Vitamin D level in summer and winter related to measured UVR exposure and behavior

Evaluation of the efficacy of a sunscreen containing ultra-long UVA1 and other UVR broad-spectrum filters on skin barrier protection and melanin content reduction in Chinese adults: A single-center study

Background and Aims

The protection for ultra-long UVA1 is lacked in the market, posing potential damage from ultra-long UVA1 irradiation. The study aims to evaluate the efficacy of a sunscreen containing multiple components, especially Mexoryl® 400 for improving skin barrier function and reducing melanin content.

Methods

This single-center study included adults with sensitive and normal skin in China in November 2022. Participants received the test sunscreen for 4 weeks. Melanin and hemoglobin content, sebum secretion skin hydration, and trans-epidermal water loss were evaluated at T0d, T7d, and T28d. The self-assessment was done at T15min, T7d, and T28d.

Results

Sixty participants were included, including 30 self-claimed sensitive skin in the sunscreen group. The sunscreen demonstrated significant improvements in skin parameters. Skin redness reduced by 9.84% at T28d, sebum content in the forehead area decreased by 22.70% at T28d, and skin stratum corneum hydration increased by 38.44% at T28d, p < 0.001 respectively. Most notably, skin melanin content significantly reduced by 13.49% after 4 weeks' usage (p < 0.001). No adverse reactions were reported in either group.

Conclusions

The study sunscreen improved the skin condition by decreasing the melanin content, regulating skin barrier function, and achieving a balance of skin hydration and sebum secretion.

Vitamin D: determinants of status, indications for testing and knowledge in a convenience sample of Irish adults

Vitamin D deficiency is common in Irish adults, though there is limited research on its determinants, knowledge of vitamin D or indications for testing. We aimed to explore the determinants of vitamin D status in adults and examine knowledge and reasons for testing. The study population comprised adults who had serum 25-hydroxyvitamin D tested by general practitioners request at a Dublin Hospital in 2020. Questionnaires detailing dietary intake, sun exposure, ethnicity, biophysical factors and vitamin D knowledge were sent to a sample stratified by age, sex and vitamin D status. In total, there were 383 participants, mean age 56·0 (sd 16·6) years. Wintertime deficiency disproportionally affected non-white v. white (60 % v. 24 %, P < 0·001). The greatest predictors of deficiency were low vitamin D intake (< 10 μg/d) (P < 0·001) and non-white ethnicity (P = 0·006), followed by sun avoidance (P = 0·022). It was also more prevalent in those with lower body exposure when outdoors. The majority (86 %) identified vitamin D as important for bone health. However, 40 % were tested for non-clinical indications and half were not aware of the recommended daily allowance (RDA). Low vitamin D intake was the most important determinant of deficiency, but ethnicity and sun exposure habits were also significant predictors. The majority had no clear indication for testing and were not aware of the RDA. Public health policies to improve knowledge and vitamin D intake, especially for those of non-white ethnicity and with reduced sun exposure, should be considered.

Interaction of Passive Smoking and Diet Habits on Vitamin D Deficiency among Women of Reproductive Age in Rural Central China

Objective: Maternal dietary undernutrition is known to be associated with the risk of vitamin D (VD) deficiency. However, whether the risk of VD deficiency in women of reproductive age is influenced by the interaction between passive smoking and inadequate nutrition remains unknown. The aim of this study is to explore the interaction between passive smoking and dietary undernutrition on the risk of VD deficiency. Methods: A population-based case−control study including 1151 non-pregnant women of reproductive age between 18 and 40 years old was conducted in Henan Province, China from 2009 to 2010. Blood samples and information on exposure factors were collected. The prevalence of VD deficiency was estimated based on a result of serum 25-hydroxyvitamin D [25(OH)D] < 26.0 ng/mL. A multivariate logistic regression analysis was performed to explore the risk of VD deficiency. Results: The prevalence of VD deficiency was 61.5%. After adjusting for potential confounding factors, the interactions between passive smoking and no nutritional supplementation, passive smoking and insufficient egg intake, and passive smoking and insufficient milk dairy products intake were associated with the risk of VD deficiency, and the adjusted ORs were 3.40 (95% CI 2.26−5.13), 2.87 (95% CI 2.20−4.10), and 2.18 (95% CI 1.33−3.58), respectively. The interaction coefficients were calculated to be 2.35, 2.79, and 1.70, respectively, indicating there were significant interaction effects, as all of the coefficients were higher than 1. Conclusions: Our findings present that the risk of VD deficiency was potentially influenced by interactions between passive smoking and inadequate nutrition. Passive smoking might strengthen the effect of inadequate nutrition on the risk of VD deficiency among rural women of reproductive age. More attention should be paid to the health education and nutritional status improvement of women of reproductive age, especially in rural areas of developing countries.

The effect of vitamin D recommendations on serum 25-hydroxyvitamin D level in patients with erythropoietic protoporphyria

OBJECTIVES

Patients with erythropoietic protoporphyria (EPP) avoid sun exposure owing to photosensitivity. For decades, sun-avoiding Danes have been recommended daily vitamin D supplements all year. We offered our EPP patients serum 25-hydroxyvitamin D (25(OH)D) monitoring, and counseling if their level was low. We aimed to investigate the effect of the general recommendation and counseling on 25(OH)D status in patients attending our clinic. Additionally, the 25(OH)D status of our EPP patients was compared to that of British patients with EPP not taking vitamin D supplements and with that of the general Danish population.

METHODS

Forty-six Danish patients with EPP had 25(OH)D measured in 721 blood samples collected between 2003 and 2021. Dates of individual counseling were noted. Data on British patients with EPP and the general Danish population were extracted from previous publications.

RESULTS

Our patients had higher 25(OH)D levels than British patients with EPP not taking vitamin D supplements, but the recommendations did not elevate their 25(OH)D levels to that of the general Danish population. Overall, 17.5% of the 25(OH)D measurements in our EPP patients were below 30 nmol/L (deficiency) and 29.4% were between 30 and 50 nmol/L (insufficiency). Patients were monitored for a median of 11 y. Thirty-one patients had a total of 74 vitamin D counseling sessions, providing an increase in 25(OH)D of about 18 nmol/L the year after. However, many patients repeatedly developed insufficiency.

CONCLUSIONS

This study documents the positive effect of vitamin D recommendations on serum 25(OH)D in patients with EPP. Follow-up on vitamin D status and recommendations is essential to increase 25(OH)D levels.

