Sunscreens block cutaneous vitamin D production with only a minimal effect on circulating 25-hydroxyvitamin D

Ultraviolet Filters: Dissecting Current Facts and Myths

Skin cancer is a global and increasingly prevalent issue, causing significant individual and economic damage. UV filters in sunscreens play a major role in mitigating the risks that solar ultraviolet ra-diation poses to the human organism. While empirically effective, multiple adverse effects of these compounds are discussed in the media and in scientific research. UV filters are blamed for the dis-ruption of endocrine processes and vitamin D synthesis, damaging effects on the environment, induction of acne and neurotoxic and carcinogenic effects. Some of these allegations are based on scientific facts while others are simply arbitrary. This is especially dangerous considering the risks of exposing unprotected skin to the sun. In summary, UV filters approved by the respective governing bodies are safe for human use and their proven skin cancer-preventing properties make them in-dispensable for sensible sun protection habits. Nonetheless, compounds like octocrylene and ben-zophenone-3 that are linked to the harming of marine ecosystems could be omitted from skin care regimens in favor of the myriad of non-toxic UV filters.

Association between food intake patterns and serum vitamin D concentrations in US adults

The objective of this study was to investigate the association between food patterns and serum vitamin D concentrations in US adults. Data from two cycles of National Health and Nutrition Examination Surveys, 2003-2004 and 2005-2006, were used (n 6637). Three major food patterns were derived using factor analysis. These three patterns were labeled as meat and processed meat foods (MPF), vegetables, fruit, nuts, and whole grains (VFNW), and sweet, snack, and beverage pattern (SSB). Serum vitamin D was measured with RIA and later standardized to reflect the assay changes over time. In multivariate-adjusted regression analysis, the MPF pattern was significantly, inversely associated with serum vitamin D concentrations (P < 0·001). However, the relation between the VFNW pattern and serum vitamin D was non-linear (P < 0·001). There was no relationship between SSB pattern and serum vitamin D in US adults. In conclusion, persons with a high intake of meat and processed meats are associated with lower serum vitamin D concentrations. Reducing processed foods and emphasizing VFNW will be beneficial from a health perspective.

Novelty Cosmetic Filters Based on Nanomaterials Composed of Titanium Dioxide Nanoparticles

The following work describes the synthesis of new physical filters based on TiO₂/SiO₂ and TiO₂/Ag nanostructures. Titanium dioxide nanoparticles (TiO₂ NPs) were applied as control material and a popular physical UV filter. The advantage of using materials on the nanometer scale is the elimination of the skin whitening effect that occurs when using photoprotective cosmetics containing titanium dioxide on a macro scale. In addition, the silica coating makes the material less harmful, and the silver coating enriches the material with antibacterial properties. Nanoparticles and nanostructures have been characterized by Energy Dispersive X-Ray Analysis (EDX), the Scanning Electron Microscope (SEM), Transmission Electron Microscopy (TEM), and Fourier-Transform Infrared Spectroscopy (FT-IR) methods. Due to the use of physical filters in anti-radiation protection cosmetics, water-in-oil (W/O) emulsion has been prepared. All cosmetic formulations have been tested for stability. The sun protection research with the Sun Protection Diagnostic SP37 was carried out. These studies made it possible to determine the natural sun protection time and to compare the synthesized materials. Furthermore, one of the most important parameters when describing this type of cosmetic is water resistance, which has also been measured. The results show that the new type of material of TiO₂/Ag used as a new physical filter in emulsion W/O shows the best sun protection compared with other obtained nanomaterials. It is most likely due to the improved optical properties of the combination of noble metals, for example, silver with TiO₂.

