Children with nutritional rickets referred to hospitals in Copenhagen during a 10-year period

Serum 25-hydroxyvitamin D threshold and risk of rickets in young children: a systematic review and individual participant data meta-analysis to inform the development of dietary requirements for vitamin D

PURPOSE

The objective of this systematic review was to determine a minimum serum 25-hydroxyvitamin D (25OHD) threshold based on the risk of having rickets in young children. This work was commissioned by the WHO and FAO within the framework of the update of the vitamin D requirements for children 0-3 years old.

METHODS

A systematic search of Embase was conducted to identify studies involving children below  4 years of age with serum 25OHD levels and radiologically confirmed rickets, without any restriction related to the geographical location or language. Study-level and individual participant data (IPD)-level random effects multi-level meta-analyses were conducted. The odds, sensitivity and specificity for rickets at different serum 25OHD thresholds were calculated for all children as well as for children with adequate calcium intakes only.

RESULTS

A total of 120 studies with 5412 participants were included. At the study-level, children with rickets had a mean serum 25OHD of 23 nmol/L (95% CI 19-27). At the IPD level, children with rickets had a median and mean serum 25OHD of 23 and 29 nmol/L, respectively. More than half (55%) of the children with rickets had serum 25OHD below 25 nmol/L, 62% below 30 nmol/L, and 79% below 40 nmol/L. Analysis of odds, sensitivities and specificities for nutritional rickets at different serum 25OHD thresholds suggested a minimal risk threshold of around 28 nmol/L for children with adequate calcium intakes and 40 nmol/L for children with low calcium intakes.

CONCLUSION

This systematic review and IPD meta-analysis suggests that from a public health perspective and to inform the development of dietary requirements for vitamin D, a minimum serum 25OHD threshold of around 28 nmol/L and above would represent a low risk of nutritional rickets for the majority of children with an adequate calcium intake.

Global Health Disparities in Childhood Rickets

Nutritional rickets is a global health problem reflecting both historical and contemporary health disparities arising from racial, ethnic, environmental, and geopolitical circumstances. It primarily affects marginalized populations and can contribute to long-term morbidity. Deficits in bone health in childhood may also contribute to osteomalacia/osteoporosis. Solutions require a global public health approach.

Demographic Characteristics, Risk Factors, and Presenting Features of Children with Symptomatic Nutritional Rickets: A French Series

AIM

To describe the demographic characteristics, risk factors, and presenting features of children with symptomatic nutritional rickets in France.

METHODS

This is a retrospective study of 38 children diagnosed with nutritional rickets from 1998 to 2019.

RESULTS

We observed a higher frequency of rickets in males (74 vs. 26%), in young children (median age at diagnosis: 23 months; 82% were younger than 5 years), and in children with a non-Caucasian ethnic background (89%). Most children were exclusively breastfed (78%) without adequate vitamin D supplementation (89%). The most common presentations were bowed legs (63%), hypocalcemic seizures (21%), and growth retardation (11%). Approximately half (62%) of the children were hypocalcemic. The children presenting with hypocalcemic seizures were significantly younger (0.8 vs. 2.2 years; p = 0.041) and had lower total serum calcium levels (1.44 vs. 2.17 mmol/L; p < 0.0001), higher phosphatemia (1.43 vs. 1.23 mmol/L; p = 0.020), and lower 25-hydroxy vitamin D levels (3 vs. 7 ng/mL; p = 0.020) but similar parathyroid hormone levels (357 vs. 289 ng/mL; p = 0.940) compared to rickets cases who did not experience hypocalcemic seizures. A dilated cardiomyopathy was detected in 14% of the children who had undergone echocardiography.

CONCLUSION

Nutritional rickets remains endemic in the pediatric population and its most severe forms can have life-threatening sequelae. Health practitioners need to be cognizant of these facts to raise awareness and screen high-risk populations.

