Sunbed Radiation Provokes Cutaneous Vitamin D Synthesis in Humans-A Randomized Controlled Trial

Indoor tanning: Evidence surrounding advertised health claims

Indoor tanning continues to remain common, despite evidence of an increased risk of skin cancer from artificial ultraviolet (UV) radiation. In the hopes of gaining customers, the tanning bed industry has marketed health benefits of indoor tanning such as increased vitamin D production, development of a base tan, enhanced mood, and treatment of certain dermatologic conditions. To better educate their patients, providers need a comprehensive reference reviewing the evidence that support or oppose these claims. In this work, we conducted an evidence-based review of the literature to identify and grade studies that investigate health claims related to UV exposure. Results indicate that there is little evidence to support each of these proposed health benefits. Tanning beds emit primarily UVA radiation, which is relatively ineffective at activating vitamin D or mood enhancing pathways, and the effects are minimal in regard to tanning beds generating a protective base tan or treating dermatologic conditions compared with the increased risk of skin cancer. Health care providers must continue to warn and educate patients about the misleading information propagated by the tanning bed industry as well as about the dangers of artificial UV radiation.

Low sun exposure habits is associated with a dose-dependent increased risk of hypertension: a report from the large MISS cohort

In prospective observational cohort studies, increasing sun exposure habits have been associated with reduced risk of cardiovascular mortality. Our aim was to assess possible observational mechanisms for this phenomenon. A written questionnaire was answered by 23,593 women in the year 2000 regarding risk factors for melanoma, including factors of possible interest for hypertension, such as detailed sun exposure habits, hypertension, marital status, education, smoking, alcohol consumption, BMI, exercise, and chronic high stress. Hypertension was measured by the proxy "use of hypertension medication" 2005-2007, and high stress by "need of anti-depressive medication". Sun exposure habits was assessed by the number of `yes' to the following questions; Do you sunbath during summer?, During winter vacation?, Do you travel south to sunbath?, Or do you use sun bed? Women answering 'yes' on one or two questions had moderate and those answering 'yes' on three or four as having greatest sun exposure. The main outcome was the risk of hypertension by sun exposure habits adjusted for confounding. As compared to those women with the greatest sun exposure, women with low and moderate sun exposure were at 41% and 15% higher odds of hypertension (OR 1.41, 95% CI 1.3‒1.6, p < 0.001 and OR 1.15, 95% CI 1.1‒1.2, p < 0.001), respectively. There was a strong age-related increased risk of hypertension. Other risk factors for hypertension were lack of exercise (OR 1.36), a non-fair phenotype (OR 1.08), chronic high stress level (OR 1.8), and lack of university education (OR 1.3). We conclude that in our observational design sun exposure was associated with a dose-dependent reduced risk of hypertension, which might partly explain the fewer deaths of cardiovascular disease with increasing sun exposure.

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

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

Overview on vitamin D and sunbed use

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

Feasibility of vitamin D supplementation interventions to mitigate HIV pre-exposure prophylaxis-related bone mineral density loss: a cross-sectional survey

BACKGROUND

Daily tenofovir disoproxil fumarate (TDF)/emtricitabine as HIV pre-exposure prophylaxis (PrEP) causes subclinical decreases in bone mineral density (BMD). We surveyed PrEP users to assess feasibility for a clinical trial of vitamin D supplementation to mitigate TDF-induced BMD loss.

METHODS

We recruited participants using or starting PrEP in Toronto and Vancouver. The primary objective was to assess the acceptability of daily or weekly vitamin D supplementation. We also assessed the acceptability of calcium supplementation, existing use of non-pharmacological bone health interventions, prevalence of osteoporosis risk factors, and bone health knowledge (Osteoporosis Knowledge Test, OKT).

RESULTS

Of 161 participants, 72.1% were current PrEP users, 18.0% were starting PrEP, and 9.9% did not indicate their PrEP status. All identified as males, 88.8% as gays, and 67.1% as Whites. Median (IQR) age was 32.0 (29.0, 40.0) years, and 62.1% reported family income $$60,000/year. Among those not already using the interventions, willingness to supplement with daily vitamin D, weekly vitamin D, or daily calcium was very high at 90.9%, 96.4%, and 93.0 %, respectively. Only 31.0% reported adequate dietary calcium intake, while 42.9% reported $1 osteoporosis risk factor (most commonly, alcohol and smoking). Overall bone health knowledge was low, as median (IQR) OKT score was 16/32. In post hoc comparisons, current PrEP users may have been more likely than new PrEP users to engage in bone loading exercise (Bone-specific Physical Activity Questionnaire score=12.5 vs 3.6, P=0.001) and have greater bone health knowledge (OKT=17 vs 14, P=0.08), but they had similar levels of current vitamin D supplementation (37.4% vs 21.4%, P=0.11), calcium supplementation (11.2% vs 13.8%, P=0.70), and adequate dietary calcium intake (32.7% vs 25.0%, P=0.43).

DISCUSSION

The high acceptability of vitamin D and calcium supplementation in this cohort suggests that enrollment into a clinical trial of such interventions to mitigate PrEP-induced BMD loss is feasible.