Physical Determinants of Vitamin D Photosynthesis: A Review

Vitamin D synthesis by exposure of skin to solar ultraviolet radiation (UVR) provides the majority of this hormone that is essential for bone development and maintenance but may be important for many other health outcomes. This process, which is the only well-established benefit of solar UVR exposure, depends on many factors including genetics, age, health, and behavior. However, the most important factor is the quantity and quality of UVR reaching the skin. Vitamin D synthesis specifically requires ultraviolet B (UVB) radiation that is the minority component (<5%) of solar UVR. This waveband is also the most important for the adverse effects of solar exposure. The most obvious of which is sunburn (erythema), but UVB is also the main cause of DNA damage to the skin that is a prerequisite for most skin cancers. UVB at the Earth's surface depends on many physical and temporal factors such as latitude, altitude, season, and weather. Personal, cultural, and behavioral factors are also important. These include skin melanin, clothing, body surface area exposed, holiday habits, and sunscreen use. There is considerable disagreement in the literature about the role of some of these factors, possibly because some studies have been done by researchers with little understanding of photobiology. It can be argued that vitamin D supplementation obviates the need for solar exposure, but many studies have shown little benefit from this approach for a wide range of health outcomes. There is also increasing evidence that such exposure offers health benefits independently of vitamin D: the most important of which is blood-pressure reduction. In any case, public health advice must optimize risk versus benefit for solar exposure. It is fortunate that the individual UVB doses necessary for maintaining optimal vitamin D status are lower than those for sunburn, irrespective of skin melanin. © 2020 The Authors. JBMR Plus published by Wiley Periodicals LLC. on behalf of American Society for Bone and Mineral Research.

Do extreme summers increase blood vitamin D (25-hydroxyvitamin D) levels?

Climate change is expected to increase the frequency of extreme weather events, such as extended heat waves and droughts in the northern hemisphere. Besides affecting ecosystems worldwide, these changes in climate patterns will also affect the environmental health of human populations. While the medical community is mostly concerned with the negative impact of climate change, there might also be some beneficial effects. In this study we used laboratory data from a large university clinic in Germany (n = 13 406), to test for any detectable impact of two extreme summers on Vitamin-D [25(OH)D] plasma concentrations over a six year period (2014-2019). For the two years with extreme summers (2018 and 2019) the 25(OH)D plasma concentrations were significantly higher than in the previous four years (p < 0.001). A time series analysis (autoregressive term, AR, φ = 0.84, with an AR of one indicating a persistent effect) showed that 25(OH)D concentrations rise by 0.04 nmol/l (95% CI: 0.04-0.05 nmol/l) per hour of sunshine. The incidence of vitamin D deficiency was generally high (60% for 2014-2017) but dropped by 10% in 2018 and 2019. As such, the summers of 2018 and 2019, which are among the hottest and driest in Germany since the start of modern climate recordings, had a measurable positive effect on 25(OH)D plasma levels of the examined population. Given that 25(OH)D deficiency is widespread in higher latitudes, this implies that while mostly considered negative, climate change might also confer some health benefits with regard to vitamin D related medical conditions.

Vitamin D status and risk of incident tuberculosis disease: A nested case-control study, systematic review, and individual-participant data meta-analysis

BACKGROUND

Few studies have evaluated the association between preexisting vitamin D deficiency and incident tuberculosis (TB). We assessed the impact of baseline vitamins D levels on TB disease risk.

METHODS AND FINDINGS

We assessed the association between baseline vitamin D and incident TB in a prospective cohort of 6,751 HIV-negative household contacts of TB patients enrolled between September 1, 2009, and August 29, 2012, in Lima, Peru. We screened for TB disease at 2, 6, and 12 months after enrollment. We defined cases as household contacts who developed TB disease at least 15 days after enrollment of the index patient. For each case, we randomly selected four controls from among contacts who did not develop TB disease, matching on gender and year of age. We also conducted a one-stage individual-participant data (IPD) meta-analysis searching PubMed and Embase to identify prospective studies of vitamin D and TB disease until June 8, 2019. We included studies that assessed vitamin D before TB diagnosis. In the primary analysis, we defined vitamin D deficiency as 25-(OH)D < 50 nmol/L, insufficiency as 50-75 nmol/L, and sufficiency as >75nmol/L. We estimated the association between baseline vitamin D status and incident TB using conditional logistic regression in the Lima cohort and generalized linear mixed models in the meta-analysis. We further defined severe vitamin D deficiency as 25-(OH)D < 25 nmol/L and performed stratified analyses by HIV status in the IPD meta-analysis. In the Lima cohort, we analyzed 180 cases and 709 matched controls. The adjusted odds ratio (aOR) for TB risk among participants with baseline vitamin D deficiency compared to sufficient vitamin D was 1.63 (95% CI 0.75-3.52; p = 0.22). We included seven published studies in the meta-analysis and analyzed 3,544 participants. In the pooled analysis, the aOR was 1.48 (95% CI 1.04-2.10; p = 0.03). The aOR for severe vitamin D deficiency was 2.05 (95% CI 0.87-4.87; p trend for decreasing 25-(OH)D levels from sufficient vitamin D to severe deficiency = 0.02). Among 1,576 HIV-positive patients, vitamin D deficiency conferred a 2-fold (aOR 2.18, 95% CI 1.22-3.90; p = 0.01) increased risk of TB, and the aOR for severe vitamin D deficiency compared to sufficient vitamin D was 4.28 (95% CI 0.85-21.45; p = 0.08). Our Lima cohort study is limited by the short duration of follow-up, and the IPD meta-analysis is limited by the number of possible confounding covariates available across all studies.

CONCLUSION

Our findings suggest vitamin D predicts TB disease risk in a dose-dependent manner and that the risk of TB disease is highest among HIV-positive individuals with severe vitamin D deficiency. Randomized control trials are needed to evaluate the possible role of vitamin D supplementation on reducing TB disease risk.

Low wintertime pre-diagnostic vitamin D status is associated with an increased risk of internal malignancies in kidney transplant recipients

Low serum 25-hydroxyvitamin D (25OHD) concentrations have been associated with increased cancer risk, but the relative importance of seasonality, i.e. high summer concentrations versus low winter concentrations, is unclear. We investigated this issue in a high risk group: kidney transplant recipients with known increased risk of cancer and low vitamin D statuses. We examined the relationship between registered concentrations of 25OHD binned by quarter and subsequent risk of internal malignancy or cutaneous squamous cell carcinoma in 1112 kidney transplant recipients. Hazard ratios for internal malignancies were significantly increased with lower pre-diagnostic 25OHD concentrations in the first quarter of the year (January-March); a 1.4 fold increase (95%CI 1.1;1.7) per 10 nmol L-1 decrease in 25OHD. Except for women in April-June (1.3 (1.01;1.7) per 10 nmol L-1 decrease) pre-diagnostic 25OHD concentrations in the other quarters were not statistically significantly associated with internal malignancies. Higher 25OHD concentrations tended to be associated with the development of cutaneous squamous cell carcinomas, independent of the time of the year. Our study indicates that low wintertime 25OHD concentrations are associated with an increased risk of internal malignancies and that transplant recipients may benefit from wintertime vitamin D supplementation. Our findings need further corroboration, but suggest that the lowest concentrations of vitamin D, which occur in winter, are important for the risk of internal malignancies.