Vitamin D Status in Japanese Young Women in 2016-2017 and 2020: Seasonal Variation and the Effect of Lifestyle Including Changes Caused by the COVID-19 Pandemic

Avoidance of sunlight and self-restraint due to the COVID-19 pandemic may contribute to reduced vitamin D status. This study provides comparable data on vitamin D status in Japanese young women and assesses the effect of lifestyle, including changes caused by the COVID-19 pandemic, on vitamin D status. In study 1, 39 young healthy Japanese women aged 21-25 y were recruited from May 2016-June 2017. Serum 25-hydroxyvitamin D (25OHD) concentration and diet and lifestyle information were obtained from participants each month (n=124). In study 2, using the same parameters as study 1, young women aged 21-23 y (n=10) were recruited in September 2020. In the results of study 1, we found the frequencies of vitamin D deficiency (25OHD<20 ng/mL) in spring, summer, fall, and winter were 90.5%, 62.5%, 81.5%, and 91.3%, respectively. The substantial difference of serum 25OHD concentration was obtained in spring (Δ3.6 ng/mL) and summer (Δ5.1 ng/mL) depending on the frequency of sunscreen use (0-2 d/wk, 3-7 d/wk). In study 2, serum 25OHD concentration in September 2020 was extremely lower than in September 2016 (13.2 ng/mL vs. 21.7 ng/mL). The number of days spent outside in 2020 decreased drastically compared with 2019. In conclusion, vitamin D deficiency was highly common in Japanese women in their early 20s, and frequent sunscreen use contributed to low vitamin D status. Moreover, because the decrease in days outside due to the COVID-19 pandemic obviously resulted in a decline in vitamin D status, both appropriate sunbathing and increased dietary vitamin D intake are recommended to young women.

Association of Sun-Protective Behaviors With Bone Mineral Density and Osteoporotic Bone Fractures in US Adults

Importance

Despite the reassuring emerging evidence on the lack of a causal relationship between sun protection and vitamin D deficiency, there is scarce data on whether multimodal sun protection is associated with reduced bone mineral density (BMD) and/or increased prevalence of osteoporotic bone fractures. This lack of data may lead to worry and decreased sun-protective behaviors on the part of patients.

Objective

To investigate the association of sun-protective behaviors with BMD z scores and the prevalence of osteoporotic fractures.

Design, Setting, and Participants

This population-based cross-sectional study included data from US adults who participated in the 2017 to 2018 cycle of the National Health and Nutrition Examination Survey (NHANES). Data were analyzed between September and November 2020.

Main Outcomes and Measures

Definition of sun-protective behaviors (staying in the shade, wearing long sleeves, and sunscreen use), site-specific and total BMD, and osteoporotic fractures (hip, wrist, and spine) in the NHANES data.

Results

Data from 3418 adults 20 years and older (average age, 39.5 [95% CI, 38.6-40.4] years; 1612 [47.2%] men and 1806 [52.9%] women) who completed the NHANES dermatology questionnaire were included in this study. The prevalence of frequent staying in the shade, wearing of long sleeves, and sunscreen use were 31.6% (95% CI, 27.8%-35.7%), 11.8% (95% CI, 10.6%-13.1%), and 26.1% (95% CI, 23.5%-28.8%), respectively. The use of individual sun-protective behaviors was not associated with diminished site-specific and total BMD z scores in the multivariate models (estimate, -0.23 [95% CI, -0.47 to 0.02], P = .18; -0.08 [-0.27 to 0.12], P = .72; and -0.10 [-0.32 to 0.13], P = .15 for frequent staying in the shade, wearing of long sleeves, and sunscreen use, respectively). Moderate to frequent staying in the shade was associated with reduced prevalence of spine fractures in the multivariate model (odds ratio, 0.19 [95% CI, 0.04-0.86], P = 0.02).

Conclusion and Relevance

In this cross-sectional study, routine use of sun-protective behaviors among the US adult population was not associated with decreased BMD or increased risk of osteoporotic fracture. Sun protection may be associated with a modest decrease in the prevalence of osteoporotic fractures, possibly owing to risk-averse behaviors. These reassuring findings add to the growing body of evidence on the safety of sun protection, with no considerable negative association with bone health.