Mechanisms and prevention of UV-induced melanoma

Melanoma is the deadliest form of skin cancer and its incidence is rising, creating a costly and significant clinical problem. Exposure to ultraviolet (UV) radiation, namely UVA (315-400 nm) and UVB (280-315 nm), is a major risk factor for melanoma development. Cumulative UV radiation exposure from sunlight or tanning beds contributes to UV-induced DNA damage, oxidative stress, and inflammation in the skin. A number of factors, including hair color, skin type, genetic background, location, and history of tanning, determine the skin's response to UV radiation. In melanocytes, dysregulation of this UV radiation response can lead to melanoma. Given the complex origins of melanoma, it is difficult to develop curative therapies and universally effective preventative strategies. Here, we describe and discuss the mechanisms of UV-induced skin damage responsible for inducing melanomagenesis, and explore options for therapeutic and preventative interventions.

Predictors of 25-Hydroxyvitamin D Concentration Measured at Multiple Time Points in a Multiethnic Population

The evidence for a relationship between serum vitamin D levels and nonskeletal health outcomes is inconsistent. The validity of single or predicted measurements of 25-hydroxyvitamin D (25(OH)D) concentration is unknown, as levels of this biomarker are highly seasonally variable. We compared models of 25(OH)D measured at baseline, at multiple time points throughout the year, and averaged over the year among 309 persons in Toronto, Ontario, Canada (43°N latitude) during 2009-2013. Information and blood samples were collected every 2 months. Baseline and average 25(OH)D concentrations were correlated (r = 0.88). Major factors associated with 25(OH)D level were similar across models and included race/ethnicity (concentrations in non-European groups were lower than those in Europeans), vitamin D supplement use of ≥1,000 IU/day (18.9 nmol/L (95% confidence interval (CI): 16.1, 21.8) vs. no supplement use in a full data set with all factors), and the presence of the group-specific component/vitamin D binding protein gene (GC/DBP) rs4588 functional polymorphism (AA vs. CC: -16.7 nmol/L (95% CI: -26.2, -7.1); CA vs. CC: -10.7 nmol/L (95% CI: -14.9, -6.5)). Most factors had similar associations in Europeans and non-Europeans. Genetic factors may play a greater role in average 25(OH)D concentrations. Prediction models for 25(OH)D are challenging and population-specific, but use of genetic factors along with a few common population-relevant, quantifiable nongenetic factors with strong associations may be the most feasible approach to vitamin D assessment over time.

Sunbeds with UVB radiation can produce physiological levels of serum 25-Hydroxyvitamin D in healthy volunteers

Vitamin D₃ is produced in the skin in response to UVB irradiation, from either sun exposure or UVB sunbeds. The objective of the current study was to characterize serum 25(OH)D response to regular sunbed use from several lamp outputs following their respective time exposure recommendations. There were three groups that tanned over 12 weeks during the winter months in dedicated sunbeds based on lamp outputs (100 W and 160 W low pressure fluorescent and 700 W high pressure filtered metal halide lamps) and a control group provided serum 25(OH)D samples at baseline and end-of-study. Tanning session lengths were calculated based on Health Canada guidelines to stay below the erythema levels. Mean 25(OH)D were increased by an average of 42 nmol/L in the sunbeds that used 100 W and 160 W fluorescents. Change in 25(OH)D was dependent on baseline 25(OH)D levels and sunbed (p = 0.003) and age (p = 0.03), but was not affected by gender, BMI, Fitzpatrick type or cumulative length of tanning sessions. There was no significant increase in 25(OH)D levels in participants using the 700 W filtered metal halide lamp sunbed or in the control participants. Skin pigmentation, ITA°, was markedly increased in all tanners and skin lightness, L*, significantly decreased at 12 weeks. Both L* and ITA° were significantly correlated with 25(OH)D concentrations for the sunbeds with fluorescent lamps emitting UVB (100 W and 160W). Participants following standardized exposure schedules meeting Health Canada regulations in sunbeds irradiating adequate UVB showed continuous increases of 25(OH)D to physiological levels even after producing a tan in a controlled manner.

ClinicalTrials.gov Registration: NCT02334592

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.

Vitamin D and Cardiovascular Disease: Controversy Unresolved

Vitamin D deficiency is typically caused by inadequate cutaneous synthesis secondary to decreased exposure to sunlight. Serum levels of 25-hydroxyvitamin D l <20 ng/ml are diagnostic of vitamin D deficiency. Vitamin D has various cardiovascular pleiotropic effects by activating its nuclear receptor in cardiomyocytes and vascular endothelial cells and by regulating the renin-angiotensin-aldosterone system, adiposity, energy expenditure, and pancreatic cell activity. In humans, vitamin D deficiency is associated with the following: vascular dysfunction; arterial stiffening; left ventricular hypertrophy; and worsened metrics of diabetes, hypertension, and hyperlipidemia. It is also linked with worse cardiovascular morbidity and mortality. However, meta-analyses of vitamin D supplementation trials have failed to show clear improvements in blood pressure, insulin sensitivity, or lipid parameters, thus suggesting that the link between vitamin D deficiency and cardiovascular disease may be an epiphenomenon. Ongoing larger randomized trials will clarify whether monitoring and supplementation of vitamin D play roles in cardiovascular protection.

25-Hydroxyvitamin-D3 serum modulation after use of sunbeds compliant with European Union standards: A randomized open observational controlled trial

BACKGROUND

Regular use of sunbed exposure has been reported to increase 25-hydroxyvitamin-D3 [25(OH)D] serum levels. However, the influence of sunbeds compliant with the recent European Union standard EN-60335-2-27 on 25(OH)D serum levels is unknown.

OBJECTIVE

We investigated the impact of standard sunbed use compliant with the European Union standard on 25(OH)D serum modulation and well-being.

