Vitamin D and bone health: What vitamin D can and cannot do.

Historically vitamin D deficiency had devastating consequences for children causing rickets resulting in severe bone deformities often leading to death. The mystery of the cause of rickets finally came to light when it was observed that cod liver oil and sunlight could prevent and cure rickets. The first vitamin D to be discovered was vitamin D2 from ergosterol in ultraviolet irradiated yeast. Vitamin D3 was discovered from UV exposure to the skin. Investigations revealed the two major functions of vitamin D were to increase intestinal calcium and phosphate absorption and mobilize calcium from the skeleton to maintain calcium and phosphorus homeostasis. Later studies demonstrated that vitamin D does not have an active role in bone mineralization. Vitamin D deficiency results in secondary hyperparathyroidism increasing bone resorption. As a result, this decreases bone mineral content and compromises the architectural integrity increasing risk for fracture. Vitamin D deficiency has also been shown to enhance aging of the bone causing cracks and enhancing bone fractures. Vitamin D deficiency also causes osteomalacia. Therefore, vitamin D sufficiency is extremely important to maximize bone health throughout life. It helps to prevent bone loss, but it cannot restore bone loss due to increased bone resorption that can occur under a variety of circumstances including menopause. The Endocrine Society Guidelines recommends for all ages that adequate vitamin D obtained from the sun, foods and supplements is necessary in order to maintain a circulating concentration of 25-hydroxyvitamin D of at least 30 ng/mL for maximum bone health.

Vitamin D deficiency or resistance and hypophosphatemia.

Vitamin D is mainly produced in the skin (cholecalciferol) by sun exposure while a fraction of it is obtained from dietary sources (ergocalciferol). Vitamin D is further processed to 25-hydroxyvitamin D and 1,25-dihydroxy vitamin D (calcitriol) in the liver and kidneys, respectively. Calcitriol is the active form which mediates the actions of vitamin D via vitamin D receptor (VDR) which is present ubiquitously. Defect at any level in this pathway leads to vitamin D deficient or resistant rickets. Nutritional vitamin D deficiency is the leading cause of rickets and osteomalacia worldwide and responds well to vitamin D supplementation. Inherited disorders of vitamin D metabolism (vitamin D-dependent rickets, VDDR) account for a small proportion of calcipenic rickets/osteomalacia. Defective 1α hydroxylation of vitamin D, 25 hydroxylation of vitamin D, and vitamin D receptor result in VDDR1A, VDDR1B and VDDR2A, respectively whereas defective binding of vitamin D to vitamin D response element due to overexpression of heterogeneous nuclear ribonucleoprotein and accelerated vitamin D metabolism cause VDDR2B and VDDR3, respectively. Impaired dietary calcium absorption and consequent calcium deficiency increases parathyroid hormone in these disorders resulting in phosphaturia and hypophosphatemia. Hypophosphatemia is a common feature of all these disorders, though not a sine-qua-non and leads to hypomineralisation of the bone and myopathy. Improvement in hypophosphatemia is one of the earliest markers of response to vitamin D supplementation in nutritional rickets/osteomalacia and the lack of such a response should prompt evaluation for inherited forms of rickets/osteomalacia.

The Effect of Vitamin D on Metabolic Bone Disease and Chronic Diseases.

The history of vitamin D begins more than 100 years ago, with the initial documentation of rickets in industrialized cities of England [...].

Vitamin D deficiency rickets in a toddler.

ABSTRACT: Nutritional rickets is the failure of normal bone formation in children, caused by vitamin D deficiency, low calcium intake, or a combination of both. In the United States, prolonged breastfeeding without vitamin D supplementation is a major risk factor. Increasing awareness of the rationale for and importance of vitamin D supplements for all breastfed infants and children should reduce the incidence of vitamin D deficiency rickets and prevent bone deformity.

Treatment of vitamin D deficiency in children.

