum 25-hydroxyvitamin D [25 (OH) D] is common in healthy children particularly in blacks. However, serum 25 (OH) D concentrations for optimal bone turnover in children is unknown and few data exist that describe effects of increasing serum 25 (OH) D on bone turnover markers during puberty. The purpose of this study was to determine the relationships between serum 25 (OH) D and changes in serum 25 (OH) D and bone turnover in white and black pubertal adolescents. Bone turnover markers were measured in 318 healthy boys and girls from Georgia (34°N) and Indiana (40°N) who participated in a study of oral vitamin D(3) supplementation (0 to 4000 IU/d). Serum 25 (OH) D, osteocalcin, bone alkaline phosphatase, and urine N-telopeptide cross-links were measured at baseline and 12 weeks. Relationships among baseline 25 (OH) D and bone biomarkers, and between changes over 12 weeks were determined and tested for effects of race, sex, latitude, and baseline 25 (OH) D. Median 25 (OH) D was 27.6 ng/mL (n=318, range 10.1-46.0 ng/mL) at baseline and 34.5 ng/mL (n=302, range 9.7-95.1 ng/mL) at 12 weeks. Neither baseline nor change in 25 (OH) D over 12 weeks was associated with bone turnover. The lack of association was not affected by race, sex, latitude, or baseline serum 25 (OH) D. Serum 25 (OH) D in the range of 10-46 ng/mL appears to be sufficient for normal bone turnover in healthy black and white pubertal adolescents.

Estimation of the dietary requirement for vitamin D in healthy adolescent white girls

BACKGROUND

Knowledge gaps have contributed to considerable variation (between 0 and 15 μg/d) in international dietary recommendations for vitamin D in adolescents.

OBJECTIVE

We aimed to establish the distribution of dietary vitamin D required to maintain serum 25-hydroxyvitamin D [25(OH)D] concentrations above several proposed cutoffs (25, 37.5, 40, and 50 nmol/L) during wintertime in adolescent white girls.

DESIGN

Data (baseline and 6 mo) from 2 randomized, placebo-controlled, double-blind, 12-mo intervention studies in Danish (55°N) and Finnish (60°N) girls (n = 144; mean age: 11.3 y; mean vitamin D intake: 3.7 μg/d) at vitamin D(3) supplementation amounts of 0, 5, and 10 μg/d were used. Serum 25(OH)D was measured with an HPLC assay in a centralized laboratory.

RESULTS

Clear dose-related increments (P < 0.0001) in serum 25(OH)D with increasing supplemental vitamin D(3) were observed. The slope of the relation between vitamin D intake and serum 25(OH)D at the end of winter was 2.43 nmol ⋅ L(-1) ⋅ μg intake(-1), and no difference in the slopes between Finnish and Danish girls was observed. The vitamin D intakes that maintained serum 25(OH)D concentrations at >25, >37.5, and >50 nmol/L in 97.5% of the sample were 8.3, 13.5, and 18.6 μg/d, respectively, whereas an intake of 6.3 μg/d maintained a serum 25(OH)D concentration >40 nmol/L in 50% of the sample.

CONCLUSION

The vitamin D intakes required to ensure that adequate vitamin D status [defined variably as serum 25(OH)D >25 and >50 nmol/L] is maintained during winter in the vast majority (>97.5%) of adolescent girls (mean age: 11.3 y) at northern latitudes (>55°N) are 8.3 and 18.6 μg/d, respectively. This trial was registered at clinicaltrials.gov as NCT00267540.

High prevalence of genu varum/valgum in European children with low vitamin D status and insufficient dairy products/calcium intakes

OBJECTIVE

The prevalence of lower limb deformities physiologically decreases after 5 years of age. It remains high in some tropical and subtropical regions where it has been associated with severe vitamin D deficiency, low calcium/milk intakes, malnutrition, and/or fluoride overexposure. Very little data is available in apparently healthy Caucasian children and adolescents.

DESIGN

We evaluated the prevalence of genu varum/valgum and other clinical symptoms, and assessed vitamin D status and markers of calcium metabolism in 226 apparently healthy European full-time boarders (7-16 years) seen during winter-spring and fed a cereal-based diet with little access to meat, milk, and dairy products. A cohort of 71 white children and adolescents hospitalized for acute illness served as age-matched controls.

