Recommended Summer Sunlight Exposure Levels Can Produce Sufficient (≥20ngml−1) but Not the Proposed Optimal (≥32ngml−1) 25(OH)D Levels at UK Latitudes

Vitamin D status of White pregnant women and infants at birth and 4 months in North West England: A cohort study

The prevalence of vitamin D deficiency in pregnant white-skinned women (WSW) and their infants has not been investigated at northern latitudes in a developed county. A 2-year observational cohort study was undertaken in the North West of England to determine 25-hydroxyvitamin D (25OHD) levels in WSW and their infants during pregnancy and 4 months postdelivery and to explore factors associated with these levels. Nutritional and lifestyle questionnaires were completed and 25OHD levels measured at 28 weeks and 4 months postdelivery. Twenty-seven percent and 7% of WSW had insufficient and deficient levels of 25OHD during pregnancy and 48% and 11% four months postdelivery. WSW with Fitzpatrick skin-type I (FST I) have significantly lower 25OHD than other skin types after controlling for time spent outside and vitamin D intake. Twenty-four percent and 13% of infants had insufficient and deficient 25OHD levels at 4 months. Unsupplemented breast-fed infants have the highest level of insufficiency (67%) compared with formula-fed infants (2%). Factors associated with infant serum 25OHD levels at 4 months included breast feeding, supplementation, and time outside. WSW have a high prevalence of insufficiency and deficiency during pregnancy which doubles 4 months after birth. Breast-fed infants of WSW are rarely considered at risk of vitamin D insufficiency but have high rates compared with formula-fed infants. This is the first study to show the finding that FST I WSW have significantly lower levels of 25OHD than those with FST II-IV (difference adjusted for diet and time outside 14 (95%CI 7-21) nmol/L).

Vitamin D-binding protein, vitamin D status and serum bioavailable 25(OH)D of young Asian Indian males working in outdoor and indoor environments

Urban Asian Indians generally have low serum 25(OH)D. Information on serum bioavailable 25(OH)D and the effect of prolonged sun-exposure in them is not known. We assessed serum 25(OH)D and bioavailable 25(OH)D in males with varying durations of sun-exposure in Delhi during August-September. Serum 25(OH)D, vitamin D-binding protein (DBP), bioavailable 25(OH)D, free 25(OH)D index, iPTH, ionized calcium and sun-index were assessed in outdoor, mixed outdoor-indoor and indoor workers (n = 88, 32 and 74, respectively). The mean sun-index (12.0 ± 6.25, 4.3 ± 2.20 and 0.7 ± 0.62, respectively; P < 0.001) was highest outdoors and lowest indoors. Serum 25(OH)D (29.0 ± 8.61, 19.1 ± 5.73 and 10.9 ± 4.19 ng/ml, respectively; P < 0.001), bioavailable 25(OH)D and free 25(OH)D index were maximum in outdoor workers followed by mixed-exposure and indoor workers. Their mean serum DBP levels (241.2 ± 88.77, 239.3 ± 83.40 and 216.6 ± 63.93 µg/ml, respectively; P = 0.12) were comparable. Mean serum iPTH was significantly lower in outdoor than indoor workers and showed inverse correlations with serum 25(OH)D, bioavailable 25(OH)D and free 25(OH)D index (r = -0.401, -0.269 and -0.236, respectively; P < 0.001 in all). Daily dietary-calorie intake was higher and calcium lower in outdoor than indoor workers. On regression analysis, sun-exposure was the only significant variable, increasing serum 25(OH)D by 2.03 ng/ml per hour of sun-exposure (95 % confidence interval 1.77-2.28; P < 0.001). Outdoor workers with prolonged sun-exposure were vitamin D-sufficient, with higher serum bioavailable 25(OH)D than the indoor workers during summer. Use of serum DBP levels did not affect the interpretation of their vitamin D status.