Factors influencing the higher incidence of tuberculosis among migrants and ethnic minorities in the UK

Migrants and ethnic minorities in the UK have higher rates of tuberculosis (TB) compared with the general population. Historically, much of the disparity in incidence between UK-born and migrant populations has been attributed to differential pathogen exposure, due to migration from high-incidence regions and the transnational connections maintained with TB endemic countries of birth or ethnic origin. However, focusing solely on exposure fails to address the relatively high rates of progression to active disease observed in some populations of latently infected individuals. A range of factors that disproportionately affect migrants and ethnic minorities, including genetic susceptibility, vitamin D deficiency and co-morbidities such as diabetes mellitus and HIV, also increase vulnerability to infection with Mycobacterium tuberculosis (M.tb) or reactivation of latent infection. Furthermore, ethnic socio-economic disparities and the experience of migration itself may contribute to differences in TB incidence, as well as cultural and structural barriers to accessing healthcare. In this review, we discuss both biological and anthropological influences relating to risk of pathogen exposure, vulnerability to infection or development of active disease, and access to treatment for migrant and ethnic minorities in the UK.

Factors influencing the higher incidence of tuberculosis among migrants and ethnic minorities in the UK

Migrants and ethnic minorities in the UK have higher rates of tuberculosis (TB) compared with the general population. Historically, much of the disparity in incidence between UK-born and migrant populations has been attributed to differential pathogen exposure, due to migration from high-incidence regions and the transnational connections maintained with TB endemic countries of birth or ethnic origin. However, focusing solely on exposure fails to address the relatively high rates of progression to active disease observed in some populations of latently infected individuals. A range of factors that disproportionately affect migrants and ethnic minorities, including genetic susceptibility, vitamin D deficiency and co-morbidities such as diabetes mellitus and HIV, also increase vulnerability to infection with Mycobacterium tuberculosis (M.tb) or reactivation of latent infection. Furthermore, ethnic socio-economic disparities and the experience of migration itself may contribute to differences in TB incidence, as well as cultural and structural barriers to accessing healthcare. In this review, we discuss both biological and anthropological influences relating to risk of pathogen exposure, vulnerability to infection or development of active disease, and access to treatment for migrant and ethnic minorities in the UK.

Assessing a portable, real-time display handheld meter with UV-A and UV-B sensors for potential application in personal sun exposure studies

BACKGROUND

Observing accurate real-time measurements of solar ultraviolet radiation (UVR) levels is important since personal excess sun exposure is associated with skin cancers. Handheld measurement devices may be helpful but their accuracy is unknown. We compare a portable, science-grade solar UVR monitoring device against two fixed, science-grade solar UVR instruments.

METHODS

Instruments were (1) a fixed Solar Light 501 UV-B biometer to measure UV-B; (2) a fixed Kipp and Zonen radiometer used to measure UV-A and UV-B; and (3) Goldilux ultraviolet probes which are commercially available portable devices. Two different probes were used, one measured UV-A and the other UV-B radiation. The Goldilux probes were levelled and secured next to the UV-B biometer. Between 10:00 and 14:40 UTC+2, the UV-B biometer was set to record at 10-minute intervals and measurements by the Goldilux probes were manually taken simultaneously. Results were compared for all data and by solar zenith angle (SZA) ranges.

RESULTS

The Goldilux UV-B probe measured UV-B relatively well in its diurnal pattern, however, its readings were ~77% higher than those made by the UV-B biometer. While UV-A measurements from the Goldilux UV-A probe and those from the radiometer were in relatively good agreement in pattern, the radiometer read ~47% higher than the Goldilux UV-A probe. UV-B data from Goldilux UV-B probe had a moderately strong correlation with UV-B biometer data for small SZAs; conversely, for UV-A, the Goldilux UV-A probe had a strong correlation with the UV-A radiometer data for large SZAs.

CONCLUSION

Handheld devices may be useful to provide real-time readings of solar UVR patterns, however, to achieve synchronicity in the magnitude of readings to those made by science-grade fixed instruments, devices may need to be used during certain times of the day and in clear-sky conditions which may not be practical in personal exposure studies.

Sun exposure and 25-hydroxyvitamin D3 levels in a community sample: Quantifying the association with electronic dosimeters

There is uncertainty about the amount of sun exposure required to increase low blood 25-hydroxyvitamin D (25(OH)D₃) levels, a possible disease risk factor. The study aimed to quantify the association between sun exposure and serum 25(OH)D₃ concentrations in a multiethnic community sample (n=502) living in Auckland (37°S) and Dunedin (46°S), New Zealand, aged 18-85 years. They wore electronic ultraviolet dosimeters between March and November (autumn, winter and spring) for 8 weeks to record their sun exposure. This was converted to standard erythemal doses (SEDs), corrected for clothing to generate equivalent full-body exposures, SED_EFB. Blood samples were collected at the end of weeks 4 and 8 to measure 25(OH)D₃. Median weekly SED_EFB was 0.33 during weeks 1-4 and 0.34 during weeks 5-8. Weekly exposures <0.5 SED_EFB during weeks 5-8 were associated with decreasing 25(OH)D₃ concentrations at the end of week 8. There was a non-linear association between sun exposure and 25(OH)D₃, with most of the increase in 25(OH)D₃ being at exposures <2 SED_EFB per week. This finding suggests that vitamin D status is increased by regular small sun exposures (<2 SED_EFB per week), and that greater exposures result in only small additional increases in 25(OH)D₃.

Environmental and genetic determinants of two vitamin D metabolites in healthy Australian children

BACKGROUND

Vitamin D deficiency has been associated with adverse health outcomes. We examined genetic and environmental determinants of serum 25(OH)D3 and 1,25(OH)2D3 in childhood.

METHODS

The study sample consisted of 322 healthy Australian children (predominantly Caucasians) who provided a venous blood sample. A parental interview was conducted and skin phototype and anthropometry measures were assessed. Concentrations of 25(OH)D3 and 1,25(OH)2D3 were measured by selective solid-phase extraction-capillary liquid chromatography-tandem mass spectrometry. These concentrations were deseasonalised where relevant to remove the effect of month of sampling.

RESULTS

Deseasonalised log 25(OH)D3 and 1,25(OH)2D3 concentrations were only moderately correlated (r=0.42, p<0.001). The following predicted both 25(OH)D3 and 1,25(OH)2D3: UVR 6 weeks before the interview, natural skin and eye colour, height and vitamin D allelic metabolism score. The following predicted 25(OH)D3 only: lifetime sunburns and vitamin D allelic synthesis score. Overall, 43.5% and 25.6% of variation in 25(OH)D3 and 1,25(OH)2D3 could be explained. After accounting for 25(OH)D3 concentrations, higher UVR 6 weeks before the interview and vitamin D allelic metabolism score further predicted 1,25(OH)2D3 concentrations.