METHODS

In a randomized controlled study, 25(OH)D serum levels were measured at enrollment, after 1 week, and after completion of the 12-week period of sunbed use with twice weekly exposure and compared with the control group without any sunbed exposure.

RESULTS

In the sunbed intervention group (N = 31), a 27% increase of mean 25(OH)D levels was noted 1 week after starting sunbed use (P < .01). However, after 12 weeks, mean 25(OH)D levels had declined and were no longer different from baseline (P = .06). After 12 weeks, 25(OH)D levels did not differ between the intervention and control group (P = .36). Also the 5-item World Health Organization Well-Being Index score did not differ between the sunbed and control groups (P = .19).

LIMITATIONS

For ethical reasons recruitment was limited to persons actively seeking sunbed exposure.

CONCLUSIONS

Standard use of sunbeds compliant with the European Union standard induced a transient increase of 25(OH)D levels, whereas no change in well-being was observed.

Short-term UVB irradiation significantly increases vitamin D serum concentration in obese patients: a clinical pilot study

PURPOSE

Deficiency of vitamin D is very common in obese people and treatment by oral supplementation is not effective in all patients. This exploratory pilot study investigated the influence of different doses of short-term ultraviolet B irradiation on serum 25-hydroxyvitamin-D₃ (25D) and 1,25-dihydroxyvitamin-D₃ (1,25D) levels in obese compared to normal weight subjects and obese controls.

METHODS

Participants with skin types II and III (Fitzpatrick skin classification) were assigned to six groups including four intervention groups receiving irradiation (three groups of obese and one group of normal weight subjects) and two control groups without treatment (obese and normal weight). Intervention groups received three sessions of whole body UVB irradiation of three different doses (cumulative doses over three sessions: 0.28, 0.70, 1.75 minimal erythema dose) within 1 week of intervention. Serum 25D and 1,25D were measured at baseline and after irradiation. Outcome differences between groups were analyzed using a linear model.

RESULTS

Serum 25D levels increased significantly in obese (+23.6 and +26.7%, respectively, p = 0.01) and normal weight (+15.6%, p = 0.02) intervention groups who received medium and high doses of ultraviolet B irradiation compared to control groups (+3.5 and -4.0%, respectively, p = 1.0). The increase in obese patients was 51.4% greater compared to normal weight controls irradiated with equal ultraviolet B doses. Low-level ultraviolet irradiation did not result in a significant change in serum 25D (+7.0%, p = 0.61). We did not detect any significant differences of 1,25D between groups (p = 0.25).

CONCLUSIONS

The current study indicates that short-term ultraviolet B irradiation increases 25D levels in obese patients.

Short-range ultraviolet irradiation with LED device effectively increases serum levels of 25(OH)D

Impairment of the activities of daily living (ADL) by osteoporosis is an important concern in developed countries with a super-aging population. Vitamin D, which is a crucial molecule in bone metabolism and mainly produced endogenously with ultraviolet (UV) light exposure, is known to be insufficient in the elderly population. We used an UV Light-Emitting Diode (UV-LED) instrument generating a narrow-range wavelength to analyze the efficacy of endogenous vitamin D production. The primary purpose of this study was to examine the effects of UV irradiation at various narrow-range wavelengths using UV-LED on vitamin D supplementation. The second one was to clarify the short-term effects of UV irradiation on bone morphology in mice. Vitamin D-starved C57BL/6 female mice (n=7 per group) were UV-irradiated (268nm, 282nm, 290nm, 305nm, and 316nm) with 1kJ/m² twice a week for 4weeks. UV irradiation using UV-LED had significant effects on increasing serum 25(OH)D levels in all wavelength groups (P<0.001, all groups) as compared to a control group. Among irradiated groups, wavelength of 316nm had a less marked effect on 25(OH)D production compared with other wavelengths at 1week of UV irradiation (P<0.05). Levels of 1,25(OH)₂D were significantly increased after 4weeks irradiation with UV-B or UV-C irradiation (P<0.05). mRNA levels of vitamin D 25-hydroxylase were increased with UV-B or UV-C irradiation (268nm-305nm), significantly. Micro-CT examination revealed that short-term (4weeks) UV-irradiation did not induce morphological change of mice in any group. This study provides essential information that narrow-range UV irradiation with LED can increase the endogenous production of vitamin D, and mRNA levels of the responsible enzyme. Although bone morphology was not altered by short-term UV irradiation in this study, an increase of serum vitamin D might improve bone morphology with long-term irradiation.

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.

Impact of demographic, environmental, and lifestyle factors on vitamin D sufficiency in 9084 Japanese adults

BACKGROUND

Little is known about correlates of vitamin D status in Asian populations. In this study, we established the prevalence of vitamin D sufficiency in the Murakami region (latitude N38°13') in Niigata, Japan, and examined demographic, environmental, and lifestyle factors that might be associated with vitamin D sufficiency, with the aim of clarifying the relative contributions of previously described determinants of vitamin D status as well as identifying new determinants in this Japanese population.

METHODS

This study involved a cross-sectional analysis of baseline data obtained from a cohort study conducted in 2011-2013. Participants were 9084 individuals aged between 40 and 74 years who provided blood samples for the determination of plasma 25-hydroxyvitamin D [25(OH)D] concentrations. Lifestyle information was obtained from 8498 participants, with some missing values regarding different lifestyle factors. Multiple logistic regression analysis was used to obtain odds ratios for vitamin D sufficiency, which was defined as a plasma 25(OH)D concentration ≥ 75 nmol/L.