Vitamin D deficiency in patients with inflammatory bowel disease

There are over 300 000 people in the UK affected by inflammatory bowel disease (IBD). Though vitamin D deficiency is common in patients with IBD, National Institute for Health and Care Excellence (NICE) guidance regarding vitamin D supplementation does not address the needs of patients with chronic inflammatory diseases. However, there is growing evidence that vitamin D plays an important role in the management of IBD. Nurses caring for patients with IBD should have an understanding of the causes and consequences of vitamin D deficiency in this patient group. This article looks at the role vitamin D plays in the body and the challenges of treating deficiency. Consideration is given to diet, sun exposure and supplementation as possible treatments and acknowledges the limitations of treatments for patients with IBD. With a lack of clear national guidance, it is hoped that raising awareness of these issues will inform nursing practice and ensure a holistic approach to care.

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

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

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

Background

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

Objectives

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

Methods

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

Results

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

Conclusions

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

What's already known about this topic?

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

What does this study add?

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

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

The findings are informative for sun‐exposure guidance.

Plain language summary available online

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

BACKGROUND

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

OBJECTIVE

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

DESIGN

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

RESULTS

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

CONCLUSIONS

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

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.

Vitamin D: Australian dietitian's knowledge and practices

AIM

To survey dietitians on their knowledge and practices regarding vitamin D (VitD) intake, sources, supplementation and effect on disease state.

METHODS

An online survey was disseminated to members of the Dietitian Association Australia via the weekly online state newsletter during April 2015. Response rate was 3%, with 134 respondents completing the survey. The survey included questions about knowledge and current practices. Descriptive statistics were used to analyse the results.

RESULTS

Dietitians have good knowledge regarding dietary sources of VitD and roles in the body, but there is confusion around supplement doses for treatment and prevention of deficiency and sun exposure guidelines.

CONCLUSIONS

Dietitians are well positioned to provide patients with advice on VitD supplementation and sun exposure practices, but not all are confident to provide this care. There is a need for clear and well-disseminated guidelines for VitD management by dietitians.

Vitamin D insufficiency and deficiency in patients with fractures of the fifth metatarsal

INTRODUCTION

The fifth metatarsal is a common site for both acute and stress fractures in the foot. They are usually isolated low-energy or stress fractures. Vitamin D deficiency has been associated with fragility fractures in many parts of the body. We believe that low Vitamin D could be a significant aetiological factor in fractures of the fifth metatarsal.

METHODOLOGY

A prospective study of patients with fractures of the fifth metatarsal was conducted. Patients presenting to fracture clinic with these fractures had their vitamin D and calcium levels measured. We also conducted a literature review of studies of vitamin D levels in the Northern Hemisphere between 1990 and 2014.

RESULTS

Forty patients with fifth metatarsal fractures were studied (22 metatarsal base fractures, 6 shaft fractures, and 2 stress fractures). The average patient age was 49 (range 22-83). 12 patients (30%) had a Vitamin D level consistent with deficiency, and a further 14 (35%) had a level consistent with insufficiency. Average Vitamin D levels in winter fractures were significantly lower (52.23nmol/L) than for those sustained in summer (76.73nmol/L).

CONCLUSIONS

Hypovitaminosis D was common in patients with fifth metatarsal fractures. Vitamin D supplementation has been shown in animal studies to improve fracture healing rates, and in humans to decrease the risk of fragility fracture. It should be part of regular practice to check Vitamin D levels in these patients, and supplement where necessary.

Farming, Foreign Holidays, and Vitamin D in Orkney

Orkney, north of mainland Scotland, has the world's highest prevalence of multiple sclerosis (MS); vitamin D deficiency, a marker of low UV exposure, is also common in Scotland. Strong associations have been identified between vitamin D deficiency and MS, and between UV exposure and MS independent of vitamin D, although causal relationships remain to be confirmed. We aimed to compare plasma 25-hydroxyvitamin D levels in Orkney and mainland Scotland, and establish the determinants of vitamin D status in Orkney. We compared mean vitamin D and prevalence of deficiency in cross-sectional study data from participants in the Orkney Complex Disease Study (ORCADES) and controls in the Scottish Colorectal Cancer Study (SOCCS). We used multivariable regression to identify factors associated with vitamin D levels in Orkney. Mean (standard deviation) vitamin D was significantly higher among ORCADES than SOCCS participants (35.3 (18.0) and 31.7 (21.2), respectively). Prevalence of severe vitamin D deficiency was lower in ORCADES than SOCCS participants (6.6% to 16.2% p = 1.1 x 10(-15)). Older age, farming occupations and foreign holidays were significantly associated with higher vitamin D in Orkney. Although mean vitamin D levels are higher in Orkney than mainland Scotland, this masks variation within the Orkney population which may influence MS risk.