Non-Musculoskeletal Benefits of Vitamin D beyond the Musculoskeletal System

Vitamin D, a fat-soluble prohormone, is endogenously synthesized in response to sunlight or taken from dietary supplements. Since vitamin D receptors are present in most tissues and cells in the body, the mounting understanding of the role of vitamin D in humans indicates that it does not only play an important role in the musculoskeletal system, but has beneficial effects elsewhere as well. This review summarizes the metabolism of vitamin D, the research regarding the possible risk factors leading to vitamin D deficiency, and the relationships between vitamin D deficiency and numerous illnesses, including rickets, osteoporosis and osteomalacia, muscle weakness and falls, autoimmune disorders, infectious diseases, cardiovascular diseases (CVDs), cancers, and neurological disorders. The system-wide effects of vitamin D and the mechanisms of the diseases are also discussed. Although accumulating evidence supports associations of vitamin D deficiency with physical and mental disorders and beneficial effects of vitamin D with health maintenance and disease prevention, there continue to be controversies over the beneficial effects of vitamin D. Thus, more well-designed and statistically powered trials are required to enable the assessment of vitamin D’s role in optimizing health and preventing disease.

Vitamin D protects against immobilization-induced muscle atrophy via neural crest-derived cells in mice

Vitamin D deficiency is a recognized risk factor for sarcopenia development, but mechanisms underlying this outcome are unclear. Here, we show that low vitamin D status worsens immobilization-induced muscle atrophy in mice. Mice globally lacking vitamin D receptor (VDR) exhibited more severe muscle atrophy following limb immobilization than controls. Moreover, immobilization-induced muscle atrophy was worse in neural crest-specific than in skeletal muscle-specific VDR-deficient mice. Tnfα expression was significantly higher in immobilized muscle of VDR-deficient relative to control mice, and was significantly elevated in neural crest-specific but not muscle-specific VDR-deficient mice. Furthermore, muscle atrophy induced by limb immobilization in low vitamin D mice was significantly inhibited in Tnfα-deficient mice. We conclude that vitamin D antagonizes immobilization-induced muscle atrophy via VDR expressed in neural crest-derived cells.

Advances in Prevention and Surveillance of Cutaneous Malignancies

Skin cancer affects 1 in 5 Americans, resulting in significant morbidity and mortality. Treatment costs and rates of skin cancer and melanoma continue to rise, making preventative measures increasingly important. However, there is conflicting evidence about efficacy of primary and secondary prevention strategies in decreasing incidence and improving early diagnosis. The US Preventative Services Task Force 2016 guidelines did not endorse routine skin cancer screening because of "insufficient evidence." Yet, countries like Australia have shown the feasibility and cost-effectiveness of primary sun safety interventions and secondary prevention measures such as routine skin cancer surveillance. Additional emerging evidence shows that regular skin cancer screening in high-risk populations improves early detection and decreases melanoma mortality. New technology may enhance prevention, promote accurate diagnoses, and improve management of melanoma and nonmelanoma skin cancers. Here, we place rising rates of melanoma within historical context, review costs, efficacy, and evidence for primary and secondary skin cancer prevention and examine the evolving role of novel technologies in the field.

Advances and controversies in studying sunscreen delivery and toxicity

This review critically evaluates the sunscreen delivery and toxicity field. We chose to focus on approved sunscreens in this review. Optimal sunscreen use prevents skin cancer and photoageing but there is an important knowledge gap in sunscreen/skin interactions. Sunscreen delivery is a key for efficacy, but studying sunscreen delivery is not straightforward. We review the strengths and weaknesses of in vitro, excised skin and clinical approaches. Understanding positive and negative sunscreen effects on skin homeostasis is also challenging. The results in this field, especially in vitro testing, are controversial and experimental design varies widely which further supports disparities between some findings. We hypothesize that bias towards showing sunscreen toxicity to increase impact could be problematic. We explore that perception through a detailed review of experimental design, especially in cell culture models. Our conclusion is that emerging, non- and minimally invasive technologies are enabling new approaches to volunteer studies that could significantly improve knowledge of sunscreen delivery and interactions.

Prevalence and predictors of vitamin D insufficiency in adult population of yazd - The sun province in center of Iran

BACKGROUND

Vitamin D insufficiency (VDI) is one of impaired calcium absorption causes. It is associated with increased risk of several diseases. The aim of this study was to survey the prevalence and predictors of VDI in Yazd.