RESULTS

The prevalence of vitamin D sufficiency (i.e., plasma 25(OH)D concentration ≥ 75 nmol/L) was 9.1%, and significant associations were observed with male gender (P<0.0001; OR=2.37, 95% CI: 1.84-3.05), older age (P for trend <0.0001), lower BMI (P for trend <0.0001), higher METs score (P for trend=0.0138), higher vitamin D intake (P for trend=0.0467), summer season (P for trend <0.0001), longer duration outdoors (P for trend=0.0026), no sunscreen use (P=0.0135; OR=1.40, 95% CI: 1.07-1.82), higher salmon consumption (P for trend <0.0001), higher alcohol consumption (P for trend <0.0001), and lower coffee consumption (P for trend=0.0025). Unlike other populations previously reported, vitamin D sufficiency was associated with older age.

CONCLUSIONS

The prevalence of vitamin D sufficiency (i.e., 25[OH]D ≥ 75 nmol/L) was low (9.1%) in this Japanese population. A number of demographic, environmental, and lifestyle factors are associated with vitamin D sufficiency, and thus lifestyle modification may present an opportunity to achieve vitamin D sufficiency.

Influence of multiple UV exposures on serum cobalamin and vitamin D levels in healthy females

Aims: Ultraviolet (UV) radiation is a major source for vitamin D production. Furthermore, UV destroys cobalamins (also called vitamin B12) in solution. However, data from humans are scarce. The aim of the present study was to clarify if UV exposure has any effect on serum cobalamins, as compared to vitamin D levels, in healthy volunteers. Methods: This single-center, open observational study was conducted in a research institute: 23 non-pregnant, non-lactating, healthy, fair-skinned female subjects had their serum cobalamin and 25-hydroxyvitamin D (25(OH)D, the marker for vitamin D status) levels measured before and after exposure to UV. Results: UV exposure increased serum 25(OH)D levels from 61.6 nmol/L to 88.5 nmol/L (44%; p < 0.001). A statistically insignificant decay in serum cobalamin levels from 300 pmol/L to 260 pmol/L (13%; p = 0.142) was observed in the volunteers after the first UV exposure; however, no additional decline of statistical significance was seen after subsequent exposures. Conclusions: Multiple exposure to UV radiation give a significant increase in 25(OH)D levels, but has no detrimental effect on cobalamin concentrations.

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.

Sunbed use and cutaneous melanoma in Norway

Aims: Incidence rates of cutaneous melanoma (CM) in light skinned people in Norway are among the highest in the world. Sunbed use has increased in Norway since 1980. We will try to elucidate whether there is any correlation between the increase in sunbed use and the CM incidence rates, whether the increase in CM risk is similar for all age groups, and whether the possible difference between young and old persons can inform future healthcare strategies. Methods: The frequency of sunbed use by different age groups in the time period 1980–2011 and incidence rates (1980–2009) of CM at different age groups in Norway were studied. Time in minutes per day spent in front of screen of computers or TVs for boys and girls was also analysed. Results: The number of sunbed sessions per year in Norway increased throughout the entire period. The number of men and women diagnosed with CM per year, all ages combined, also increased. Sunbed use increased at a similar rate for three age groups (0–19, 20–50, and >50 years old), while the age-adjusted CM incidence rate increased only for the oldest group. Time spent in front of the screen of computers or TVs increased from 1985 to 2005 and is still increasing. Conclusions: CM incidence is decreasing while sunbed use is increasing in younger age groups. The present data indicate that more work needs to be done before one can know whether the overall health effects of sunbed exposure are positive or negative.

Vitamin D and cardiovascular disease: is the evidence solid?

Vitamin D deficiency, prevalent in 30-50% of adults in developed countries, is largely due to inadequate cutaneous production that results from decreased exposure to sunlight, and to a lesser degree from low dietary intake of vitamin D. Serum levels of 25-hydroxyvitamin D (25-OH D) <20 ng/mL indicate vitamin D deficiency and levels >30 ng/mL are considered optimal. While the endocrine functions of vitamin D related to bone metabolism and mineral ion homoeostasis have been extensively studied, robust epidemiological evidence also suggests a close association between vitamin D deficiency and cardiovascular morbidity and mortality. Experimental studies have demonstrated novel actions of vitamin D metabolites on cardiomyocytes, and endothelial and vascular smooth muscle cells. Low 25-OH D levels are associated with left ventricular hypertrophy, vascular dysfunction, and renin-angiotensin system activation. Despite a large body of experimental, cross-sectional, and prospective evidence implicating vitamin D deficiency in the pathogenesis of cardiovascular disease, a causal relationship remains to be established. Moreover, the cardiovascular benefits of normalizing 25-OH D levels in those without renal disease or hyperparathyroidism have not been established, and questions of an epiphenomenon where vitamin D status merely reflects a classic risk burden have been raised. Randomized trials of vitamin D replacement employing cardiovascular endpoints will provide much needed evidence for determining its role in cardiovascular protection.

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.