INTRODUCTION: Vitamin D deficiency affects from 10% to 50% in various pediatric population groups and causes life-threatening hypocalcemia in infants, crippling rickets in infants and children, and increased risk of subsequent adult metabolic and neurologic problems. AREAS COVERED: An English language literature search of PubMed was performed since 1940 as were the authors' personal literature collections. References identified in the reviewed literature are considered. DIAGNOSIS: The diagnosis of vitamin D deficiency is based on serum 25-hydroxyvitamin D levels. Clinical features of rickets include bone deformities and elevated alkaline phosphatase. Most children and adolescents who are biochemically vitamin D deficient do not have specific symptoms or signs of deficiency. PREVENTION: Prevention of vitamin D deficiency is via exposure to sunshine, food and beverage fortification, and dietary supplementation. TREATMENT: Effective treatment of vitamin D deficiency is via oral or injectable administration of vitamin D. Dosing and duration of vitamin D therapy have been described for healthy children and for children with underlying medical conditions, but recommendations vary. EXPERT OPINION: Further investigation is needed to determine long-term non-skeletal effects of childhood vitamin D deficiency, benefits of supplementation in asymptomatic individuals with biochemical vitamin D deficiency, and appropriate screening for vitamin D deficiency in asymptomatic children and adolescents.

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.

Assessment, treatment and prevention of vitamin D deficiency.

Vitamin D deficiency is prevalent among various groups in the UK, and can result from insufficient sunlight exposure and dietary intake. There is a population-wide recommendation of 10 micrograms (400 international units) of vitamin D per day, with a daily supplement advised. However, supplement use is often suboptimal, compounding the risk of deficiency. Long-term vitamin D deficiency can cause rickets in children and osteomalacia or osteoporosis in adults. Therefore, it is important that nurses recognise which groups are at increased risk of vitamin D deficiency and understand how to assess people's vitamin D status. Nurses also need to be able to support the prevention and treatment of low vitamin D levels, which typically involves supplementation and lifestyle changes.

Vitamin D Deficiency in Chronic Childhood Disorders: Importance of Screening and Prevention.

Vitamin D plays a vital role in regulating calcium and phosphate metabolism and maintaining bone health. A state of prolonged or profound vitamin D deficiency (VDD) can result in rickets in children and osteomalacia in children and adults. Recent studies have demonstrated the pleiotropic action of vitamin D and identified its effects on multiple biological processes in addition to bone health. VDD is more prevalent in chronic childhood conditions such as long-standing systemic illnesses affecting the renal, liver, gastrointestinal, skin, neurologic and musculoskeletal systems. VDD superimposed on the underlying disease process and treatments that can adversely affect bone turnover can all add to the disease burden in these groups of children. The current review outlines the causes and mechanisms underlying poor bone health in certain groups of children and young people with chronic diseases with an emphasis on the proactive screening and treatment of VDD.

Refractory Rickets.

Nutritional rickets, caused by vitamin D and/or calcium deficiency is by far the most common cause of rickets. In resource-limited settings, it is therefore not uncommon to treat rickets with vitamin D and calcium. If rickets fails to heal and/or if there is a family history of rickets, then refractory rickets should be considered as a differential diagnosis. Chronic low serum phosphate is the pathological hallmark of all forms of rickets as its low concentration in extracellular space leads to the failure of apoptosis of hypertrophic chondrocytes leading to defective mineralisation of the growth plate. Parathyroid hormone (PTH) and fibroblast growth factor 23 (FGF23) control serum phosphate concentration by facilitating the excretion of phosphate in the urine through their action on the proximal renal tubules. An increase in PTH, as seen in nutritional rickets and genetic disorders of vitamin D-dependent rickets (VDDRs), leads to chronic low serum phosphate, causing rickets. Genetic conditions leading to an increase in FGF23 concentration cause chronic low serum phosphate concentration and rickets. Genetic conditions and syndromes associated with proximal renal tubulopathies can also lead to chronic low serum phosphate concentration by excess phosphate leak in urine, causing rickets.In this review, authors discuss an approach to the differential diagnosis and management of refractory rickets.