METHOD AND MATERIAL

This cross sectional study was conducted on 700 participant aged between 20 and 70 years old on second phase of the Iranian Multi-Center Osteoporosis Study (IMOS) in Yazd province. All analyzes were performed with the SPSS 20 and Stata 14.1 software. Chi-squared test, Pearson correlation and binary logistic regression were used. A significance level was considered for all tests P ≤ 0.05.

RESULTS

The prevalence of VDI was 55.1% (51.37-58.87%) in total participant of this study. Predictors of VDI including: age 31-45 years old (OR = 1.68, CI = 1.04-2.70), female (OR = 3.49, CI = 1.80-6.78), live in the apartment houses (OR = 2.15, CI = 1.06-4.35), inability of climbing of steps (OR = 2.59, CI = 1.17-5.69), serum Calcium (OR = 0.53, CI = 0.34-0.81) and serum PTH (OR = 1.04, CI = 1.02-1.06).

CONCLUSIONS

The prevalence of VDI in Yazd is high. It is recommended to people that to be exposed to sunlight per day. And people should consumption vitamin D supplements under their physician.

Sunscreen products: Rationale for use, formulation development and regulatory considerations

The association of sunrays with skin damage have been known since medieval times. The description of the electromagnetic spectrum facilitated the identification of the ultraviolet light spectrum as being responsible for skin damage resulting from prolonged skin exposure. Sunscreens have been used since ancient civilizations with various measures to limit exposure to sun exposure being employed. Awareness of the risks associated with sunrays has been increasing in the last century, and as a result, the science, technologies, and formulation have advanced significantly. The use of sunscreen products continues rising as government health agencies seek to contain increasing cases of UV induced melanomas. Recreational sunbathing and artificial tanning have increased the risk for these diseases significantly. This review article sought to expound the scientific basis of sunscreen use, the classification, formulation, quality control and regulation across the different countries around the world. The literature review was conducted on Google scholar, PubMed, SCOPUS, Cochrane, BMJ, SCIELO among others.

Sunscreen photoprotection and vitamin D status

Background

Global concern about vitamin D deficiency has fuelled debates on photoprotection and the importance of solar exposure to meet vitamin D requirements.

Objectives

To review the published evidence to reach a consensus on the influence of photoprotection by sunscreens on vitamin D status, considering other relevant factors.

Methods

An international panel of 13 experts in endocrinology, dermatology, photobiology, epidemiology and biological anthropology reviewed the literature prior to a 1‐day meeting in June 2017, during which the evidence was discussed. Methods of assessment and determining factors of vitamin D status, and public health perspectives were examined and consequences of sun exposure and the effects of photoprotection were assessed.

Results

A serum level of ≥ 50 nmol L⁻¹ 25(OH)D is a target for all individuals. Broad‐spectrum sunscreens that prevent erythema are unlikely to compromise vitamin D status in healthy populations. Vitamin D screening should be restricted to those at risk of hypovitaminosis, such as patients with photosensitivity disorders, who require rigorous photoprotection. Screening and supplementation are advised for this group.

Conclusions

Sunscreen use for daily and recreational photoprotection does not compromise vitamin D synthesis, even when applied under optimal conditions.

What's already known about this topic?

Knowledge of the relationship between solar exposure behaviour, sunscreen use and vitamin D is important for public health but there is confusion about optimal vitamin D status and the safest way to achieve this.

Practical recommendations on the potential impact of daily and/or recreational sunscreens on vitamin D status are lacking for healthy people.

What does this study add?

Judicious use of daily broad‐spectrum sunscreens with high ultraviolet (UV) A protection will not compromise vitamin D status in healthy people.

However, photoprotection strategies for patients with photosensitivity disorders that include high sun‐protection factor sunscreens with high UVA protection, along with protective clothing and shade‐seeking behaviour are likely to compromise vitamin D status.

Screening for vitamin D status and supplementation are recommended in patients with photosensitivity disorders.

Linked Comment: https://doi.org/10.1111/bjd.18126.

https://doi.org/10.1111/bjd.18494 available online

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.

The effect of sunscreen on vitamin D: a review

BACKGROUND

Sunscreen use can prevent skin cancer, but there are concerns that it may increase the risk of vitamin D deficiency.