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

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

Are the current Australian sun exposure guidelines effective in maintaining adequate levels of 25-hydroxyvitamin D?

An adequate vitamin D status, as measured by serum 25-hydroxyvitamin D (25(OH)D) concentration, is important in humans for maintenance of healthy bones and muscle function. Serum 25(OH)D concentration was assessed in participants from Melbourne, Australia (37.81S, 144.96E), who were provided with the current Australian guidelines on sun exposure for 25(OH)D adequacy (25(OH)D ≥50 nmol/L). Participants were interviewed in February (summer, n=104) and August (winter, n=99) of 2013. Serum 25(OH)D concentration was examined as a function of measures of sun exposure and sun protection habits with control of key characteristics such as dietary intake of vitamin D, body mass index (BMI) and skin colour, that may modify this relationship. The mean 25(OH)D concentration in participants who complied with the current sun exposure guidelines was 67.3 nmol/L in summer and 41.9 nmol/L in winter. At the end of the study, 69.3% of participants who complied with the summer sun exposure guidelines were 25(OH)D adequate, while only 27.6% of participants who complied with the winter sun exposure guidelines were 25(OH)D adequate at the end of the study. The results suggest that the current Australian guidelines for sun exposure for 25(OH)D adequacy are effective for most in summer and ineffective for most in winter. This article is part of a Special Issue entitled '17th Vitamin D Workshop'.

The action spectrum for vitamin D3: initial skin reaction and prolonged exposure

The action spectrum concept for vitamin D photosynthesis in skin is assessed for prolonged exposure, including side- and return-reactions. A generalized expression for the action spectrum is presented. Production estimates per erythemal dose are given.

Comparing the effects of sun exposure and vitamin D supplementation on vitamin D insufficiency, and immune and cardio-metabolic function: the Sun Exposure and Vitamin D Supplementation (SEDS) Study

Background

Adults living in the sunny Australian climate are at high risk of skin cancer, but vitamin D deficiency (defined here as a serum 25-hydroxyvitamin D (25(OH)D) concentration of less than 50 nmol/L) is also common. Vitamin D deficiency may be a risk factor for a range of diseases. However, the optimal strategies to achieve and maintain vitamin D adequacy (sun exposure, vitamin D supplementation or both), and whether sun exposure itself has benefits over and above initiating synthesis of vitamin D, remain unclear.

The Sun Exposure and Vitamin D Supplementation (SEDS) Study aims to compare the effectiveness of sun exposure and vitamin D supplementation for the management of vitamin D insufficiency, and to test whether these management strategies differentially affect markers of immune and cardio-metabolic function.

Methods/Design

The SEDS Study is a multi-centre, randomised controlled trial of two different daily doses of vitamin D supplementation, and placebo, in conjunction with guidance on two different patterns of sun exposure. Participants recruited from across Australia are aged 18–64 years and have a recent vitamin D test result showing a serum 25(OH)D level of 40–60 nmol/L.

Discussion

This paper discusses the rationale behind the study design, and considers the challenges but necessity of data collection within a non-institutionalised adult population, in order to address the study aims. We also discuss the challenges of participant recruitment and retention, ongoing engagement of referring medical practitioners and address issues of compliance and participant retention.

Trial registration

Australia New Zealand Clinical Trials Registry: ACTRN12613000290796 Registered 14 March 2013.

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

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

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

Ozone depletion, climate and human health.

Vitamin D: Photobiological and Ecological Aspects

Vitamin D was discovered as a result of its ability to cure rickets, but recently a wide range of other functions for it in the human body has been suggested. Vitamin D is not a vitamin in the strict sense as it can be synthesised in the human body following exposure of the skin to ultraviolet radiation. Provitamin D (7-dehydrocholesterol) is converted to previtamin D which is further modified by a series of reactions to the active form, 1,25-dihydroxyvitamin D. This Chapter summarises the discovery of vitamin D and reviews the chemistry and photochemistry of its precursors, transformations and metabolites. The production of vitamin D in various human populations is described, and how to assess vitamin D status. The skeletal and non-skeletal effects of vitamin D are discussed, particularly its role in immunomodulation with consequences for protection against a variety of human diseases. The Chapter concludes with evolutionary aspects, the occurrence and role of vitamin D in the plant kingdom, biogeographical considerations, and the nonphotochemical production of vitamin D in certain plants.

