Estimated equivalency of vitamin D production from natural sun exposure versus oral vitamin D supplementation across seasons at two US latitudes

CYP3A4 Mutation Causes Vitamin D-Dependent Rickets Type 3: A Case Report in Saudi Arabia

Rickets is a childhood disorder of vitamin D deficiency that is characterized by growth retardation and impairment in skeletal mineralization. Vitamin D deficiency is usually due to decreased dietary vitamin D intake, decreased sunlight exposure, or genetic defects. A recurrent gain-of-function missense mutation (p.I301T) in the gene encoding CYP3A4 has been identified as a cause of excessive inactivation of vitamin D metabolites that causes vitamin D-dependent rickets type 3 (VDDR3). We hereby report a case of a six-year-old girl with poor growth and bone deformities, such as genu valgum. In addition, the patient has a strong family history of short stature and bone deformities. She continues to receive multidisciplinary care, and the finding of a heterozygous missense variant in CYP3A4: c.902 T > C; p.Ile301Thr in the CYP3A4 gene confirms the diagnosis of VDDR3. To our knowledge, this is the first case to be reported in Saudi Arabia and the fourth case in the literature. Our findings highlight the importance of vitamin D in those with high activity in CYP3A4 to maintain vitamin D hemostasis, and we need to reach optimal doses to help them maintain their biochemical and radiological finding within the normal range.

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.

Endogenous Photosensitizers in Human Skin

Endogenous photosensitizers play a critical role in both beneficial and harmful light-induced transformations in biological systems. Understanding their mode of action is essential for advancing fields such as photomedicine, photoredox catalysis, environmental science, and the development of sun care products. This review offers a comprehensive analysis of endogenous photosensitizers in human skin, investigating the connections between their electronic excitation and the subsequent activation or damage of organic biomolecules. We gather the physicochemical and photochemical properties of key endogenous photosensitizers and examine the relationships between their chemical reactivity, location within the skin, and the primary biochemical events following solar radiation exposure, along with their influence on skin physiology and pathology. An important take-home message of this review is that photosensitization allows visible light and UV-A radiation to have large effects on skin. The analysis presented here unveils potential causes for the continuous increase in global skin cancer cases and emphasizes the limitations of current sun protection approaches.

The Role of Vitamin D in Cardiovascular Diseases

Cardiovascular diseases (CVD) are the leading cause of death in the United States. The previous literature demonstrates the importance of vitamin D for overall health, and a significant body of literature has examined the benefits of optimal serum 25-hydroxyvitamin D [25(OH)D] on cardiovascular health, but the results remain inconclusive. The objective of this study was to determine the association between reported CVD and [25(OH)D]. We utilized the 2015-2018 National Health and Nutrition Examination Survey and included adults aged 20 years and older (n = 9825). CVD was defined as having a stroke, heart attack, heart failure, or coronary heart disease. Vitamin D status was categorized as a serum 25(OH)D deficiency at <30 nmol/L; insufficiency at 30 to 49.9 nmol/L; normal/optimal at 50 to 125 nmol/L; and adequacy at >125 nmol/L. Statistical analysis was performed using Chi-square tests, t-tests were conducted to investigate the differences in participant characteristics among those with CVD and without CVD, and regression models were used to explore the association between vitamin D levels and CVD status. We found 25(OH)D deficiency associated with CVD (Adjusted Odds Ratio (AOR) = 1.48; 95% CI = 1.11-1.98; p < 0.05). [25(OH)D] insufficiency was also associated with CVD (AOR = 1.28; 95% CI = 1.06-1.54; p < 0.05). The 25(OH)D adequacy was not associated with reported CVD. For the prevention of CVD, healthcare professionals may recommend the use of vitamin D supplementation to improve cardiovascular health in adults while considering individual needs.

Risk perception of sun exposure and knowledge of vitamin D among the healthcare providers in a high-risk country: a cross-sectional study

BACKGROUND

High levels of vitamin D deficiency are commonly reported even in regions with abundant sunshine. This necessitates a comprehensive understanding of the determinants that influence sun exposure practices. As the primary source of health-related knowledge for the general public, the attitude of the healthcare professionals towards sunlight and their awareness related to vitamin D deficiency can be critical in this regard.

METHODS

A cross-sectional survey was conducted among 2,242 physicians, intern doctors, and senior medical students in Bangladesh from October 2019 to February 2020. A pre-tested structured questionnaire (containing twelve close-ended questions) was used. The perceptions of health risks due to sun exposure, and basic knowledge of the physiological and epidemiological aspects of vitamin D deficiency were tested.

RESULTS

An overall negative attitude towards sunlight in the context of Bangladesh was highlighted - 68% participants thought regular sun exposure would be harmful or very harmful; 26% thought the level of UV radiation was very high; 44% recommended using sunscreen always; skin burns, heat stroke, and cancer were selected as potential consequences of regular sun exposure by 45%, 21%, and 30% respondents respectively. Overall knowledge regarding vitamin D deficiency appeared to be biased towards bone health; other symptoms and associated illnesses not having obvious link to Calcium-metabolism were identified much lesser frequently. Furthermore, 'sunrise to 10 am' was identified as the best time to get vitamin D by 69% participants; 60% believed < 30 min of weekly sun exposure would be sufficient for the Bangladeshi population; an only 33% identified that prevalence of vitamin D insufficiency in Bangladesh would be 50% or more. Taking vitamin D-rich food was suggested by more respondents over regular sun exposure (43% vs. 33%) as more effective remedial strategy to curb vitamin D deficiency in Bangladesh.

CONCLUSION

In addition to highlighting some crucial knowledge gaps, results from this study provides a comprehensive baseline dataset for knowledge and attitude regarding the public health aspects of vitamin D deficiency among the healthcare providers in Bangladesh, which would be generalizable to other countries with similar socio-demographic context, and will facilitate taking more effective policies worldwide.

Sun-protective Properties of Technical Sportswear Fabrics 100% Polyester: The Influence of Moisture and Sweat on Protection against Different Biological Effects of Ultraviolet (UV) Radiation

The use of technical sportswear is now widespread, but the degree of protection these fabrics offer against UV radiation is not known. We have analyzed the capacity of different types of technical sportswear fabrics to protect against different UV biological effects. A sample of 34 100% polyester t-shirts from different manufactures was classified by color, fabric structure, cover factor, and due to different tonalities, dark, and clear color. Ultraviolet protection factor was calculated according to UNE-EN13758. The protection factor for other biological effects as pre-vitamin D₃ production, non-melanoma skin cancer, photoimmunosuppression, and photoaging was analyzed. The effects of moisture and sweat in protection were also evaluated. From the analyzed sample garments, more than 75% achieved an excellent protection value (protection factor 40-50+). Higher values were found in double-layer type (P < 0.05). Cover factor was the main determinant of biological protection factors with correlation coefficients of 0.81 for UPF (erythema), 0.77 for NMSC, and 0.63 for photoimmunosuppression. Water or sweat humidity saturation increased biological protection factors over a 20% (P < 0.05). The 83% of the fabrics analyzed showed less than 5% of transmittance with labeling as UVA protective elements. No effect of fabric color was found related to biological protection factors. The 100% polyester sports T-shirts of the analyzed sample offer general protection against UV for different biological effects that can be increased by humidity but no affected by fabric color.