Approach to nutritional rickets.

Rickets is the disease of a growing skeleton and results from impaired apoptosis of hypertrophic chondrocytes and mineralization of the growth plate. Nutritionally induced rickets, secondary to vitamin D and/or calcium deficiency, remains a major global problem. In this review, we discuss pathogenesis, clinical signs, investigation and management of nutritional rickets.

The One-Hundred-Year Anniversary of the Discovery of the Sunshine Vitamin D3: Historical, Personal Experience and Evidence-Based Perspectives.

The discovery of a fat-soluble nutrient that had antirachitic activity and no vitamin A activity by McCollum has had far reaching health benefits for children and adults. He named this nutrient vitamin D. The goal of this review and personal experiences is to give the reader a broad perspective almost from the beginning of time for how vitamin D evolved to became intimately involved in the evolution of land vertebrates. It was the deficiency of sunlight causing the devastating skeletal disease known as English disease and rickets that provided the first insight as to the relationship of sunlight and the cutaneous production of vitamin D3. The initial appreciation that vitamin D could be obtained from ultraviolet exposure of ergosterol in yeast to produce vitamin D2 resulted in the fortification of foods with vitamin D2 and the eradication of rickets. Vitamin D3 and vitamin D2 (represented as D) are equally effective in humans. They undergo sequential metabolism to produce the active form of vitamin D, 1,25-dihydroxyvitamin D. It is now also recognized that essentially every tissue and cell in the body not only has a vitamin D receptor but can produce 1,25-dihydroxyvitamin D. This could explain why vitamin D deficiency has now been related to many acute and chronic illnesses, including COVID-19.

Serum 1,25-dihydroxyvitamin D levels in the diagnosis and pathogenesis of nutritional rickets - a multivariable re-analysis of a case-control study.

BACKGROUND: A multivariable logistic regression model resulting from a case-control study of nutritional rickets in Nigerian children suggested that higher levels of serum 25(OH)D may be required to prevent nutritional rickets in populations with low-calcium intakes. OBJECTIVES: This current study evaluates if adding serum 1,25-dihydroxyvitamin D [1,25(OH)2D] to that model shows that increased levels of serum 1,25(OH)2D are independently associated with risk of children on low-calcium diets having nutritional rickets. METHODS: Multivariable logistic regression analysis was used to model the association between serum 1,25(OH)2D and risk of having nutritional rickets in cases (n = 108) and controls (n = 115) after adjusting for age, sex, weight-for age z-score, religion, phosphorus intake and age began walking and the interaction between serum 25(OH)D and dietary calcium intake (Full Model). RESULTS: Serum 1,25(OH)2D levels were significantly higher (320 pmol/L vs. 280 pmol/L) (P = 0.002), and 25(OH)D levels were lower (33 nmol/L vs. 52 nmol/L) (P < 0.0001) in children with rickets than in control children. Serum calcium levels were lower in children with rickets (1.9 mmol/L) than in control children (2.2 mmol/L) (P < 0.001). Dietary calcium intakes were similarly low in both groups (212 mg/d) (P = 0.973). In the multivariable logistic model, 1,25(OH)2D was independently associated with risk of having rickets [coefficient = 0.007 (95% confidence limits: 0.002-0.011)] after adjusting for all variables in the Full Model. CONCLUSIONS: Results confirmed theoretical models that in children with low dietary calcium intake, 1,25(OH)2D serum concentrations are higher in children with rickets than in children without rickets. The difference in 1,25(OH)2D levels is consistent with the hypothesis that children with rickets have lower serum calcium concentrations which prompt the elevation of PTH levels resulting in an elevation of 1,25(OH)2D levels. These results support the need for additional studies to identify dietary and environmental risks for nutritional rickets.