RESULTS

Association studies showed a high prevalence of lower limb deformities (36%) and higher alkaline phosphate activities in the 21% of children and adolescent full-time boarders with serum 25-(OH)D levels ≤ 30 nmol/l, and low serum calcium in the 74% of boarders with 25-(OH)D levels ≤ 50 nmol/l, compared with boarders with higher vitamin D status. No such anomalies were found in the control cohort despite lower serum 25-(OH)D levels.

CONCLUSIONS

Low 25-(OH)D levels, at least during winter-spring, combined with additional risk factors such as very low calcium/milk intakes and possibly digestive disorders, are associated with an increased risk of genu varum/valgum in European children and adolescents. Thus, dietary fortification, or supplementation with vitamin D, may be recommended, at least during the winter, to European children and adolescents with either none or insufficient calcium/dairy product intakes.

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

No consensus has been reached on the serum 25-hydroxyvitamin D [25(OH)D] levels required to ensure optimal bone health around menarche. We searched for a possible interaction of 25(OH)D levels and calcium intake on lumbar spine mineralization and on biologic features of bone metabolism in healthy late-pubertal girls. Lumbar spine parameters (ie, area, mineral content, and density) and calcium intake were evaluated in 211 healthy white adolescent girls at pubertal stages IV-V (11 to 16.9 years), together with biologic markers of calcium and bone metabolism and with International External Quality Assessment Scheme for Vitamin D Metabolite (DEQAS)-validated serum 25(OH)D levels. A high prevalence of 25(OH)D levels ≤ 30 nmol/L (41%), ≤ 40 nmol/L (61%), and ≤ 50 nmol/L (70%) was found during winter-spring. Parathyroid hormone (PTH) levels were inversely associated with 25(OH)D levels (p = .0021). In contrast, lumbar spine mineral content and density were not associated with 25(OH)D, excepted when calcium intake was below 600 mg/day (p = .0081). Girls with such low calcium intake and 25(OH)D levels of 40 nmol/L or less (9% of the cohort) had a 0.4 to 0.7 SD lower mean areal bone mineral density Z-score than girls with higher calcium intake and/or higher 25(OH)D status. The adverse association between lumbar spine mineralization and combined calcium deficiency-low 25(OH)D levels remained significant in the 91 girls who could be followed over 4 years after their initial evaluation. We conclude that low 25(OH)D levels (≤40 nmol/L) are observed frequently during winter-spring in late-pubertal European girls, which may exacerbate the negative impact of calcium deficiency on lumbar spine mineralization.

Vitamin D-vitamin K interaction: effect of vitamin D supplementation on serum percentage undercarboxylated osteocalcin, a sensitive measure of vitamin K status, in Danish girls

There is some evidence for a nutritional interaction between vitamin D and vitamin K status. We have recently reported that serum percentage undercarboxylated osteocalcin (%ucOC; a marker of vitamin K status) was inversely correlated with serum 25-hydroxyvitamin D (25(OH)D) concentration (reflective of vitamin D status) in healthy Danish girls (aged 11-12 years), in line with a similar relationship reported in elderly women. While the causal nature of the relationship between vitamin D status and serum %ucOC has been tested in studies of elderly women, it has not been investigated in children. The objective of the present study was to test the hypothesis that improving vitamin D status significantly lowers serum %ucOC. Serum samples from sixty-seven healthy Danish girls (aged 11-12 years), who participated in a 12-month double-blind, placebo-controlled, vitamin D3 intervention trial were used for the present study. These girls were a subset of subjects which began and finished the intervention during wintertime, thus avoiding the influence of seasonality on vitamin D status. A total of thirty-three and thirty-four of the girls had been randomised to treatment with 10 μg vitamin D3 per d and placebo, respectively, for 12 months. Total osteocalcin and the fraction of ucOC in serum (via enzyme-immunoassay) as well as serum 25(OH)D (via HPLC) were assessed at baseline and end-point. Vitamin D3 supplementation significantly increased serum 25(OH)D (21.6 %; P < 0.002) but had no effect on serum %ucOC (P>0.8). In conclusion, the findings of the present intervention study in young girls suggest that vitamin D supplementation does not affect serum %ucOC, a marker of vitamin K status.