OBJECTIVES

We aimed to review the literature to investigate associations between sunscreen use and vitamin D₃ or 25 hydroxyvitamin D [25(OH)D] concentration.

METHODS

We systematically reviewed the literature following the Meta-analysis Of Observational Studies in Epidemiology (MOOSE) guidelines. We identified manuscripts published in English between 1970 and 21 November 2017. Eligible studies were experimental [using an artificial ultraviolet radiation (UVR) source], field trials or observational studies. The results of each of the experimental studies and field trials are described in detail. Two authors extracted information from observational studies, and applied quality scoring criteria that were developed specifically for this question. These have been synthesized qualitatively.

RESULTS

We included four experimental studies, three field trials (two were randomized controlled trials) and 69 observational studies. In the experimental studies sunscreen use considerably abrogated the vitamin D₃ or 25(OH)D production induced by exposure to artificially generated UVR. The randomized controlled field trials found no effect of daily sunscreen application, but the sunscreens used had moderate protection [sun protection factor SPF) ~16]. The observational studies mostly found no association or that self-reported sunscreen use was associated with higher 25(OH)D concentration.

CONCLUSIONS

There is little evidence that sunscreen decreases 25(OH)D concentration when used in real-life settings, suggesting that concerns about vitamin D should not negate skin cancer prevention advice. However, there have been no trials of the high-SPF sunscreens that are now widely recommended. What's already known about this topic? Previous experimental studies suggest that sunscreen can block vitamin D production in the skin but use artificially generated ultraviolet radiation with a spectral output unlike that seen in terrestrial sunlight. Nonsystematic reviews of observational studies suggest that use in real life does not cause vitamin D deficiency. What does this study add? This study systematically reviewed all experimental studies, field trials and observational studies for the first time. While the experimental studies support the theoretical risk that sunscreen use may affect vitamin D, the weight of evidence from field trials and observational studies suggests that the risk is low. We highlight the lack of adequate evidence regarding use of the very high sun protection factor sunscreens that are now recommended and widely used.

Optimizing ultraviolet B radiation exposure to prevent vitamin D deficiency among pregnant women in the tropical zone: report from cohort study on vitamin D status and its impact during pregnancy in Indonesia

Background

Vitamin D deficiency during pregnancy carries potential threat to fetal well being. Natural conversion of vitamin D in the skin can be facilitated by direct ultra violet B (UVB) radiation, but the effect is reduced by wearing umbrellas, clothes, or sunblock cream. Muslim women wear hijab that allows only face and hands to be seen. With increasing proportion of muslim women wearing hijab and the lack of vitamin D fortification and fish consumption in Indonesia, it poses a problem for vitamin D deficiency among pregnant women. This study aimed at finding the best timing of UVB exposure and the duration of exposure which can be suggested to prevent vitamin D deficiency among pregnant women, for those wearing hijab or not.

Methods

This study recruited 304 pregnant women in the first trimester, 75–76 women from 4 cities of the most populated province, West Java, Indonesia which represented 70–80% percent of pregnancy per year. A 3-day notes on duration, time and type of outdoor activity and the clothing wore by the women were collected. UVB intensity radiation were obtained. Calculation on body surface area exposed to direct UVB radiation and UVB radiation intensity were done. Measurement of vitamin D level in sera were done on the same week.

Results

The median of maternal sera vitamin D level was 13.6 ng/mL and the mean exposed area was around 0.48 m2 or 18.59% of total body surface area. Radiation intensity reached its peak around 10.00 and 13.00, but the mean duration of exposure to UVB during this window was lower than expected. Significant correlation was found between maternal sera vitamin D level and exposed body surface area (r = 0.36, p < 0.002) or percentage of exposed body surface (r = 0.39, p < 0.001) and radiation intensity (r = 0.15, p = 0.029). Further analysis showed that duration of exposure to UVB should be longer for pregnant women wearing hijab as compared to women without hijab.

Conclusion

This study suggested that the best timing to get UVB exposure was between 10.00–13.00, with longer duration for women wearing hijab (64.5 vs 37.5 min) of continuous exposure per day.