Vitamin D response of older people in residential aged care to sunlight-derived ultraviolet radiation

The aim of this study was to determine the vitamin D response to sunlight ultraviolet radiation in older people. Increases in vitamin D depended on the season of exposure, but the changes were small. Natural sun exposure is not a practical intervention for vitamin D deficiency in this population.

PURPOSE

The purpose of this study is to measure the ultraviolet radiation (UVR) exposure of those in residential aged care in an earlier trial of sunlight exposure and to determine its effect on their vitamin D response.

METHODS

Attendance data, demographic, clinical and biochemical variables for 248 participants were used for a secondary analysis of a previous cluster randomized trial of sunlight exposure and falls. The ambient solar UV Index data were used to calculate the participants' UVR dose. Multiple linear regression was used to test if UVR exposure over 6 months, as measured by the standard erythemal dose (SED), was a predictor of vitamin D response, controlling for age, gender, BMI, calcium intake, baseline vitamin D and season of exposure.

RESULTS

The median 25-hydroxyvitamin D (25OHD) was 32.4 nmol/L at baseline and 34.6 nmol/L at 6 months (p = 0.35). The significant predictors of 25OHD at 6 months were UVR exposures in spring-summer (coefficient = 0.105, 95 % confidence interval (CI) 0.001-0.209, p = 0.05) and autumn-winter (coefficient = 0.056, 95 % CI 0.005-0.107, p = 0.03) and baseline vitamin D (adjusted coefficient = 0.594, 95 % CI 0.465-0.724, p = 0.00). In those starting sunlight sessions in spring, an increase of 1 unit in log SED was associated with 11 % increase in 25OHD.

CONCLUSIONS

Natural UVR exposure can increase 25OHD levels in older people in residential care, but depends on the season of exposure. However, due to inadequate sun exposure, 25OHD did not reach optimal levels. Nevertheless, where sun exposure is encouraged in this group, the focus for the start of exposure should be in the months of spring or autumn, as this timing was associated with a vitamin D response.

The relationship between ultraviolet light exposure and mortality in dialysis patients

BACKGROUND

Emerging data suggest that reduced exposure to ultraviolet (UV) radiation is associated with increased mortality in the general population. To date, the association between UV exposure and mortality in dialysis patients has not been examined.

METHODS

We examined the association between UV index, a proxy of UV exposure, and all-cause mortality among 47,286 US dialysis patients (entry period 2001-2006, with follow-up through 2009) from a large national dialysis organization using multivariable Cox regression. The UV index was ascertained by linking individual patients' residential zip codes to National Oceanic and Atmospheric Administration data, and was categorized as low (0-<3), moderate (3-<5), moderate-high (5-<6), high (6-<7), and very-high (≥7). In secondary analyses, we examined the UV index-mortality association within subgroups of age (<65 vs. ≥65 years old), sex, and race (white vs. non-white).

RESULTS

The study population's mean ± SD age was 60 ± 16 and included 46% women and 56% diabetics. Compared to patients residing in moderate-high UV index regions, those residing in high and very-high UV index regions had a lower mortality risk: adjusted HRs 0.84 (95% CI) 0.81-0.88 and 0.83 (95% CI) 0.75-0.91, respectively. A similar inverse association between UV index and mortality was observed across all subgroups, although there was more pronounced reduction in mortality among whites vs. non-whites.

CONCLUSION

These data suggest that dialysis patients residing in higher UV index regions have lower all-cause mortality compared to those living in moderate-high UV regions. Further studies are needed to determine the mechanisms underlying the UV index-mortality association.