Developing Low-Cost Mobile Device and Apps for Accurate Skin Spectrum Measurement via Low-Cost Spectrum Sensors and Deep Neural Network Technology

In recent years, skin spectral information has been gradually applied in various fields, such as the cosmetics industry and clinical medicine. However, the high price and the huge size of the skin spectrum measurement device make the related applications of the skin spectrum unable to be widely used in practical applications. We used convolutional neural network (CNN) to achieve a satisfying accuracy of the Fitzpatrick skin-type classification by using a simple self-developed device in 2018. Leveraging on the hardware, firmware, and software app-developing experience, a low-cost miniature skin spectrum measurement system (LMSSMS) using deep neural network (DNN) technology was further studied, and the feasibility of the system is verified in this paper. The developed LMSSMS is divided into three parts: (1) miniature skin spectrum measurement device (MSSMD), (2) DNN model, and (3) mobile app. The MSSMD was developed with innovative low-cost MSSC, 3D printing, and a simple LED light source. The DNN model is designed to enhance measurement accuracy. Finally, the mobile app is used to control and show the measurement results. The developed app also includes a variety of skin-spectrum-related applications, such as erythema index and melanin index (EI/MI) measurement, Fitzpatrick skin-type classification, Pantone SkinTone classification, sun-exposure estimation, and body-fat measurement. In order to verify the feasibility of LMSSMS, we used the standard instrumentation device as a reference. The results show that the accuracy of the LMSSMS can reach 94.7%, which also confirms that this development idea has much potential for further development.

Pleiotropic Effects of Vitamin D in Patients with Inflammatory Bowel Diseases

The multifaceted activity of vitamin D in patients with inflammatory bowel disease (IBD) presents a challenge for further research in this area. Vitamin D is involved in the regulation of bone mineral metabolism, it participates in the regulation of the immune system, and it is an underlying factor in the pathogenesis of IBD. Additionally, vitamin D affects Th1 and Th2 lymphocytes, influencing the release of cytokines and inhibiting tumor necrosis factor (TNF) expression and the wnt/β-catenin pathway. As far as IBDs are concerned, they are associated with microbiota dysbiosis, abnormal inflammatory response, and micronutrient deficiency, including vitamin D hypovitaminosis. In turn, the biological activity of active vitamin D is regulated by the vitamin D receptor (VDR) which is associated with several processes related to IBD. Therefore, in terms of research on vitamin D supplementation in IBD patients, it is essential to understand the metabolic pathways and genetic determinants of vitamin D, as well as to identify the environmental factors they are subject to, not only in view of osteoporosis prevention and therapy, but primarily concerning modulating the course and supplementation of IBD pharmacotherapy.

Serum, Dietary, and Supplemental Vitamin D Levels and Insulin Resistance in 6294 Randomly Selected, Non-Diabetic U.S. Adults

The primary aim of this study was to determine the associations between serum, dietary, and supplemental vitamin D levels and insulin resistance in 6294 non-diabetic U.S. adults. A total of 8 years of data from the 2011−2018 National Health and Nutrition Examination Survey (NHANES) and a cross-sectional design were utilized to answer the research questions. Serum vitamin D levels were quantified using high-performance liquid chromatography−tandem mass spectrometry. Dietary and supplemental vitamin D intakes were assessed using the average of two 24 h dietary recalls taken 3−10 days apart. The homeostatic model assessment (HOMA), based on fasting glucose and fasting insulin levels, was employed to index insulin resistance. Demographic covariates were age, sex, race, and year of assessment. Differences in physical activity, body mass index (BMI), cigarette smoking, body weight, season, and energy intake were also controlled statistically. Serum levels of vitamin D differed significantly, and in a dose−response order, across quartiles of HOMA-IR, after adjusting for year, age, sex, and race (F = 30.3, p < 0.0001) and with all the covariates controlled (F = 5.4, p = 0.0029). Dietary vitamin D levels differed similarly across HOMA-IR quartiles, but to a lesser extent, respectively (F = 8.1, p = 0.0001; F = 2.9, p = 0.0437). Likewise, supplemental vitamin D levels also differed across the HOMA-IR quartiles, respectively (F = 3.5, p = 0.0205; F = 3.3, p = 0.0272). With all the covariates controlled, the odds of having insulin resistance were significantly greater for those in the lowest quartile of serum and supplemental vitamin D intake compared to the other quartiles combined. In conclusion, in this nationally representative sample, serum, dietary, and supplemental vitamin D were each predictive of insulin resistance, especially in those with low serum levels and those with no supplemental intake of vitamin D.

Role of Vitamin D in Cardiovascular Diseases

Vitamin D represents a group of secosteroids involved in the calcium and phosphate metabolism. The active form of vitamin D, 1,25-dihydroxylcalciferol, exerts its biological mechanisms via the VDR (vitamin D receptor) which acts as a regulator of several target genes. Hypovitaminosis D is associated with many diseases, which are not only limited to the metabolism of the skeleton, but growing evidence links the deficit of vitamin D to cardiovascular, metabolic, immune, and neoplastic diseases. In regard to the cardiovascular system, current evidence shows the presence of VDR in endothelial cells. Moreover, both in vitro and animal experimental models demonstrated that the deficit of vitamin D can promote endothelial dysfunction and atherosclerosis development. Vitamin D can interfere with vascular functions also by affecting the production of vasodilator mediators. VDR is also expressed in left ventricle cardiomyocytes, and hypovitaminosis D can relate to cardiac hypertrophy and heart failure. Randomized clinical trials (RCT) designed to prove the therapeutic role of vitamin D supplementation have been inconclusive to date. The aim of this review is to highlight the main interactions between vitamin D metabolism and cardiovascular diseases; thus, focusing on pathogenic mechanisms and related clinical manifestations.