Electronic supplementary material

The online version of this article (10.1186/s12884-019-2306-7) contains supplementary material, which is available to authorized users.

Lung disease and vitamin D levels in cystic fibrosis infants and preschoolers

INTRODUCTION

Vitamin D acts on the immune system and lung response. Patients with cystic fibrosis (CF) may be deficient in this vitamin. The aims of the study were to evaluate vitamin D levels and severity of lung disease in infants and preschoolers diagnosed with CF, and to compare them to a group of children without pancreatic insufficiency (PI).

METHODS

Patients with CF up to 4 years old were included, and compared to an age-matched group of children without diagnosis of CF. CF group had medical records and High Resolution Thorax Computed Tomography (HRCCT) evaluated in order to verify the severity of lung disease. Information on demographic data, sun exposure habits, supplemental vitamin D therapy, and on the season at the time of vitamin D sampling were collected for both groups.

RESULTS

This study included 45 patients in the CF group and 102 in the non-CF group, with no differences in age (P = 0.327) between them. There was no association between vitamin D levels and markers of lung disease in the CF group. The non-CF group had lower daily sun exposure (P = 0.034), and lower supplementation than the CF group (P < 0.001). Supplementation and seasonality were the determinant variables for vitamin D levels, which were lower for non-supplemented children and for assessments during fall/winter.

CONCLUSION

There was no association between lung disease severity and vitamin D levels in CF group. Supplementation and seasonality were associated to higher vitamin levels.

The Role of Vitamin D in Pediatric Orthopedics

Understanding the role of vitamin D is an important component of the proper care of the pediatric orthopedic patient. Vitamin D is an essential component of bone metabolism in the growth and development of the pediatric skeleton, which can be acutely affected by changes to the body's vitamin D, calcium, and phosphate levels, resulting in pathologic conditions such as rickets or fractures. This article reviews the main areas in which vitamin D relates to pediatric orthopedics and highlights some of the areas where future research is being directed.

When to apply sunscreen: a consensus statement for Australia and New Zealand

INTRODUCTION

Cancers of the skin are the most common cancers in humans, with Australia and New Zealand having the world's highest incidence. Primary prevention campaigns advise people to apply sunscreen to exposed body sites when outdoors. However, despite growing evidence that cumulative sub-erythemal exposures cause mutational damage, and trial data demonstrating benefit from daily sunscreen use, current policies do not consider the hazards of incidental (everyday) sun exposure. Thus, a Sunscreen Summit was convened to review the evidence and update the policies for people living in Australia and New Zealand.

RESULTS

After reviewing the benefits and risks of sunscreen application, the policy group concluded that people living in Australia and New Zealand should be advised to apply sunscreen to the face/head/neck and all parts of the body not covered by clothing on all days when the ultraviolet index is forecast to reach three or greater, irrespective of their anticipated activities. For planned outdoors activities, sunscreen should be used alongside other sun protection measures.

CONCLUSIONS

People living in Australia and New Zealand are now advised to apply sunscreen every day when the UV index is predicted to reach 3 or above. Implications for public health: Increased use of sunscreen as part of the daily routine to reduce incidental sun exposure will lead to decreased incidence of skin cancer in the future.

Evaluation of vitamin D plasma levels after mild exposure to the sun with photoprotection

BACKGROUND

Most of the organism's vitamin D (VD) is obtained through the cutaneous synthesis after exposure to the sun's UVB radiation. Sunscreens are indicated for the prevention of actinic damage to the skin, however, there are few clinical trials assessing the synthesis of cutaneous VD in real-life situations of sun exposure with ordinary clothing and usual photoprotection.

OBJECTIVES

To evaluate the synthesis of VD with suberythemal sun exposure in healthy adults using topical photoprotection (SPF 30).

METHODS

Quasi-experimental study, conducted at Rio de Janeiro (Brazil), during winter, with 95 healthy adults who had 25-OH-VD checked twice, 24 hours apart, and were exposed to the sun (UVB=20 mJ/cm2), according to a randomized grouping: SC - use of SPF 30 on the face, neck and chest (n=64), NO - no sunscreens (n=10), CO - confined from sun exposure for 24h (n=21). The groups were matched according to the propensity score related to gender, age, phototype, body mass index, glycosylated hemoglobin and baseline levels of VD. The outcome evaluated was the variation (ΔVD) in serum level of 25-OH-VD (ng/ml) between the groups.