Evidence That Loss-of-Function Filaggrin Gene Mutations Evolved in Northern Europeans to Favor Intracutaneous Vitamin D3 Production

Skin pigmentation lightened progressively to a variable extent, as modern humans emigrated out of Africa, but extreme lightening occurred only in northern Europeans. Yet, loss of pigmentation alone cannot suffice to sustain cutaneous vitamin D3 (VD3) formation at the high latitudes of northern Europe. We hypothesized that loss-of-function mutations in the epidermal structural protein, filaggrin (FLG), could have evolved to sustain adequate VD3 status. Loss of FLG results in reduced generation of trans-urocanic acid, the principal endogenous ultraviolet-B (UV-B) filter in lightly-pigmented individuals. Accordingly, we identified a higher prevalence of FLG mutations in northern European populations when compared to more southern European, Asian and African populations that correlates significantly with differences in circulating 25-OH-VD3 levels in these same populations. By allowing additional UV-B penetration and intracutaneous VD3 formation, the latitude-dependent gradient in FLG mutations, likely together with other concurrent mutations in VD3 metabolic pathways, provide a non-pigment-based mechanism that sustains higher levels of circulating VD3 in northern Europeans. At the time that FLG mutations evolved, xerosis due to FLG deficiency was a lesser price to pay for enhanced VD3 production. Yet, the increase in FLG mutations has inadvertently contributed to an epidemic of atopic diseases that has emerged in recent decades.

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).

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.

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

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

Vitamin D and solar ultraviolet radiation in the risk and treatment of tuberculosis

Improved understanding of the association between tuberculosis and vitamin D is needed to inform clinical practice. Vitamin D has both immunostimulatory and immunosuppressive effects relevant to human antimycobacterial responses. Ultraviolet radiation, the main source of vitamin D, also induces immunomodulation and could affect the relation between vitamin D and tuberculosis. Clinical trials of vitamin D supplementation in patients with tuberculosis have produced largely negative results, prompting the review of dosing regimens-an explanation for low 25-hydroxyvitamin D status in patients with active tuberculosis is also needed. The reporting of vitamin D deficiency needs to address assay inaccuracies, rising thresholds to define sufficiency, and scarce knowledge of the concentrations needed for optimum immune responses. Future research to measure the effect of the inflammatory setting on serum concentrations of 25-hydroxyvitamin D, at tuberculosis diagnosis and during recovery, could help to account for 25-hydroxyvitamin D changes in these concentrations in patients with tuberculosis. Studies into the role of vitamin D supplementation in latent tuberculosis justify clinical trials in this population, but pose methodological challenges. Vitamin D trials in patients with active tuberculosis should be done in well selected populations using adequate vitamin D doses, although such doses remain undefined.

Contributions of sunlight and diet to vitamin D status

Vitamin D is made in the skin using ultraviolet radiation of specific low wavelength, 290-315 nm (UVB). For many parts of the world there is a period when there is insufficient intensity of UVB to make vitamin D, which is reflected by a clear seasonal variation in vitamin D status. Sun avoidance practices, melanin in pigmented skin, and sun protection creams (sunscreen), if used properly, can dramatically reduce vitamin D synthesis. Few foods naturally contain vitamin D, although some countries fortify foods with vitamin D. Regulatory mechanisms in the skin mean there is no danger of vitamin D toxicity through sunlight synthesis. Although oral vitamin D is potentially toxic with high-dose supplements, there is a wide safety margin. Long-term safety data covering a range of potential adverse outcomes are limited.

Modelling vitamin D status due to oral intake and sun exposure in an adult British population

A mathematical model is described for estimating changes in plasma 25-hydroxyvitamin D (25(OH)D) levels throughout the year as a consequence of varying the oral intake of vitamin D and the behaviour outdoors of white British adults resident in different regions of the UK. The model yields seasonal and geographical patterns of 25(OH)D concentrations that agree closely with observational studies. Use of the model allows estimates to be easily made of the sun exposure and oral intake necessary to avoid vitamin D deficiency in defined proportions of the population, as well as strategies that would lead to vitamin D sufficiency throughout the year. The analysis demonstrates that addressing concerns about insufficient vitamin D levels, especially during the winter, may be achieved by modifying oral vitamin D intake over the winter, increasing summer sun exposure or a combination of both.

Seasonal variation in 25(OH)D at Aberdeen (57°N) and bone health indicators--could holidays in the sun and cod liver oil supplements alleviate deficiency?