The relationship of maternal bone density with nutritional rickets in Nigerian children

Factors that affect maternal bone mineral density may be related to the risk of nutritional rickets in their offspring. Our aim was to determine the relationship between maternal areal bone mineral density (aBMD) and rickets in Nigerian children. Using a case-control design, we measured forearm aBMD in 56 and 135 mothers of children with and without nutritional rickets, respectively. Active rickets was confirmed or excluded in all children radiographically. Using logistic regression, we assessed the association of maternal aBMD, adjusted for parity, pregnancy and lactation status, duration of most recent completed lactation, age of menarche, height, body mass index, and maternal age with nutritional rickets. The median (range) age of all mothers was 30years (17-47years), and parity was 4 (1-12). A total of 36 (19%) were pregnant and 55 (29%) were currently breast feeding. Mean (±SD) metaphyseal forearm aBMDs were 0.321±0.057 and 0.316±0.053g/cm² in mothers of children with and without rickets, respectively (P=0.60). Diaphyseal forearm aBMDs were 0.719±0.071 and 0.715±0.072g/cm², respectively (P=0.69). In an adjusted analysis, maternal forearm aBMD, bone mineral content and bone area at metaphyseal and diaphyseal sites were not associated with rickets in the child. In the adjusted analysis, rickets was associated with shorter duration of most recently completed lactation (aOR 0.91 for each additional month; 95% CI 0.83-0.99), older maternal age (aOR 1.07 for each additional year; 1.00-1.14), and less frequent maternal use of lead-containing eye cosmetics (aOR 0.20; 95% CI 0.05-0.64), without any difference in maternal blood lead levels. Maternal age, parity, age of menarche, height, and body mass index were not associated with having had a child with rickets in multivariate analysis. Nutritional rickets in Nigerian children was not associated with maternal forearm aBMD. Other unidentified maternal characteristics and practices likely contribute to the risk of rickets in Nigerian children.

Global Consensus Recommendations on Prevention and Management of Nutritional Rickets

BACKGROUND

Vitamin D and calcium deficiencies are common worldwide, causing nutritional rickets and osteomalacia, which have a major impact on health, growth, and development of infants, children, and adolescents; the consequences can be lethal or can last into adulthood. The goals of this evidence-based consensus document are to provide health care professionals with guidance for prevention, diagnosis, and management of nutritional rickets and to provide policy makers with a framework to work toward its eradication.

EVIDENCE

A systematic literature search examining the definition, diagnosis, treatment, and prevention of nutritional rickets in children was conducted. Evidence-based recommendations were developed using the Grading of Recommendations, Assessment, Development and Evaluation (GRADE) system that describes the strength of the recommendation and the quality of supporting evidence.

PROCESS

Thirty-three nominated experts in pediatric endocrinology, pediatrics, nutrition, epidemiology, public health, and health economics evaluated the evidence on specific questions within five working groups. The consensus group, representing 11 international scientific organizations, participated in a multiday conference in May 2014 to reach a global evidence-based consensus.

RESULTS

This consensus document defines nutritional rickets and its diagnostic criteria and describes the clinical management of rickets and osteomalacia. Risk factors, particularly in mothers and infants, are ranked, and specific prevention recommendations including food fortification and supplementation are offered for both the clinical and public health contexts.

CONCLUSION

Rickets, osteomalacia, and vitamin D and calcium deficiencies are preventable global public health problems in infants, children, and adolescents. Implementation of international rickets prevention programs, including supplementation and food fortification, is urgently required.

The Effects of Vitamin D Deficiency and Insufficiency on the Endocrine and Paracrine Systems

Individuals are capable of producing vitamin D with proper exposure to sunlight. However, several factors can interfere with the effectiveness of this process. Most sunscreens filter out UVB light, thus inhibiting vitamin D production. Individuals with more darkly pigmented skin have greater difficulty producing vitamin D because melanin acts as an effective natural sunscreen, requiring longer sun exposure to produce an adequate daily allotment of vitamin D. Additionally, solely breastfed infants whose mothers suffered from vitamin D deficiency or insufficiency when pregnant have smaller reserves of the nutrient and are at greater risk of developing nutritional rickets. Vitamin D deficiency leads to rickets, osteomalacia, and osteoporosis. Long-term vitamin D insufficiency can lead to paracrine effects such as type 1 diabetes, cancer, and multiple sclerosis. This article reviews the current literature on vitamin D deficiency and insufficiency and their relation to different disease states. Potential areas for research are discussed.