Baseline Levels of Vitamin D in a Healthy Population from a Region with High Solar Irradiation

The use of vitamin D (VitD) supplements has become widespread in the last decade due not only to the dissociation between the blood levels recommended as "optimal" and those shown by the healthy population but also to its presumed beneficial effects on multiple disorders. This work evaluated the levels of 25-hydroxyvitamin D (25(OH)D) in a healthy population of European origin living in a region with high solar irradiation. In serum samples from a population-based study conducted in the Canary Islands, levels of 25(OH)D were analyzed. In 876 individuals who had no history of kidney or malabsorption disorders and, who had not been treated with calcium and/or VitD supplementation, the median 25(OH)D level was 26.3 (5th; 95th percentile, 14.3; 45.8) ng/mL. Notably, 65.4% of the population had 25(OH)D blood levels below 30 ng/mL, 23.4% below 20 ng/mL and 6.4% below 15 ng/mL. Based on the lack of evidence supporting causality between 25(OH)D levels below what is recommended as optimal (≥20 ng/mL, or even ≥30 ng/mL) and major skeletal and non-skeletal diseases, and in light of the distribution of the concentration of this vitamin in healthy adults living under optimal conditions of solar irradiation, it seems reasonable to consider 25(OH)D levels below 20 ng/mL and close to 15 ng/mL as adequate for the general population.

Vitamin D and cardiovascular health

The principal source of vitamin D in humans is its biosynthesis in the skin through a chemical reaction dependent on sun exposure. In lesser amounts, the vitamin can be obtained from the diet, mostly from fatty fish, fish liver oil and mushrooms. Individuals with vitamin D deficiency, defined as a serum level of 25 hydroxyvitamin D < 20 ng/dl, should be supplemented. Vitamin D deficiency is a prevalent global problem caused mainly by low exposure to sunlight. The main role of 1,25 dihydroxyvitamin D is the maintenance of calcium and phosphorus homeostasis. However, vitamin D receptors are found in most human cells and tissues, indicating many extra-skeletal effects of the vitamin, particularly in the immune and cardiovascular (CV) systems. Vitamin D regulates blood pressure by acting on endothelial cells and smooth muscle cells. Its deficiency has been associated with various CV risk factors and appears to be linked to a higher mortality and incidence of CV disease (CVD). Several mechanisms have been proposed relating vitamin D deficiency to CV risk factors such as renin-angiotensin-aldosterone system activation, abnormal nitric oxide regulation, oxidative stress or altered inflammatory pathways. However, in the latest randomized controlled trials no benefits of vitamin D supplementation for CVD have been confirmed. Although more work is needed to establish the protective role of vitamin D in this setting, according to current evidences vitamin D supplements should not be recommended for CVD prevention.

Vitamin D Metabolism and Guidelines for Vitamin D Supplementation

Vitamin D is essential for bone health and is known to be involved in immunomodulation and cell proliferation. Vitamin D status remains a significant health issue worldwide. However, there has been no clear consensus on vitamin D deficiency and its measurement in serum, and clinical practice of vitamin D deficiency treatment remains inconsistent. The major circulating metabolite of vitamin D, 25-hydroxyvitamin D (25(OH)D), is widely used as a biomarker of vitamin D status. Other metabolic pathways are recognised as important to vitamin D function and measurement of other metabolites may become important in the future. The utility of free 25(OH)D rather than total 25(OH)D needs further assessment. Data used to estimate the vitamin D intake required to achieve a serum 25(OH)D concentration were drawn from individual studies which reported dose-response data. The studies differ in their choice of subjects, dose of vitamin D, frequency of dosing regimen and methods used for the measurement of 25(OH)D concentration. Baseline 25(OH)D, body mass index, ethnicity, type of vitamin D (D₂ or D₃) and genetics affect the response of serum 25(OH)D to vitamin D supplementation. The diversity of opinions that exist on this topic are reflected in the guidelines. Government and scientific societies have published their recommendations for vitamin D intake which vary from 400-1000 IU/d (10-25 μg/d) for an average adult. It was not possible to establish a range of serum 25(OH)D concentrations associated with selected non-musculoskeletal health outcomes. To recommend treatment targets, future studies need to be on infants, children, pregnant and lactating women.

Effect of Short-Term Sunlight Exposure on Blood Pressure and Pulse Rate in Vitamin D3-Insufficient, Prehypertensive Patients: A Pilot Study

INTRODUCTION

This study was conducted to evaluate the effect of short-term sunlight exposure on blood pressure (BP) and pulse rate (PR) in vitamin D3-insufficient, prehypertensive patients.

METHODS

Twenty prehypertensive male participants were prospectively enrolled in this pilot study. BP and PR were measured using 24-hour ambulatory BP monitoring and endocrine biomarkers were assessed.

RESULTS

Sunlight exposure decreased 24-hour systolic BP (SBP), diastolic BP (DBP), and PR (SBP: 132.6 mm Hg to 129.3 mm Hg, DBP: 77.6 mm Hg to 75.7 mm Hg, and PR: 76.1 bpm to 71.3 bpm, p values: 0.0011, 0.0012, and <0.0001, respectively). The decrement patterns of SBP, DBP, and PR during nighttime (SBP: 123.5 mm Hg to 117.9 mm Hg, DBP: 72.2 mm Hg to 68.0 mm Hg, and PR: 68.2 bpm to 59.1 bpm, p values: 0.0015, 0.0003, and <0.0001, respectively) were more profound compared between daytime and nighttime. Blood levels of 25-hydroxyvitamin D3 were significantly increased (p = 0.0001) but aldosterone levels were significantly decreased (p = 0.0014) after sunlight exposure. In addition, an inverse relationship between 25-hydroxyvitamin D3 and aldosterone levels was observed (R = -0.4709, p = 0.0419).

DISCUSSION/CONCLUSION

The pilot study gives promising results that it is worthwhile to evaluate short-term sunlight exposure as a potentially effective approach in decreasing BP and PR in 25-hydroxyvitamin D3-insufficient prehypertensive patients in a larger trial with a control group.

Prevalence and Risk Factors for Hypovitaminosis D among Healthy Adolescents in Kota Bharu, Kelantan

OBJECTIVE

We aim to study the prevalence and risk factors of hypovitaminosis D among healthy adolescents in Kota Bharu, Kelantan based on the most recent Paediatric Consensus guideline.

METHODOLOGY

Ten public schools were selected from Kota Bharu, Kelantan. We analysed their demography (age, gender, ethnicity, income), measured their anthropometry (height, weight, BMI) and finally analysed their vitamin D and intactParathyroid hormone levels.

RESULTS

The prevalence of hypovitaminosis D was 16.9% among healthy teenagers with mean age of 15.9±1.39 years. Multivariate analysis showed female gender (adjusted OR, 95% CI): 23.7 (5.64, 100.3) and Chinese 0.24 (0.07, 0.84) were the significant predictors for hypovitaminosis D.

CONCLUSION

The prevalence of healthy adolescents with hypovitaminosis D in Kota Bharu, Kelantan was 16.9% using the most recent cut off value of 30 nmol/L from the global consensus 2016. Female and Malay were the significant risk factors associated with hypovitaminosis D. Higher cut off value would result in overestimation of prevalence rate of hypovitaminosis D.