Vitamin D has been linked with many health outcomes. The aim of this longitudinal study, was to assess predictors of seasonal variation of 25-hydroxy-vitamin D (25(OH)D) (including use of supplements and holidays in sunny destinations) at a northerly latitude in the UK (57°N) in relation to bone health indicators. 365 healthy postmenopausal women (mean age 62.0 y (SD 1.4)) had 25(OH)D measurements by immunoassay, serum C-telopeptide (CTX), estimates of sunlight exposure (badges of polysulphone film), information regarding holidays in sunny destinations, and diet (from food diaries, including use of supplements such as cod liver oil (CLO)) at fixed 3-monthly intervals over 15 months (subject retention 88%) with an additional 25(OH)D assessment in spring 2008. Bone mineral density (BMD) at the lumbar spine (LS) and dual hip was measured in autumn 2006 and spring 2007 (Lunar I-DXA). Deficiency prevalence (25(OH)D<25 nmol/L) was reduced in women who went on holiday to sunny destinations 3 months prior to their visit, compared to women who did not go on holidays [5.4% vs. 24.6% in Spring (p<0.001) and 3.8% vs. 25.6% in Winter (p = 0.001), respectively]. Similarly deficiency was lower amongst those who took CLO supplements compared to women that did not consume these supplements [2.0% vs. 23.7% in Spring (p = 0.001) and 4.5% vs. 24.8% in winter (p = 0.005), respectively]. There was no seasonal variation in CTX; 25(OH)D predicted a small proportion (1.8% variation) of LS BMD in spring 2007 [unstandardized β (SE): 0.039 (0.016), p = 0.017]. Seasonal variation of 25(OH)D had little effect on BMD and no effect on CTX. It appears that small increments in vitamin D (e.g. those that can be achieved by cod liver oil supplements of 5 µg/day) are sufficient to ensure that 25(OH)D is above 25 nmol/L for most people throughout the year. Similarly, holidays in sunny destinations show benefit.

Vitamin D and health in adults in Australia and New Zealand: a position statement

The prevalence of vitamin D deficiency varies, with the groups at greatest risk including housebound, community-dwelling older and/or disabled people, those in residential care, dark-skinned people (particularly those modestly dressed), and other people who regularly avoid sun exposure or work indoors. Most adults are unlikely to obtain more than 5%-10% of their vitamin D requirement from dietary sources. The main source of vitamin D for people residing in Australia and New Zealand is exposure to sunlight. A serum 25-hydroxyvitamin D (25-OHD) level of ≥ 50 nmol/L at the end of winter (10-20 nmol/L higher at the end of summer, to allow for seasonal decrease) is required for optimal musculoskeletal health. Although it is likely that higher serum 25-OHD levels play a role in the prevention of some disease states, there is insufficient evidence from randomised controlled trials to recommend higher targets. For moderately fair-skinned people, a walk with arms exposed for 6-7 minutes mid morning or mid afternoon in summer, and with as much bare skin exposed as feasible for 7-40 minutes (depending on latitude) at noon in winter, on most days, is likely to be helpful in maintaining adequate vitamin D levels in the body. When sun exposure is minimal, vitamin D intake from dietary sources and supplementation of at least 600 IU (15 µg) per day for people aged ≤ 70 years and 800 IU (20 µg) per day for those aged > 70 years is recommended. People in high-risk groups may require higher doses. There is good evidence that vitamin D plus calcium supplementation effectively reduces fractures and falls in older men and women.

Prevalence and predictors of low vitamin D status in patients referred to a tertiary photodiagnostic service: a retrospective study

BACKGROUND/PURPOSE

Low vitamin D levels have been associated with adverse effects on health. The primary source of vitamin D is cutaneous production during sunlight exposure. Sun avoidance can restrict vitamin D photosynthesis and is common practice amongst patients with photosensitivity. Few studies have examined vitamin D status in this population, particularly those in northern latitudes. The purpose of this study was therefore to investigate the prevalence and possible predictors of low vitamin D status in patients referred to a tertiary photodiagnostic service.

METHODS

A case note review of 165 patients who attended the National Photodiagnostic Service for assessment at the Photobiology Unit in Dundee, Scotland (latitude 56 °N) over 1 year was conducted. Clinical information and serum 25-hydroxyvitamin D (25(OH)D) concentration were documented. Multivariate analyses were used to identify predictors of vitamin D status.