Maximizing bone mineral mass gain during growth for the prevention of fractures in the adolescents and the elderly

Bone mass is a key determinant of fracture risk. Maximizing bone mineral mass during childhood and adolescence may contribute to fracture risk reduction during adolescence and possibly in the elderly. Although more than 60% of the variance of peak bone mass (PBM), the amount of bone present in the skeleton at the end of its maturation process, is genetically determined, the remainder is likely influenced by factors amenable to positive intervention, such as adequate dietary intake of dairy products as a natural source of calcium and proteins, vitamin D, and regular weight-bearing physical activity. Low calcium and vitamin D intakes are associated with negative effects on bone, including suboptimal PBM acquisition. As suggested by intervention studies, regular intake of dairy products may have positive and possibly sustained effects on bone mineral mass gain, contributing thereby to fracture risk reduction. Further evidence from intervention studies suggests that weight-bearing physical activities, such as jumping, may contribute to bone mineral mass gain in children. Optimizing PBM acquisition through dietary and physical exercise measures may represent a valuable primary method for the prevention of fractures.

Does vitamin D supplementation of healthy Danish Caucasian girls affect bone turnover and bone mineralization?

INTRODUCTION

A high peak bone mass may be essential for reducing the risk of osteoporosis later in life and a sufficient vitamin D level during puberty may be necessary for optimal bone accretion and obtaining a high peak bone mass. Dietary intake and synthesis during winter of vitamin D might be limited but the effect of vitamin D supplementation in adolescence on bone mass is not well established.

OBJECTIVE

To investigate the effect of supplementation with 5 and 10 microg/day vitamin D(3) for 12 months in 11- to 12-year-old girls on bone mass and bone turnover as well as the possible influence of VDR and ER genotype on the effect of the supplementation.

METHODS

The girls (n=221) were randomized to receive either 5 microg or 10 microg vitamin D(3) supplementation per day or placebo for 12 months. Whole body and lumbar spine bone mass measured by DXA and pubertal status were determined at baseline and after 12 months whereas physical activity and dietary intake of calcium and vitamin D were assessed at baseline. Serum (S) 25-hydroxyvitamin D (25OHD), S-osteocalcin, S-parathyroid hormone, S-calcium, S-inorganic phosphate, urinary (U) pyridinoline (Pyr) and deoxpyridinoline (Dpyr) were measured at baseline and after 6 and 12 months.

RESULTS

The S-25OHD concentration increased (p<0.001) relative to the baseline values in the groups receiving either 5 microg/day (mean+/-SD; 11.0+/-10.3 nmol/l, baseline 41.9+/-17.6 nmol/l) or 10 microg/day (13.3+/-11.8 nmol/l, baseline 44.4+/-16.6 nmol/l) vitamin D(3) for 12 months compared to placebo (-3.1+/-9.8 nmol/l, baseline 43.4+/-17.1 nmol/l). There was no effect of vitamin D-supplementation on biomarkers for bone turnover or on whole body or spine bone mineral augmentation. However, vitamin D supplementation increased whole body bone mineral density (BMD) (p=0.007) and bone mineral content (BMC) (p=0.048) in the FF VDR genotype but not in the Ff or ff VDR genotypes.

CONCLUSION

Supplementation with vitamin D (5 or 10 microg/day) over 12 months increased the S-25OHD concentration but there was no effect on indices of bone health in the entire group of girls. However, there was an effect on BMD for a subgroup with the FF VDR genotype indicating an influence of genotype.

Vitamin D and adolescents: what do we know?

PURPOSE OF REVIEW

Vitamin D has become the focus of many studies in recent years. Vitamin D deficiency has been linked to many chronic illnesses other then the well known musculoskeletal complications. In this review, we summarize new data regarding causes, prevalence, and complications of vitamin deficiency in adolescents and discuss them in the context of what is known in adults. In addition, we emphasize adolescence as a unique period for growth and development, and distinguish the consequences of vitamin D deficiency in young teenage patients from those in adults with regard to the presentation and potential health implications.

RECENT FINDINGS

Vitamin D deficiency is common among both healthy and ill adolescents worldwide, even in sunny countries. Although much of the data relating vitamin D status to biological markers and complications has been obtained in adults, the information emerging from studies of adolescents supports the premise that maintaining sufficient levels of vitamin D during the teenage years can improve long-term health outcomes. There are currently knowledge gaps regarding the most well tolerated and appropriate supplementation regimen to prevent vitamin D deficiency among adolescents.

