Fractional Sunburn Threshold UVR Doses Generate Equivalent Vitamin D and DNA Damage in Skin Types I-VI but with Epidermal DNA Damage Gradient Correlated to Skin Darkness

Characterization of the effects of vitamin D synthesis and sunburn in the population due to solar radiation exposure using PROBIT methodology

The main objective of this work is to present a set of equations that relates exposure time to solar radiation, the ultraviolet index (UVI), and its effects, both positive (vitamin D synthesis) and negative (sunburns), including the influence of repeated doses and the incorporation of protective factors. To do so, expressions are proposed for both effects and a time range is specified where repeated doses can be applied. Moreover, we propose expressions (PROBIT equations) that relate the percentage of a population that would reach the recommended daily amount of vitamin D and the repeated dosage to which the population is exposed for skin types I to IV. For all the cases studied, protective factors, such as the use of clothes or sunscreens, were taken into account. Additionally, comparisons were made based on skin types between the generation of daily vitamin D and the onset of sunburn, being able to establish a percentage of those who would suffer from first-degree sunburns when this population reached the recommended daily amount of vitamin D. Thus, it can be noted that when a large percentage of a population wants to obtain the recommended daily allowance of vitamin D of 2000 IU or more, and by exposing a small portion of skin to solar radiation, a considerable percentage of that population would suffer from first-degree sunburn as vitamin D generation is related to the area of exposed skin. Therefore, by increasing the area of skin that is exposed to solar radiation, vitamin D needs can be safely met even with higher daily amounts.

Comparative Analysis of Efficacy of Lactic Acid 30% with Ferulic Peel 12% (Combination Peel) Versus TCA 10% with Ferulic Peel 12% (Combination Peel) for Photoageing Skin

OBJECTIVES

Chemical peels are used to treat photoageing, pigmentation, improve complexion and dull skin, fine lines and scars. The objective of this study is to do comparative analysis of Lactic Acid 30% with Ferulic peel 12% (combination peel) versus TCA 10% with Ferulic peel 12% (combination peel) for Photoageing Skin.

MATERIALS AND METHODS

This is a retrospective study from September 2021 to 2022 with total 50 female patients aged between 25 and 40 years were treated. Randomisation of patients was done (simple randomisation using lottery method) for both groups with 25 patients enrolled in each group. The first group (Group A-25 patients) were treated with lactic acid 30% with Ferulic peel 12% (combination peel). The second group (Group B-25 patients) were treated with TCA 10% with Ferulic peel 12% (combination peel). Inclusion and exclusion criteria have been defined for the study. Two scales have been used for assessing the results: Allergan Skin Roughness Scale (ASRS) and Allergan Fine Line Scale (AFLS). ASRS and AFLS scores were assessed at pre-treatment (pre) and post treatment (post-1 month after last peel session). Data were summarised in Mean ± SD (standard deviation). Pre and post groups were compared by paired t test. The pre to post change in outcome measures between two independent groups were compared by independent Student's t test. Discrete (categorical) groups were compared by Chi-square (χ2) test. A two-tailed (α=2) P < 0.05 was considered statistically significant. Analyses were performed on SPSS software (Windows version 22.0). Patients were followed up for 6 months post treatment.

RESULTS

In Group A, comparing the pre and post ASRS score, paired t test showed significant (P < 0.001) decrease or improvement of 56.1%. In Group B, comparing the pre and post ASRS score, paired t test showed significant (P < 0.001) decrease or improvement of 52.8%. Comparing the pre to post mean decrease or improvement in ASRS score of two groups, Student's t test showed similar (P > 0.05) improvement between the two groups though it was 2.5% higher in Group B as compared to Group A. In Group A, comparing the pre and post AFLS score, paired t test showed significant (P < 0.001) decrease or improvement of 63.2% at post as compared to pre. In Group B, comparing the pre and post AFLS score, paired t test showed significant (P < 0.001) decrease or improvement of 58.8% at post as compared to pre. Further, comparing the pre to post mean decrease or improvement in AFLS score of two groups, Student's t test showed similar (P > 0.05) improvement between the two groups though it was 16.7% higher in Group A as compared to Group B.