RESULTS

Mean 25(OH)D concentration was 41.9 nmol/L [standard deviation (SD) 22.0]. Forty percent of patients had insufficient vitamin D levels [25(OH)D 25-49 nmol/L] and 25% were vitamin D deficient [25(OH)D<25 nmol/L]. Blood collection in winter was the strongest predictor of low 25(OH)D status (P<0.001); strict photoprotection (P=0.04), onset of symptoms within an hour of sunlight exposure (P=0.01) and abnormal monochromator phototesting responses (P=0.009) also predicted low vitamin D levels. Supplement use was associated with higher vitamin D levels (P<0.001), even amongst patients who strictly avoided sunlight (P=0.03).

CONCLUSIONS

Patients with photosensitivity who live in northern latitudes are at high risk of low vitamin D levels, particularly in winter and spring. Increased awareness of this risk is crucial to ensure preventative strategies, such as supplementation, are implemented.

Serum 25-hydroxyvitamin-D responses to multiple UV exposures from solaria: inferences for exposure to sunlight

We investigate the relationship between blood serum 25-hydroxyvitamin D (25(OH)D) and UV exposure from two artificial sources. We then use the results to test the validity of the action spectrum for vitamin D production, and to infer the production from summer and winter sunlight. The results are based on a two-arm randomised clinical trial of biweekly UV exposure for 12 weeks using two different types of dermatological booths: one emitting primarily UV-A radiation, and the other emitting primarily UV-B radiation (booth A and booth B respectively). In terms of the vitamin D production per unit erythema, one of the booths mimics summer noon sunlight, while the other mimics winter noon sunlight. Blood samples were taken before and after the exposures. For all participants, the phototherapy booth treatments arrested the usual wintertime decline in 25(OH)D, and for most the treatments from either booth resulted in significant increases. The increases were highly non-linear and there was a high degree of variability in 25(OH)D and its response to UV from person to person. By the end of the 12 week period, the mean increase was >30 nmol l(-1) from a cumulative exposure of 17 SED from the UV-A booth, and twice that for the UV-B booth for which the cumulative exposure was 268 SED. Assuming a logarithmic relationship between UV and vitamin D, the results for the two booths show no obvious inconsistency in the action spectrum for pre-vitamin D production. However, further measurements with similar exposures from each booth are required to confirm its validity. A model was developed to describe the increases in serum 25(OH)D resulting from the UV exposures, which differed markedly between the two booths. The deduced initial rate of increase of 25(OH)D was approximately 5 nmol l(-1) per SED. From the large increases in 25(OH)D from each booth, along with knowledge of the spectral distribution of sunlight and assuming the currently-accepted action spectrum for photo-conversion to pre-vitamin D, we infer that the production of 25(OH)D from sunlight should be possible throughout the year, although in winter the exposures necessary to maintain optimal levels of 25(OH)D would be impractically long. This finding is at variance with the commonly-held view that no vitamin D is produced at mid-latitudes in the winter. Further work is needed to resolve that inconsistency.

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

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

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 deficiency and sun avoidance among university students at Abu Dhabi, United Arab Emirates

This study offers evidence that vitamin D deficiency could be a major public health burden among young Emirati adults, mostly because of sun deprivation in a sun-blessed country. This study included a random sample of 138 females and 70 males tested for serum 25-hydroxyvitamin D [25(OH)D] status. To further evaluate the predictors of vitamin D status in this population, the study examined diet, obesity and sun exposure. In summer, the mean serum 25(OH)D concentration for females was 20.9 ± 14.9 nmol/L, whereas that for males was 27.3 ± 15.7 nmol/L. Females scored significantly higher than males on the sun avoidance inventory (SAI), indicating that females avoid sun exposure to a greater extent than males, possibly explaining the lower vitamin D status. A significant negative correlation also existed between SAI and vitamin D status (Pearson's r = -0.33; p < 0.01), but no significant association was evident between vitamin D status and body mass index (Pearson's r = 0.03; p = 0.33) or low dietary intake of vitamin D-fortified foods (Pearson's r = 0.08; p = 0.13). The mean serum 25(OH)D concentration for females tested in winter was 31.3 ± 12.3 nmol/L while in the summer, it was 20.9 ± 14.9 nmol/L. This difference was statistically significant, suggesting that seasonal variation plays an important role in vitamin D status in the United Arab Emirates. Fortification of foods and drinks with vitamin D, supplementation and sensible sun exposure are important steps toward minimizing vitamin D deficiency.