THE VITAMIN D STATUS OF ASIAN ELEPHANTS (ELEPHAS MAXIMUS) MANAGED IN A NORTHERN TEMPERATE CLIMATE

Knowledge about the normal metabolism and involvement of vitamin D in elephant calcium homeostasis is essential to understanding the possible role of vitamin D in Asian elephant (Elephas maximus) health, as well as to informing accurate diet formulation. This study provides an evaluation of analytes involved in vitamin D metabolism, in conjunction with dietary intake and ultraviolet light (UV) exposure, in Asian elephants managed in a northern temperate climate. Once monthly, for a total of 12 mo, serum from six adult Asian elephants was analyzed for 25-hydroxyvitamin D [25(OH)D], 24,25-dihydroxyvitamin D [24,25(OH)₂D], 1,25-dihydroxyvitamin D [1,25(OH)₂D], parathyroid hormone (PTH), total calcium (Ca), ionized calcium (iCa), phosphorus (P), and magnesium (Mg). The diet was analyzed monthly for vitamin D, Ca, and P. Monthly average vitamin D-weighted UV daily sums were determined to gauge average UV light exposure within the vitamin D action spectrum. No serum or diet parameters were affected by time or season. Average serum 25(OH)D₂ was 7.02 ± 0.85 ng/ml. 25(OH)D₃ levels were nondetectable in all samples despite supplementation of the diet with recommended levels of vitamin D₃, and UV exposure was at sufficient levels for cutaneous vitamin D synthesis for 6 mo of the year. Levels of 24,25(OH)₂D averaged 31.7% higher than 25(OH)D, and average 1,25(OH)₂D₂ was 11.24 ± 1.04 pg/ml. Values for PTH, Ca, iCa, P, and Mg were within expected ranges for Asian elephants. The information gained from this research expands the knowledge base for these analytes, evaluates 24,25-dihydroxyvitamin D for the first time, and provides new information regarding vitamin D metabolism and test interpretation in the Asian elephant.

Vitamin D Synthesis Following a Single Bout of Sun Exposure in Older and Younger Men and Women

Older adults are frequently cited as an at-risk population for vitamin D deficiency that may in part be due to decreased cutaneous synthesis, a potentially important source of cholecalciferol (vitamin D₃). Previous studies found that cutaneous D₃ production declines with age; however, most studies have been conducted ex vivo or in the photobiology lab. The purpose of this study was to characterize the response of vitamin D metabolites following a 30-min bout of sun exposure (15-min each to the dorsal and ventral sides) at close to solar noon in younger and older adults.

METHODS

30 healthy individuals with skin type II/III were recruited; a younger cohort, aged 20-37 (n = 18) and an older cohort (n = 12), age 51-69 years. Exposure was at outer limits of sensible sun exposure designed to enhance vitamin D synthesis without increasing risk of photo ageing and non-melanoma skin cancer. Serum D₃ concentration was measured at baseline, 24, 48 and 72 h post-exposure. Serum 25(OH)D was measured at baseline and 72 h post-exposure plus 168 h post-exposure in the older cohort.

RESULTS

D₃ increased in response to sun exposure (time effect; p = 0.002) with a trend for a difference in D₃ between cohorts (time*group; p = 0.09). By regression modeling of continuous data, age accounted for 20% of the variation in D₃ production. D₃ production decreased by 13% per decade. Despite changes in D₃, however, serum 25(OH)D did not change from baseline to 72 or 168 h post exposure (p > 0.10).

CONCLUSIONS

Serum D₃ concentration increased significantly in response to outdoor sun exposure in younger and older adults. While ageing may dampen cutaneous synthesis, sunlight exposure is still a significant source of vitamin D₃.

Differential Frequency of CYP2R1 Variants Across Populations Reveals Pathway Selection for Vitamin D Homeostasis

CONTEXT

Normal vitamin D homeostasis is necessary to ensure optimal mineral metabolism. Dietary insufficiency of vitamin D and the lack of sunlight each have well understood roles in vitamin D deficiency; however, the extent to which common genetic variations in vitamin D metabolizing enzymes contribute to alterations in vitamin D homeostasis remains uncertain.

OBJECTIVE

To examine the possibility that common coding variation in vitamin D metabolizing enzymes alters vitamin D homeostasis we determined the effect of 44 nonsynonymous polymorphisms in CYP2R1, the vitamin D 25-hydroxylase, on enzyme function.

RESULTS

Twenty-one of these polymorphisms decreased activity, while 2 variants increased activity. The frequency of CYP2R1 alleles with decreased 25-hydroxylase activity is 3 in every 1000 Caucasians and 7 in every 1000 African Americans. In populations where exposure to sunlight is high, alleles with decreased function occur at a frequency as high as 8%. The pattern of selected variation as compared to nonselected variation is consistent with it being the result of positive selection for nonfunctional alleles closer to the equator. To examine this possibility, we examined the variation pattern in another protein in the vitamin D pathway, the vitamin D binding protein (GC protein). The pattern of selected variation in the GC protein as compared to nonselected variation is also consistent with it being the result of positive selection for nonfunctional alleles closer to the equator.

CONCLUSIONS

CYP2R1 polymorphisms have important effects on vitamin D homeostasis, and the geographic variability of CYP2R1 alleles represents an adaptation to differential exposures to UVB irradiation from sunlight.

Sun Exposure in Children: Balancing the Benefits and Harms

There is a common belief among the laity and even physicians that sun exposure is a useful source of vitamin D. However, despite the fact that sun exposure occurs almost throughout the year in India, vitamin D deficiency is widely prevalent. Although several authors have reported on the duration of sun exposure required to synthesize adequate amounts of vitamin D in the human body, they have not followed a standard and uniform protocol for measurement of sun exposure and vitamin D synthesis. For these and many other reasons, the results are difficult to interpret. The American Academy of Pediatrics (AAP) has clearly stated that infants should be protected from the sun as much as possible and vitamin D requirements should be met through diet and fortified foods rather than deliberate sun exposure. However, this recommendation is frequently ignored in clinical practice. This review aims to summarize the available literature on benefits and harm of unprotected sun exposure in infants and children with a focus on skin phototype IV to VI. Dermatologists and pediatricians in India should counsel parents about the need for sun protection, especially in fair-skinned infants and children.

Vitamin D binding protein is required to utilize skin-generated vitamin D

Vitamin D is produced in the skin following exposure to sunlight. Ultraviolet (UV) B (UVB, 280-310 nm) results in isomerization of 7-dehydrocholesterol to previtamin D that spontaneously isomerizes to vitamin D. This pool of skin-derived vitamin D is the major source of vitamin D for animals. However, the mechanisms by which it becomes available remain undefined. It has been assumed that cutaneous vitamin D is transported into the circulation by vitamin D binding protein (DBP), but experimental evidence is lacking. To determine whether cutaneous vitamin D is transported by DBP, we utilized DBP^-/- mice that were made vitamin D-deficient. These animals lack measurable 25(OH)D in blood and are hypocalcemic. As controls, DBP^+/+ animals were vitamin D depleted and made equally hypocalcemic. UV irradiation of DBP^+/+ animals restored serum calcium and serum 25(OH)D while the same treatment of DBP^-/- animals failed to show either a serum calcium or 25(OH)D response despite having normal vitamin D production in skin. Intravenous injection of small amounts of recombinant DBP to the vitamin D-deficient DBP^-/- mice restored the response to UV light. These results demonstrate a requirement for DBP to utilize cutaneously produced vitamin D.

