The Vitamin D Debate: Translating Controlled Experiments into Reality for Human Sun Exposure Times

Globally Estimated UVB Exposure Times Required to Maintain Sufficiency in Vitamin D Levels

A paucity of vitamin D is a common deficiency globally, with implications for many aspects of health besides the well-known impact on musculoskeletal health. The two sources of vitamin D are through oral intake, or through endogenous synthesis in the skin when exposed to ultraviolet radiation in sunlight. Assessing nutritional needs, whether by food, food fortification or supplementation, is aided by an understanding of local potential for cutaneous synthesis of the vitamin, dependent on latitude and climate, personal skin type and local culture. To aid these discussions we provide indicative exposure times for the maintenance of vitamin D status as a function of latitude, month and skin type, for the clear-sky case and all-sky conditions, for an ambulatory person wearing modest skirt/shorts and T-shirt. At latitudes greater than ±40 degrees, lack of available sunlight limits vitamin D synthesis in some months for all, while at the equator exposure times range from 3 to 15 min at noontime, for white and black skin, respectively. Rather than a sun exposure prescription, the data are intended to show where nutritional vitamin D intake is necessary, advisable, or can be mitigated by sun exposure, and allows for such advice to be personalized to account for different sub-groups in a multicultural population.

Making the sunshine vitamin - How much sun exposure is needed to maintain 25-hydroxy vitamin D concentration?

Our objective was to calculate the time in the sun necessary to maintain existing 25-hydroxyvitamin D (25(OH)D) concentration at locations across Australia and New Zealand. We used a microsimulation model to estimate changes in monthly 25(OH)D concentration using data on standard erythemal dose, solar zenith angle, and climatological ozone. We estimated the number of standard vitamin D doses per 10-min interval and used a dose-response equation to determine the average time in the sun to maintain existing 25(OH)D concentration according to month and time of day. Across all locations in summer, 5-10 min outdoors between 8 a.m. and 4 p.m. on most days of the week, with 35% of the body surface area exposed, is sufficient to maintain existing 25(OH)D concentration. In winter, at mid-to-high latitudes, time outdoors during the middle of the day is required. In winter, with 10% of the body surface area exposed, greater than 45 min in the middle of the day is required in most locations to maintain existing 25(OH)D concentration. These data can be used to inform guidelines regarding maintaining vitamin D via sun exposure and may help health practitioners identify patients who may be vitamin D deficient.

UV index-based model for predicting synthesis of (pre-)vitamin D3 in the mediterranean basin

The importance of solar radiation for the body's ability to synthesize Vitamin D3 is well documented, yet the precise amount of sun exposure required to avoid Vitamin D insufficiency is less clear. To address this knowledge gap, this study sought to utilize the sun in a suitable period at the optimum dose by utilizing numerical simulations to determine the amount of Vitamin D3 synthesis in the skin according to season, time of day, and geographical location in Turkey. The study was carried out in three stages; in the first stage, daily, monthly, and annual values were determined in cases where the solar zenith angle has the active UV-B wavelength. The second stage determined the level of Vitamin D that can be synthesized in all skin types at 25% solar radiation exposure. In the third stage, the sun exposure time required for 1000 International Units (IU) for all skin types was calculated. According to the analysis, the yearly period of active synthesis of D3 on Earth lasts from the beginning of March to the third week of October. During the day, it is between 10:00 and 16:00. For 1000 IU/day, the average annual estimated times (minutes) are 5.05 for Type I, 6.3 for Type II, 7.6 for Type III, 11.35 for Type IV, 15.15 for Type V, and 25.25 for Type VI. The results of this paper will impact awareness for academic-medical users.

Vitamin D and Sun Exposure: A Community Survey in Australia

Sun exposure carries both harms and benefits. Exposing the skin to the sun is the main modifiable cause of skin cancers, which exert a considerable health and economic burden in Australia. The most well-established benefit of exposure to ultraviolet (UV) radiation is vitamin D production. Australia has the highest incidence of skin cancer in the world but, despite the high ambient UV radiation, approximately one quarter of the population is estimated to be vitamin D deficient. Balancing the risks and benefits is challenging and requires effective communication. We sought to provide a snapshot of public knowledge and attitudes regarding sun exposure and vitamin D and to examine the associations between these factors and sun protective behaviors. In 2020 we administered an online survey; 4824 participants with self-reported fair or medium skin color were included in this analysis. Only 25% and 34% of participants were able to identify the amount of time outdoors needed to maintain adequate vitamin D status in summer and winter, respectively and 25% were concerned that sunscreen use inhibits vitamin D synthesis. This lack of knowledge was associated with suboptimal sun protection practices. Public education is warranted to prevent over-exposure, while supporting natural vitamin D production.

Retinol Binding Protein, Sunlight Hours, and the Influenza Virus-Specific Immune Response

Healthy pediatric immune responses depend on adequate vitamin A and D levels. Relationships between solar ultraviolet B (UVB) radiation and vitamin D are well understood, while relationships between sunlight, vitamin A, and its serum escort, retinol binding protein (RBP), are not. A pediatric clinical study enrolled 2–8-year-old children at various times between September 2016 and March 2017, inclusive, in Memphis, Tennessee. A serum sample from each child was then assayed to examine the influence of season on vitamin levels. We found that RBP and RBP/retinol molar ratios decreased in winter months and RBP/retinol ratios correlated positively with the average daily sunlight hours per month. A food frequency questionnaire given to parents/guardians indicated a shift in dietary intake from plant-based foods to animal-based foods by children between winter and spring months. This translated to higher retinol and zinc (integral to RBP–transthyretin–retinol complexes) in the spring, perhaps explaining the seasonal influence on RBP/retinol. RBP and retinol were associated positively with IgG/IgM and IgA/IgM ratios. RBP and retinol, but not 25(OH)D, also correlated positively with influenza virus-specific antibodies. Retinol correlated negatively, while 25(OH)D correlated positively, with certain serum cytokine/chemokine levels. Significant differences in 25(OH)D, immunoglobulin ratios, and cytokines/chemokines were observed between black and white children. In sum, seasonal changes in dietary foods rich in retinol and zinc may have influenced RBP levels, which in turn influenced innate and adaptive immune responses. Results encourage routine monitoring and reporting of season, RBP, and vitamin levels in future clinical studies, as seasons may affect sunlight exposures, diet, vitamin levels, and immune protection against infectious disease.

Vitamin D Sources, Metabolism, and Deficiency: Available Compounds and Guidelines for Its Treatment

Studies on vitamin/hormone D deficiency have received a vast amount of attention in recent years, particularly concerning recommendations, guidelines, and treatments. Moreover, vitamin D’s role as a hormone has been confirmed in various enzymatic, metabolic, physiological, and pathophysiological processes related to many organs and systems in the human body. This growing interest is mostly due to the evidence that modest-to-severe vitamin D deficiency is widely prevalent around the world. There is broad agreement that optimal vitamin D status is necessary for bones, muscles, and one’s general health, as well as for the efficacy of antiresorptive and anabolic bone-forming treatments. Food supplementation with vitamin D, or the use of vitamin D supplements, are current strategies to improve vitamin D levels and treat deficiency. This article reviews consolidated and emerging concepts about vitamin D/hormone D metabolism, food sources, deficiency, as well as the different vitamin D supplements available, and current recommendations on the proper use of these compounds.