RESULTS

A statistically significant difference was identified between CO and SC groups [median (p25-p75)]: ΔVD =1.4 (-0.3-3.6) vs. 5.5 (4.8-6.6); p<0.01. There was no difference between SC and NO groups: 5.4 (3.1-6.1) vs. 4.1 (2.5-6.0); p=0.17.

STUDY LIMITATIONS

Laboratory analysis technique (chemiluminescence) with great variability, loss of food intake standardatization, unbalanced groups.

CONCLUSIONS

Suberythemal sun exposure with sunscreen (SPF 30) provides similar vitamin D serum variation than without photoprotection in healthy adults.

Effect of sun exposure on cognitive function among elderly individuals in Northeast China

Background

Previous findings on the relationship between serum 25-hydroxyvitamin D [25(OH)D] level and cognitive impairment have been inconsistent. One reason is that serum 25(OH)D has a relatively short half-life, but the development of cognitive impairment is a long-term process. Skin exposure to solar ultraviolet radiation is the primary source of vitamin D synthesis. For this study, we hypothesized that people with different sun exposure behaviors would have different cognitive functions.

Methods

This study included 1,192 rural-dwelling elders in People’s Republic of China whose sun exposure behaviors, including the duration of outdoor activities, use of sun protection, and time of day participants engaged in outdoor activities, were collected. Their global cognitive function was assessed by Mini-Mental State Examination (MMSE). Partitioning cluster analysis was used to classify participants into groups based on their sun exposure behaviors. Ordinal logistic regression analysis was used to examine the association between sun exposure and cognitive function.

Results

The participants were divided into high-, medium-, and low-sun-exposure groups by cluster analysis. The participants in the high-sun-exposure group had the longest sun exposure time, reported the least sun-protective behaviors, and usually spent time outdoors in the morning (8:00–11:00) and afternoon (13:00–16:00). The participants in the low-sun-exposure group had the shortest sun exposure time, had the most positive sun-protective behaviors, and mainly spent time outdoors in the early morning (6:00–8:00) and late afternoon (16:00–18:00). After adjusting for potential confounders, participants with habitually high sun exposure were more likely to have higher MMSE score (25.4) than those with habitually low sun exposure (MMSE score =24.4).

Conclusion

Long-term high sun exposure is positively related with better cognitive functioning.

Predicting serum vitamin D concentrations based on self-reported lifestyle factors and personal attributes

Evidence supports the role of vitamin D in various conditions of development and ageing. Serum 25-hydroxyvitamin D (25(OH)D) is the best indicator for current vitamin D status. However, the cost of its measurement can be prohibitive in epidemiological research. We developed and validated multivariable regression models that quantified the relationships between vitamin D determinants, measured through an in-person interview, and serum 25(OH)D concentrations. A total of 200 controls participating in a population-based case-control study in Montreal, Canada, provided a blood specimen and completed an in-person interview on socio-demographic, reproductive, medical and lifestyle characteristics and personal attributes. Serum 25(OH)D concentrations were quantified by liquid chromatography-tandem MS. Multivariable least squares regression was used to build models that predict 25(OH)D concentrations from interview responses. We assessed high-order effects, performed sensitivity analysis using the lasso method and conducted cross-validation of the prediction models. Prediction models were built for users and non-users of vitamin D supplements separately. Among users, alcohol intake, outdoor time, sun protection, dose of supplement use, menopausal status and recent vacation were predictive of 25(OH)D concentrations. Among non-users, BMI, sun sensitivity, season and recent vacation were predictive of 25(OH)D concentrations. In cross-validation, 46-47 % of the variation in 25(OH)D concentrations were explained by these predictors. In the absence of 25(OH)D measures, our study supports that predicted 25(OH)D scores may be used to assign exposure in epidemiological studies that examine vitamin D exposure.