CONCLUSIONS

Environmental factors and genetic factors contributed to both vitamin D metabolite concentrations. The intriguing finding that the higher ambient UVR contributed to higher 1,25(OH)2D3 after accounting for 25(OH)D3 concentrations requires further evaluation.

Comparing Handheld Meters and Electronic Dosimeters for Measuring Ultraviolet Levels under Shade and in the Sun

This study aimed to compare the validity, reliability and practicality of alternative portable methods for measuring erythemal UVR levels in passive recreation areas in public parks. UVR levels were measured for point in time comparisons between Solarmeter 6.5 handheld meters and time-stamped electronic dosimeters in a large central park in Melbourne, Australia. Observations were made at 20 locations in the park by two research assistants under two conditions: (1) matched shade (2) contrasting shade-no shade. Comparisons were also made with scientific instruments on the UVR monitoring station rooftop and by remotely selecting UV records and forecasts on cloud-free dates of park observations. There was good agreement between the portable UVR instruments in the park setting as confirmed via Bland Altman plots, while the dosimeter appeared less sensitive to change in shade conditions. The rooftop measurements showed that the Solarmeter 6.5 UVR readings were comparable to those of the adjacent rooftop instruments. The practicalities of using the dosimeters and Solarmeters for behavioral studies are discussed. These findings provide a basis for use of the Solarmeter 6.5 to measure changes in UVR levels due to different environmental conditions with relative accuracy for intervention studies in outdoor settings.

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.

High-dose vitamin D3 reduces deficiency caused by low UVB exposure and limits HIV-1 replication in urban Southern Africans

Cape Town, South Africa, has a seasonal pattern of UVB radiation and a predominantly dark-skinned urban population who suffer high HIV-1 prevalence. This coexistent environmental and phenotypic scenario puts residents at risk for vitamin D deficiency, which may potentiate HIV-1 disease progression. We conducted a longitudinal study in two ethnically distinct groups of healthy young adults in Cape Town, supplemented with vitamin D3 in winter, to determine whether vitamin D status modifies the response to HIV-1 infection and to identify the major determinants of vitamin D status (UVB exposure, diet, pigmentation, and genetics). Vitamin D deficiency was observed in the majority of subjects in winter and in a proportion of individuals in summer, was highly correlated with UVB exposure, and was associated with greater HIV-1 replication in peripheral blood cells. High-dosage oral vitamin D3 supplementation attenuated HIV-1 replication, increased circulating leukocytes, and reversed winter-associated anemia. Vitamin D3 therefore presents as a low-cost supplementation to improve HIV-associated immunity.

Environmental and genetic determinants of vitamin D insufficiency in 12-month-old infants

We aimed to investigate the relationship between genetic and environmental exposure and vitamin D status at age one, stratified by ethnicity. This study included 563 12-month-old infants in the HealthNuts population-based study. DNA from participants' blood samples was genotyped using Sequenom MassARRAY MALDI-TOF system on 28 single nucleotide polymorphisms (SNPs) in six genes. Using logistic regression, we examined associations between environmental exposure and SNPs in vitamin D pathway and filaggrin genes and vitamin D insufficiency (VDI). VDI, defined as serum 25-hydroxyvitamin D3(25(OH)D3) level ≤50nmol/L, was measured using liquid chromatography-tandem mass spectrometry (LC-MS/MS). Infants were stratified by ethnicity determined by parent's country of birth. Infants formula fed at 12 months were associated with reduced odds of VDI compared to infants with no current formula use at 12 months. This association differed by ethnicity (Pinteraction=0.01). The odds ratio (OR) of VDI was 0.29 for Caucasian infants (95% CI, 0.18-0.47) and 0.04 for Asian infants (95% CI, 0.006-0.23). Maternal vitamin D supplementation during pregnancy and/or breastfeeding were associated with increased odds of infants being VDI (OR, 2.39; 95% CI, 1.11-5.18 and OR, 2.5; 95% CI, 1.20-5.24 respectively). Presence of a minor allele for any GC SNP (rs17467825, rs1155563, rs2282679, rs3755967, rs4588, rs7041) was associated with increased odds of VDI. Caucasian infants homozygous (AA) for rs4588 had an OR of 2.49 of being associated with VDI (95% CI, 1.19-5.18). In a country without routine infant vitamin D supplementation or food chain fortification, formula use is strongly associated with a reduced risk of VDI regardless of ethnicity. There was borderline significance for an association between filaggrin mutations and VDI. However, polymorphisms in vitamin D pathway related genes were associated with increased likelihood of being VDI in infancy.

Effect of vitamin D supplementation and ultraviolet B exposure on serum 25-hydroxyvitamin D concentrations in healthy volunteers: a randomized, crossover clinical trial

BACKGROUND

Solar ultraviolet (UV) radiation during the summer and vitamin D supplementation are two major sources of vitamin D for humans at northern latitudes. However, little is known about the relative efficiency of these two vitamin D sources.

OBJECTIVES

The main goal was to compare the efficiency of high-dose oral vitamin D3 supplementation (2000 IU per day for 30 days) with a simulated summer UV exposure [10 sunbed sessions to a total dose of 23·8 standard erythema doses (SED)] to improve vitamin D status.

METHODS

Healthy volunteers were randomized into two groups: group 1 received vitamin D supplementation followed by 10 whole-body sunbed exposures; group 2 started with 10 sunbed exposures followed by vitamin D supplementation.

RESULTS

The oral supplementation with vitamin D3 resulted in a mean (SEM) serum 25-hydroxyvitamin D [25(OH)D] increase of 25·3 (5·4) nmol L(-1) . A similar increase, 19·8 (5·4) nmol L(-1) , was observed after simulated summer UV exposure. At the end of the study, serum 25(OH)D concentrations were similar in both groups.

CONCLUSIONS

Twice-weekly whole-body sunbed exposure to a dose of 4·8 SED is equal to 2000 IU daily of oral vitamin D supplementation for 30 days and enough to achieve and maintain serum 25(OH)D concentrations > 75 nmol L(-1) in ~55% of cases. Based on our calculations, this dose corresponds to a cumulative weekly whole-body exposure of 3·4 SED (~ 40 min around midday during the summer at the latitude of Oslo).

North-South gradients of melanomas and non-melanomas: A role of vitamin D?

Incidence rates of skin cancer increase with decreasing latitude in Norway, as in many other countries with white populations. The latitudinal trends of the incidence rates of skin cancer were studied and compared with data for vitamin D-induced by UV and for vitamin D intake. The north-south gradient for CMM incidence rates on sun exposed skin is much smaller than those for BCC and SCC, and that for BCC is smaller than that for SCC. This indicates that SCC and BCC are mainly due to solar UVB, while UVA may play a significant role for CMM and a smaller role for BCC, since the north-south gradient of annual UVB fluences is larger than that of UVA fluences. However, there is an inverse latitudinal gradient of skin cancer in central Europe. This is probably due to a gradient of skin color, since white skin is an important determinant of increased risk of skin cancer. The role of vitamin D for skin cancer risk is difficult to evaluate, since serum levels of 25-hydroxyvitamin D, as well as vitamin D intakes, are widely different from country to country. Still, epidemiological evidence indicates a role: for melanomas arising on non-sun exposed body localizations (uveal melanomas, melanomas arising in the vulva and perianal/anorectal regions) there appears to be no latitudinal gradient, or, a negative gradient, i.e., increasing rates with decreasing latitude as would be expected if UV-generated vitamin D plays a protective role. Both skin cancer risk and vitamin D photosynthesis decrease with increasing skin darkness.