CONCLUSION

Study found both the treatments equally effective in the management of ageing skin after 6 months of treatment. However, study needs further validation on larger sample size, varied age groups and male gender.

LEVEL OF EVIDENCE V

This journal requires that authors assign a level of evidence to each article. For a full description of these Evidence-Based Medicine ratings, please refer to the Table of Contents or the online Instructions to Authors www.springer.com/00266 .

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

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

Retinoids in the treatment of photoageing: A histological study of topical retinoid efficacy in black skin

BACKGROUND

Photoageing describes complex cutaneous changes that occur due to chronic exposure to solar ultraviolet radiation (UVR). The 'gold standard' for the treatment of photoaged white skin is all-trans retinoic acid (ATRA); however, cosmetic retinol (ROL) has also proven efficacious. Recent work has identified that black skin is susceptible to photoageing, characterized by disintegration of fibrillin-rich microfibrils (FRMs) at the dermal-epidermal junction (DEJ). However, the impact of topical retinoids for repair of black skin has not been well investigated.

OBJECTIVES

To determine the potential of retinoids to repair photoaged black skin.

METHODS

An exploratory intervention study was performed using an in vivo, short-term patch test protocol. Healthy but photoaged black volunteers (>45 years) were recruited to the study, and participant extensor forearms were occluded with either 0.025% ATRA (n = 6; 4-day application due to irritancy) or ROL (12-day treatment protocol for a cosmetic) at concentrations of 0.3% (n = 6) or 1% (n = 6). Punch biopsies from occluded but untreated control sites and retinoid-treated sites were processed for histological analyses of epidermal characteristics, melanin distribution and dermal remodelling.

RESULTS

Treatment with ATRA and ROL induced significant acanthosis (all p < 0.001) accompanied by a significant increase in keratinocyte proliferation (Ki67; all p < 0.01), dispersal of epidermal melanin and restoration of the FRMs at the DEJ (all p < 0.01), compared to untreated control.

CONCLUSIONS

This study confirms that topical ATRA has utility for the repair of photoaged black skin and that ROL induces comparable effects on epidermal and dermal remodelling, albeit over a longer timeframe. The effects of topical retinoids on black photoaged skin are similar to those reported for white photoaged skin and suggest conserved biology in relation to repair of UVR-induced damage. Further investigation of topical retinoid efficacy in daily use is warranted for black skin.

Irradiation of human oral mucosa by 233 nm far UV-C LEDs for the safe inactivation of nosocomial pathogens

The inactivation of multi resistant pathogens is an important clinical need. One approach is UV-C irradiation, which was previously not possible in vivo due to cytotoxicity. Recently, far UV-C irradiation at λ < 240 nm was successfully used on skin with negligible damage. A potential application site is the nasal vestibule, where MRSA accumulates and cannot be treated using antiseptics. We irradiated 3D mucosa models and excised human mucosa with 222 and 233 nm far UV-C in comparison to 254 nm and broadband UV-B. Eradication efficiency was evaluated by counting colony forming units; irritation potential was evaluated by hen's egg-chorioallantoic membrane assay and trans epithelial electrical resistance; cell viability was assessed by MTT. DNA damage and cell protective mechanisms were evaluated immunohistopathologically. On mucosa models, MRSA reduced by ≈ 5 log10 for 60 mJ/cm2 irradiation at 233 nm. A slightly increased cell viability was observed after 24 h. Lower doses showed lower irritation potential than the positive controls or commercial mouthwash, while 80 mJ/cm2 had strong irritation potential. DNA damage occurred only superficially and decreased after 24 h. On excised human mucosa, < 10% of keratinocytes were affected after 150 mJ/cm2 222 nm or 60 mJ/cm2 233 nm.