SUMMARY

Further studies are needed to examine the implications of vitamin D deficiency among adolescents and the most appropriate treatment regimens to prevent this problem. There are sufficient data to support the importance of educating, preventing, and treating vitamin D deficiency in adolescents to improve their long-term health.

Hypovitaminosis D in obese and overweight schoolchildren

AIM

To determine the prevalence of vitamin D hypovitaminosis among obese and overweight schoolchildren.

DESIGN

A cross-sectional population based sample.

METHODS

In a cross-sectional study, 301 students (177 girls and 124 boys) aged 11-19 years were selected by multistage stratified sampling design. Subjects were classified according to their body mass index as obese, overweight and normal. Serum 25-hydroxyvitamin D (25-OHD), intact parathyroid hormone (iPTH) and alkaline phosphatase (ALP) were measured in late winter months. Vitamin D deficiency was defined as a 25-OHD 20 ng/ml.

RESULTS

The prevalence of hypovitaminosis D was found as 65% in all students. Vitamin D deficiency was found in 12% and insufficiency in 53% of all students. Vitamin D deficiency in female students was about two times more common than in males. In obese and overweight schoolchildren with hypovitaminosis D, serum 25-OHD levels decreased as BMI increased. There were no correlations between serum 25-OHD and ALP and iPTH levels.

CONCLUSION

Vitamin D deficiency and insufficiency are common in obese and overweight schoolchildren, especially in girls. Obesity could be a risk factor in terms of hypovitaminosis D in adolescents. Vitamin D supplementation should be administered particularly to adolescent girls.

Effects of antiepileptic drug therapy on vitamin D status and biochemical markers of bone turnover in children with epilepsy

Reports of decreased serum 25-hydroxyvitamin D (25-OHD) and altered bone metabolism associated with antiepileptic drug (AED) treatment are inconsistent and predominantly restricted to adults. In this cross-sectional observational study, the aim was to evaluate the influence of AED treatment on vitamin D status and markers of bone turnover in children with epilepsy. In 38 children taking AEDs and 44 healthy control subjects, blood samples were collected to determine the levels of serum 25-OHD, intact parathyroid hormone (iPTH), calcium (Ca), phosphate (P), bone alkaline phosphatase (BAP), osteocalcin (OC) and C terminal telopeptide of type I collagen (ICTP). More than 75% of the patients were vitamin D deficient (serum 25-OHD<20 ng/mL) and 21% of the patients had an insufficient vitamin D status (serum 25-OHD=20-30 ng/mL). In the patients, the serum levels of OC (p = 0.002) and BAP (p < 0.001) were significantly increased, but ICTP (p = 0.002) concentrations were significantly decreased compared with the control group. When patients where divided into two groups according to their medication (mono- or polytherapy), significantly lower 25-OHD (p = 0.038) and ICTP (p = 0.005) levels and elevated BAP (p = 0.023) concentrations were found in patients under polytherapy. An association between 25-OHD and the measured bone markers could not be determined. Our results indicate that the prevalence of vitamin D deficiency in epilepsy patients under AED treatment is high, especially under polytherapy, and alteration markers of bone formation and resorption suggests an accelerated skeletal turnover. The routine monitoring of serum 25-OHD and vitamin D supplementation on an individual basis should be considered.

Vitamin D: a growing perspective

Vitamin D deficiency has been widely reported in all age groups in recent years. Rickets has never been eradicated in developed countries, and it most commonly affects children from recent immigrant groups. There is much evidence that current vitamin D guidelines for the neonatal period, 5-10 microg (200-400 IU)/day, prevent rickets at the typical calcium intakes in developed countries. The annual incidence of vitamin D-deficiency rickets in developed countries ranges between 2.9 and 7.5 cases per 100,000 children. The prevalence of vitamin D deficiency in mothers and their neonates is remarkable, and the results of one study suggest that third-trimester 25-hydroxyvitamin D (25(OH)D) is associated with fetal bone mineral accrual that may affect prepubertal bone mass accumulation. Beyond infancy, the evidence indicates that 5 microg (200 IU)/day of vitamin D has little effect on vitamin D status as measured by the serum 25(OH)D concentration. Two randomized clinical trials show that higher vitamin D intake improves one-year gain in bone density in adolescent girls. The functions of vitamin D extend beyond bone to include immune system regulation and anti-proliferative effects on cells. Early life vitamin D inadequacy is implicated in the risk of bone disease, autoimmune disease, and certain cancers later in life; however, long-term interventional studies do not exist to validate the widespread implementation of greater vitamin D consumption. Here we review the available data concerning vitamin D status and health effects of vitamin D in pregnancy through to and including adolescence.