The Combined Effect of Ozone and Aerosols on Erythemal Irradiance in an Extremely Low Ozone Event during May 2020

In this study we focus on measurements and modeled UV index in the region of Athens, Greece, during a low ozone event. During the period of 12–19 May 2020, total ozone column (TOC) showed extremely low values, 35–55 Dobson Units (up to 15%) decrease from the climatic mean (being lower than the −2σ). This condition favors the increase of UV erythemal irradiance, since stratospheric ozone is the most important attenuator at the UVB spectral region. Simultaneously, an intrusion of Saharan dust aerosols in the region has masked a large part of the low ozone effect on UV irradiance. In order to investigate the event, we have used spectral solar irradiance measurements from the Precision Solar Radiometer (PSR), TOC from the Brewer spectrophotometer, and Radiative Transfer Model (RTM) calculations. Model calculations of the UV Index (UVI) showed an increase of ~30% compared to the long-term normal UVI due to the low TOC while at the same time and for particular days, aerosols masked this effect by ~20%. The RTM has been used to investigate the response in the UV spectral region of these variations at different solar zenith angles (SZAs). Spectra simulated with the RTM have been compared to measured ones and an average difference of ~2% was found. The study points out the importance of accurate measurements or forecasts of both ozone and aerosols when deriving UVI under unusual low ozone–high aerosol conditions.

Nutrition and Athlete Immune Health: New Perspectives on an Old Paradigm

Respiratory and gastrointestinal infections limit an athlete's availability to train and compete. To better understand how sick an athlete will become when they have an infection, a paradigm recently adopted from ecological immunology is presented that includes the concepts of immune resistance (the ability to destroy microbes) and immune tolerance (the ability to dampen defence yet control infection at a non-damaging level). This affords a new theoretical perspective on how nutrition may influence athlete immune health; paving the way for focused research efforts on tolerogenic nutritional supplements to reduce the infection burden in athletes. Looking through this new lens clarifies why nutritional supplements targeted at improving immune resistance in athletes show limited benefits: evidence supporting the old paradigm of immune suppression in athletes is lacking. Indeed, there is limited evidence that the dietary practices of athletes suppress immunity, e.g. low-energy availability and train- or sleep-low carbohydrate. It goes without saying, irrespective of the dietary preference (omnivorous, vegetarian), that athletes are recommended to follow a balanced diet to avoid a frank deficiency of a nutrient required for proper immune function. The new theoretical perspective provided sharpens the focus on tolerogenic nutritional supplements shown to reduce the infection burden in athletes, e.g. probiotics, vitamin C and vitamin D. Further research should demonstrate the benefits of candidate tolerogenic supplements to reduce infection in athletes; without blunting training adaptations and without side effects.

Spectral transmission of solar radiation by plastic and glass materials

It is well known that excessive exposure to solar ultraviolet (UV) radiation can have serious adverse effects. Many everyday materials influence the UV radiation received by humans, for example, those used in construction and on the exterior of buildings such as plastics and glass can reduce the UV exposure of persons exposed to solar radiation. In this paper we analyse the spectral transmission of solar radiation of widely used materials using the transmittance parameter. The measurements were performed on clear days, at 8 h and 12 solar hours, in July 2018 (five days) and in January 2019 (three days). The spectral transmittances of these materials and the integrated transmittances in the UVB from 300 nm, UVA, visible (VIS) and near infrared ranges (NIR) were calculated. In summer in the UVB range from 300 nm methacrylate and smoked glass have the highest transmittance values (56%) and polycarbonate present the lowest (30%). In the VIS and NIR ranges methacrylate (95%) and smoked glass (80%) have the highest transmittances and polycarbonate the lowest (45%). In general the 8 h transmittances are higher than those at 12 h and are also higher in winter than summer. For two biological functions (erythemal and DNA-damage) and for the UVB range from 300 nm, the transmittance for most materials (except fibreglass) is in the range 6-14%. The exposure times obtained show that erythemal damage could occur after long exposure to solar radiation through the materials studied, information which should be made available to the general public.

Vitamin D and the hepatitis B vaccine response: a prospective cohort study and a randomized, placebo-controlled oral vitamin D3 and simulated sunlight supplementation trial in healthy adults

Purpose

To determine serum 25(OH)D and 1,25(OH)₂D relationship with hepatitis B vaccination (study 1). Then, to investigate the effects on hepatitis B vaccination of achieving vitamin D sufficiency (serum 25(OH)D ≥ 50 nmol/L) by a unique comparison of simulated sunlight and oral vitamin D₃ supplementation in wintertime (study 2).

Methods

Study 1 involved 447 adults. In study 2, 3 days after the initial hepatitis B vaccination, 119 men received either placebo, simulated sunlight (1.3 × standard-erythema dose, 3 × /week for 4 weeks and then 1 × /week for 8 weeks) or oral vitamin D₃ (1000 IU/day for 4 weeks and 400 IU/day for 8 weeks). We measured hepatitis B vaccination efficacy as percentage of responders with anti-hepatitis B surface antigen immunoglobulin G ≥ 10 mIU/mL.

Results

In study 1, vaccine response was poorer in persons with low vitamin D status (25(OH)D ≤ 40 vs 41–71 nmol/L mean difference [95% confidence interval] − 15% [− 26, − 3%]; 1,25(OH)₂D ≤ 120 vs ≥ 157 pmol/L − 12% [− 24%, − 1%]). Vaccine response was also poorer in winter than summer (− 18% [− 31%, − 3%]), when serum 25(OH)D and 1,25(OH)₂D were at seasonal nadirs, and 81% of persons had serum 25(OH)D < 50 nmol/L. In study 2, vitamin D supplementation strategies were similarly effective in achieving vitamin D sufficiency from the winter vitamin D nadir in almost all (~ 95%); however, the supplementation beginning 3 days after the initial vaccination did not effect the vaccine response (vitamin D vs placebo 4% [− 21%, 14%]).

Conclusion

Low vitamin D status at initial vaccination was associated with poorer hepatitis B vaccine response (study 1); however, vitamin D supplementation commencing 3 days after vaccination (study 2) did not influence the vaccination response.

Clinical trial registry number

Study 1 NCT02416895; https://clinicaltrials.gov/ct2/show/study/NCT02416895; Study 2 NCT03132103; https://clinicaltrials.gov/ct2/show/NCT03132103.

Electronic supplementary material

The online version of this article (10.1007/s00394-020-02261-w) contains supplementary material, which is available to authorized users.

Development and Effect Analysis of UVB-LED General Lighting to Support Vitamin D Synthesis

Ultraviolet rays from sunlight are involved in vitamin D synthesis, which is essential in maintaining health. Most in vivo vitamin D synthesis occurs via exposure to sunlight, whereas a small portion is obtained through diet. Therefore, appropriate exposure to sunlight is recommended to satisfy vitamin D requirement. However, vitamin D deficiency still poses a serious issue to numerous people. To resolve this problem, artificial lighting has been studied to provide rays of UV light with characteristics similar to that of sunlight. The present study introduced vitamin D synthesis stimulating UVB-LED light via the general diffusion lighting type to indoor dwellers. However, despite the strides of advancement made in this type of lighting, studies on UVB with relation to vitamin D synthesis are limited. This study aimed to suggest UVB-LED lighting for indoor dwellers and confirm the effectiveness of vitamin D stimulation through animal testing. For this, a UVB-LED providing safe UVB dosage was developed based on the photobiological safety (IEC 62471) of lighting. Next, a comparison study of the suggested lighting and general lighting was executed in an isolated system. The study continued for two weeks and the vitamin D levels within the animal test subject (Rat, Wistar, male) were measured. At this time, the lighting was turned on for 06:00~22:00 considering the sunrise timing and average lighting time for modern people, and blood was collected from the caudal veins of the rats and analyzed for the amount of 25-hydroxyvitamin D [25(OH)D]. Analysis results showed that the amount of 25-hydroxyvitamin D [25(OH)D] in blood was higher, on average, by 6.8% (0.97 ng/mL) and 7.3% (0.9 ng/ml) in rats reared under UVB-LED lighting on the seventh and fourteenth experimental days, respectively, than those under general lighting. It was, therefore, confirmed that vitamin D synthesis in the human body can be supported by the proposed lighting in this study.