Vitamin D and the skin: what should a dermatologist know?

Although first discovered in 1931, vitamin D has seen an increased interest in the scientific community over the past decades, including the dermatology field. Vitamin D promotes calcium and phosphorus absorption; however, the actions of vitamin D are not confined to bone. Indeed, there is now overwhelming and compelling scientific data that vitamin D plays a crucial role in a plethora of cellular function and in extra-skeletal health. Except for fatty fish livers, very few foods naturally contain vitamin D; and the major source of vitamin D comes from skin exposure to sunlight via ultraviolet B. Keratinocytes are unique in the body as not only do they provide the primary source of vitamin D for the body, but they also possess both the enzymatic machinery to metabolize the vitamin D produced to active metabolites. This has been referred to as the photoendocrine vitamin D system. Vitamin D regulates keratinocytes proliferation and differentiation; and plays a role in the defense against opportunistic infections. Multiple factors are linked to vitamin D status; and a growing number of dermatologic diseases has been linked to vitamin D status such as atopic dermatitis, psoriasis, vitiligo, and cutaneous cancers. In this article, we reviewed the potential determinants of vitamin D status, as its implications in dermatologic diseases.

Overview on vitamin D and sunbed use

Vitamin D seems to be associated with a protective effect in a vast range of diseases, including cardiovascular, autoimmune and oncologic conditions. Since ultraviolet (UV) B light is the most important prerequisite for the cutaneous synthesis of vitamin D, sunbeds are able to increase serum vitamin D levels, although only transiently in most cases. In this scenario, the artificial tanning industry relentlessly tries to promote the use of sunbeds as a 'safe' therapeutic measure to achieve an adequate serum vitamin D status. The World Health Organization classified UV-emitting tanning devices, as well as the whole UV spectrum, as group-1 carcinogens, as they significantly increase the risk of melanoma and non-melanoma skin cancer. In case of vitamin D deficiency or insufficiency, the current risk-benefit ratio is therefore in favour of vitamin D supplementation instead of sunbed use. Artificial tanning devices should never be considered as an option to achieve an appropriate vitamin D status. Their supposedly beneficial effects, vastly publicised by the artificial tanning industry, are not worth the carcinogenic risk associated with sunbed use.

Low 25-hydroxyvitamin D levels are more prevalent in Canadians of South Asian than European ancestry inhabiting the National Capital Region of Canada

The US Institute of Medicine defined serum 25-hydroxyvitamin D (25OHD) cut point values of 30 nmol/L and 40 nmol/L were used to assess the vitamin D status of South Asian and European Canadians of self-identified ancestry living in the National Capital Region of Canada. Serum 25OHD values were measured in the spring and fall of 2012 to represent status during the winter and summer months, respectively. A total of 1238 measurements were obtained from 669 participants (49% South Asian ancestry): some participants were measured only once (spring or fall). Median 25OHD values were significantly higher in participants of European ancestry: 70.8 nmol/L (68.1, 73.5; 95% CI) versus South Asian ancestry: 42.7 nmol/L (40.5, 45.0; P<0.001). Spring vs. fall differences were small for each ethnic group and significant only for those of European ancestry (2.9, CI: 1.0–4.9 nmol/L; P = 0.01). Among participants of South Asian ancestry, 27.3% (fall) and 29.1% (spring) of females had values <40 nmol/L while the percentages for males were considerably higher (36.5% and 44.2%, respectively). The corresponding values for participants of European ancestry were ≤10%, showing that the South Asian participants were less likely to achieve the 25OHD concentrations established by the IOM for optimum bone health. Investigation of the factors related to serum 25OHD levels showed that supplement intake and ethnic background were associated with the biggest differences. Skin color was not a major factor, suggesting that genetic factors are responsible for the observed differences between participants of different ethnic backgrounds.

Recurrent pregnancy loss and vitamin D: A review of the literature

Recurrent pregnancy loss (RPL) affects approximately 1%-2% of reproductive women. Auto- and cellular immune responses seem to be associated with RPL. Vitamin D (VD) has been shown to play a role in the modulation of the immune system. Effects of VD deficiency (VDD) in pregnancy have been associated with preeclampsia, gestational diabetes, fetal growth restriction, preterm labor, and sporadic spontaneous abortion (SA). We systematically reviewed articles that studied women with 2 or more SA and its association with VD. Eleven studies were included. Studies reported a high prevalence of VD insufficiency (VDI) or VDD in women with RPL and suggested that this could be associated with immunological dysregulation and consequently with RPL. Immunological benefits were reported in the peripheral blood of women with RPL after VD exposure. Thus, it is possible to speculate a beneficial role for VD supplementation in RPL. It seems that there are not differences in the vitamin D receptor (VDR) and CYP27B1 expression in endometrium of women with RPL but, in villous and decidual tissues, RPL women seem to have a decreased expression of VDR and, perhaps, a decreased expression of CYP27B1. Further randomized controlled studies are required to investigate the association between VDD or VDI and RPL.

CYP3A4 mutation causes vitamin D-dependent rickets type 3

Genetic forms of vitamin D-dependent rickets (VDDRs) are due to mutations impairing activation of vitamin D or decreasing vitamin D receptor responsiveness. Here we describe two unrelated patients with early-onset rickets, reduced serum levels of the vitamin D metabolites 25-hydroxyvitamin D and 1,25-dihydroxyvitamin D, and deficient responsiveness to parent and activated forms of vitamin D. Neither patient had a mutation in any genes known to cause VDDR; however, using whole exome sequencing analysis, we identified a recurrent de novo missense mutation, c.902T>C (p.I301T), in CYP3A4 in both subjects that alters the conformation of substrate recognition site 4 (SRS-4). In vitro, the mutant CYP3A4 oxidized 1,25-dihydroxyvitamin D with 10-fold greater activity than WT CYP3A4 and 2-fold greater activity than CYP24A1, the principal inactivator of vitamin D metabolites. As CYP3A4 mutations have not previously been linked to rickets, these findings provide insight into vitamin D metabolism and demonstrate that accelerated inactivation of vitamin D metabolites represents a mechanism for vitamin D deficiency.