Global Consensus Recommendations on Prevention and Management of Nutritional Rickets

BACKGROUND

Vitamin D and calcium deficiencies are common worldwide, causing nutritional rickets and osteomalacia, which have a major impact on health, growth, and development of infants, children, and adolescents; the consequences can be lethal or can last into adulthood. The goals of this evidence-based consensus document are to provide health care professionals with guidance for prevention, diagnosis, and management of nutritional rickets and to provide policy makers with a framework to work toward its eradication.

EVIDENCE

A systematic literature search examining the definition, diagnosis, treatment, and prevention of nutritional rickets in children was conducted. Evidence-based recommendations were developed using the Grading of Recommendations, Assessment, Development and Evaluation (GRADE) system that describe the strength of the recommendation and the quality of supporting evidence.

PROCESS

Thirty-three nominated experts in pediatric endocrinology, pediatrics, nutrition, epidemiology, public health, and health economics evaluated the evidence on specific questions within five working groups. The consensus group, representing 11 international scientific organizations, participated in a multiday conference in May 2014 to reach a global evidence-based consensus.

RESULTS

This consensus document defines nutritional rickets and its diagnostic criteria and describes the clinical management of rickets and osteomalacia. Risk factors, particularly in mothers and infants, are ranked, and specific prevention recommendations including food fortification and supplementation are offered for both the clinical and public health contexts.

CONCLUSION

Rickets, osteomalacia, and vitamin D and calcium deficiencies are preventable global public health problems in infants, children, and adolescents. Implementation of international rickets prevention programs, including supplementation and food fortification, is urgently required.

Vitamin D and skeletal health in infancy and childhood

During growth, severe vitamin D deficiency in childhood can result in symptomatic hypocalcaemia and rickets. Despite the suggestion from some studies of a secular increase in the incidence of rickets, this observation may be driven more by changes in population demographics than a true alteration to age, sex and ethnicity-specific incidence rates; indeed, rickets remains uncommon overall and is rarely seen in fair-skinned children. Additionally, the impact of less severe vitamin D deficiency and insufficiency has received much interest in recent years, and in this review, we consider the evidence relating vitamin D status to fracture risk and bone mineral density (BMD) in childhood and adolescence. We conclude that there is insufficient evidence to support the suggestion that low serum 25-hydroxyvitamin D [25(OH)D] increases childhood fracture risk. Overall, the relationship between 25(OH)D and BMD is inconsistent across studies and across skeletal sites within the same study; however, there is evidence to suggest that vitamin D supplementation in children with the lowest levels of 25(OH)D might improve BMD. High-quality randomised trials are now required to confirm this benefit.

Periodontitis associated with osteomalacia

Osteomalacia is a metabolic bone disorder characterized by an alternation of bone mineralization, bone pain, increased bone fragility and fractures. A 23-year-old female patient reported with short stature and depressed nasal bridge with oral manifestation showing partial anodontia and periodontitis. This case report attempt to highlights clinical, radiographic, biochemical features of osteomalacia and periodontitis.

Vitamin D deficiency and lifestyle risk factors in a Norwegian adolescent population

AIM

The aim was to study vitamin D status in a healthy adolescent Norwegian population at 69°N.

METHODS

The data presented come from The Tromsø Study: Fit Futures, during the school year 2010/2011 (not including the summer months), where 1,038 (92% of those invited) participated. Physical examinations, questionnaires and blood samples were collected, and serum 25-hydroxyvitamin D (25(OH)D) were analyzed using LC-MS/MS.

RESULTS

RESULTS are presented from 475 boys and 415 girls (15-18 years old) with available blood samples. A total of 60.2% had vitamin D deficiency or insufficiency (serum 25(OH)D <50 nmol/l), 16.5% were deficient (<25 nmol/l) and 1.6% had severe vitamin D deficiency (<12.5 nmol/l). Only 12.4% had levels >75 nmol/l. A significant gender difference with a mean (SD) serum 25(OH)D level of 40.5 (20.5) nmol/l in boys and 54.2 (23.2) nmol/l in girls (p <0.01) was present. Furthermore, 51.3% of girls had levels >50 nmol/l in comparison to 29.7% of boys (p <0.01). There was an inverse correlation between parathyroid hormone levels and 25(OH)D, rs= -0.30 (p<0.01). Explanatory factors that were significantly associated with serum 25(OH)D levels in multivariate models were use of snuff, consumption of vitamin D fortified milk, cod liver oil and vitamin/mineral supplements, physical activity, sunbathing holiday and use of solarium in boys, and vitamin/mineral supplements, physical activity, sunbathing holiday and use of solarium in girls .