Ultraviolet Exposure Scenarios: Balancing Risks of Erythema and Benefits of Cutaneous Vitamin D Synthesis

Exposure to sunlight is a major source of vitamin D for most people. Yet public health advice has focused overwhelmingly on avoiding exposure of unprotected skin because of the risks of erythema and skin cancer. Given that there are also health risks associated with low vitamin D status, we explore the possibilities of achieving a range of targets associated with vitamin D and the accompanying erythema risk. We have calculated the exposure required to gain a number of proposed oral-equivalent doses of vitamin D, as functions of latitude, season, skin type and skin area exposed, together with the associated risk of erythema, expressed in minimum erythema doses. The model results show that a recommended daily intake of 400 IU is readily achievable through casual sun exposure in the midday lunch hour, with no risk of erythema, for all latitudes some of the year, and for all the year at some (low) latitudes. We also show that such daily, sub-erythemal doses at lunchtime during the summer months is sufficient to avoid winter-time vitamin D deficiency for the UK all-weather climate, provided that lower arms and legs are exposed in the warmer months. At the higher proposed vitamin D dose of 1000 IU, lunchtime sun exposure is still a viable route to the vitamin but requires the commitment to expose greater areas of skin and is effective for a shorter period of the year. The highest vitamin D requirement considered was 4000 IU per day. For much of the globe and much of the year, this is not achievable in a lunchtime hour and where it is possible large areas of skin must be exposed to prevent erythema. When the only variable considered was skin type, latitudinal and seasonal limits on adequate vitamin D production were more restrictive for skin type 5 than skin type 2.

A Critical Appraisal of Strategies to Optimize Vitamin D Status in Germany, a Population with a Western Diet

During the last decade, our scientific knowledge of the pleiotropic biological effects of vitamin D metabolites and their relevance to human health has expanded widely. Beyond the well-known key role of vitamin D in calcium homeostasis and bone health, it has been shown that vitamin D deficiency is associated with a broad variety of independent diseases, including several types of cancer, and with increased overall mortality. Moreover, recent findings have demonstrated biological effects of the vitamin D endocrine system that are not mediated via activation of the classical nuclear vitamin D receptor (VDR) by binding with high affinity to its corresponding ligand, the biologically active vitamin D metabolite 1,25-dihydroxyvitamin D (1,25(OH)₂D). In contrast, many of these new biological effects of vitamin D compounds, including regulation of the circadian clock and many metabolic functions, are mediated by other vitamin D metabolites, including 20-hydroxyvitamin D and 20,23-dihydroxyvitamin D, and involve their binding to the aryl hydrocarbon receptor (AhR) and retinoid-orphan receptor (ROR). In most populations, including the German population, UVB-induced cutaneous vitamin D production is the main source for fulfilling the human body’s requirements of vitamin D. However, this causes a dilemma because solar or artificial UVR exposure is associated with skin cancer risk. In addition to UVB-induced vitamin D production in skin, in humans, there are two other possible sources of vitamin D: from diet and supplements. However, only a few natural foods contain substantial amounts of vitamin D, and in most populations, the dietary source of vitamin D cannot fulfill the body´s requirements. Because an increasing body of evidence has convincingly demonstrated that vitamin D deficiency is very common worldwide, it is the aim of this paper to (i) give an update of the vitamin D status in a population with a western diet, namely, the German population, and to (ii) develop strategies to optimize the vitamin D supply that consider both the advantages as well as the disadvantages/risks of different approaches, including increasing vitamin D status by dietary intake, by supplements, or by UVB-induced cutaneous synthesis of vitamin D.

Estimation of exposure durations for vitamin D production and sunburn risk in Switzerland

Although overexposure to solar ultraviolet radiation (UVR) is responsible for cutaneous melanoma and epithelial skin cancer and can cause negative health effects such as sunburn, a "little and often" exposure regime is often suggested to produce naturally recommended vitamin D levels, being essential for skeletal health. This study aimed to quantify solar UV doses needed to trigger 1000 International Units (IU) vitamin D doses and, at the same time, producing sunburn in Switzerland. Solar UV erythema irradiance (in mW/m2) measured at four meteorological stations in Switzerland for the period 2005-2017 were used to evaluate effective solar UV radiation producing 1000 IU vitamin D doses in skin phototype II and III individuals. Daily solar UV exposure durations (in minutes) needed to produce vitamin D with limited sunburn risk were estimated while considering mean vitamin D food intake of the Swiss population and seasonal skin coverage. In summer and spring, with 22% of uncovered skin, 1000 IU vitamin D doses are synthesized in 10-15 min of sun exposure for adults. Exposure durations between erythema risk and 1000 IU vitamin D production vary between 9 and 46 min. In winter and autumn, the recommended vitamin D production without sunburn risks often unachievable, since up to 6.5 h of sun exposure might be necessary considering 8-10% of uncovered skin surface. The vitamin D food intake only represented 10% of the recommended vitamin D production and remained unchanged throughout the year. These findings might clarify why vitamin D deficiency is common in Switzerland. Moreover, exposure durations between recommended vitamin D and increased sunburn risk might only differ by few minutes. Without additional oral vitamin D supplementation, daily doses of vitamin D (1000 IU) are not reachable in autumn and winter months in Switzerland.

Influence of Vitamin D Supplementation by Sunlight or Oral D3 on Exercise Performance

Purpose

To determine the relationship between vitamin D status and exercise performance in a large, prospective cohort study of young men and women across seasons (study 1). Then, in a randomized, placebo-controlled trial, to investigate the effects on exercise performance of achieving vitamin D sufficiency (serum 25(OH)D ≥ 50 nmol·L⁻¹) by a unique comparison of safe, simulated-sunlight and oral vitamin D₃ supplementation in wintertime (study 2).

Methods

In study 1, we determined 25(OH)D relationship with exercise performance in 967 military recruits. In study 2, 137 men received either placebo, simulated sunlight (1.3× standard erythemal dose in T-shirt and shorts, three times per week for 4 wk and then once per week for 8 wk) or oral vitamin D₃ (1000 IU·d⁻¹ for 4 wk and then 400 IU·d⁻¹ for 8 wk). We measured serum 25(OH)D by high-pressure liquid chromatography tandem mass spectrometry and endurance, strength and power by 1.5-mile run, maximum dynamic lift and vertical jump, respectively.

Results

In study 1, only 9% of men and 36% of women were vitamin D sufficient during wintertime. After controlling for body composition, smoking, and season, 25(OH)D was positively associated with endurance performance (P ≤ 0.01, ΔR² = 0.03–0.06, small f² effect sizes): 1.5-mile run time was ~half a second faster for every 1 nmol·L⁻¹ increase in 25(OH)D. No significant effects on strength or power emerged (P > 0.05). In study 2, safe simulated sunlight and oral vitamin D₃ supplementation were similarly effective in achieving vitamin D sufficiency in almost all (97%); however, this did not improve exercise performance (P > 0.05).