General Medical Emergencies in Athletes

This article focuses on the management of the most common on-field medical emergencies. As with any discipline in medicine, a well-defined plan and systematic approach is the cornerstone of quality health care delivery. In addition, the team-based collaboration is necessary for the safety of the athlete and the success of the treatment plan.

Effects of donkey milk on UVB-induced skin barrier damage and melanin pigmentation: A network pharmacology and experimental validation study

Introduction

Dairy products have long been regarded as a controversial nutrient for the skin. However, a clear demonstration of donkey milk (DM) on skincare is required.

Methods

In this study, spectrum and chemical component analyses were applied to DM. Then, the effects of DM on UVB-induced skin barrier damage and melanin pigmentation were first evaluated in vitro and in vivo. Cell survival, animal models, and expression of filaggrin (FLG) were determined to confirm the effect of DM on UVB-induced skin barrier damage. Melanogenesis and tyrosinase (TYR) activity were assessed after UVB irradiation to clarify the effect of DM on whitening activities. Further, a network pharmacology method was applied to study the interaction between DM ingredients and UVB-induced skin injury. Meanwhile, an analysis of the melanogenesis molecular target network was developed and validated to predict the melanogenesis regulators in DM.

Results

DM was rich in cholesterols, fatty acids, vitamins and amino acids. The results of evaluation of whitening activities in vitro and in vivo indicated that DM had a potent inhibitory effect on melanin synthesis. The results of effects of DM on UVB‑induced skin barrier damage indicated that DM inhibited UVB-induced injury and restored skin barrier function via up-regulation expression of FLG (filaggrin). The pharmacological network of DM showed that DM regulated steroid biosynthesis and fatty acid metabolism in keratinocytes and 64 melanin targets which the main contributing role of DM might target melanogenesis, cell adhesion molecules (CAMs), and Tumor necrosis factor (TNF) pathway.

Discussion

These results highlight the potential use of DM as a promising agent for whitening and anti-photoaging applications.

Vitamin D and Sun Exposure: A Community Survey in Australia

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

Nucleic acid adductomics - The next generation of adductomics towards assessing environmental health risks

This Discussion article aims to explore the potential for a new generation of assay to emerge from cellular and urinary DNA adductomics which brings together DNA-RNA- and, to some extent, protein adductomics, to better understand the role of the exposome in environmental health. Components of the exposome have been linked to an increased risk of various, major diseases, and to identify the precise nature, and size, of risk, in this complex mixture of exposures, powerful tools are needed. Modification of nucleic acids (NA) is a key consequence of environmental exposures, and a goal of cellular DNA adductomics is to evaluate the totality of DNA modifications in the genome, on the basis that this will be most informative. Consequently, an approach which encompasses modifications of all nucleic acids (NA) would be potentially yet more informative. This article focuses on NA adductomics, which brings together the assessment of both DNA and RNA modifications, including modified (2'-deoxy)ribonucleosides (2'-dN/rN), modified nucleobases (nB), plus: DNA-DNA, RNA-RNA, DNA-RNA, DNA-protein, and RNA-protein crosslinks (DDCL, RRCL, DRCL, DPCL, and RPCL, respectively). We discuss the need for NA adductomics, plus the pros and cons of cellular vs. urinary NA adductomics, and present some evidence for the feasibility of this approach. We propose that NA adductomics provides a more comprehensive approach to the study of nucleic acid modifications, which will facilitate a range of advances, including the identification of novel, unexpected modifications e.g., RNA-RNA, and DNA-RNA crosslinks; key modifications associated with mutagenesis; agent-specific mechanisms; and adductome signatures of key environmental agents, leading to the dissection of the exposome, and its role in human health/disease, across the life course.