Vitamin D status and its determinants in adolescents from the Northern Ireland Young Hearts 2000 cohort

Despite recent concerns about the high prevalence of sub-clinical vitamin D deficiency in adolescents, relatively few studies have investigated the underlying reasons. The objective of the present study was to investigate the prevalence and predictors of vitamin D inadequacy among a large representative sample of adolescents living in Northern Ireland (54–55°N). Serum concentrations of 25-hydroxyvitamin D (25(OH)D) were analysed by enzyme-immunoassay in a subgroup of 1015 of the Northern Ireland Young Hearts 2000 cohort; a cross-sectional study of 12 and 15 year-old boys and girls. Overall mean 25(OH)D concentration throughout the year was 64·3 (range 5–174) nmol/l; 56·7 and 78·1 nmol/l during winter and summer, respectively. Reported intakes of vitamin D were very low (median 1·7 μg/d). Of those adolescents studied, 3 % and 36 % were vitamin D deficient and inadequate respectively, as defined by serum 25(OH)D concentrations < 25 and < 50 nmol/l. Of the subjects, 46 % and 17 % had vitamin D inadequacy during winter and summer respectively. Gender differences were also evident with 38 % and 55 % of boys and girls respectively classified as vitamin D inadequate during winter (P < 0·001). Predictors of vitamin D inadequacy during winter were vitamin D intake and gender. In conclusion, there is a high prevalence of vitamin D inadequacy in white-skinned adolescents in Northern Ireland, particularly during wintertime and most evident in girls. There is a clear need for dietary recommendations for vitamin D in this age group and for creative strategies to increase overall vitamin D status in the population.

Low vitamin D status adversely affects bone health parameters in adolescents

BACKGROUND

The effects of subclinical vitamin D deficiency on bone mineral density (BMD) and bone turnover in adolescents, especially in boys, are unclear.

OBJECTIVE

We aimed to investigate the relations of different stages of vitamin D status and BMD and bone turnover in a representative sample of adolescent boys and girls.

DESIGN

BMD was measured by dual-energy X-ray absorptiometry at the nondominant forearm and dominant heel in a random sample of 12- (n = 260) and 15-y-old (n = 239) boys and 12- (n = 266) and 15-y-old (n = 250) girls. Serum 25-hydroxyvitamin D, parathyroid hormone, osteocalcin, and type I collagen cross-linked C-telopeptide were assessed by using enzyme-linked immunoassays. Relations between vitamin D status and bone health indexes were assessed by using regression modeling.

RESULTS

Using multivariate regression to adjust for potential physical, lifestyle, and dietary confounding factors, we observed that 12- and 15-y-old girls with high vitamin D status (>/=74.1 nmol/L) had significantly greater forearm (but not heel) BMD (beta = 0.018; SE = 0.008; P < 0.05 for each age group) and lower serum parathyroid hormone concentrations and bone turnover markers than did those with low vitamin D status. These associations were evident in subjects sampled throughout the year and in winter only. There was no significant relation between vitamin D status and BMD in boys.

CONCLUSIONS

Maintaining serum 25-hydroxyvitamin D concentrations above approximately 50 nmol/L throughout the year may be a cost-effective means of improving bone health. Increased emphasis on exploring strategies for improving vitamin D status in adolescents is needed.

Assessing, understanding and modifying nutritional status, eating habits and physical activity in European adolescents: The HELENA (Healthy Lifestyle in Europe by Nutrition in Adolescence) Study

Objectives

To identify the main knowledge gaps and to propose research lines that will be developed within the European Union-funded ‘Healthy Lifestyle in Europe by Nutrition in Adolescence’ (HELENA) project, concerning the nutritional status, physical fitness and physical activity of adolescents in Europe.