Serum vitamin D profile of Nigerian children with asthma: Association with asthma severity and control

OBJECTIVE

Childhood asthma is a chronic inflammatory airway disorder with increasing prevalence even in Africa. Vitamin D, with anti-inflammatory and immune-modulatory properties, may have effects on the severity and level of symptoms control in childhood asthma. We aimed to assess the serum vitamin D levels in children with asthma as related to disease severity and control in a tropical region.

METHODS

A hospital based comparative cross sectional study was conducted in western Nigeria. Serum vitamin D (25-OH-D) levels of all the children, assayed using high-performance liquid chromatography (HPLC), were compared to the various disease severity and levels of asthma control as well as between the asthmatic and non-asthmatic children.

RESULTS

A total of 206 children (103 asthmatics and 103 non-asthmatics) were recruited with a mean (SD) age of 6.6 (3.7) years. The majority (82.5%) of the children with asthma had mild intermittent form, 63.1% had well controlled symptoms while 33.0% and 3.9% had partly controlled and uncontrolled symptoms, respectively. None of the children were deficient in vitamin D. The mean (SD) serum vitamin D levels of the children with asthma (49.2 [7.2] ng/mL) was significantly lower than those without asthma (51.2 [6.9] ng/mL, P = 0.043). Varying degrees of asthma severity and levels of symptoms control were not affected by serum vitamin D levels.

CONCLUSION

Children with asthma in Nigeria had marginally but significantly lower mean serum vitamin D levels when compared with their counterparts without asthma. However, serum vitamin D level does not seem to be associated with childhood asthma severity and control in these children with normal serum vitamin D levels.

Non-musculoskeletal benefits of vitamin D

The aim of this study is to determine and critically evaluate the plausible relationships of vitamin D with extra-skeletal tissues in humans. Severe vitamin D deficiency results in rickets in children and osteomalacia in adults; these beneficial effects in the musculoskeletal system and certain physiological functions are well understood. Nevertheless, mounting reports support additional beneficial effects of vitamin D, outside the musculoskeletal system. This review explores the recent advances in knowledge about the non-skeletal effects of vitamin D. Peer-reviewed papers were extracted from research databases using key words, to assess correlations between vitamin D and extra-skeletal diseases and conditions. As per the guidelines of the Preferred Reporting Items for Systematic Reviews (PRISMA); general interpretations of results are included; taking into consideration the broader evidence and implications. This review summarizes current knowledge of the effects of vitamin D status on extra-skeletal tissues with special attention given to relationships between vitamin D status and various diseases commonly affecting adults; the effects of intervention with vitamin D and exposure to sunlight. Evidence suggests that vitamin D facilitates the regulation of blood pressure; and cardiac; endothelial; and smooth muscle cell functions; playing an important role in cardiovascular protection. In addition; 1,25(OH)₂D improves immunity; subdues inflammation; and reduces the incidence and severity of common cancers; autoimmune diseases and infectious diseases. Almost all adequately powered; epidemiological and biological studies that use; adequate doses of vitamin D supplementation in D-deficient populations have reported favorable outcomes. These studies have concluded that optimizing 25(OH)D status improves the functionality of bodily systems; reduces comorbidities; improves the quality of life; and increases survival. Although accumulating evidence supports biological associations of vitamin D sufficiency with improved physical and mental functions; no definitive evidence exists from well-designed; statistically powered; randomized controlled clinical trials. Nevertheless, most studies point to significant protective effects of vitamin D in humans when the minimum 25(OH)D serum level exceeds 30ng/mL and is maintained throughout the year.

Solar ultraviolet doses and vitamin D in a northern mid-latitude

Solar ultraviolet (UV) radiation is one of the most important factors in the development of skin cancer in human, solar erythema and skin aging. Nevertheless, numerous studies have shown the benefits of UV solar radiation in moderate doses, such as the reduction of blood pressure and mental health, treatment of various diseases, and the synthesis of vitamin D in the skin. This paper analyses data from solar ultraviolet erythemal (UVER) irradiance in W/m² measured in a northern mid-latitude as Valencia (Spain) for the period 2003-2010. To estimate effective solar UV radiation in the production of vitamin D (UVD) we used the relationship proposed by McKenzie et al. (2009). It was obtained for one month for each season the minimum exposure time needed around solar noon and at 9 UTC and 15 UTC (Coordinated Universal Time) to obtain the recommended daily dose of 1000IU. Also, it has been calculated time for erythema induction around solar noon for the same months. The median UVER daily dose during the summer months was 4000J/m²day, and 700J/m²day in winter. With regard to UVD, the median UVD daily dose in summer season was 7700J/m²day, and in winter it was 1000J/m²day. Around noon in January it takes more than two hours of solar exposure to obtain the recommended daily dose of vitamin D, whereas the rest of the year range between 7min on July and 31min on October. For the same months around noon, exposure times to produce erythema were obtained, these being of higher value to the previous. The results show that it is difficult to obtain the recommended vitamin D doses in winter in a northern mid-latitude, as the human body is almost entirely covered in this season.

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.

Seasonal Vitamin D Status in Polish Elite Athletes in Relation to Sun Exposure and Oral Supplementation

Vitamin D does not only influence the musculoskeletal health and mineral homeostasis but it also affects cardiovascular, endocrine, nervous, immune and mental functions, thus it is of considerable importance for both physically active people and elite athletes. However, vitamin D deficiency is common worldwide and results from inadequate endogenous skin synthesis (insufficient ultraviolet B exposure) and diet. To improve the vitamin D status elite athletes often travel to lower latitude during winter. The aim of the study was to evaluate the seasonal vitamin D status in Polish elite athletes according to the sun exposure and oral supplementation. Serum concentration of 25-hydroxyvitamin D (25(OH)D) was measured in the years 2010–2014 in 409 elite athletes, who were divided into the following groups: OUTD—outdoor sports, represented by track and field athletes, who trained in Poland; IND—weightlifters, handball and volleyball players who trained indoors in Poland; SUN—track and field athletes who trained during Polish winter in lower latitude with high sunshine exposure; SUPL—track and field athletes who trained in Poland, had an inadequate vitamin D status (25(OH)D < 30 ng/ml) and were supplemented orally. Inadequate Vitamin D status was observed in 80% of OUTD and 84% of IND athletes in winter, whereas in summer the values amounted to 42% and 83%, respectively. The athletes exposed to sun in winter had significantly higher vitamin D concentration than OUTD group. Oral supplementation improved vitamin D concentration by 45%, whereas winter sun exposure caused its increase by 85%. Except for a few summer months an inadequate status of vitamin D was found in the majority of Polish elite athletes, with the deficiency level being similar to the one observed in non-athletic population. The most serious deficiency was observed in indoor disciplines. Adequate vitamin D status can be achieved by both increased sun exposure, especially in winter, and oral supplementation. Athletes should therefore routinely assess their vitamin D status and be educated how to approach their sunlight exposure, diet and supplementation.