Biologically efficient solar radiation: Vitamin D production and induction of cutaneous malignant melanoma

Solar ultraviolet (UV) radiation is the main source of vitamin D production and is also the most important environmental risk factor for cutaneous malignant melanoma (CMM) development. In the present study the relationships between daily or seasonal UV radiation doses and vitamin D status, dietary vitamin D intake and CMM incidence rates at different geographical latitudes were investigated. North-South gradients of 25-hydroxyvitamin D (25(OH)D) generation and CMM induction were calculated, based on known action spectra, and compared with measured vitamin D levels and incidence rates of CMM. The relative roles of UVA and UVB in CMM induction are discussed. Latitudinal dependencies of serum 25(OH)D levels and CMM incidence rates can only partly be explained by ambient UV doses. The UV sensitivity is different among populations with different skin color. This is well known for CMM, but seems also to be true for vitamin D status. The fact that UV-induced vitamin D may reduce the risk of CMM complicates the discussion. To some extent high dietary vitamin D intake seems to compensate low UV doses.

Sun exposure, vitamin D receptor genetic variants, and risk of breast cancer in the Agricultural Health Study

BACKGROUND

Epidemiologic evidence suggests a negative relation between sunlight exposure and breast cancer risk. The hypothesized mechanism is sunlight-induced cutaneous synthesis of vitamin D.

OBJECTIVES

Our goal was to examine sun exposure and its interaction with vitamin D receptor (VDR) gene variants on breast cancer risk.

METHODS

We examined sun exposure and breast cancer incidence among 31,021 private pesticide applicators' wives, including 578 cases, enrolled in the prospective Agricultural Health Study cohort and followed 8.6 years on average. We estimated interactions between sun exposure, VDR variants, and breast cancer in a nested case-control study comprising 293 cases and 586 matched controls. Information on sun exposure was obtained by questionnaire at cohort enrollment. Relative risks were estimated using Cox proportional hazards regression for the cohort data and conditional logistic regression for the nested case-control data.

RESULTS

We observed a small decrease in breast cancer risk in association with usual sun exposure of ≥ 1 hr/day (versus < 1 hr/day) 10 years before the start of follow-up among all participants [hazard ratio (HR) = 0.8; 95% CI: 0.6, 1.0]. The association appeared to be slightly stronger in relation to estrogen receptor-positive tumors (HR = 0.7; 95% CI: 0.5, 0.9) than estrogen receptor-negative tumors (HR = 1.1; 95% CI: 0.6, 2.1). The HR for joint exposure ≥ 1 hr/day of sunlight and one VDR haplotype was less than expected given negative HRs for each individual exposure (interaction p-value = 0.07).

CONCLUSION

Our results suggest that sun exposure may be associated with reduced risk of breast cancer, but we did not find clear evidence of modification by VDR variants. Larger studies are warranted, particularly among populations in whom low levels of usual sun exposure can be more precisely characterized.

Vitamin D status and dietary intake in a Swedish COPD population

INTRODUCTION

Emerging evidence indicates that patients with chronic obstructive pulmonary disease (COPD) have a poorer vitamin D status than the general population, possibly affecting several comorbidities. In northern latitudes, these problems could be even more accentuated in wintertime because of the low ultraviolet B radiation.

OBJECTIVES

To examine the dietary intake of vitamin D and the levels of 25-hydroxyvitamin D (25-OH-D) in a COPD population compared with a reference group in Swedish settings.

METHODS

Ninety-eight COPD patients (forced expiratory volume in 1 s/vital capacity ratio < 0.65) recruited from the outpatient clinics at the university hospitals in Gothenburg and Uppsala, Sweden were included in this cross-sectional study. The reference group (149 individuals) was randomly selected from the Swedish National Registry. The serum concentrations of 25-OH-D, intact parathyroid hormone, creatinine and calcium were measured. A trained dietitian conducted a dietary history interview to evaluate food intake of vitamin D, prescribed drugs and supplements containing vitamin D.

RESULTS AND CONCLUSIONS

The mean serum concentration of 25-OH-D was significantly higher in the reference group (57.6 ± 23 nmol/L) compared with the COPD group (51.5 ± 22 nmol/L) (P = 0.039). The dietary intake was predominantly below the recommendations in both groups. Mean total daily intake of vitamin D and mean daily supplementation of vitamin D was significantly higher in the COPD group (P = 0.012 and P = 0.030, respectively). Low intake of vitamin D and low serum levels of 25-OH-D are common in both COPD patients and an elderly Swedish population. Monitoring vitamin D status and possibly routinely treating COPD patients with vitamin D and calcium should be considered to minimise the risk of severe vitamin D deficiency among COPD patients.

Vitamin D status: multifactorial contribution of environment, genes and other factors in healthy Australian adults across a latitude gradient

Vitamin D deficiency is common and implicated in risk of several human diseases. Evidence on the relative quantitative contribution of environmental, genetic and phenotypic factors to vitamin D status (assessed by the serum concentration of 25-hydroxyvitamin D, 25(OH)D) in free-living populations is sparse. We conducted a cross-sectional study of 494 Caucasian adults aged 18-61years, randomly selected from the Australian Electoral Roll according to groups defined by age, sex and region (spanning 27°-43°South). Data collected included personal characteristics, sun exposure behaviour, biomarkers of skin type and past sun exposure, serum 25(OH)D concentration and candidate single nucleotide polymorphisms. Ambient ultraviolet radiation (UVR) levels in the month six weeks before blood sampling best predicted vitamin D status. Serum 25(OH)D concentration increased by 10nmol/L as reported time in the sun doubled. Overall, 54% of the variation in serum 25(OH)D concentration could be accounted for: 36% of the variation was explained by sun exposure-related factors; 14% by genetic factors (including epistasis) and 3.5% by direct measures of skin phenotype. Novel findings from this study are demonstration of gene epistasis, and quantification of the relative contribution of a wide range of environmental, constitutional and genetic factors to vitamin D status. Ambient UVR levels and time in the sun were of prime importance but it is nonetheless important to include the contribution of genetic factors when considering sun exposure effects. This article is part of a Special Issue entitled 'Vitamin D Workshop'.

Vitamin d status and anthropometric indices of an omani study population

OBJECTIVES

Serum 25-hydroxyvitamin D [25(OH)D] concentrations reflect vitamin D status, with deficiency implicated as causative of many diseases. This study assessed vitamin D status and anthropometric indices in a sample of healthy Omanis.