The effects of a mid-winter 8-week course of sub-sunburn sunbed exposures on tanning, vitamin D status and colds

Like UV irradiation, which generates vitamin D(3) in the skin, the hormonally active metabolite, 1,25-dihydroxyvitamin D(3), boosts innate immunity against viruses and bacteria. Epidemiologic studies have found high vitamin D levels to be associated with lower risk of infections of the upper respiratory tract (colds). We have therefore performed an intervention study in 105 young adults (ages 18-30 years; 91% female) over a mid-winter 8-week period (January-March 2010). The participants were randomised to 3 groups: (A) subjected to 3 times a week sub-sunburn sunbed exposure (n = 35), (B) daily vitamin D supplementation, @ 1000 IU (n = 37), and (C) a control group without any intervention (n = 33). The mean serum level of 25-hydroxyvitamin D (25(OH)D) dropped from 62 to 55 nmol l(-1) in group C, while these levels rose from 62 to 109 and from 58 to 93 nmol l(-1) in groups A and B, respectively (p < 0.001). The skin on the chest darkened significantly in group A (mean difference in lightness, L*, equalled -5.7, p < 0.001), correlating significantly, but weakly, with increases in 25(OH)D (3.3 nmol l(-1) per unit drop in L*, R(2) = 0.17, p = 0.014). The percentage of self-reported colds with proper signs and symptoms was only slightly and not significantly reduced in groups A and B in comparison to group C: 57 and 51 versus 67%, respectively. Hence, the sub-sunburn sunbed treatment was effective in tanning and increasing the 25(OH)D serum level, more so than 1000 IU per day, but had no appreciable effect on colds.

Increased vitamin D-binding protein and decreased free 25(OH)D in obese women of reproductive age

PURPOSE

Obese subjects have lower circulating 25-hydroxyvitamin D (25(OH)D) than normal-weight subjects. Knowledge is scarce regarding differences in vitamin D-binding protein (DBP), free 25(OH)D, and intake of vitamin D between normal-weight and obese subjects. The purpose of this study was to examine intake and vitamin D status in obese compared with normal-weight women.

METHODS

Between September 2009 and October 2011, 43 obese and 43 normal-weight women, 22-45 years of age, mean BMI of 39.1 ± 4.6 and 21.6 ± 1.8 kg/m(2), respectively, were recruited in the western Sweden region (latitude 57°N). Blood samples, data regarding diet, and sun exposure were collected.

RESULTS

DBP concentrations were 320 ± 121 and 266 ± 104 μg/mL (P = 0.02) in obese and normal-weight women, respectively. Calculated free 25(OH)D was 13.3 ± 5.5 (obese) and 23.7 ± 10.7 (normal-weight) (P < 0.001). The obese women had a 20.1 nmol/L lower mean 25(HO)D concentration compared to normal-weight women (P < 0.001). 56 % of obese women and 12 % of normal-weight women had 25(OH)D concentrations ≤50 nmol/L. There was no statistically significant difference in total vitamin D intake between the groups. 39 % of the women had a total vitamin D intake <7.5 μg/day, the current national recommendation for vitamin D in Sweden.

CONCLUSIONS

Obese women had higher DBP concentrations compared with normal-weight women and lower free 25(OH)D. The obese women were more likely to have 25(OH)D concentrations that could be considered suboptimal. Vitamin D intake was generally low in normal-weight and obese women of childbearing age.

Determinants of vitamin D status in fair-skinned women of childbearing age at northern latitudes

BACKGROUND AND OBJECTIVE

Poor vitamin D status during pregnancy has been associated with unfavorable outcomes for mother and child. Thus, adequate vitamin D status in women of childbearing age may be important. The aim of this study is to investigate the determinants of 25-hydroxyvitamin D (25(OH)D) serum concentrations in women of childbearing age living in Sweden, at latitude 57-58° north.

METHOD

Eighty four non-pregnant, non-lactating, healthy, fair-skinned women aged between 25-40 years were included. All subjects provided blood samples, four day food records and answered questionnaires about sun exposure and lifestyle. Total serum 25(OH)D was analyzed using Roche Cobas® electrochemoluminiescent immunoassay.

RESULTS

Mean 25(OH)D was 65.8±19.9 nmol/l and 23% of the subjects had concentrations <50 nmol/l. Only 1% had concentrations <25 nmol/l. Determinants of 25(OH)D concentrations were recent sunbed use, recent travel to southern latitude, season, estrogen contraceptive use and use of supplementary vitamin D (R(2) = 0.27).

CONCLUSION

Every fifth woman had 25(OH)D concentrations <50 nmol/l. About 30% of the variation in vitamin D status was explained by sun exposure, use of vitamin D supplements and use of estrogen contraceptives. Cutaneous vitamin D synthesis seems to be a major contributor to vitamin D status, even at northern latitudes. Thus, recommendations on safe UV-B exposure could be beneficial for vitamin D status.

Sunlight and other determinants of circulating 25-hydroxyvitamin D levels in black and white participants in a nationwide U.S. study

Circulating 25-hydroxyvitamin D (25(OH)D), a marker for vitamin D status, is associated with bone health and possibly cancers and other diseases; yet, the determinants of 25(OH)D status, particularly ultraviolet radiation (UVR) exposure, are poorly understood. Determinants of 25(OH)D were analyzed in a subcohort of 1,500 participants of the US Radiologic Technologists (USRT) Study that included whites (n = 842), blacks (n = 646), and people of other races/ethnicities (n = 12). Participants were recruited monthly (2008-2009) across age, sex, race, and ambient UVR level groups. Questionnaires addressing UVR and other exposures were generally completed within 9 days of blood collection. The relation between potential determinants and 25(OH)D levels was examined through regression analysis in a random two-thirds sample and validated in the remaining one third. In the regression model for the full study population, age, race, body mass index, some seasons, hours outdoors being physically active, and vitamin D supplement use were associated with 25(OH)D levels. In whites, generally, the same factors were explanatory. In blacks, only age and vitamin D supplement use predicted 25(OH)D concentrations. In the full population, determinants accounted for 25% of circulating 25(OH)D variability, with similar correlations for subgroups. Despite detailed data on UVR and other factors near the time of blood collection, the ability to explain 25(OH)D was modest.