Design

Review of the currently existing literature.

Results

The main gaps identified were: lack of harmonised and comparable data on food intake; lack of understanding regarding the role of eating attitudes, food choices and food preferences; lack of harmonised and comparable data on levels and patterns of physical activity and physical fitness; lack of comparable data about obesity prevalence and body composition; lack of comparable data about micronutrient and immunological status; and lack of effective intervention methodologies for healthier lifestyles.

Conclusions

The HELENA Study Group should develop, test and describe harmonised and state-of-the-art methods to assess the nutritional status and lifestyle of adolescents across Europe; develop and evaluate an intervention on eating habits and physical activity; and develop and test new healthy food products attractive for European adolescents.

Prospective study on food fortification with vitamin D among adolescent females in Finland: minor effects

Vitamin D insufficiency is common particularly during winter time. After the recommendation by the Ministry of Social Affairs and Health, Finnish fluid milks and margarines have been fortified with vitamin D since February 2003. The aims of the present study were to examine the impact of vitamin D fortification of food supplies on serum 25-hydroxyvitamin D (S-25(OH)D) concentrations and on daily dietary vitamin D intake among adolescent females. One hundred and forty-two girls of Caucasian ethnicity aged 12-18 years completed semi-quantitative FFQ from which the dietary vitamin D and Ca intakes were calculated. S-25(OH)D was measured by radioimmunoassay. The study was performed from February-March 2000 to February-March 2004, one year after the initiation of fortification. The mean dietary intake of vitamin D was < 7.5 microg in 91.5 % of the adolescent girls in 2000 and 83.8 % in 2004. The midwinter mean S-25(OH)D concentration did not change significantly during the follow-up period (48.3 v. 48.1 nmol/l, NS). The proportion of participants who had S-25(OH)D concentration < 50 nmol/l was 60.6 % in 2000 and 65.5 % in 2004. Only 7.0 % of the participants had an adequate S-25(OH)D ( >or= 75 nmol/l) level in 2000 or 4 years later. The vitamin D fortification of fluid milks and margarines was inadequate to prevent vitamin D insufficiency. There are numerous adolescent girls and women who are not reached by the current fortification policy. Therefore new innovative and feasible ways of improving vitamin D nutrition are urged.

Estimated net endogenous acid production and intake of bone health-related nutrients in Hong Kong Chinese adolescents

BACKGROUND/OBJECTIVES

To examine the daily intake of bone health-related nutrients and to explore the association between diet composition and estimated net endogenous acid production (estimated NEAP) in Hong Kong Chinese adolescents.

SUBJECT/METHODS

In total, 171 boys and 180 girls aged 10-12 years of Chinese origin from nine primary schools from the Hong Kong Adolescent Bone Health Cohort Study. The study design used food frequency questionnaire. Mean daily intakes of foods and selected nutrients were estimated. Mean percentage of nutrient intake contributed by different food groups was presented. Frassetto's method was used to calculate the estimated NEAP from the diet's protein to potassium ratio.

RESULTS

There was no significant difference in the energy-adjusted intakes of most nutrients between boys and girls, except for intakes of vitamins C and D. Mean protein, sodium and potassium intakes were higher than the Chinese dietary reference intake (DRI), whereas mean intakes of magnesium, calcium and vitamin D were lower than the DRI. Boys had significantly higher estimated NEAP than girls (P=0.0051). Estimated NEAP was significantly positively correlated with meat intake and negatively associated with the consumption of fruits, vegetables, legumes, beverages and dairy products.

CONCLUSIONS

The results highlight the importance of considering whole diet quality when interpreting the effects of single nutrient or diet's net acid load on bone. The effect on high protein intake and low fruit and vegetable intake on the long-term bone health of Hong Kong Chinese adolescents warrants attention.