CONCLUSIONS

Vitamin D deficiency is prevalent during the school year among adolescents in northern Norway, particularly among boys.

Population groups in dietary transition

Background

Little is known about the effects of dietary acculturation in minority groups in the Nordic countries, including immigrants from non-Western societies.

Methods

A search was performed in Medlin33e/PubMed and SweMed+ for articles published in 1990–2011.

Results

A total of 840 articles were identified, with a final 32 articles used to tabulate results which were included in the primary analysis. High rates of vitamin D deficiency (23 articles) were found in immigrants of non-Western origin; deficiency rates were very high among both pregnant and non-pregnant women, and also among children, with young children of immigrant parents showing 50 times higher risk for rickets when compared to children of indigenous parents. The risk of iron deficiency (two articles) was high among immigrant women, while the results were inconclusive regarding children. High rates of dental caries (seven articles) were found among pre-school and younger school children of immigrant origin, while the risk of caries was not as evident among older children. In a secondary analysis, including 48 articles (results not tabulated), overweight and obesity (14 articles) were seen in many immigrant groups, resulting in a high prevalence of diabetes (2 review articles from a total of 14 original articles) and incidence of coronary heart disease (CHD; seven articles). For hypertension (three articles), dyslipidemia (four articles), and dietary patterns among immigrants (10 articles), the results were contradictory.

Conclusions

Risk of vitamin D deficiency is alarmingly high in the Nordic countries among immigrants of non-Western origin, especially among women. Dental caries is high among immigrant children aged 0–7 years due to a higher intake of sugary products. Overweight and obesity, associated with a higher risk of diabetes and CHD, are prevalent in many immigrant groups and need further attention.

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.

Vitamin D status in infants: relation to nutrition and season

In a cross-sectional study, the primary objective was to assess the plasma concentration of 25-hydroxyvitamin D (25(OH)D) in healthy 9-month-old infants (n=255). The secondary objective was to evaluate nutritional variables and season in relation to 25(OH)D. The concentration of 25(OH)D was 77.2 ± 22.7 nmol/l (mean ± s.d.), ranging from 12 to 151 nmol/l. During the first 9 months, 97% received vitamin D supplementation (10 μg/day) and 89% had sufficient levels of 25(OH)D (50-250 nmol/l). In multiple regression analysis, controlled for body mass index (BMI) and intake of infant formula, a longer period of exclusive breastfeeding (P=0.026) and breastfeeding at 9 months (P=0.001) were both associated with lower levels. Dietary vitamin D intake was 4.4 ± 3.1 μg/day and in multiple regression analysis, controlled for BMI, intake of infant formula and mean energy intake, it was positively associated with 25(OH)D (P=0.001). There was a significant seasonal difference in 25(OH)D, with higher levels during summer-autumn compared with winter-spring (P=0.021) after control for BMI.

Postnatal vitamin D supplementation following maternal dietary vitamin D deficiency does not affect bone mass in weanling guinea pigs

Although vitamin D deficiency is common at birth, the consequences to growth and bone mass by weaning are unclear. This study was designed to determine whether maternal dietary vitamin D deficiency in pregnancy has a negative impact on the bone mass of full-term neonates and if postnatal supplementation could restore bone mass. Forty guinea pigs were randomized to receive a control (C) or deficient (D) diet (0.03 microg vs. 0.00 microg cholecalciferol/g) during pregnancy. Offspring were randomized at birth to receive 0.25 microg of cholecalciferol supplement (S) or a placebo (P) orally per day for 28 d. Measurements at birth and d 28 included whole body and regional bone mass and serum osteocalcin and deoxypyridinoline, plus biomechanical testing and peripheral quantitative computed tomography of excised tibias and femurs. Main and interactive effects were tested using mixed model ANOVA and post hoc Bonferroni's tests. At birth and d 28, offspring of the D sows had lower serum vitamin D and osteocalcin concentration, lower body weight, length, whole body and total tibia bone mineral content, and lower biomechanical integrity of tibia compared with those of the C sows, regardless of supplementation. Although postnatal vitamin D supplementation improved vitamin D status at d 28 in D offspring, values remained significantly lower than C groups. This study suggests that efforts should be made to optimize maternal vitamin D status in pregnancy, along with maintenance of vitamin D status in infancy, rather than relying on postnatal supplementation to normalize vitamin D status and bone mass.