Modulation of the immune system by UV radiation: more than just the effects of vitamin D?

Humans obtain most of their vitamin D through the exposure of skin to sunlight. The immunoregulatory properties of vitamin D have been demonstrated in studies showing that vitamin D deficiency is associated with poor immune function and increased disease susceptibility. The benefits of moderate ultraviolet (UV) radiation exposure and the positive latitude gradients observed for some immune-mediated diseases may therefore reflect the activities of UV-induced vitamin D. Alternatively, other mediators that are induced by UV radiation may be more important for UV-mediated immunomodulation. Here, we compare and contrast the effects of UV radiation and vitamin D on immune function in immunopathological diseases, such as psoriasis, multiple sclerosis and asthma, and during infection.

Sun-seeking behavior to increase cutaneous vitamin D synthesis: when prevention messages conflict

OBJECTIVES

The public has long been encouraged to engage in sun-safe practices to minimize exposure to sunlight, the major cause of nonmelanoma skin cancer. More recently, some have advocated unprotected sun exposure to increase cutaneous synthesis of vitamin D as a way to promote health. We assessed the net result of these conflicting messages.

METHODS

In a cross-sectional survey in 2007, questionnaires were mailed to participants of an ongoing cohort study in Washington County, Maryland. The study population consisted of 8,027 adults (55% response rate).

RESULTS

Thirty percent of respondents were aware that unprotected sun exposure increased endogenous vitamin D levels. Among those who were aware of this benefit, 42% reported going out into the sun to increase vitamin D levels. Sun-seeking to increase vitamin D production did not significantly differ according to self-reported personal history of skin cancer, but was significantly higher among women, older age groups, those with less education, and vitamin D supplement users.

CONCLUSION

A substantial proportion of respondents reported sun-seeking behavior expressly to increase endogenous vitamin D levels. The message about sun exposure and vitamin D is reaching the general public; however, this finding poses challenges to skin cancer prevention efforts.

Diet, environmental factors, and lifestyle underlie the high prevalence of vitamin D deficiency in healthy adults in Scotland, and supplementation reduces the proportion that are severely deficient

Vitamin D deficiency has recently been implicated as a possible risk factor in the etiology of numerous diseases, including nonskeletal conditions. In humans, skin synthesis following exposure to UVB is a potent source of vitamin D, but in regions with low UVB, individuals are at risk of vitamin D deficiency. Our objectives were to describe the prevalence of vitamin D deficiency and to investigate determinants of plasma 25-hydroxyvitamin D (25-OHD) concentrations in a high northern latitude country. Detailed dietary, lifestyle, and demographic data were collected for 2235 healthy adults (21-82 y) from Scotland. Plasma 25-OHD was measured by liquid chromatography-tandem MS. Among study participants, 34.5% were severely deficient (25-OHD <25 nmol/L) and 28.9% were at high risk of deficiency (25-40 nmol/L). Only 36.6% of participants were at low risk of vitamin D deficiency or had adequate levels (>40 nmol/L). Among participants who were taking supplements, 21.3% had a May-standardized 25-OHD concentration >50 nmol/L, 54.2% had 25-50 nmol/L, and 24.5% had <25 nmol/L, whereas this was 15.6, 43.3, and 41%, respectively, among those who did not take supplements (P < 0.0001). The most important sources of vitamin D were supplements and fish consumption. Vitamin D deficiency in Scotland is highly prevalent due to a combination of insufficient exposure to UVB and insufficient dietary intake. Higher dietary vitamin D intake modestly improved the plasma 25-OHD concentration (P = 0.02) and reduced the proportion of severely deficient individuals (P < 0.0001). In regions with low UVB exposure, dietary and supplement intake may be much more important than previously thought and consideration should be given to increasing the current recommended dietary allowance of 0-10 μg/d for adults in Scotland.