Vitamin D in childhood and adolescence

It is well-established that prolonged and severe vitamin D deficiency leads to rickets in children and osteomalacia in adults. More marginal vitamin D deficiency is likely to be a significant contributing factor to osteoporosis risk. However, recent emerging data from studies of adults suggest that low vitamin D status (serum 25-hydroxyvitamin D levels <50 nmol/l) may be contributing to the development of various chronic diseases, including cardiovascular disease, hypertension, diabetes mellitus, some inflammatory and autoimmune diseases, and certain cancers. Adequacy of vitamin D status in children and adolescents has been the focus of a number of recent investigations, and these studies have shown a high prevalence of low vitamin D status during the winter (especially in adolescents), with lower prevalence during the summer. Therefore, consideration of potential corrective strategies to allow children and adolescents to maintain adequate vitamin D status throughout the year, even in the absence of adequate summer sun exposure, is warranted.

Relationships between biochemical bone turnover markers, season, and inflammatory status indices in prepubertal Gambian boys

Seasonal and interindividual differences in food availability and illnesses cause variations in growth, including bone growth, in children in developing countries. We investigated seasonal differences in biochemical (serum) markers of bone metabolism and relationships between these markers (procollagen type I N propeptide [P1NP], serum C-terminal telopeptide of type 1 collagen [S-CTX]) and serum markers of inflammation (alpha(1)- antichymotrypsin [ACT], C-reactive protein [CRP], sialic acid) in prepubertal Gambian boys. Three seasonal time points were chosen: August, mid-rainy season; October, late rainy season (both are associated with decreased food supply, increased prevalence of infection, reduced weight gain, and stunting); and April, late dry season, when environmental conditions are better and rates of weight gain are higher. The prevalence of raised inflammatory markers was high: 29% of ACT values >0.40 g/L in August, 42% >0.40 g/L in October, and 18% >0.40 g/L in April. Of CRP values, 92-96% were >0.47 mg/L and 30%, 46%, and 18% were >3.95 mg/L in August, October, and April, respectively. Also, 42-52% of sialic acid values were >648 mg/L. Of the bone markers, S-CTX exhibited the highest values in August; P1NP did not vary with season. Inverse relationships between each bone marker and the acute phase markers occurred, with the strongest relationships between P1NP and ACT or sialic acid. We conclude that bone collagen synthesis and turnover are reduced during inflammation in rural Gambian boys. Biochemical indices can provide powerful, single-time point evidence of infection and growth-faltering episodes.

PIXImus bone densitometer and associated technical measurement issues of skeletal growth in the young rat

The PIXImus dual-energy X-ray absorptiometer (DXA) is designed to measure body composition, bone mineral content (BMC), area (BA), and density (BMD) in mice and rats. The aims of this study were to longitudinally measure BMC, BA, and BMD in growing rats and to identify potential technical problems associated with the PIXImus. Total femur and lumbar DXA measurements, body weight, and length of initially 3-week-old rats (n = 10) were taken at weeks 5, 9, and 14. BMC and BMD of femoral metaphyseal and diaphyseal regions rich in trabecular and cortical bone, respectively, were obtained. Results showed significant increases in body weight, total femur BMC and BMD, lumbar area, length, BMC, and BMD at each time point. There was a significant positive correlation between body weight and total femur BMD (r = 0.97, P < 0.001) as well as lumbar BMD (r = 0.99, P < 0.001). BMD values for the femoral metaphyseal region and the lumbar spine were also positively correlated (r = 0.96, P < 0.01). Several technical issues (e.g., positioning of animals), difficulties (e.g., in analysis of images), and limitations (e.g., inability to detect underdeveloped calcified bone in growing animals and bone edge detection) of the software pertinent to the PIXImus were evident. In conclusion, despite limitations in the software, the PIXImus is a valuable tool for studying skeletal development of growing rats.

Effect of vitamin D supplementation on vitamin D status and bone turnover markers in young adults

OBJECTIVE

To assess the vitamin D status of healthy young people living in Northern Ireland and the effect of vitamin D supplementation on vitamin D status and bone turnover.

DESIGN

Double-blinded randomised controlled intervention study.

SETTING

University of Ulster, Coleraine, Northern Ireland.

SUBJECTS

In total, 30 apparently healthy students (15 male and 15 female subjects), aged 18-27 years, were recruited from the university, with 27 completing the intervention.

INTERVENTIONS

Subjects were randomly assigned, to receive either 15 microg (600 IU) vitamin D(3) and 1,500 mg calcium/day (vitamin D group), or 1,500 mg calcium/day (control group) for 8 weeks between January and March. Vitamin D status, bone turnover markers, serum calcium and parathyroid hormone concentrations were measured at baseline and post intervention.