Vitamin D metabolism and rickets in domestic animals: a review

Rickets and osteomalacia are increasing in prevalence in people because of cultural practices, breast-feeding, decreased sun exposure, and increased sunscreen usage. Several hereditary forms of rickets owing to either renal phosphate wasting or defects in vitamin D metabolism are also reported in people. Rickets is well recognized in domestic animals, but published reports are not always supported by microscopic findings, and diagnoses based on clinical signs and radiology are unreliable. Most cases in domestic animals are caused by dietary deficiency of either vitamin D or phosphorus, but occasional inherited forms are reported in pigs, sheep, cats, and dogs. There is variation between species in susceptibility to dietary vitamin D and phosphorus deficiency and in the ability to manufacture vitamin D in their skin. A number of mouse models have been discovered or created to study human skeletal diseases and skeletal homeostasis. With the discovery that vitamin D is involved in not only calcium and phosphorus homeostasis but also in the immune system and cancer, there is great potential for new and existing animal models to generate valuable information about vitamin D and its many functions. This review presents an overview of vitamin D metabolism and rickets in domestic and laboratory animals and makes comparisons where appropriate with the disease in humans.

The clinical characteristics of vitamin D deficiency in childhood: a systematic literature review of Japanese patients

To describe the characteristics of children with vitamin D deficiency, we reviewed the reports of vitamin D deficiency among Japanese children that were published between 1989 and 2008. We identified 25 patients with vitamin D deficiency in 9 published studies and evaluated their clinical characteristics together with those of 3 patients we recently treated. The patients were distributed in two distinct age groups at diagnosis: < 1 year old and > or = 1 year old. The main symptom of the < 1 year old age group was hypocalcemic convulsions and that of the > or = 1 year old age group was bowed legs. Serum calcium, intact PTH, and 1,25(OH)2D levels were significantly lower in the < 1 year age group than in the > or = 1 year age group. It would be useful to find and make early interventions in cases of children at a high-risk of vitamin D deficiency.

Nutritional rickets in Denmark: a retrospective review of children's medical records from 1985 to 2005

INTRODUCTION

This study describes clinical and biochemical characteristics of nutritional rickets and risk factors at diagnosis among children living in Denmark. All medical records from patients with rickets referred to or discharged from hospitals in Southern Denmark from 1985 to 2005 were identified by register search.

MATERIALS AND METHODS

Patients included were younger than 15 years of age and fulfilled the diagnostic criteria of primary, nutritional rickets. A total of 112 patients with nutritional rickets were included: 29 were of ethnic Danish origin, and 83 were immigrants.

RESULTS

Patients diagnosed before the age of 4 (median 1.4) years displayed the classic clinical signs of rickets, whereas patients diagnosed after the age of 4 (median 12.5) years had few clinical signs and unspecific symptoms. Ethnic Danish patients were only diagnosed before age 24 months, and they accounted for 73% of all cases presenting with hypocalcemic seizures, but biochemically, they did not have more severe rickets. Of patients diagnosed before the age of 4 years, 45% were ethnic Danish. In early childhood, insufficient or no vitamin D supplementation was given in 88% of all cases. Among immigrant girls older than 4 years of age, 78% were veiled.

DISCUSSION

Nutritional rickets in Denmark is predominantly a disease among immigrants, but ethnic Danish patients comprised nearly half of all patients diagnosed before the age of 4 years, and they presented more frequently with hypocalcemic seizures. The main risk factors were omitted, such as vitamin D prophylaxis among the youngest patients and veiling among older children/teenagers.

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.

Incidence and prevalence of nutritional and hereditary rickets in southern Denmark

OBJECTIVE

To estimate the incidence of nutritional rickets and the incidence and prevalence of hereditary rickets.

DESIGN

Population-based retrospective cohort study based on a review of medical records.