Conclusions

Vitamin D status was associated with endurance performance but not strength or power in a prospective cohort study. Achieving vitamin D sufficiency via safe, simulated summer sunlight, or oral vitamin D₃ supplementation did not improve exercise performance in a randomized-controlled trial.

[UV radiation in Germany: influences of ozone depletion and climate change and measures to protect the population]

Ultraviolet radiation (UV radiation) can lead to numerous skin and eye diseases, both immediately and later in life. The most serious consequence is skin cancer. The risk of skin cancer increases, among other things, with increasing UV irradiance and/or with increasing outdoor exposure times. Due to the fact that UV radiation is carcinogenic, protection of the population against harmful UV exposure is an important radiation protection and health objective.In Germany, ozone depletion and climate change can also influence the UV irradiance and outdoor exposure times to such an extent that the UV exposure of the population and thus the skin cancer risk can increase. This is why protection against harmful UV exposure is even more important. Since ozone depletion and climate change can further increase the UV exposure of humans, protection against high UV exposure is even more important. A country's adaptation strategies to the health consequences of ozone depletion and climate change should therefore also include strategies to reduce UV exposure.In this review, the health effects of UV radiation and the risk factors for UV-related skin cancer are first presented. The measurement of UV irradiance and exposure in Germany is explained. The effects of ozone depletion and climate change on UV exposure are then described and measures to protect the population are presented.

Designing Safe General LED Lighting that Provides the UVB Benefits of Sunlight

The ultraviolet (UV) rays emitted from sunlight greatly influence human health. Excessive exposure to UV rays can be harmful to eyes and skin; however, limited UVB exposure is essential for the synthesis of vitamin D. Nowadays, owing to insufficient exposure to natural light, there is increasing concerns about low vitamin D amongst individuals. To address this issue, many lighting devices that provide UVB doses have been released; however, such devices are only used for treatments or for special purposes. This study proposes a general indoor lighting system with a UVB LED light source to provide safe UVB doses to users who spend large amounts of time indoors. The optical characteristics of two UVB LEDs with output of 20 and 100 mW were analyzed based on their distances and applied currents. The light source combination of UVB LEDS that meets the UV hazard standard of IEC-62471 was derived; this is a photobiological safety evaluation standard of LED lighting devices. We then produced a lighting module in which the UVB LED light source was applied to general LED lighting and measured and analyzed the spectral irradiance of the proposed lighting according to the measurement standard for the general lighting of IEC 62471. The actinic UV hazard (AUV) and near-UV hazard (NUV) were calculated to be 0.001 and 10 W/m2, respectively. Thus, the provision of UVB dose did not pose any risks. In addition, the total EUV (Erythemal weighted UV) dose when the proposed lighting was implemented for 16 h was 187.66 J/m2, confirming that this dose did not cause erythema for the general skin types (Skin Types 1–6). Further, the design plan of general indoor lighting with a UVB LED light source is presented.

Sun Exposure Public Health Directives

There have been many public health recommendations for avoiding UV radiation exposures. This is primarily due to concerns about skin cancer and especially melanoma, the most serious type of skin cancer. However, UV radiation is also known as the primary source of vitamin D and other compounds needed for good health. This brief commentary lists several of the many important recent studies of adverse health effects associated with low sun exposure, including some specific cancers, multiple sclerosis, diabetes, cardiovascular disease, autism, Alzheimer's disease, and age-related macular degeneration. Our conclusion is that non-burning UV exposure is a health benefit and-in moderation-should be recommended as such.

Predictive Factors for Vitamin D Concentrations in Swiss Athletes: A Cross-sectional Study

Vitamin D concentrations corresponding to 75 nmol/L 25(OH)D have been associated with maintained muscle function, growth and regeneration, optimal bone health and immunology in athletes. The objective of this study was to investigate the prevalence and predictors of insufficient 25(OH)D concentrations in athletes. Six hundred three Swiss athletes were assessed. 25(OH)D was analysed by high-performance liquid chromatography (HPLC). A standardized questionnaire was used to gather information about potential predictors for 25(OH)D concentrations; 50.5% showed insufficient 25(OH)D concentrations. Differences in predicted probability of insufficient 25(OH)D were found for those vitamin D supplemented (42%) versus not supplemented (52%), in those performing indoor (58%) versus outdoor sports (43%), and during the sun-deprived seasons of fall (49%), winter (70%) and spring (57%) compared with summer (17%). Higher BMI z-scores and age were associated with higher 25(OH)D concentrations. In conclusion, insufficient 25(OH)D concentrations were common among athletes especially at a younger age, among those not supplemented, in athletes who trained indoors, and during the sun-deprived seasons. Because the prevalence of insufficient 25(OH)D concentrations in this study was high, regular supplementation in athletes may be indicated, except perhaps during the summer season. Further research is needed to determine which 25(OH)D concentrations lead to optimal health and performance in athletes.

UV Monitoring for Public Health

Overexposure to solar ultraviolet (UV) radiation is a risk for public health. Therefore, it is important to provide information to the public about the level of solar UV. The UV-Index (UVI) is the relevant quantity, expressing the erythemally weighted irradiance to a horizontal plane on a simple scale. As solar UV irradiance is strongly variable in time and space, measurements within a network provide the best source of information, provided they can be made available rapidly. However, to ensure the information is reliable, strict quality assurance/quality control (QA/QC) procedures for the monitoring networks are necessary. Near real time presentation of the measured UVI on web-pages is the best way to inform the public. The interpretation of the data in terms of the individual 'allowable' exposure time is heavily impacted by skin type, behavior, and clothing, and must be learned for each person through experience and guidance. Nonetheless, reliable knowledge of the actual level of the intensity of erythemally weighted irradiance and its variability forms the basis of education and public awareness. The challenges and requirements in providing comprehensive UVI data for public health guidance are here considered.

Is Sunlight Exposure Enough to Avoid Wintertime Vitamin D Deficiency in United Kingdom Population Groups?

Solar ultraviolet radiation (UVR) is required for cutaneous vitamin D synthesis, and experimental studies have indicated the levels of sun exposure required to avoid a vitamin D deficient status. Our objectives are to examine the sun exposure behaviours of different United Kingdom sectors and to identify if their exposure is enough to maintain winter circulating 25-hydroxyvitamin D above deficiency (>25 nmol/L). Data are from a series of human studies involving >500 volunteers and performed using the same protocols in Greater Manchester, UK (53.5° N) in healthy white Caucasian adolescents and working-age adults (skin type I⁻IV), healthy South Asian working-age adults (skin type V), and adults with photodermatoses (skin conditions caused or aggravated by cutaneous sun exposure). Long-term monitoring of the spectral ambient UVR of the Manchester metropolitan area facilitates data interpretation. The healthy white populations are exposed to 3% ambient UVR, contrasting with ~1% in South Asians. South Asians and those with photodermatoses wear clothing exposing smaller skin surface area, and South Asians have the lowest oral vitamin D intake of all groups. Sun exposure levels prevent winter vitamin D deficiency in 95% of healthy white adults and 83% of adolescents, while 32% of the photodermatoses group and >90% of the healthy South Asians were deficient. The latter require increased oral vitamin D, whilst their sun exposure provides a tangible contribution and might convey other health benefits.