[Skin, sun exposure and vitamin D: facts and controversies]

Vitamin D plays a clearly defined role in phosphorus, calcium and bone metabolism. In addition to its effects on cellular proliferation and differentiation, and on immunity, it appears to exert other action, poorly understood to date, on human physiology and disease. A number of epidemiological studies have demonstrated a protective role of sun exposure with regard to the incidence of certain immune diseases and cancer, and upon the related mortality rates. Furthermore, over the last 10 years, studies have purported to find levels judged "inadequate" in numerous populations, and, in the absence of any strict scientific arguments, a correlation was established by certain authors between supposedly "inadequate" levels, sun exposure and risk of cancer. However, analysis of the literature shows that there is in fact no precise and consensual definition of normal ranges and that the notion of inadequacy was created artificially using assay techniques lacking in sensitivity and reproducibility. Photosynthesis of vitamin D can in fact be considered perfectly adequate in the majority of populations. However, greater care is needed with elderly subjects and with subjects exposed very little to sunlight. Current studies show that the means of photoprotection used in everyday life do not adversely affect such photosynthesis. In the event of documented vitamin D deficiency, oral supplements should be given, and exposure to natural or artificial UV radiation should not be prescribed. Ultraviolet radiation has been shown to be carcinogenic and responsible for the onset of most skin cancers, and the population must be warned against misleading advertising from the tanning industry. Care should also be taken with regard to the potential harmful effects of inappropriate vitamin D supplementation.

Vitamin D and melanoma incidence and mortality

The role of vitamin D (25-OH-D, or 25-hydroxyvitamin D) and its potential confounders in relationship to melanoma risk and mortality is discussed. The paradox that ultraviolet radiation (UVR) exposure is the major environmental risk factor for melanoma etiology as well as a major source of vitamin D might be explained by viewing vitamin D levels as the result of a healthy lifestyle rather than a cause of health.

Changes in serum 25-hydroxyvitamin D and cholecalciferol after one whole-body exposure in a commercial tanning bed: a randomized study

We wanted to evaluate the cutaneous synthesis of 25OHD and cholecalciferol after one whole-body exposure to ultraviolet radiation type B (UVB) in a randomized setup. Healthy volunteers were randomized to one whole-body exposure in a commercial tanning bed with UVB emission (UVB/UVA ratio 1.8-2.0%) or an identical placebo tanning bed without UVB. The output in the 280-320 nm range was 450 µW/cm². Blood samples were analyzed for 25OHD and cholecalciferol at baseline and during 7 days after treatment. We included 20 volunteers, 11 to UVB and 9 to placebo treatment. During the first 6 h, no significant differences in 25OHD between the groups were found. At the end of the study, we found a mean increase of 25OHD in the UVB group of 4.5 nmol/l (SD 7 nmol/l) compared to a decline of -1.2 nmol/l (SD 7 nmol/l) in the placebo group (p = 0.1). A linear mixed model yielded an increase of 25OHD in the UVB group of 1.0 nmol/l per 24 h (p < 0.01). For cholecalciferol, we found a near significant increase of 1 pmol/l per hour in the UVB group compared to the placebo group during the first 6 h (p = 0.052). One tanning bed session had significant, but modest impact on the level of 25OHD during 7 days after exposure to UVB.

Recommended summer sunlight exposure amounts fail to produce sufficient vitamin D status in UK adults of South Asian origin

BACKGROUND

The cutaneous synthesis of vitamin D is dependent on UVB from sunlight, but melanin reduces the penetration of UVB and thus contributes to vitamin D insufficiency in individuals with darker skin. The national guidance provided on amounts of sunlight exposure in the United Kingdom is for the light-skinned population, and in the absence of dedicated information, darker-skinned people may attempt to follow this guidance.

OBJECTIVES

We determined the relative effect of a simulation of UK recommendations of summer sunlight exposure on the vitamin D status of individuals of South Asian ethnicity compared with that of whites.

DESIGN

In a prospective cohort study, simulated summer sunlight exposures were provided under rigorous dosimetric conditions to 15 adults (aged 20-60 y) of South Asian ethnicity, and serum 25-hydroxyvitamin D [25(OH)D] was measured weekly. Dietary vitamin D intake was estimated. Outcomes were compared with those of 109 whites (aged 20-60 y) treated with the identical UV-radiation exposure protocol.

RESULTS

At baseline (winter trough), all South Asians were vitamin D-insufficient [25(OH)D concentrations <20 ng/mL], and 27% of South Asians were vitamin D-deficient [25(OH)D concentrations <5 ng/mL]; although 25(OH)D concentrations increased postcourse (P < 0.0001), all South Asians remained vitamin D-insufficient. The mean increase in 25(OH)D was 4.3 compared with 10.5 ng/mL in the South Asian and white groups, respectively (P < 0.0001), and 90% of the white group reached vitamin D sufficiency postcourse. The median dietary vitamin D intake was very low in both groups.

CONCLUSIONS

Sunlight-exposure recommendations are inappropriate for individuals of South Asian ethnicity who live at the UK latitude. More guidance is required to meet the vitamin D requirements of this sector of the population. This study was registered at www.isrctn.org as ISRCTN 07565297.

Vitamin D, sun, sunbeds and health

Objective

To review the health effects of solar radiation, sunbeds and vitamin D.