METHODS

Patients aged 0-14.9 years referred to or discharged from hospitals in southern Denmark from 1985 to 2005 with a diagnosis of rickets were identified by register search, and their medical records were retrieved. Patients fulfilling the diagnostic criteria of primary rickets were included.

RESULTS

We identified 112 patients with nutritional rickets of whom 74% were immigrants. From 1995 to 2005, the average incidence of nutritional rickets in children aged 0-14.9 and 0-2.9 years was 2.9 and 5.8 per 100,000 per year respectively. Among immigrant children born in Denmark, the average incidence was 60 (0-14.9 years) per 100,000 per year. Ethnic Danish children were only diagnosed in early childhood and the average incidence in the age group 0-2.9 years declined from 5.0 to 2.0 per 100,000 per year during 1985-1994 to 1995-2005. Sixteen cases of hereditary rickets were diagnosed during the study period giving an average incidence of 4.3 per 100,000 (0-0.9 years) per year. The prevalence of hypophosphatemic rickets and vitamin D-dependent rickets type 1 was 4.8 and 0.4 per 100,000 (0-14.9 years) respectively.

CONCLUSIONS

Nutritional rickets is rare in southern Denmark and largely restricted to immigrants, but the incidence among ethnic Danish children was unexpectedly high. Hereditary rickets is the most common cause of rickets in ethnic Danish children, but nutritional rickets is most frequent among all young children.

Vitamin D deficiency: a global perspective

The prevalence of clinical vitamin D deficiency (rickets and osteomalacia) is high in many parts of the world, and there is a resurgence of rickets among children of ethnic minority groups in Europe and Australasia. Plasma 25-hydroxyvitamin D concentration (25OHD) is a useful risk marker of clinical vitamin D deficiency. This review summarizes the factors that contribute to differences in 25OHD among populations and provides an overview of the prevalence of low vitamin D status worldwide. It discusses the controversies that surround the interpretation of 25OHD, other proposed indices of vitamin D adequacy and dietary reference values for vitamin D, and describes the emerging evidence that a very low calcium intake may contribute to the etiology of rickets in Africa and Asia. There is an urgent need for action to address the global burden of rickets and osteomalacia.

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 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.

Vitamin D levels in children of asylum seekers in The Netherlands in relation to season and dietary intake

Low dietary intake and limited sun exposure during Dutch winters, in particular when combined with highly pigmented skin, could compromise the vitamin D status of asylum seekers' children in The Netherlands. We determined the vitamin D status of children living in The Netherlands, but originating from Africa, Central Asia, or Eastern Europe. In a subgroup, we reassessed the vitamin D status after the summer, during which the children had been assigned at random to remain unsupplemented or to receive vitamin D supplementation. In total 112 children (median age 7.1 yr, range 2-12 yr) were assessed for serum concentrations of 25-Hydroxyvitamin D [25(OH)D], intact parathyroid hormone (I-PTH) and plasma alkaline phosphatase (ALP). Vitamin D deficiency (VDD) and hypovitaminosis D were defined as 25(OH)D below 30 or 50 nmol/L, respectively. Dietary intake of vitamin D and calcium was estimated using a 24 h recall interview. In mid-spring, 13% of the children had VDD, and 42% had hypovitaminosis D. I-PTH and ALP levels were significantly higher in children with VDD. The dietary intake of vitamin D was below 80% of the recommended daily allowances (RDA) in 94% of the children, but the dietary calcium intake was not significantly related to the s-25(OH)D levels found. After the summer, median s-25(OH)D increased with +35 nmol/L (+85%) and +19 nmol/L (+42%) in children with or without supplementation, respectively. The effect of supplementation was most prominent among African children. VDD and hypovitaminosis D are highly prevalent in mid-spring among asylum seekers' children in The Netherlands. Although 25(OH)D levels increase in African children during Dutch summer months, this does not completely correct the compromised vitamin D status. Our data indicate that children from African origin would benefit from vitamin D supplementation.

Nutritional rickets around the world: causes and future directions

INTRODUCTION

Nutritional rickets has been described from at least 59 countries in the last 20 years. Its spectrum of causes differs in different regions of the world.

METHODS

We conducted a systematic review of articles on nutritional rickets from various geographical regions published in the last 20 years. We extracted information about the prevalence and causes of rickets.