Prevalence of hypovitaminosis D among children and adolescents of Kabul: a descriptive cross-sectional study.

BACKGROUND: Vitamin D is one of the most important fat-soluble vitamins necessary for normal growth and development of the human body. According to a study done in Kabul shows that economic, racial, and social concerns are thought to be the main impediments to receiving appropriate amounts of this vitamin through dietary sources in countries like Afghanistan. Hypovitaminosis D, on the other hand, is now recognized as a pandemic in both industrialized and developing countries. METHODS: To find out how common hypovitaminosis D is in children aged one month to eighteen years in afghan children Kabul, Afghanistan. Vitamin D deficiency and insufficiency are defined as serum levels of less than 20 ng/mL and 20 to 30 ng/mL, respectively. Children aged between 1 month to 18 years attending our hospital, AMC (Ariana Medical Complex) for health examination were checked for their 25-hydroxyvitamin D [25(OH)D]. Age, gender and address were recorded. 25(OH)D were determined using immunoassay auto analyzers. According to their serum 25(OH)D, the 25(OH)D were categorized into five categories: sufficiency: ≥ 30-100 ng/mL; insufficiency: ≥ 20-29 ng/mL; deficiency: < 20 ng/mL; severe deficiency: < 10 ng/mL; and intoxication: > 150 ng/mL. Participants who were intoxicated with vitamin D were excluded from the study. RESULTS: A total of 4008 children aged 1 month to 18 years participated in this cross-sectional study. Hypovitaminosis D was found to be prevalent in 62.5 percent of the population. When compared to boys, female children were 1.2 times more likely to be vitamin D deficient. When compared to children of illiterate women, the odds of hypovitaminosis D were 1.4, 1.9, and 5.8 times lower in children with mothers educated up to primary school, graduation, and post-graduate. The average vitamin D level was 23 ng/mL, with a median of 15 ng/mL and maximum and minimum values of 135 ng/mL and 3 ng/mL, respectively. In all, 2500 (62.5%) of the children had low levels of vitamin D in their serum. Only 400 (16%) of the patients were sufficient, whereas 917 (36.7%) were severely deficient, 733 (29.3%) were deficient, and 450 (18%) were insufficient. With a female to male ratio of 1.2:1, the majority of those, 1335 (53.4%), were females and 1165 (46.6%) were males. Patients were 8.14 years old on average, with a median age of 7 years. The majority of the patients, 2152 (86.1%), were urban, while 348 (13.9%) were rural. CONCLUSION: The prevalence of hypovitaminosis D was very high in Afghan children. Female sex, higher socio economic status, higher educational status of the mother and living at urban areas were the factors with strong positive association with hypovitaminosis D.

The role of dietary calcium in the etiology of childhood rickets in the past and the present.

For more than two centuries, lack of sunlight has been understood to cause vitamin D deficiency and documented as a primary cause of rickets. As such, evidence of rickets in the archeological record has been used as a proxy for vitamin D status in past individuals and populations. In the last decade, a clinical global consensus has emerged wherein it is recognized that dietary calcium deficiency also plays a role in the manifestation of rickets and classic skeletal deformities may not form if dietary calcium is normal even if vitamin D is deficient. This disease is now clinically called "nutritional rickets" to reflect the fact that rickets can take calcium deficiency-predominant or vitamin D deficiency-predominant forms. However, there are currently no paleopathological studies wherein dietary calcium deficiency is critically considered a primary etiology of the disease. We review here the interplay of calcium, vitamin D, and phosphorous in bone homeostasis, examine the role of dietary calcium in human health, and critically explore the clinical literature on calcium deficiency-predominant rickets. Finally, we report a case of rickets from the late Formative Period (~2500-1500 years ago) of the Atacama Desert and argue the disease in this infant is likely an example of calcium deficiency-predominant rickets. We conclude that most archeological cases of rickets are the result of multiple micronutrient deficiencies that compound to manifest in macroscopic skeletal lesions. For clinicians, these factors are important for implementing best treatment practice, and for paleopathologists they are necessary for appropriate interpretation of health in past communities.