Body weight and 25-hidroxyvitamin D follicular levels: a prospective study of women submitted to in vitro fertilization

Objective

Vitamin D deficiency has been largely related to infertility in animals. However, data demonstrating a direct association between hypovitaminosis D and infertility in humans are still conflicting. Increased body weight and an elevated body mass index (BMI) are known for their association with infertility. Therefore, this study attempted to verify whether increases in body weight and the BMI were associated with lower 25-hidroxyvitamin D [25(OH)D3] levels in the follicular fluid (FF) of patients treated for infertility with intracytoplasmic sperm injections (ICSI). This study aimed to assess the FF levels of 25(OH)D3 in women submitted to ICSI and correlate these levels with the different body weight and BMI values observed in the enrolled cohort.

Methods

The FF aspirates of 199 patients submitted to ICSI were collected after oocyte aspiration to check whether FF 25(OH)D3 levels were associated with weight regardless of the etiology of infertility. Chemiluminescent assays were used to assess FF 25(OH)D3 levels. The etiology of infertility was defined based on patient clinical history and follow-up.

Results

The patients enrolled in the study were divided into three groups according to their FF 25(OH)D3 levels, as follows: a) deficient (n=71; <20 ng/ml); b) insufficient (n=64; 21< 25(OH) D3>29 ng/ml); and c) sufficient (n=56 >30ng/ml) levels. Patients with lower FF 25(OH)D3 levels had a greater mean weight (64.1kg) when compared to patients with higher 25(OH)D3 levels (60.7kg), p<0.01. No differences were observed in terms of age or etiology of infertility.

Conclusion

The body weight of the individuals with FF 25(OH)D3 deficiency measured in single follicles was significantly higher regardless of the etiology of infertility. Further epidemiologic and molecular studies are required to verify whether the amount of follicular 25(OH)D3 affects the outcome of IVF procedures.

Arsenic and ultraviolet radiation exposure: melanoma in a New Mexico non-Hispanic white population

Cases of cutaneous melanoma and controls were enrolled in a New Mexico population-based study; subjects were administered questionnaires concerning ultraviolet (UV) and inorganic arsenic (iAs) exposure. Historical iAs exposure was estimated. UV exposure estimates were also derived using geospatial methods. Drinking water samples were collected for iAs analysis. Blood samples were collected for DNA repair (Comet) and DNA repair gene polymorphism assays. Arsenic concentrations were determined in urine and toenail samples. UV exposures during the previous 90 days did not vary significantly between cases and controls. Mean (±SD) current home iAs drinking water was not significantly different for cases and controls [3.98 μg/L (±3.67) vs. 3.47 μg/L (±2.40)]. iAs exposure showed no effect on DNA repair or association with melanoma. Results did not corroborate a previously reported association between toenail As and melanoma risk. Arsenic biomarkers in urine and toenail were highly significantly correlated with iAs in drinking water. A UV-DNA repair interaction for UV exposure over the previous 7-90 days was shown; cases had higher DNA damage than controls at low UV values. This novel finding suggests that melanoma cases may be more sensitive to low-level UV exposure than are controls. A UV-APEX1 interaction was shown. Subjects with the homozygous rare APEX1 DNA repair gene allele had a higher risk of early melanoma diagnosis at low UV exposure compared with those with the homozygous wild type or the heterozygote. Notably, a UV-arsenic interaction on inhibition of DNA repair was not observed at iAs drinking water concentrations below 10 ppb (μg/L).

Regional and seasonal variations in ultraviolet B irradiation and vitamin D synthesis in India

Evaluation of ultraviolet B index (UVBI) and its impact on vitamin D synthesis is important. We observed the maximum UVBI between 11 am and 1 pm. There was no increase in serum 25(OH)D levels following sun exposure during winter as the UVBI was significantly low, emphasizing the need for vitamin D supplementation during these months.

INTRODUCTION

The amount of vitamin D3 synthesizing UVB irradiation (290-320 nm) reaching the earth's surface at different altitudes and seasons in different parts of India and it's impact on vitamin D synthesis has not been well studied.

METHODS

The hourly UVB index (UVBI) from 10 am to 3 pm everyday for 12 months was measured by a solar meter in 4 different zones (North, Northeast, West and South) of the country. To study the impact of sun light exposure on vitamin D synthesis during winter, healthy school children aged 10-15 years were exposed to sunlight for a period of 30 min per day, between 11 am to 12 noon with 10 % body surface area, for 4 weeks. The main outcome measures were serum 25(OH)D, PTH, calcium, phosphate, and alkaline phosphatase levels before and after sun exposure.

RESULTS

The mean UVBI was highest between 11 am and 1 pm throughout the year in all locations. The highest UVBI was recorded from the North zone (4.5 ± 2.7 μW/Cm(2)), while the least was recorded in the Northeast zone (2.1 ± 1.2 μW/Cm(2)). UVBI readings in the Northeast zone were consistently low throughout the year, while all the other three zones showed significant seasonal fluctuations. Surprisingly, we observed a significant decrease in serum 25(OH)D levels from baseline (6.3 ± 4.6 to 5.1 ± 2.7 ng/mL; p < 0.001) despite sun exposure.

CONCLUSION

The mean UVBI was highest between 11 am and 1 pm throughout the year in all locations. No increase in the serum 25(OH)D levels was observed following sun exposure in winter, emphasizing the need for vitamin D supplementation during these months.

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.

Assessment of the feasibility of using sunlight exposure to obtain the recommended level of vitamin D in Canada

BACKGROUND

Endogenous vitamin D synthesis can be affected by a number of variables, including skin colour, amount of skin exposed and levels of ultraviolet radiation. The objective of this study was to assess the feasibility of using only sunlight exposure in Canada to meet the daily recommended level of vitamin D, given differences in these variables and adherence to guidelines for sun protection.

METHODS

Ultraviolet index data for 13 Canadian sites were obtained from Environment Canada. The sun exposure times required to synthesize 1000 IU of vitamin D in fair- and dark-skinned people who exposed either 1/4 or 1/8 of their body surface area to the sun were calculated for each hour of the year. These times were then classified according to whether the ultraviolet index was 3 or more (when sun protection is advised) or less than 3.

RESULTS

During the fall and winter months and in the more northern sites, ultraviolet radiation levels were too low for all skin types to use sun exposure alone to obtain enough vitamin D within one time period. The required exposure time became longer when a smaller surface area was exposed. For people with darker skin, it can be difficult even in the summer to find opportunities outside of when sun protection is advised to use sunlight to obtain the recommended dose of vitamin D.

INTERPRETATION

Although sun exposure is an important source of vitamin D, Canadians should look to other safe sources to meet the body's vitamin D requirements throughout the year.

Determinants of vitamin D supplement use in Canadians

OBJECTIVE

To determine the prevalence of vitamin D supplement use in Canadian adults and associations with demographic and socio-economic variables.