METHODS

Serum 25(OH)D concentrations were measured by high performance liquid chromatography in 206 healthy Omanis, aged 18-55 years (mean age: men 31.1, women 26.8) in Muscat, Oman. Of this number, 95% indicated that they had never taken vitamin D supplements. Findings were compared with published values for populations domiciled in more northerly latitudes. Classical procedures were used to determine global obesity (body mass index [BMI]), and central obesity determined by waist circumference, waist-to-hip ratio (WHR), and waist-to-height ratio.

RESULTS

Women, as compared to men, had markedly lower concentrations of 25(OH)D. Applying the cut-off point of serum 25(OH)D levels at 50 nmol/L, the prevalence of vitamin D deficiency in the study population was 87.5%; this was higher than the rates reported for the British, and European-, Hispanic-, and African-Americans. At a BMI cut-point of ≥30 kg/m(2), the prevalence of obesity was 14.6%; this was lower than the rates reported for European-, Hispanic-, and African-Americans. Levels of 25(OH) D increased relative to age and obesity. WHR was the main predictor of 25(OH)D levels.

CONCLUSION

The striking vitamin D deficiency seen in the study population, relative to more northerly populations, may be linked to sun avoidance, inadequate dietary vitamin D, and virtual non-intake of supplemental vitamin D. Age and male-gender determined the status of vitamin D and of obesity.

Serum 25-hydroxyvitamin D levels in preschool-age children in northern Sweden are inadequate after summer and diminish further during winter

BACKGROUND AND OBJECTIVE

Despite studies indicating that vitamin D intake among Swedish children does not meet the recommendation, little is known of their vitamin D status. The aim of the present study was to examine vitamin D status in preschool-age children in relation to vitamin D intake, season, body mass index, and skin color.

METHODS

Preschool-age children (n = 90; mean age 54 ± 7.1 months), all living in northern Sweden (latitude 63° north), half of them with fair skin, half with darker complexion, were recruited from well-baby clinics. The study group was examined first in August-September (late summer) and then the following January-February (winter). Skin type, vitamin D intake, anthropometrics, serum 25-hydroxyvitamin D (S-25[OH] D), and serum parathyroid hormone were assessed.

RESULTS

Mean ± SD S-25(OH) D in summer and winter were 60 ± 15 nmol/L and 55 ± 16 nmol/L, respectively (P < 0.001). Fifteen percent and 10% had S-25(OH) D ≥ 75 nmol/L, and 25% and 40% had S-25(OH) D <50 nmol/L, respectively. The mean vitamin D intake was higher in dark-skinned compared with fair-skinned children. In spite of this, S-25(OH) D in dark-skinned children was lower compared with fair-skinned children during both seasons. The dietary intake of vitamin D was positively associated with S-25(OH) D levels.

CONCLUSIONS

Vitamin D status is inadequate in preschool-age children living in northern Sweden, especially in dark-skinned children and during the winter despite vitamin D intakes meeting the recommendations, prompting strategies to improve intake of vitamin D in this population.

Using genetic proxies for lifecourse sun exposure to assess the causal relationship of sun exposure with circulating vitamin d and prostate cancer risk

BACKGROUND

Ecological and epidemiological studies have identified an inverse association of intensity and duration of sunlight exposure with prostate cancer, which may be explained by a reduction in vitamin D synthesis. Pigmentation traits influence sun exposure and therefore may affect prostate cancer risk. Because observational studies are vulnerable to confounding and measurement error, we used Mendelian randomization to examine the relationship of sun exposure with both prostate cancer risk and the intermediate phenotype, plasma levels of vitamin D.

METHODS

We created a tanning, a skin color, and a freckling score as combinations of single nucleotide polymorphisms that have been previously associated with these phenotypes. A higher score indicates propensity to burn, have a lighter skin color and freckles. The scores were tested for association with vitamin D levels (25-hydroxyvitamin-D and 1,25-dihydroxyvitamin-D) and prostate-specific antigen detected prostate cancer in 3,123 White British individuals enrolled in the Prostate Testing for cancer and Treatment (ProtecT) study.

RESULTS

The freckling score was inversely associated with 25(OH)D levels [change in 25(OH)D per score unit -0.27; 95% CI, -0.52% to -0.01%], and the tanning score was positively associated with prostate cancer risk (OR = 1.05; 95% CI, 1.02-1.09), after adjustment for population stratification and potential confounders.

CONCLUSIONS

Individuals who tend to burn are more likely to spend less time in the sun and consequently have lower plasma vitamin D levels and higher susceptibility to prostate cancer.

IMPACT

The use of pigmentation-related genetic scores is valuable for the assessment of the potential benefits of sun exposure with respect to prostate cancer risk.

Accuracy of self-reported sun exposure and sun protection behavior

The objective of this study was to compare the accuracy of self-reported skin cancer risk outcome measures proposed as standards by prevention experts to aggregated estimates of behavior from weekly diaries. Weekly electronic diaries of ultraviolet radiation (UVR) behaviors, initially validated by comparison with daily electronic diaries, were used to assess the accuracy of commonly used end-of-summer self-reported measures among 250 adults. Results revealed low biases, and good correspondence between simple open-ended self-reported estimates of days outside, hours outside, sunbathing days and hours, and days outside when not protected by either sunscreen, long-sleeved shirts, hats, or shade. Rating scale measures commonly used in the current literature and those recently recommended as standards by a workshop of experts showed evidence of being non-interval and lacking precision for more frequent behavior (e.g., >1 h sun exposure daily). These data indicated that open-ended frequency self-reports of skin cancer risk behaviors that follow procedures designed to increase accuracy were reliable over a summer-long period.

Vitamin D status in healthy Romanian caregivers and risk of respiratory infections

OBJECTIVES

To investigate the vitamin D status during winter of a healthy population of hospital employees and to assess the correlation between vitamin D status and risk of infections in the upper respiratory tract.

DESIGN

One hundred and ten healthy volunteers answered a questionnaire on their solar exposure habits and vitamin D intake and delivered one blood sample for quantification of vitamin D level (serum 25-hydroxyvitamin D (25(OH)D) concentration) during December 2007-January 2008. At the end of the winter we screened for the occurrence of respiratory infections and sought associations with vitamin D status.

SETTING

Bucharest, Romania, 45°N.

SUBJECTS

One hundred and ten healthy hospital employees.

RESULTS

Eighty per cent of participants were vitamin D deficient (25(OH)D level below 50 nmol/l). The main determinant of serum 25(OH)D was sun exposure during the summer previous to the study (P = 0·02 in multivariate analysis). Intake of vitamin D, BMI and age played no significant role for the level of 25(OH)D. Overall we found a non-significant negative correlation between 25(OH)D level and new cases of infection (Spearman correlation coefficient of -0·12, P = 0·2).