Meeting Vitamin D Requirements in White Caucasians at UK Latitudes: Providing a Choice

The body gains vitamin D through both oral intake (diet/supplementation) and synthesis in skin upon exposure to ultraviolet radiation (UVR). Sun exposure is the major source for most people even though sun exposure is complex and limited by climate and culture. We aimed to quantify the sun exposure required to meet vitamin D targets year-round and determine whether this can be safely achieved in a simply defined manner in the UK as an alternative to increasing vitamin D oral intake. Data from observation (sun exposure, diet, and vitamin D status) and UVR intervention studies performed with white Caucasian adults were combined with modeled all-weather UVR climatology. Daily vitamin D effective UVR doses (all-weather) were calculated across the UK based on ten-year climatology for pre-defined lunchtime exposure regimes. Calculations then determined the time necessary to spend outdoors for the body to gain sufficient vitamin D levels for year-round needs without being sunburnt under differing exposure scenarios. Results show that, in specified conditions, white Caucasians across the UK need nine minutes of daily sunlight at lunchtime from March to September for 25(OH)D levels to remain ≥25 nmol/L throughout the winter. This assumes forearms and lower legs are exposed June-August, while in the remaining, cooler months only hands and face need be exposed. Exposing only the hands and face throughout the summer does not meet requirements.

Colour Counts: Sunlight and Skin Type as Drivers of Vitamin D Deficiency at UK Latitudes

Sunlight exposure, with resulting cutaneous synthesis, is a major source of vitamin D for many, while dietary intake is low in modern diets. The constitutive pigment in skin determines skin type, observed as white, brown, or black skin. The melanin pigment absorbs ultraviolet radiation (UVR) and protects underlying skin from damage caused by UVR. It also reduces the UVR available for vitamin D synthesis in the skin. It has been shown that the white-skinned population of the UK are able to meet their vitamin D needs with short, daily lunchtime exposures to sunlight. We have followed the same methodology, based on a 10-year UK all-weather UVR climatology, observation (sun exposure, diet, vitamin D status), and UVR intervention studies with Fitzpatrick skin type V (brown) adults, to determine whether sunlight at UK latitudes could provide an adequate source of vitamin D for this section of the population. Results show that to meet vitamin D requirements, skin type V individuals in the UK need ~25 min daily sunlight at lunchtime, from March to September. This makes several assumptions, including that forearms and lower legs are exposed June-August; only exposing hands and face at this time is inadequate. For practical and cultural reasons, enhanced oral intake of vitamin D should be considered for this population.

Serum endocannabinoids and N-acyl ethanolamines and the influence of simulated solar UVR exposure in humans in vivo

Solar ultraviolet radiation (UVR) exposure of human skin has beneficial and harmful effects on health, including impact on immune function, inflammation and reportedly mood, but these are not fully elucidated. Since the endocannabinoid system is implicated in many activities including mood alteration, our objective was to (i) determine and quantify circulating levels of a wide range of endocannabinoid and N-acyl ethanolamine (NAE) species (ii) evaluate whether these are modulated by cutaneous UVR exposures, as attained through repeated low level summer sunlight exposure. Wearing goggles to prevent eye exposure, 16 healthy volunteers (23-59 y; 10 light skin, phototype II, and 6 dark skin, phototype V) received the same UVR exposures (1.3 SED, 95% UVA/5% UVB) thrice weekly for 6 weeks, whilst casually dressed to expose ∼35% skin surface area. Blood samples were taken at baseline, days 1, 3 and 5 of week one, then at weekly intervals, and analysed by LC-MS/MS. Eleven endocannabinoids and NAEs were detected and quantified at baseline, with N-palmitoyl ethanolamine the most abundant (30% of total). Levels did not vary according to phototype (p > 0.05), except for the NAE docosapentaenoyl ethanolamide, which was higher in phototype II than V (p = 0.0002). Level of the endocannabinoid, 2-AG, was elevated during the UVR exposure course (p < 0.05 vs. baseline for all subjects; p < 0.01 for each phototype group), with maximum levels reached by week 2-3, while NAE species did not significantly alter. These findings suggest differential involvement of the cutaneous endocannabinoid system in low dose solar UVR responses in humans.

Contribution of sun exposure to the vitamin D dose received by various groups of the Spanish population

Although the harmful effects of excessive exposure to solar ultraviolet (UV) radiation are well known, the recommended dose of UV radiation is beneficial for the synthesis of vitamin D by the skin, in addition to being useful in the treatment of various illnesses and mental problems. Numerous studies have shown that vitamin D performs important functions in the human organism, such as absorbing calcium and phosphorous and contributing to the immune system, among others. Several studies have found that a high percentage of various groups of the Spanish population suffer from vitamin D deficiency, and since very few natural foods contain vitamin D, it was considered important to determine whether groups such as schoolchildren, outdoor workers and athletes, receive enough solar radiation to produce adequate levels of vitamin D in their daily activities. It was found that the amount of vitamin D (in IU) produced by personal effective solar UV doses could exceed the recommended dose of 1000IU/day in spring and summer, while the winter estimate (about 220IU/day) is only one quarter of the recommended dose. These results suggest that most people would not receive the recommended daily vitamin D dose in winter from exposure to solar UV radiation, the main source of vitamin D.

A new in vitro assay to test UVR protection of dermal extracellular matrix components by a flat spectrum sunscreen

The efficacy of topical sunscreens is currently assessed by crude, costly and time consuming in vivo assays. We have previously demonstrated that components of the dermal extracellular matrix (ECM), rich in UV-absorbing amino acids, are susceptible to damage by solar simulated radiation (SSR) in vitro. Here we developed an in vitro method to test the ability of sunscreens to protect fibrillin-rich microfibrils (FRM) and fibronectin, key components of the dermal ECM from UV-induced damage. Solutions of FRM or fibronectin were irradiated without protection, in the presence of a vehicle or a commercially-available flat-spectrum sunscreen. The effect of SSR on molecular structure was determined by atomic force microscopy (FRM) and SDS-PAGE (fibronectin). Following irradiation, FRM periodicity became bi-modally distributed (peaks: 40nm & 59nm) compared to the unimodal distribution in unexposed controls (peak: 50nm). Irradiation in the presence of flat-spectrum sunscreen protected against this change, maintaining the unimodal distribution. SSR induced significant aggregation of fibronectin (p=0.005), which was abrogated by sunscreen. These results demonstrate that this in vitro assay system is sufficiently sensitive to act as an initial/additional screen of sunscreen efficacy. We conclude that sunscreen can reduce UV-mediated damage of key dermal ECM in vitro and thereby prevent remodelling associated with photoageing.

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.

Concurrent beneficial (vitamin D production) and hazardous (cutaneous DNA damage) impact of repeated low-level summer sunlight exposures

Background

The concurrent impact of repeated low‐level summer sunlight exposures on vitamin D production and cutaneous DNA damage, potentially leading to mutagenesis and skin cancer, is unknown.

Objectives

This is an experimental study (i) to determine the dual impact of repeated low‐level sunlight exposures on vitamin D status and DNA damage/repair (via both skin and urinary biomarkers) in light‐skinned adults; and (ii) to compare outcomes following the same exposures in brown‐skinned adults.

Methods

Ten white (phototype II) and six South Asian volunteers (phototype V), aged 23–59 years, received 6 weeks’ simulated summer sunlight exposures (95% ultraviolet A/5% ultraviolet B, 1·3 standard erythemal doses three times weekly) wearing summer clothing exposing ~35% body surface area. Assessments made were circulating 25‐hydroxyvitamin D [25(OH)D], immunohistochemistry for cyclobutane pyrimidine dimer (CPD)‐positive nuclei and urinary biomarkers of direct and oxidative (8‐oxo‐deoxyguanosine) DNA damage.