RESULTS

At baseline, vitamin D status was low in both the vitamin D group (47.9 (s.d. 16.0)) and the control group (55.5 (s.d. 18.6) nmol/l 25(OH)D). Post intervention vitamin D status was significantly higher in the vitamin D-treated group (86.5 (s.d. 24.5)) compared to the control group (48.3 (s.d. 16.8) nmol/l) (P<0.0001). There was no significant effect of supplementation on bone turnover markers or PTH concentrations.

CONCLUSIONS

This study suggests that young adults in Northern Ireland do not consume an adequate daily dietary intake of vitamin D to maintain plasma vitamin D concentrations in the wintertime. A daily supplement of 15 microg vitamin D(3) significantly increased vitamin D status in these individuals to levels of sufficiency. Achievement of an optimum vitamin D status among young adults may have future positive health implications.

Are national vitamin D guidelines sufficient to maintain adequate blood levels in children?

BACKGROUND

Vitamin D insufficiency (defined as 25-hydroxyvitamin D [25(OH)D] concentrations <40 nmol/L) may be associated with subclinical adverse effects on bone mineralization. The current vitamin D status of children and adolescents in Canada has not been described. The purpose of this study was to describe the association between 25(OH)D serum concentration and dietary vitamin D intake, and other potential determinants of vitamin D status, among a sample of children and adolescents aged 2-16 years presenting to a pediatric emergency department in Edmonton, Alberta (latitude 52 degrees N) at the end of winter.

METHODS

In early April 2003, 90 patients between the ages of 2 and 16 years who presented to the pediatric emergency department in Edmonton volunteered to participate. All participants and/or parents or guardians completed questionnaires regarding potential risk factors for vitamin D insufficiency, detailed dietary assessments, and anthropometric measurements. Serum 25(OH)D concentrations were measured in 68 of 90 participants.

RESULTS

The mean serum 25(OH)D concentration was 47.2 nmol/L (95% CI 43.8-50.8 nmol/L). 34% of participants had vitamin D insufficiency (<40 nmol/L) and 6% were deficient (<25 nmol/L). Boys and girls aged 9-16 years had a prevalence of insufficiency of 69% and 35% respectively, while boys and girls 2-8 years old had a prevalence of insufficiency of 22% and 8% respectively. Dietary vitamin D intake per kilogram body weight was the most important independent determinant of 25(OH)D concentration (r = 0.446, p<0.001). Vitamin D intake, age and male sex best predicted insufficiency. No subject was insufficient if they had an intake >0.45 mcg/kg/day.

INTERPRETATION

Vitamin D insufficiency may be common among children and adolescents at the beginning of spring. The risk may be highest among older children because vitamin D intake does not adequately rise in proportion with increases in body mass. Further studies are needed to assess whether Canadian dietary vitamin D recommendations should be changed.

Vitamin D intake: a global perspective of current status

Global high prevalence of vitamin D insufficiency and re-emergence of rickets and the growing scientific evidence linking low circulating 25-hydroxyvitamin D to increased risk of osteoporosis, diabetes, cancer, and autoimmune disorders have stimulated recommendations to increase sunlight (UVB) exposure as a source of vitamin D. However, concern over increased risk of melanoma with unprotected UVB exposure has led to the alternative recommendation that sufficient vitamin D should be supplied through dietary sources alone. Here, we examine the adequacy of vitamin D intake worldwide and evaluate the ability of current fortification policies and supplement use practices among various countries to meet this recommendation. It is evident from our review that vitamin D intake is often too low to sustain healthy circulating levels of 25-hydroxyvitamin D in countries without mandatory staple food fortification, such as with milk and margarine. Even in countries that do fortify, vitamin D intakes are low in some groups due to their unique dietary patterns, such as low milk consumption, vegetarian diet, limited use of dietary supplements, or loss of traditional high fish intakes. Our global review indicates that dietary supplement use may contribute 6-47% of the average vitamin D intake in some countries. Recent studies demonstrate safety and efficacy of community-based vitamin D supplementation trials and food staple fortification introduced in countries without fortification policies. Reliance on the world food supply as an alternative to UVB exposure will necessitate greater availability of fortified food staples, dietary supplement use, and/or change in dietary patterns to consume more fish.