CONCLUSIONS

Vitamin D status is alarmingly poor in active, relatively young women residing in Romania. If our results are reproduced by other investigations, action to improve vitamin D status at the population level is necessary. We were not able to show a statistically significant relationship between vitamin D status and infection risk in our material.

Development and validation of sunlight exposure measurement questionnaire (SEM-Q) for use in adult population residing in Pakistan

Background

Vitamin D deficiency has been identified as a major public health problem worldwide. Sunlight is the main source of vitamin D and its measurement using dosimeters is expensive and difficult for use in population-based studies. Hence, the aim of this study was to develop and validate questionnaires to assess sunlight exposure in healthy individuals residing in Karachi, Pakistan.

Methods

Two questionnaires with seven important items for sunlight exposure assessment were developed. Fifty four healthy adults were enrolled based on their reported sunlight exposure (high = 17, moderate = 18, low = 19) from Aga Khan University, Karachi. Over four days, study participants were asked to wear a dosimeter between sunrise and sunset and report time spent and activities undertaken in the sun for questionnaire validation. Algorithm for item weightage was created as an average score based on ultraviolet B percentage received. Blood samples were obtained for serum vitamin D.

Results

The mean time (minutes) spent in sun over 4 days (±SD) was 69.5 (±32) for low, 83.5 (±29.7) for moderate and 329 (±115) for high exposure group. The correlation between average time (minutes) spent in sun over 4 days and mean change in absorbance of UV dosimeters for 4 days was 0.60 (p < 0.01). Correlation between average score and vitamin D levels was found to be 0.36 (p = 0.01) for short term questionnaire score, 0.43 (p = 0.01) for long term questionnaire score in summers and 0.48 (p = 0.01) in winters.

Conclusions

The sunlight exposure measurement questionnaires were valid tools for use in large epidemiological studies to quantify sunlight exposure.

Availability of vitamin D photoconversion weighted UV radiation in southern South America

Ultraviolet radiation (UVR) plays a key role in several biological functions, including human health. Skin exposure to UVR is the main factor in vitamin D photoconversion. There is also evidence relating low levels of vitamin D with certain internal cancers, mainly colon, breast and prostate, as well as other diseases. Several epidemiological studies have shown an inverse relationship between the above-mentioned diseases and latitude, in accordance with the ultraviolet radiation latitudinal gradient. The aim of this study is to determine whether UV irradiance levels in the southern South America are sufficient to produce suitable levels of vitamin D year around. For this purpose, vitamin D photoconversion weighted-irradiance was analyzed between S.S. de Jujuy (24.17°S, 65.02°W) and Ushuaia (54° 50'S, 68° 18'W). In addition to irradiance, skin type and area of body exposed to sunlight are critical factors in vitamin D epidemiology. Due to a broad ethnic variability, it was assumed that the skin type in this region varies between II and V (from the most to the less sensitive). All sites except South Patagonia indicate that skin II under any condition of body area exposure and skin V when exposing head, hands, arms and legs, would produce suitable levels of vitamin D year round (except for some days in winter at North Patagonian sites). At South Patagonian sites, minimum healthy levels of vitamin D year round can be reached only by the more sensitive skin II type, if exposing head, hands, arms and legs, which is not a realistic scenario during winter. At these southern latitudes, healthy vitamin D levels would not be obtained between mid May and beginning of August if exposing only the head. Skin V with head exposure is the most critical situation; with the exception of the tropics, sun exposure would not produce suitable levels of vitamin D around winter, during a time period that varies with latitude. Analyzing the best exposure time during the day in order to obtain a suitable level of vitamin D without risk of sunburn, it was concluded that noon is best during winter, as determined previously. For skin type II when exposing head, exposure period in winter varies between 30 and 130 min, according to latitude, except for South Patagonian sites. During summer, noon seems to be a good time of day for short periods of exposure, while during leisure times, longer periods of exposure without risk of sunburn are possible at mid-morning and mid-afternoon. At 3 h from noon, solar zenith angles are almost the same for sites between the tropics and North Patagonia, and at 4 h from noon, for all sites. Then, in these cases, the necessary exposure periods varied slightly between sites, only due to meteorological differences.

Solar UV doses of adult Americans and vitamin D(3) production

BACKGROUND

Sunlight contains UV radiation that affects human health in both detrimental (skin cancers) and beneficial (vitamin D(3)) ways. An evaluation of the vitamin D status of adult Americans (22-40, 41-59, 60+ yr) show many have deficient or insufficient serum levels of 25-hydroxyvitamin D, indicating they are not getting enough from dietary sources or sunlight. Those findings are in conflict with calculated values from the American Academy of Dermatology who insist people make "ample" vitamin D(3) (≥1,000 IU/day) from their "casual," or everyday, outdoor UV exposures even if they use sunscreens with sun protection factor 15.

OBJECTIVE

We investigated this situation using the everyday outdoor UV doses of indoor-working adult Americans (∼7,000) in the north (45°N) and south (35°N) to calculate how much vitamin D(3) they produce each season with and without vacationing.

RESULTS

Only during the summer can skin type II Caucasian adults (21-59 yr) meet their minimum (600 IU/day) vitamin D(3) needs from everyday exposures, but only if they do not wear professional clothes or sunscreens (except beach vacations).

METHOD

To do vitamin D(3) calculations properly, we used action spectrum and geometric conversion factors, not previously incorporated into other calculations.

CONCLUSIONS

Most adult Americans do not go outside enough to meet their minimum or optimum (≥1,200 IU/day) vitamin D(3) needs all year. The darker skin types (III-VI) and the oldest people (>59 yr) are at the highest risk for not making enough vitamin D(3) during the year from everyday outdoor exposures even with a 2-3 week summer vacation.

Low 25-hydroxyvitamin D levels and mortality in non-dialysis-dependent CKD

BACKGROUND

Low 25-hydroxyvitamin D (25[OH]D) levels are common in patients with non-dialysis-dependent chronic kidney disease (CKD). The associations between low 25(OH)D levels and mortality in non-dialysis-dependent patients with CKD are unclear.

STUDY DESIGN

Retrospective cohort study.

SETTING & PARTICIPANTS

Patients with stages 3-4 CKD (estimated glomerular filtration rate, 15-59 mL/min/1.73 m(2); n = 12,673) who had 25(OH)D levels measured after the diagnosis of CKD in the Cleveland Clinic Health System.

PREDICTOR

25(OH)D levels categorized into 3 groups: <15, 15-29, and ≥30 ng/mL.

OUTCOMES

We examined factors associated with low 25(OH)D levels and associations between low 25(OH)D levels and all-cause mortality (ascertained using the Social Security Death Index and our electronic medical record) using logistic regression, Cox proportional hazard models, and Kaplan-Meier survival curves.

MEASUREMENTS

25(OH)D was measured using chemiluminescence immunoassay.