DESIGN

Data from the Healthy Aging module of the Canadian Community Health Survey were used to investigate the prevalence of vitamin D supplement use in Canadians aged 45 years and over. The prevalence of supplement use stratified by various behavioural and demographic characteristics was calculated and adjusted models were used to find associations with those factors.

SETTING

The ten provinces of Canada.

SUBJECTS

Canadians aged 45 years and over who participated in the Healthy Aging module of the Canadian Community Health Survey from 2008-2009.

RESULTS

The highest observed prevalence for women was 48·0 % in the 65-69 years age group and the highest prevalence for men was 25·3 % in the 70-74 years age group. Women had higher odds of vitamin D supplement use than men in all age groups. Not using supplements was more common in smokers, those who did not engage in leisure-time physical activities and who were either overweight or obese. Vitamin D supplement use increased with household income and level of education, and decreased with self-perceived health. Supplement use was higher in those with chronic conditions.

CONCLUSIONS

The inverse association with self-perceived health could be partly explained by age, chronic conditions and increased use of health-care services. Associations with higher income and education suggest a strong socio-economic influence and that individuals may not have the expendable income to purchase vitamin D supplements or knowledge of their health benefits.

Photocarcinogenesis: an epidemiologic perspective on ultraviolet light and skin cancer

Photocarcinogenesis is the result of a complex interplay between ultraviolet radiation, DNA damage, mutation formation, DNA repair, apoptosis, and the immune system. Recent trends show an increase in incidence of both melanoma and nonmelanoma skin cancers. Some individuals have a genetic predisposition toward increased risk for skin cancer, whereas others experience increased risk through ultraviolet exposure and subsequent mutation formation. The initiation and propagation pathways of melanoma and nonmelanoma skin cancers differ but have some elements in common. The increase in incidence of skin cancer has been discovered to vary among age groups and gender.

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

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

Association of serum 25-hydroxyvitamin D with race/ethnicity and constitutive skin color in urban schoolchildren

The objective of this study was to determine the extent to which constitutive skin color explains racial/ethnic differences in serum 25-hydroxyvitamin D (25OHD) concentrations in urban schoolchildren. Analysis of covariance (ANCOVA) was used to determine associations of 25OHD with parent-reported race/ethnicity and constitutive skin color as measured by reflectance colorimeter [individual typology angle (ITA°; higher value corresponds to lighter skin)] in 307 Greater Boston schoolchildren aged 9-15 during October-December 2011. Nearly 60% of all children were inadequate in 25OHD (<20 ng/mL). Prevalence of inadequate 25OHD differed by race/ethnicity (p<0.001): white (46.6%), black (74.5%), Hispanic (64.7%), Asian (88.9%), and multi-racial/other (52.7%). Serum 25OHD increased 0.6 ng/mL per 10° increase in ITA° value (p<0.001). The prediction of 25OHD by race/ethnicity was slightly stronger than the prediction by skin color in separate models (R2=0.19, R2=0.16, respectively). Most of the variability in 25OHD in race/ethnicity was due to constitutive skin color in this group of racially diverse US children.

Vitamin D and asthma-life after VIDA?

The vitamin D hypothesis postulates that lower vitamin D levels are causally associated with increased asthma risk and asthma severity. Multiple epidemiological studies have shown an inverse relationship between circulating vitamin D levels (in the form of 25-hydroxy vitamin D) and asthma severity and control and lung function. However, in the recently published vitamin D and asthma (VIDA) study, vitamin D supplementation failed to show an improvement in asthma control in adults. This article reviews the current epidemiological and trial evidence for vitamin D and asthma and explores some of the possible alternative explanations for previous findings (including "reverse causation" and the importance of studying children and adults). We also address some of the unique challenges of conducting vitamin D trials and potential ways to address them. Finally, I will argue for further clinical trials of vitamin D in asthma, especially in children, using knowledge gained from the VIDA trial.

New advances in protection against solar ultraviolet radiation in textiles for summer clothing

Clothing is considered one of the most important tools for photoprotection against harmful solar ultraviolet radiation (UVR). The standard for sun-protective clothing is based on erythema despite other biological effects of UVR on the skin. We analyzed the potential protection against UVR in fabrics destined for summer clothing based on several action spectra. We examined 50 garments classified by type of fabric composition, structure of the fiber yarn and color. The ultraviolet protection factor was calculated based on fabric ultraviolet transmittance corrected for erythema according to the EU standard E-13758 as well as the UVA transmittance of fabrics. UVR protection was also analyzed in base of different action spectra as for previtamin D3, nonmelanoma skin cancer, photoimmunosuppression and photoaging. Most knitted fabrics used for sports T-shirts offered excellent ratings for ultraviolet protection while normal shirts showed very low ratings, particularly against photoaging. The cover is the most influential variable in fabric photoprotection, having an exponential relationship with the UPF. The relation between cover and UVA protection was linearly negative. Information about ultraviolet protection in textiles used for summer clothing should be included in labeling as some types of fabrics, especially those used for shirts, offer very low UVR protection.

Vitamin D deficiency in minority populations

OBJECTIVE

Black and Hispanic individuals synthesize less vitamin D per unit of sun exposure than white individuals. The relationship between UV radiation and vitamin D insufficiency in minorities has not been well explored.

DESIGN

Prospective cohort study.

SETTING

Using the National Health and Nutrition Examination Survey, we obtained serum vitamin D levels for non-Hispanic Whites, Hispanics and non-Hispanic Blacks aged ≥18 years from 2000-2006. We linked these data with the average monthly solar UV index by census tract and data on sun exposure, vitamin D supplementation, health and demographics. We used multivariable regression analyses to assess vitamin D deficiency (<15 ng/ml) and insufficiency (<20 ng/ml) in January (when the UV index was lowest) by race/ethnicity and geography.

SUBJECTS

Adults (n 14,319) aged ≥18 years.

RESULTS

A 1-point increase in the UV index was associated with a 0·51 ng/ml increase in vitamin D (95% CI 0·35, 0·67 ng/ml; P<0·001). Non-Hispanic Black race and Hispanic ethnicity were associated with a 7·47 and 3·41 ng/ml decrease in vitamin D, respectively (both P<0·001). In January, an estimated 65·4% of non-Hispanic Blacks were deficient in vitamin D, compared with 28·9% of Hispanics and 14·0% of non-Hispanic Whites. An estimated 84·2% of non-Hispanic Blacks were insufficient in vitamin D v. 56·3% of Hispanics and 34·8% of non-Hispanic Whites. More non-Hispanic Blacks were estimated to be deficient in vitamin D in January in the highest UV index quartile than were non-Hispanic Whites in the lowest UV index quartile (60·2% v. 25·7%).

CONCLUSIONS

Wintertime vitamin D insufficiency is pervasive among minority populations, and not uncommon among non-Hispanic Whites.