Results

Serum 25(OH)D rose from mean 36·5 ± 13·0 to 54·3 ± 10·5 nmol L⁻¹ (14·6 ± 5·2 to 21·7 ± 4·2 ng mL⁻¹) in phototype II vs. 17·2 ± 6·3 to 25·5 ± 9·5 nmol L⁻¹ (6·9 ± 2·5 to 10·2 ± 3·8 ng mL⁻¹) in phototype V (P < 0·05). Phototype II skin showed CPD‐positive nuclei immediately postcourse, mean 44% (range 27–84) cleared after 24 h, contrasting with minimal DNA damage and full clearance in phototype V (P < 0·001). The findings did not differ from those following single ultraviolet radiation (UVR) exposure. Urinary CPDs remained below the detection threshold in both groups; 8‐oxo‐deoxyguanosine was higher in phototype II than V (P = 0·002), but was unaffected by UVR.

Conclusions

Low‐dose summer sunlight exposures confer vitamin D sufficiency in light‐skinned people concurrently with low‐level, nonaccumulating DNA damage. The same exposures produce minimal DNA damage but less vitamin D in brown‐skinned people. This informs tailoring of sun‐exposure policies.

What's already known about this topic?

Repeated low‐level exposures to simulated U.K. sunlight can produce vitamin D sufficiency in light‐skinned people, but the concurrent impact on cutaneous DNA damage is unknown.

What does this study add?

Low‐level simulated sunlight exposures in people of skin phototype II conferred vitamin D sufficiency concurrently with DNA damage, which showed partial clearance at 24 h and no evidence of accumulated damage after 6 weeks of exposures.

The same exposures produced minimal DNA damage but less vitamin D in brown‐skinned people (phototype V).

The findings are informative for sun‐exposure guidance.

Plain language summary available online

Vitamin D production in UK Caucasian and South Asian women following UVR exposure

BACKGROUND

It is known that skin pigmentation reduces the penetration of ultraviolet radiation (UVR) and thus photosynthesis of 25-hydroxvitamin D (25(OH)D). However ethnic differences in 25(OH)D production remain to be elucidated.

OBJECTIVE

The aim of this study was to investigate differences in vitamin D production between UK South Asian and Caucasian postmenopausal women, in response to a defined and controlled exposure to UVR.

DESIGN

Seventeen women; 9 white Caucasian (skin phototype II and III), 8 South Asian women (skin phototype IV and V) participated in the study, acting as their own controls. Three blood samples were taken for the measurement of vitamin D status during the run in period (9days, no sunbed exposure) after which, all subjects underwent an identical UVR exposure protocol irrespective of skin colour (9 days, 3 sun bed sessions, 6, 8 and 8min respectively with approximately 80% body surface exposed). Skin tone was measured four times during the study.

RESULTS

Despite consistently lower 25(OH)D levels in South Asian women, they were shown to synthesise vitamin D as efficiently as Caucasians when exposed to the same dose of UVR. Interestingly, the baseline level of vitamin D rather than ethnicity and skin tone influenced the amount of vitamin D synthesised.

CONCLUSIONS

This study have found no ethnic differences in the synthesis of 25(OH)D, possibly due to the baseline differences in 25(OH)D concentration or due to the small population size used in this study. Applying mixed linear model, findings indicated no effect of ethnicity and skin tone on the production of vitamin D; baseline level and length of exposure were the critical factors. To confirm that ethnicity and skin tone has no effect on 25(OH)D production, a larger sample size study is required that considers other ethnic groups with highly pigmented skin. Initial vitamin D status influences the amount of UVB needed to reach equal serum concentrations.

UV "Indices"-What Do They Indicate?

Ultra-Violet (UV) radiation covers the spectrum of wavelengths from 100 to 400 nm. The potency and biological activity for a variety of endpoints differ by wavelength. For monitoring and communication purposes, different UV action spectra have been developed. These spectra use different weighting functions. The action spectrum for erythemal dose is the most widely used one. This erythemal dose per time or dose-rate has been further simplified into a “UV index”. Following this example, in our review we use the term “index” or (plural) “indices” in a more general description for all simplified single-value measures for any biologically effective UV dose, e.g., for human non-melanoma skin cancer and for previtamin D production rate. Ongoing discussion about the existence of an increased melanoma risk due to UV-A exposure underscores the uncertainties inherent in current weighting functions. Thus, we performed an online literature search to review the data basis for these indices, to understand their relevance for an individual, and to assess the applicability of the indices for a range of exposure scenarios. Even for natural (solar) UV, the spectral composition varies spatially and temporally. Artificial UV sources and personal protection introduce further variation to the spectral composition. Many biological effects are proposed for UV radiation. Only few endpoints have been studied sufficiently to estimate a reliable index. Weighting functions for chronic effects and most importantly for cancer endpoints have been developed in animal models, and often for proxy endpoints only. Epidemiological studies on biological effects of UV radiation should not only depend on single-value weighted UV dose estimates (indexes) but should strive for a more detailed description of the individual exposure. A better understanding of the adverse and beneficial effects of UV radiation by wavelength would also improve medical counseling and health communication regarding individual health-supportive behavior.

Ultraviolet radiation and effects on humans: the paradigm of maternal vitamin D production during pregnancy

Current evidence indicates that neonates born of mothers with vitamin D deficiency during pregnancy have greater risk for developing hypocalcemia, rickets and extra-skeletal disorders. Despite the classic knowledge that ultraviolet-B (UVB) exposure is the most efficient way for a future mother to obtain optimal vitamin D concentrations, no current consensus or clinical recommendations exist regarding the duration and timing of UVB exposure for pregnant women. This article offers a narrative review of available data regarding how UVB exposure affects maternal vitamin D production during pregnancy, along with a discourse on clinical implications of this public health issue. Future studies would benefit from adopting UVB exposure estimates to recommend appropriate UVB exposure to pregnant women. Doing so could provide a more holistic and practical approach in managing maternal hypovitaminosis D during pregnancy.

Optimal vitamin D3 daily intake of 2000IU inferred from modeled solar exposure of ancestral humans in Northern Tanzania

Recently, high serum 25-hydroxyvitamin D concentration (~110nmol/L) was found in the Hadza tribe still keeping ancient hunter-gather life style. This level could serve as optimal vitamin D level that was built during millennia of human evolution. The personal vitamin D3 effective solar exposures of the Hadza adults are estimated using radiative model simulations with input from the satellite observations over lake Eyasi (3.7°S, 35.0°E). The calculations are carried out assuming the Hadza typical clothing habits and specific scenarios of the out-door activity comprising early morning and late afternoon working time in sun and prolonged midday siesta in the shade. The modeled doses received by the Hadza are converted to the vitamin D3 effective daily doses pertaining to the lighter skinned persons. We propose a novel formula to get adequate vitamin D level - exposure of 1/3 MED around local noon to 1/3 part of the whole body during warm sub-period of the year in the low- and mid-latitude regions. Such daily solar exposure is equivalent to ~2000IU of vitamin D3 taken orally. For many contemporary humans with limited out-door activity habit achieving such daily norm requires vitamin D3 supplementation of 2000IU throughout the whole year.