RESULTS

Calcium deficiency is the major cause of rickets in Africa and some parts of tropical Asia, but is being recognised increasingly in other parts of the world. A resurgence of vitamin D deficiency has been observed in North America and Europe. Vitamin D-deficiency rickets usually presents in the 1st 18 months of life, whereas calcium deficiency typically presents after weaning and often after the 2nd year. Few studies of rickets in developing countries report values of 25(OH)D to permit distinguishing vitamin D from calcium deficiency.

CONCLUSIONS

Rickets exists along a spectrum ranging from isolated vitamin D deficiency to isolated calcium deficiency. Along the spectrum, it is likely that relative deficiencies of calcium and vitamin D interact with genetic and/or environmental factors to stimulate the development of rickets. Vitamin D supplementation alone might not prevent or treat rickets in populations with limited calcium intake.

Rickets in an adolescent girl

The authors present a case of rickets in an adolescent girl who presented to the emergency department with bone pain. Emergency department staff should be aware that rickets is not just a disease of early childhood.

The re-emerging burden of rickets: a decade of experience from Sydney

AIM

To define the demographics and clinical characteristics of cases presenting with nutritional rickets to paediatric centres in Sydney, Australia.

METHODS

Retrospective descriptive study of 126 cases seen from 1993 to 2003 with a diagnosis of vitamin D deficiency and/or confirmed rickets defined by long bone x ray changes.

RESULTS

A steady increase was seen in the number of cases per year, with a doubling of cases from 2002 to 2003. Median age of presentation was 15.1 months, with 25% presenting at less than 6 months of age. The most common presenting features were hypocalcaemic seizures (33%) and bowed legs (22%). Males presented at a younger age, with a lower weight SDS, and more often with seizures. The caseload was almost exclusively from recently immigrated children or first generation offspring of immigrant parents, with the region of origin predominantly the Indian subcontinent (37%), Africa (33%), and the Middle East (11%). Seventy nine per cent of the cases were born in Australia. Eleven cases (all aged <7 months) presented atypically with hyperphosphataemia.

CONCLUSIONS

This large case series shows that a significant and increasing caseload of vitamin D deficiency remains, even in a developed country with high sunlight hours. Cases mirror recent immigration trends. Since birth or residence in Australia does not appear to be protective, screening of at risk immigrant families should be implemented through public health policies.

Vitamin D deficiency and whole-body and femur bone mass relative to weight in healthy newborns

BACKGROUND

Vitamin D is required for normal bone growth and mineralization. We sought to determine whether vitamin D deficiency at birth is associated with bone mineral content (BMC) of Canadian infants.

METHODS

We measured plasma 25-hydroxyvitamin D [25(OH)D] as an indicator of vitamin D status in 50 healthy mothers and their newborn term infants. In the infants, anthropometry and lumbar, femur and whole-body BMC were measured within 15 days of delivery. Mothers completed a 24-hour recall and 3-day food and supplement record. We categorized the vitamin D status of mothers and infants as deficient or adequate and then compared infant bone mass in these groups using nonpaired t tests. Maternal and infant variables known to be related to bone mass were tested for their relation to BMC using backward stepwise regression analysis.

RESULTS

Twenty-three (46%) of the mothers and 18 (36%) of the infants had a plasma 25(OH)D concentration consistent with deficiency. Infants who were vitamin D deficient were larger at birth and follow-up. Absolute lumbar spine, femur and whole-body BMC were not different between infants with adequate vitamin D and those who were deficient, despite larger body size in the latter group. In the regression analysis, higher whole-body BMC was associated with greater gestational age and weight at birth as well as higher infant plasma 25(OH)D.

CONCLUSION

A high rate of vitamin D deficiency was observed among women and their newborn infants. Among infants, vitamin D deficiency was associated with greater weight and length but lower bone mass relative to body weight. Whether a return to normal vitamin D status, achieved through supplements or fortified infant formula, can reset the trajectory for acquisition of BMC requires investigation.

Nutritional rickets: deficiency of vitamin D, calcium, or both?