Not all the bowlegs is rickets! (a case report).

Bowing of the legs is common in childhood. Most times it is considered to be rickets without considering other possibilities. Blount´s disease is a close differential diagnosis which is developmental deformity characterized by intorsion of tibia leading to varus angulation. This case report aims to encourage pediatricians to expand their vision and consider other possibilities when a case of bowing of legs is encountered. Here we report a case of a four-year-old boy with bowing of both legs noticed first at 2.5 years of age. There was no history suggestive of trauma. Development of the child was age appropriate in all domains. He was receiving treatment for rickets for 1.5 years in form of oral vitamin D3 and calcium supplementations. He had no other clinical signs of rickets like frontal bossing, widening of wrists, and rachitic rosary except bowing of legs. His biochemical parameters did not show any alterations that would support the diagnosis of rickets. Weight-bearing radiographs of lower limbs showed medial intorsion of bilateral tibia with metaphyseo-diaphysial angle to be 25º on the right side and 20º on the left side, which was beyond the physiological normal angulation, therefore he was diagnosed as a case of Blount´s disease, stage III as per Langenskiöld classification. All the bow legs is not always rickets in pediatric practice. Therefore, various differential diagnoses should be kept in mind as early diagnosis and intervention can change a child´s life.

800 IU versus 400 IU per day of vitamin D3 in term breastfed infants: a randomized controlled trial from an LMIC.

This open-label, block-randomized controlled trial compared the effect of 800 IU/day and 400 IU/day of oral vitamin D3 supplementation in reducing vitamin D insufficiency (VDI) among healthy-term breastfed infants at 14 weeks of postnatal age. All eligible infants were randomized to receive either 800 or 400 IU/day of oral vitamin D3 (starting within the first week until 14 weeks). The primary outcome was the proportion of infants with VDI (25-OH-D < 20 ng/ml) at 14 weeks. Secondary outcomes were vitamin D deficiency (VDD, < 12 ng/ml), severe VDD (< 5 ng/ml), anthropometry, biochemical or clinical rickets, and any adverse events related to vitamin D toxicity (VDT). Among 102 enrolled infants, the distribution of baseline variables (including cord 25-OH-D levels; 13.0 versus 14.2 ng/ml) was similar in both groups. On intention-to-treat analysis, the proportions of infants with VDI at 14 weeks were significantly lower in the 800 IU group compared to those in the 400 IU group [24% versus 55%; RR 0.44; 95% CI: 0.25-0.76]. The proportions of infants with elevated parathormone (6% versus 26.5%; p = 0.012) and severe VDD (0% versus 12.2%; p = 0.033) were significantly lower in the 800 IU group. Clinical rickets developed in three (6.2%) infants in the 400 IU group. No infant developed VDT.      Conclusions: Daily oral supplementation with 800 IU of vitamin D3 resulted in an almost 50% reduction in the proportion of infants with VDI and prevented the occurrence of severe VDD at 14 weeks of age compared to 400 IU with no evidence of vitamin D toxicity.     Trial Registration: Clinical Trial Registry of India (CTRI/2019/02/017374). What is Known: • Breastfeeding is the ideal source of nutrition for healthy-term breastfed infants; however, vitamin D content of breastmilk is suboptimal. • AAP recommends daily oral supplementation of 400 IU of vitamin D to all healthy-term breastfed infants; however, trials from high-income countries support insufficiency of this dose in maintaining serum 25-OH-D levels >20 ng/ml with no such information from low-middle-income countries. What is New: • 800 IU/day of oral vitamin D3 supplementation among term breastfed infants significantly reduces vitamin D insufficiency at 14 weeks' age as compared to the recommended dose of 400 IU/day. • This higher supplemental dose is safe with no evidence of vitamin D toxicity.