European Code against Cancer 4th Edition: Ultraviolet radiation and cancer

Ultraviolet radiation (UVR) is part of the electromagnetic spectrum emitted naturally from the sun or from artificial sources such as tanning devices. Acute skin reactions induced by UVR exposure are erythema (skin reddening), or sunburn, and the acquisition of a suntan triggered by UVR-induced DNA damage. UVR exposure is the main cause of skin cancer, including cutaneous malignant melanoma, basal-cell carcinoma, and squamous-cell carcinoma. Skin cancer is the most common cancer in fair-skinned populations, and its incidence has increased steeply over recent decades. According to estimates for 2012, about 100,000 new cases of cutaneous melanoma and about 22,000 deaths from it occurred in Europe. The main mechanisms by which UVR causes cancer are well understood. Exposure during childhood appears to be particularly harmful. Exposure to UVR is a risk factor modifiable by individuals' behaviour. Excessive exposure from natural sources can be avoided by seeking shade when the sun is strongest, by wearing appropriate clothing, and by appropriately applying sunscreens if direct sunlight is unavoidable. Exposure from artificial sources can be completely avoided by not using sunbeds. Beneficial effects of sun or UVR exposure, such as for vitamin D production, can be fully achieved while still avoiding too much sun exposure and the use of sunbeds. Taking all the scientific evidence together, the recommendation of the 4th edition of the European Code Against Cancer for ultraviolet radiation is: "Avoid too much sun, especially for children. Use sun protection. Do not use sunbeds."

A modeling approach to determine how much UV radiation is available across the UK and Ireland for health risk and benefit studies

Monthly average vitamin D effective UV doses (J m⁻²) over UK based on data for years 2003–2012. The southern part receives 1.5–2 times more UV than the north during spring, summer and autumn. Doses at coastal sites being up to 25% higher than inland areas.

Projected changes in erythemal and vitamin D effective irradiance over northern-hemisphere high latitudes

Changes in the effective dose for the production of vitamin D and in the UV index are investigated for the past and future relative to the present over the northern high latitudes for two socioeconomic scenarios. Large decreases (the order of 30–50%) have been found between the present and the future.

The consequences for human health of stratospheric ozone depletion in association with other environmental factors

Ozone depletion, climate and human health.

Ozone depletion and climate change: impacts on UV radiation

Percentage changes in the UV Index (UVI) for 2090 relative to 2015 due to changes in ozone (left) and aerosols (right) only. Large decreases are projected over Antarctica due to stratospheric ozone recovery. Increases are projected for parts of Asia due to decreases in aerosols, partly reversing the possible large reductions in UVI after the 1950s.

Serum lipoprotein composition and vitamin D metabolite levels in clinically isolated syndromes: Results from a multi-center study

CONTEXT

High serum cholesterol is adversely associated with clinical and imaging disease progression outcomes in multiple sclerosis (MS) and in clinically isolated syndrome (CIS), the earliest stage of MS. Low vitamin D levels are associated with an increased risk of disease progression.

OBJECTIVES

To investigate the mechanisms mediating the adverse effects of cholesterol in CIS and to determine the role of the nexus between the vitamin D3 (D3) and cholesterol pathways.

DESIGN

Multi-center, prospective, longitudinal prospective study.

SETTING

University hospital multiple sclerosis centers.

INTERVENTION

Serum samples were obtained prior to any treatment from study subjects.

METHODS

Serum obtained prior to any treatment from 172 CIS patients enrolled in a multi-center, prospective, longitudinal study (119 females: 53 males, age: 28.1 ± SD 8.1 years) were analyzed for high-density lipoprotein cholesterol (HDL-C), low-density lipoprotein cholesterol (LDL-C), apolipoprotein AI (ApoAI), ApoAII, ApoB, ApoE, and lipoprotein-a. Levels of 25-hydroxy vitamin D3 (25(OH)D3), 1,25-dihydroxy D3, and 24,25-dihydroxy D3 were measured using liquid chromatography-mass spectrometry.

RESULTS

Greater levels of HDL-C biomarkers (e.g., HDL-C itself, ApoAI, ApoAII and paroxonase arylesterase activity) and LDL-C biomarkers (e.g., LDL-C itself, Apo B) were associated with greater 25(OH)D3. The effects of HDL-C biomarkers were stronger than those of LDL-C. Free cholesterol and cholesteryl ester levels were positively associated with higher 25(OH)D3 levels. Cholesterol palmitate was particularly potent. The nexus between the D3 and cholesterol pathways was proximal to, or in linkage disequilibrium with, 7-dehydrocholesterol reductase DHCR7 rs1790349, endothelial lipase LIPG rs4939883 and proprotein convertase subtilisin/kexin type 9 PCSK9 rs11206510.

CONCLUSIONS

The associations between cholesterol biomarkers and vitamin D metabolite levels in CIS are consistent with the biochemical inter-dependence between the two pathways. Cholesterol biomarkers should be considered for inclusion as covariates when assessing vitamin D levels in CIS.

Influence of external, intrinsic and individual behaviour variables on serum 25(OH)D in a German survey

The objective of the present study was to identify external, intrinsic or behavioural factors that significantly influenced serum 25-hydroxyvitamin D (25(OH)D) concentrations in a German survey. Data from 3061 participants in the Cooperative Health Research in the Region of Augsburg, Germany (KORA) F4 survey were used to relate potential determinants to measured mean serum 25(OH)D concentrations using multivariable regression models. The factors significantly associated with hypovitaminosis D (defined as 25(OH)D<25 nmolL(-1)) were season (winter, spring and autumn), urban environment and high body mass index. In contrast, times spent in sunny regions, hours per day spent outdoors in the summer as well as additional oral intake were associated with higher 25(OH)D concentrations. These results suggest that mainly ambient UV exposure but also individual behaviour are the most important determinants for personal 25(OH)D concentrations. The analyses further showed that in winter 43% of subjects were vitamin D deficient and 42% insufficient. Even in summer over half the population has insufficient vitamin D status with 8% deficient and 47% insufficient. Therefore measures to mitigate widespread vitamin D insufficiency such as regular short-term sun exposure and/or improved dietary intake/supplementation recommendations by public health bodies need to be considered.

Occupational UV exposure of environmental agents in Valencia, Spain

Excessive exposure to ultraviolet radiation (UVR) is considered the most important environmental risk factor in the development of melanoma and skin cancer. Outdoor workers are among those with the highest risk from exposure to solar UVR, as their daily activities constantly expose them to this radiation source. A study was carried out in Valencia, Spain, in summer 2012 and involved a group of 11 workers for a period of six 2-day recordings. Sensitive spore-film filter-type personal dosimeters (VioSpor) were used to measure erythemal UVR received by environmental agents in the course of their daily work. Median 2-day UV exposure was 6.2 standard erythema dose (SED), with 1 SED defined as effective 100 J m(-2) when weighted with the Commission Internationale de L'Eclairage's (CIE) erythemal response function. These workers were found to receive a median of 8.3% total daily ambient ultraviolet erythemal radiation. Comparison with the occupational UV exposure limit showed that the subjects had received an erythemal UV dose in excess of occupational guidelines, indicating that protective measures against this risk are highly advisable.

Personal UV exposure for different outdoor sports

The aim of this paper is to measure UV exposure for three groups of amateur athletes in their training/recreational schedules using VioSpor personal dosimeters and we found that two of these groups exceeded the international UV threshold level for non-sun-adapted Mediterranean skin.