RESULTS

Of 12,763 patients with CKD, 15% (n = 1,970) had 25(OH)D levels <15 ng/mL, whereas 45% (n = 5,749) had 25(OH)D levels of 15-29 ng/mL. Male sex, African American race, diabetes, coronary artery disease, and lower estimated glomerular filtration rate were associated significantly with 25(OH)D level <30 ng/mL. A graded increase in risk of 25(OH)D level <30 ng/mL was evident across increasing body mass index levels. Patients who had 25(OH)D levels measured in fall through spring had higher odds for 25(OH)D levels <30 ng/mL. After covariate adjustment, patients with CKD with 25(OH)D levels <15 ng/mL had a 33% increased risk of mortality (95% CI, 1.07-1.65). The group with 25(OH)D levels of 15-29 ng/mL did not show a significantly increased risk of mortality (HR, 1.03; 95% CI, 0.86-1.22) compared with patients with 25(OH)D levels ≥30 ng/mL.

LIMITATIONS

Single-center observational study, lack of data for albuminuria and other markers of bone and mineral disorders, and attrition bias.

CONCLUSIONS

25(OH)D level <15 ng/mL was associated independently with all-cause mortality in non-dialysis-dependent patients with CKD.

Ultraviolet sunlight exposure during adolescence and adulthood and breast cancer risk: a population-based case-control study among Ontario women

Recent studies suggest that vitamin D may be associated with reduced breast cancer risk, but most studies have evaluated only dietary vitamin D intake. The associations among ultraviolet radiation from sunlight, factors related to cutaneous vitamin D production, and breast cancer risk were evaluated in a population-based case-control study conducted in Ontario, Canada, between 2003 and 2004 (n = 3,101 cases and n = 3,471 controls). Time spent outdoors was associated with reduced breast cancer risk during 4 periods of life (>21 vs. ≤6 hours/week age-adjusted odds ratio (OR) = 0.71, 95% confidence interval (CI): 0.60, 0.85 in the teenage years; OR = 0.64, 95% CI: 0.53, 0.76 in the 20s-30s; OR = 0.74, 95% CI: 0.61, 0.88 in the 40s-50s; and OR = 0.50, 95% CI: 0.37, 0.66 in the 60s-74 years). Sun protection practices and ultraviolet radiation were not associated with breast cancer risk. A combined solar vitamin D score, including all the variables related to vitamin D production, was significantly associated with reduced breast cancer risk. These associations were not confounded or modified by menopausal status, dietary vitamin D intake, or physical activity. This study suggests that factors suggestive of increased cutaneous production of vitamin D are associated with reduced breast cancer risk.

Sufficient vitamin D from casual sun exposure?

Next to the adverse effects of solar UV exposure, the beneficial effects mediated by vitamin D(3) have come into the limelight. The question then is "how much sun exposure do we actually need?" Estimates have been made, but the data are not quite adequate. The groups of Drs. Rhodes and Webb bridged the gap between experiments and everyday life by a study in which 109 volunteers were exposed in mid-winter to simulated solar UV radiation in summertime clothing at dosages of 1.3 SED three times a week. Thus, 90% reached sufficiently high vitamin D statuses (>50 nmol L(-1)). In this issue, these researchers transpose these experimental exposures in a cabinet to summertime noon exposures of people walking around for about half an hour in open terrain on a clear day in Manchester, UK. This result is an improvement over earlier estimates and shows that casual mid-day summer sun exposure should indeed suffice.

The human health effects of ozone depletion and interactions with climate change

Depletion of the stratospheric ozone layer has led to increased solar UV-B radiation (280-315 nm) at the surface of the Earth. This change is likely to have had an impact on human exposure to UV-B radiation with consequential detrimental and beneficial effects on health, although behavioural changes in society over the past 60 years or so with regard to sun exposure are of considerable importance. The present report concentrates on information published since our previous report in 2007. The adverse effects of UV radiation are primarily on the eye and the skin. While solar UV radiation is a recognised risk factor for some types of cataract and for pterygium, the evidence is less strong, although increasing, for ocular melanoma, and is equivocal at present for age-related macular degeneration. For the skin, the most common harmful outcome is skin cancer, including melanoma and the non-melanoma skin cancers, basal cell carcinoma and squamous cell carcinoma. The incidence of all three of these tumours has risen significantly over the past five decades, particularly in people with fair skin, and is projected to continue to increase, thus posing a significant world-wide health burden. Overexposure to the sun is the major identified environmental risk factor in skin cancer, in association with various genetic risk factors and immune effects. Suppression of some aspects of immunity follows exposure to UV radiation and the consequences of this modulation for the immune control of infectious diseases, for vaccination and for tumours, are additional concerns. In a common sun allergy (polymorphic light eruption), there is an imbalance in the immune response to UV radiation, resulting in a sun-evoked rash. The major health benefit of exposure to solar UV-B radiation is the production of vitamin D. Vitamin D plays a crucial role in bone metabolism and is also implicated in protection against a wide range of diseases. Although there is some evidence supporting protective effects for a range of internal cancers, this is not yet conclusive, but strongest for colorectal cancer, at present. A role for vitamin D in protection against several autoimmune diseases has been studied, with the most convincing results to date for multiple sclerosis. Vitamin D is starting to be assessed for its protective properties against several infectious and coronary diseases. Current methods for protecting the eye and the skin from the adverse effects of solar UV radiation are evaluated, including seeking shade, wearing protective clothing and sunglasses, and using sunscreens. Newer possibilities are considered such as creams that repair UV-induced DNA damage, and substances applied topically to the skin or eaten in the diet that protect against some of the detrimental effects of sun exposure. It is difficult to provide easily understandable public health messages regarding "safe" sun exposure, so that the positive effects of vitamin D production are balanced against the negative effects of excessive exposure. The international response to ozone depletion has included the development and deployment of replacement technologies and chemicals. To date, limited evidence suggests that substitutes for the ozone-depleting substances do not have significant effects on human health. In addition to stratospheric ozone depletion, climate change is predicted to affect human health, and potential interactions between these two parameters are considered. These include altering the risk of developing skin tumours, infectious diseases and various skin diseases, in addition to altering the efficiency by which pathogenic microorganisms are inactivated in the environment.

Is casual exposure to summer sunlight effective at maintaining adequate vitamin D status?

BACKGROUND/PURPOSE

The advice that an adequate vitamin D status can be achieved by short, casual exposure to summer sunlight is ubiquitous. This review will examine the value of this advice.

METHODS

The results of experimental studies on changes in serum 25-hydroxyvitamin D [25(OH)D] concentrations following ultraviolet exposure are interpreted in the context of human exposure to sunlight.

RESULTS

It is shown that current advice about modest sun exposure during the summer months does little in the way of boosting overall 25(OH)D levels, while sufficient sun exposure that could achieve a worthwhile benefit would compromise skin health.

CONCLUSIONS

Failure to understand the nature of human exposure to sunlight has led to misguided advice concerning the sun exposure necessary for an adequate vitamin D status.