Design

The literature was searched in the electronic database MEDLINE to indentify published data between 1981 and 2011. Studies were included if they reported relative risk for cutaneous malignant melanoma (CMM) associated with sunbed use, vitamin D and UV effects on human health.

Setting

Data from different time periods for populations at different latitudes.

Subjects

Persons of different ages and ethnic groups.

Results

UV from sun and sunbeds is the main vitamin D source. Young people with white or pigmented skin in northern Europe have a low vitamin D status. A number of health benefits from sufficient levels of vitamin D have been identified. However, UV exposure has been suspected of causing skin cancer, notably CMM, and authorities warn against it.

Conclusions

The overall health benefit of an improved vitamin D status may be more important than the possibly increased CMM risk resulting from carefully increasing UV exposure. Important scientific facts behind this judgement are given.

Genetic Ancestry, Skin Reflectance and Pigmentation Genotypes in Association with Serum Vitamin D Metabolite Balance

BACKGROUND

Lower serum vitamin D (25(OH)D) among individuals with African ancestry is attributed primarily to skin pigmentation. However, the influence of genetic polymorphisms controlling for skin melanin content has not been investigated. Therefore, we investigated differences in non-summer serum vitamin D metabolites according to self-reported race, genetic ancestry, skin reflectance and key pigmentation genes (SLC45A2 and SLC24A5).

MATERIALS AND METHODS

Healthy individuals reporting at least half African American or half European American heritage were frequency matched to one another on age (+/- 2 years) and sex. 176 autosomal ancestry informative markers were used to estimate genetic ancestry. Melanin index was measured by reflectance spectrometry. Serum vitamin D metabolites (25(OH)D₃, 25(OH)D ₂ and 24,25(OH)₂D₃) were determined by high performance liquid chromatography (HPLC) tandem mass spectrometry. Percent 24,25(OH)₂D₃ was calculated as a percent of the parent metabolite (25(OH)D₃). Stepwise and backward selection regression models were used to identify leading covariates.

RESULTS

Fifty African Americans and 50 European Americans participated in the study. Compared with SLC24A5 111^Thr homozygotes, individuals with the SLC24A5 111^Thr/Ala and 111^Ala/Ala genotypes had respectively lower levels of 25(OH)D₃ (23.0 and 23.8 nmol/L lower, p-dominant=0.007), and percent 24,25(OH)₂D₃ (4.1 and 5.2 percent lower, p-dominant=0.003), controlling for tanning bed use, vitamin D/fish oil supplement intake, race/ethnicity, and genetic ancestry. Results were similar with melanin index adjustment, and were not confounded by glucocorticoid, oral contraceptive, or statin use.

CONCLUSIONS

The SLC24A5 111^Ala allele was associated with lower serum vitamin 25(OH)D₃ and lower percent 24,25(OH)₂D₃, independently from melanin index and West African genetic ancestry.

Oral cholecalciferol versus ultraviolet radiation B: effect on vitamin D metabolites in patients with chronic pancreatitis and fat malabsorption - a randomized clinical trial

BACKGROUND

Patients with chronic pancreatitis (CP) often develop fat malabsorption and are susceptible to hypovitaminosis D.

AIM

We wanted to evaluate the intestinal uptake of cholecalciferol in patients with CP and fat malabsorption.

METHODS

We did a prospective placebo-controlled study including patients with verified CP and fat malabsorption. They were randomized to 10 weeks of (A) ultraviolet radiation B (UVB) 6 min weekly in a commercial tanning bed, (B) vitamin D supplement 1,520 IU/daily, or (C) placebo. The vitamin D metabolites 25-hydroxyvitamin D (25OHD) and 1,25-dihydroxyvitamin D (calcitriol) were quantified at the start and end of the study.

RESULTS

In total 30 patients were randomized and 27 completed the study. Compliance to tablets and tanning sessions was >80%. The changes in 25OHD levels in group B (32.3 nmol/l; 95% CI 15-50) were significantly greater than changes in group A (p < 0.001) and group C (p < 0.001). Changes in group A (1.1 nmol/l) did not differ from the placebo group (p = 0.9). Changes in calcitriol levels were identical between groups.

CONCLUSIONS

Daily vitamin D supplements increased 25OHD in patients with CP compared to placebo whereas weekly tanning bed sessions did not.

Adverse effects of ultraviolet radiation from the use of indoor tanning equipment: time to ban the tan

The incidence of melanoma skin cancer is increasing rapidly, particularly among young women in the United States. Numerous studies have documented an association between the use of indoor tanning devices and an increased risk of skin cancer, especially in young women. Studies have shown that ultraviolet exposure, even in the absence of erythema or burn, results in DNA damage. Countries and regulatory bodies worldwide have recognized the health risks associated with indoor tanning. In the United States, 32 states have passed legislation to regulate the indoor tanning industry, but there is an urgent need to restrict the use of indoor tanning devices at the federal level. The Food and Drug Administration is currently reviewing the classification of these devices. For all of these reasons, the Food and Drug Administration should prohibit the use of tanning devices by minors and reclassify tanning devices to at least class II to protect the public from the preventable cancers and other adverse effects caused by ultraviolet radiation from indoor tanning.

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.