Nutritional rickets remains a public health problem in many countries, despite dramatic declines in the prevalence of the condition in many developed countries since the discoveries of vitamin D and the role of ultraviolet light in prevention. The disease continues to be problematic among infants in many communities, especially among infants who are exclusively breast-fed, infants and children of dark-skinned immigrants living in temperate climates, infants and their mothers in the Middle East, and infants and children in many developing countries in the tropics and subtropics, such as Nigeria, Ethiopia, Yemen, and Bangladesh. Vitamin D deficiency remains the major cause of rickets among young infants in most countries, because breast milk is low in vitamin D and its metabolites and social and religious customs and/or climatic conditions often prevent adequate ultraviolet light exposure. In sunny countries such as Nigeria, South Africa, and Bangladesh, such factors do not apply. Studies indicated that the disease occurs among older toddlers and children and probably is attributable to low dietary calcium intakes, which are characteristic of cereal-based diets with limited variety and little access to dairy products. In such situations, calcium supplements alone result in healing of the bone disease. Studies among Asian children and African American toddlers suggested that low dietary calcium intakes result in increased catabolism of vitamin D and the development of vitamin D deficiency and rickets. Dietary calcium deficiency and vitamin D deficiency represent 2 ends of the spectrum for the pathogenesis of nutritional rickets, with a combination of the 2 in the middle.

Prevalence and predictors of vitamin D deficiency in five immigrant groups living in Oslo, Norway: the Oslo Immigrant Health Study

OBJECTIVE

To study the prevalence of vitamin D deficiency and to identify possible predictors of vitamin D deficiency in five main immigrant groups in Oslo.

DESIGN

Cross-sectional, population-based.

SETTING

City of Oslo.

SUBJECTS

In total, 491 men and 509 women with native countries Turkey, Sri Lanka, Iran, Pakistan and Vietnam living in the county of Oslo.

RESULTS

Median serum 25(OH)D level (s-25(OH)D) was 28 nmol/l, ranging from 21 nmol/l in women born in Pakistan to 40 nmol/l in men born in Vietnam. Overall prevalence of vitamin D deficiency defined as s-25(OH)D<25 nmol/l was 37.2%, ranging from 8.5% in men born in Vietnam to 64.9% in women born in Pakistan. s-25(OH)D did not vary significantly with age. s-25(OH)D was higher in blood samples drawn in June compared to samples obtained in April, but not significantly for women. Reported use of fatty fish and cod liver oil supplements showed a strong positive association with s-25(OH)D in all groups. Education length was positively associated with s-25(OH)D in women, whereas body mass index (BMI) was inversely associated with s-25(OH)D in women. These two variables were not related to vitamin D deficiency in men.

CONCLUSIONS

There is widespread vitamin D deficiency in both men and women born in Turkey, Sri Lanka, Iran, Pakistan and Vietnam residing in Oslo. The prevalence of vitamin D deficiency is higher in women than in men, and it is higher in those born in Pakistan and lower in those born in Vietnam compared to the other ethnic groups. Fatty fish intake and cod liver oil supplements are important determinant factors of vitamin D status in the groups studied. BMI and education length are also important predictors in women.

Vitamin D and bone health in early life

Prolonged vitamin D deficiency resulting in rickets is seen mainly during rapid growth. A distinct age distribution has been observed in the Copenhagen area where all registered hospital cases of rickets were either infants and toddlers or adolescents from immigrant families. Growth retardation was only present in the infant and toddler group. A state of deficiency occurs months before rickets is obvious on physical examination. Growth failure, lethargy and irritability may be early signs of vitamin D deficiency. Mothers with low vitamin D status give birth to children with low vitamin D status and increased risk of rickets. Reports showing increasing rates of rickets due to insufficient sunlight exposure and inadequate vitamin D intake are cause for serious concern. Many countries (including the USA from 2003) recommend vitamin D supplementation during infancy to avoid rickets resulting from the low vitamin D content of human milk. Without fortification only certain foods such as fatty fish contain more than low amounts of vitamin D, and many children will depend entirely on sun exposure to obtain sufficient vitamin D. The skin has a high capacity to synthesize vitamin D, but if sun exposure is low vitamin D production is insufficient, especially in dark-skinned infants. The use of serum 25-hydroxyvitamin D to evaluate vitamin D status before development of rickets would be helpful; however, there is no agreement on cut-off levels for deficiency and insufficiency. Furthermore, it is not known how marginal vitamin D insufficiency affects children's bones in the long term.