The Mangosteen Peel Ethyl Acetate Extract-based Cream Inhibits Ultraviolet-B Radiation-induced Hyperpigmentation in Guinea Pig Skin

BACKGROUND: Ultraviolet B (UVB) radiation is the main factor causing the aberrant melanin pigments leading to skin hyperpigmentation. Retinoic acid and hydroquinone are the primary preference for the skin whitening agents in preventing hyperpigmentation. However, these treatments could induce slight-to-severe irritation leading to skin cancer. Mangosteen peel possesses α-mangostin, the primary constituent of xanthones in mangosteen peel that has potency as an anti-tyrosinase for treating issues of skin hyperpigmentation. AIM: This study aims to demonstrate the capacity of mangosteen peel ethyl acetate extract-based cream in inhibiting the UVB radiation-induced skin hyperpigmentation in guinea pig. MATERIALS AND METHODS: A total of 25 female guinea pigs were used to produce UVB-irradiated skin hyperpigmentation model. Guinea pig skins were treated with 12% mangosteen ethyl acetate extract-based cream. Mushroom tyrosinase inhibitor activity was used to evaluate the capacity of mangosteen extract in inhibiting tyrosinase activity in vitro. The melanin index in guinea pig skin after treatments was analyzed using a mexameter. The percentage of epidermal melanin-contained keratinocytes of skin tissues were analyzed using masson fontana. Pmel17 expression in cell surface was determined using immunohistochemistry. The level of tyrosinase in tissue homogenates was analyzed using Enzyme-linked immunosorbent assays. RESULTS: Mangosteen peel ethyl acetate extract showed potent inhibitory activity against the mushroom tyrosinase. Its-based cream decreased melanin index, epidermal melanin, Pmel17 expression, and tyrosinase level in hyperpigmentation skin tissues. CONCLUSION: Overall, our study demonstrates the capacity of mangosteen peel ethyl acetate extract-based cream in inhibiting the UVB radiation-induced skin hyperpigmentation in guinea pig.

DNA photoproducts released by repair in biological fluids as biomarkers of the genotoxicity of UV radiation

UV-induced formation of photoproducts in DNA is a major initiating event of skin cancer. Consequently, many analytical tools have been developed for their quantification in DNA. In the present work, we extended our previous liquid chromatography-mass spectrometry method to the quantification of the short DNA fragments containing photoproducts that are released from cells by the repair machinery. We designed a robust protocol including a solid-phase extraction step (SPE), an enzymatic treatment aimed at releasing individual photoproducts, and a liquid chromatography method combining on-line SPE and ultra-high-performance liquid chromatography for optimal specificity and sensitivity. We also added relevant internal standards for a better accuracy. The method was validated for linearity, repeatability, and reproducibility. The limits of detection and quantification were found to be in the fmol range. The proof of concept of the use of excreted DNA repair products as biomarkers of the genotoxicity of UV was obtained first in in vitro studies using cultured HaCat cells and ex vivo on human skin explants. Further evidence was obtained from the detection of pyrimidine dimers in the urine of human volunteers collected after recreational exposure in summer. An assay was designed to quantify the DNA photoproducts released from cells within short fragments by the DNA repair machinery. These oligonucleotides were isolated by solid-phase extraction and enzymatically hydrolyzed. The photoproducts were then quantified by on-line SPE combined with UHPLC-MS/MS with isotopic dilution.

Clinicophotobiological Characterization of Photoaggravated Atopic Dermatitis

Importance

Photoaggravated atopic dermatitis (PAD) is estimated to affect 1.4% to 16% of patients with AD but remains poorly characterized with limited published data.

Objective

To provide detailed clinical and photobiological characterization of PAD.

Design, Setting, and Participants

This case series study used cross-sectional data collected from 120 consecutive patients diagnosed with PAD from January 2015 to October 2019 at a tertiary center referral unit for photobiology.

Main Outcomes and Measures

Routinely collected standardized clinical and photobiological data were analyzed using descriptive statistics, and regression analysis explored associations between demographic and clinical data.