Review Article: Health benefit of increased serum 25(OH)D levels from oral intake and ultraviolet-B irradiance in the Nordic countries

Aims: A low serum 25-hydroxyvitamin D [25(OH)D] level is a risk factor for many diseases, including musculoskeletal diseases, many types of cancer, cardiovascular diseases, diabetes mellitus, infectious diseases, autoimmune diseases, and brain diseases. This report estimates the reduction in mortality rates for the five Nordic countries for an increase in population mean serum 25-hydroxyvitamin D level to 105 nmol/L. Methods: Serum vitamin D dose—incidence/prognosis relationships can be developed with significant levels of reliability for most vitamin D-sensitive diseases on the basis of ecological, cross-sectional, and observational studies, randomized controlled trials, and meta-analysis of such studies. These dose—response relations are used to estimate the population-wide benefit of raising mean serum 25(OH)D concentration to 105 nmol/L for the five Nordic countries. Results: From this study, the reductions in mortality rates possible by raising population mean serum 25(OH)D levels to 105 nmol/L are: Denmark, 17% (estimated range,11%—24%); Finland, 24% (17%—32%); Iceland, 24% (17%—32%); Norway, 18% (11%—26%); and Sweden, 18% (8%—25%). Conclusions: Reaching these levels would require changes in health policies with respect to solar ultraviolet-B (UVB) irradiance, vitamin D fortification of food, availability of vitamin D and calcium supplements, and attitude toward use of UVB lamps. Adverse effects of oral vitamin D intake are limited, and those from UVB irradiance are minor compared with the benefits.

Are active sun exposure habits related to lowering risk of type 2 diabetes mellitus in women, a prospective cohort study?

AIM

An inverse relationship exists between vitamin D levels and diabetes mellitus. However, little is known about the correlation of sun exposure habits and type 2 diabetes mellitus (DM).

METHODS

A South Swedish cohort study comprising 1000 women from each age group between 25 and 64 (n=40,000) drawn from the Southern Swedish population registry 1990-1992. At the inception of the study 74% answered the inquiry (n=29,518) and provided detailed information on their sun exposure habits and other variables. A follow-up inquiry was sent 2000-2002 which 24,098 women answered. The mean follow-up time was 11 years. Logistic regression analysis was used and the main outcome was the relationship between type 2 DM and sun exposure habits.

RESULTS

Our findings indicated that women with active sun exposure habits were at a 30% lower risk of having DM, as compared to those with non-active habits. There was an inverse relation between this risk reduction and BMI.

CONCLUSION

Our investigation gives possible epidemiological explanation to ethnic and seasonal differences in type 2 DM and metabolic control. The study supports that sunlight is involved in the glucose metabolism.

Variability of pre-vitamin D3 effectiveness of UV appliances for skin tanning

While there is limited documentation that certain indoor tanning lamps effectively produce vitamin D, the diversity of such devices has not been extensively surveyed. This study compares the spectral effectiveness of a variety of tanning units, and solar spectra, for ultraviolet (UV) photosynthesis of pre-vitamin D3 (preD3) and UV induced erythema. Well-established techniques exist for the calculation of spectral effectiveness for photobiological responses that have defined action spectra. Using spectroradiometric data from sunlamp measurements, and standard solar reference spectra, we computed effective irradiances using the CIE action spectrum for the production of preD3 in human skin and the ISO/CIE human erythema reference action spectrum. We found, as with sunlight at different times or latitude, the preD3 and erythemal effectiveness of sunlamps varied as a function of the UV-B proportion of the spectrum. Ratios of sunlamp preD3 to erythemal effectiveness ranged from approximately 0.5 to nearly 2.0, similar to ratios for sunlight. Optimal risk to benefit conditions for preD3 from solar UV exposure occurs under high solar altitude, low zenith angle, midday midsummer sunlight. Analogous optimal preD3 exposure conditions are provided by low to intermediate pressure sunlamps with greater UV-B spectral overlap with the preD3 action spectrum. Similar to low altitude or high latitude sunlight, high pressure tanning units, filtered for negligible UV-B emissions, have insignificant vitamin D benefit. We conclude that while vitamin D can be made by both UVB exposure from indoor tanning units and by exposure UVB from sunlight, the effect is also comparably variable. Unlike sunlight, indoor tanning offers privacy and environmental conditions for practical full body exposure, lowering the requisite exposure per skin surface area, and device timers limit the potential of overexposure. Guidance for optimal use of tanning sources for vitamin D benefit is needed.

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

The influence of the summer UVR exposure on serum-25-hydroxyvitamin D (25(OH)D) in late summer and winter was investigated in an open study on 25 healthy, adult volunteers. The UVR exposure dose in standard erythema dose (SED) was monitored continuously during a summer season with personal, electronic wristwatch UVR dosimeters and sun exposure diaries. Constitutive and facultative skin pigmentation was measured in September. 25(OH)D was measured in September and February and was in mean 82 nmol/L +/- 25 (mean +/- SD) in September and 56 nmol/L +/- 19 (mean +/- SD) in February. The received cumulative UVR dose measured during a mean of 121 days was 156 SED +/- 159 (mean +/- SD). The following UVR exposure parameters correlated with 25(OH)D in September and February, respectively: (1) The cumulative UVR dose (r = 0.53; P < 0.01) and (r = 0.43; P = 0.03); (2) Mean daily hours with UVR measurements monitored by the dosimeter (r = 0.64, P = 0.001) and (r = 0.53; P = 0.007); (3) Days "with sun-exposed upper body" (r = 0.58, P = 0.003) and (r = 0.50; P = 0.01); (4) Facultative pigmentation (r = 0.47; P < 0.02) and (r = 0.7; P < 0.001); (5) Constitutive pigmentation (r = 0.06, n.s.) and (r = 0.43, P = 0.03). Neither days "sunbathing" nor days with "sunscreen applied" correlated with 25(OH)D. The fall in 25(OH)D during winter was dependent on the entry value.