Solar UV exposure in construction workers in Valencia, Spain

Exposure to ultraviolet radiation (UVR) has long been recognized as the most important environmental risk factor for melanoma and skin cancer. Outdoor workers are among the groups most at risk from exposure to solar UVR in their daily activities. Sensitive spore-film filter-type personal dosimeters (VioSpor) were used to measure the biologically effective UVR received by construction workers in the course of their daily work. The study took place in Valencia, Spain, in July 2010 and involved a group of eight workers for a period of 5 days. The median UV exposure was 6.11 standard erythema dose (SED) per day, with 1 SED defined as effective 100 J/m(2) when weighted with the Commission Internationale de L'Eeclairage erythemal response function. These workers were found to receive a median of 13.9% of total daily ambient ultraviolet erythemal radiation (UVER). Comparison with the occupational UVR exposure limit showed that the subjects had received UVER exposure in excess of occupational guidelines, indicating that protective measures against this risk are highly advisable.

Efficacy of a dose range of simulated sunlight exposures in raising vitamin D status in South Asian adults: implications for targeted guidance on sun exposure

BACKGROUND

Vitamin D is essential for bone health, and cutaneous synthesis is an important source. South Asians cannot attain adequate amounts of vitamin D by following general recommendations on summer sunlight exposure at northerly latitudes, and increased exposure may be appropriate for improving their vitamin D status.

OBJECTIVE

We examined the efficacy of a dose range of simulated summer sunlight exposures in raising vitamin D status in UK adults of South Asian ethnicity.

DESIGN

In a dose-response study, healthy adults of South Asian ethnicity (n = 60; 20-60 y old) received 1 of 6 ultraviolet exposures ranging from 0.65 to 3.9 standard erythema doses (SEDs), which were equivalent to 15-90 min unshaded noontime summer sunlight at 53.5°N (Manchester, United Kingdom), 3 times/wk for 6 wk, while wearing casual clothes that revealed a 35% skin area. Serum 25-hydroxyvitamin D [25(OH)D] was measured weekly, and dietary vitamin D was estimated.

RESULTS

At baseline, all completing participants (n = 51) were vitamin D insufficient [25(OH)D concentrations <20 ng/mL], and a high proportion of participants were deficient [35% of subjects had 25(OH)D concentrations <5 ng/mL, and 90% of subjects had 25(OH)D concentrations <10 ng/mL, which are concentrations at which osteomalacia and rickets occur). The 25(OH)D concentration rose significantly in all dose groups. Postcourse, all participants achieved 25(OH)D concentrations ≥5 ng/mL, whereas only 6 subjects attained 25(OH)D concentrations ≥20 ng/mL. Participants who received exposures ≥1.95 SEDs (equivalent to 45 min unshaded sunlight; n = 33) attained a mean (±SD) 25(OH)D concentration of 15.7 ± 5 ng/mL (mean rise: 8.7 ± 5.7 ng/mL; 95% CI: 6.8, 10.6 ng/mL; P < 0.001), and 94% of subjects achieved concentrations >10 ng/mL.

CONCLUSIONS

Targeted guidance on sunlight exposure could usefully enhance vitamin D status to avoid deficiency [25(OH)D concentration >10 ng/mL] in South Asians living at latitudes distant from the equator. This trial was registered at the ISRCTN Register (www.isrctn.org) as 07565297.

Minimal Erythema Dose (MED) testing

Ultraviolet radiation (UV) therapy is sometimes used as a treatment for various common skin conditions, including psoriasis, acne, and eczema. The dosage of UV light is prescribed according to an individual's skin sensitivity. Thus, to establish the proper dosage of UV light to administer to a patient, the patient is sometimes screened to determine a minimal erythema dose (MED), which is the amount of UV radiation that will produce minimal erythema (sunburn or redness caused by engorgement of capillaries) of an individual's skin within a few hours following exposure. This article describes how to conduct minimal erythema dose (MED) testing. There is currently no easy way to determine an appropriate UV dose for clinical or research purposes without conducting formal MED testing, requiring observation hours after testing, or informal trial and error testing with the risks of under- or over-dosing. However, some alternative methods are discussed.

A novel method to calculate solar UV exposure relevant to vitamin D production in humans

We present a novel method to calculate vitamin D3 -weighted exposure by integrating the incident solar spectral radiance over all relevant parts of the human body. Earlier investigations are based on the irradiance on surfaces, whereas our calculated exposure of a voxel model of a human takes into account the complex geometry of the radiation field. Assuming that sufficient vitamin D3 (1000 international units) can be produced within the human body in one minute for a completely uncovered body in vertical posture in summer at midlatitudes (e.g. Rome, June 21, noon, UV index of 10), we calculate the exposure times needed in other situations or seasons to gain enough vitamin D3 . Our calculations show that the UV index is not a good indicator for the exposure which depends on the orientation of the body (e.g. vertical (standing) or horizontal (lying down) posture). Without clothing the exposure is dominated by diffuse sky radiation and it is nearly irrelevant how the body in vertical posture is oriented toward the sun. At the winter solstice (December 21, noon, cloudy) at least in central Europe sufficient vitamin D3 cannot be obtained with realistic clothing, even if the exposure were extended to all daylight hours.

Vitamin D supply: from sun or pill? - Attitudes and recommendation on vitamin D and impact on sun protection practices among German general practitioners evaluated by the network of dermato-oncologists, Onkoderm e.V

Recommendations concerning the intake of vitamin D and/or sunlight exposure in the handling of patients with vitamin D deficiency remain a matter of debate. The present study of the German network of dermato-oncologists (Onkoderm e.V.) refers to an inquiry conducted among general practitioners on this and related issues. Based on 448 answers provided to 10 distinct questions, the consulted physicians recommended vitamin D intake (94% replies) and/or exposure to sunlight (63% replies) in their patients with vitamin D deficiency. An average of approximately 26 min daily unprotected exposure to sunlight at midday in spring and summer was recommended. Nevertheless, 91% of the physicians considered the use of creams protecting against sunlight to be judicious. However, only 54% of physicians considered it worthwhile practice to protect oneself intensively against UV radiation. This study indicates evidence of a reduction in sun protection practices. Yet, approximately 25% of the patients were considered to present vitamin D deficiency and, hence, recommendations to prevent or correct the latter situation should not be ignored. Nevertheless, we consider that there is a need to focus messages regarding sun exposure and for continued sun protection practices. These messages should specifically focus on the vitamin D issue to ensure that the incidence of skin cancer does not increase.

Associations of Sun Exposure with 25-Hydroxyvitamin D and Parathyroid Hormone Levels in a Cohort of Hypertensive Patients: The Graz Endocrine Causes of Hypertension (GECOH) Study

Sunlight-induced vitamin D, synthesis in the skin is the major source of vitamin D, but data on the relationship of sun-related behaviour with vitamin D and parathyroid hormone (PTH) levels are relatively sparse. We evaluated whether habitual sun exposure is associated with 25-hydroxyvitamin D (25[OH]D) and PTH levels and whether there exist seasonal variations. We examined 111 hypertensive patients in Austria (latitude 47° N). Frequent sunbathing at home and outdoor sports were associated with higher 25(OH)D levels (P < 0.05 for both). Red or blond scalp hair as a child, memory of sunburns, preferring sunbathing, frequent stays on the beach or in open-air pools, and solarium use were associated with lower PTH levels (P < 0.05 for all). Multiple linear regression analyses including age, sex, and body mass index showed that sun exposure score was significantly associated with 25(OH)D (beta coefficient = 0.27; P = 0.004) and by trend with PTH (beta coefficient = -0.16; P = 0.09). These associations were more prominent in summer in which 25(OH)D levels were significantly higher compared to winter. Translation of these findings into recommendations for the prevention and treatment of vitamin D deficiency remains a challenge for the future.