Results

Of 869 patients who underwent photoinvestigation, 120 (14%) were diagnosed with PAD (69 female [58%]; median age, 45 [IQR, 31-61] years; range, 5-83 years; skin phototypes [SPTs] I-VI). Of these patients, 104 (87%) were adults. All patients had a history of AD, and most (62 of 104 [60%]) presented with sunlight-provoked or photodistributed eczema; median age at photosensitivity onset was 37 years (range, 1-72 years). Past-year Dermatology Life Quality Index score was greater than 10 for 80 of 103 adults (78%), and 82 of 119 (69%) had vitamin D (25-hydroxyvitamin D) level insufficiency or deficiency (<20 ng/mL; to convert ng/mL to nmol/L, multiply by 2.496). Broadband UV radiation provocation test results were positive for 112 patients (93%). In 28 patients (23%) with abnormal monochromator phototest findings, sensitivity occurred to UV-A, UV-B, and/or visible light, and UV-A of 350 ± 10 nm was the most prevalent wavelength. Photopatch test reactions were positive for 18 patients (15%). Patients with SPTs V to VI (31 [26%]) vs SPTs I to IV (89 [74%]) were younger at photosensitivity onset (median age, 24 years [IQR, 15-37 years] vs 40 years [IQR, 25-55 years]; P = .003), were more likely to be female (23 [74%] vs 46 [52%]; P = .03), and had a lower vitamin D status and a higher frequency of abnormal monochromator phototest findings.

Conclusions and Relevance

In this case series study, PAD affected patients with different ages and SPTs and was associated with substantially impaired quality of life. The findings suggest that confirming PAD through phototesting may provide better personalized care for patients through identification of provoking wavelengths, relevant photocontact allergies, and appropriate photoprotection advice.

Application of 233 nm far-UVC LEDs for eradication of MRSA and MSSA and risk assessment on skin models

A newly developed UVC LED source with an emission wavelength of 233 nm was proved on bactericidal efficacy and skin tolerability. The bactericidal efficacy was qualitatively analysed using blood agar test. Subsequently, quantitative analyses were performed on germ carrier tests using the MRSA strain DSM11822, the MSSA strain DSM799, S. epidermidis DSM1798 with various soil loads. Additionally, the compatibility of the germicidal radiation doses on excised human skin and reconstructed human epidermis was proved. Cell viability, DNA damage and production of radicals were assessed in comparison to typical UVC radiation from discharge lamps (222 nm, 254 nm) and UVB (280–380 nm) radiation for clinical assessment. At a dose of 40 mJ/cm², the 233 nm light source reduced the viable microorganisms by a log₁₀ reduction (LR) of 5 log₁₀ levels if no soil load was present. Mucin and protein containing soil loads diminished the effect to an LR of 1.5–3.3. A salt solution representing artificial sweat (pH 8.4) had only minor effects on the reduction. The viability of the skin models was not reduced and the DNA damage was far below the damage evoked by 0.1 UVB minimal erythema dose, which can be regarded as safe. Furthermore, the induced damage vanished after 24 h. Irradiation on four consecutive days also did not evoke DNA damage. The radical formation was far lower than 20 min outdoor visible light would cause, which is classified as low radical load and can be compensated by the antioxidant defence system.

Vitamin D and Pigmented Skin

The default supply of vitamin D₃ to humans is its endogenous production in UV-B-exposed skin [...].

A newly developed and validated LC-MS/MS method for measuring 7-dehydrocholesterol (7DHC) concentration in human skin: a tool for vitamin D photobiology research

BACKGROUND

UVB absorption by 7-dehydrocholesterol (7DHC) in the skin triggers the production of vitamin D and its metabolites, which maintain calcium homeostasis. Detection and measurement of 7DHC in skin using modern liquid chromatography-tandem mass spectrometry (LC-MS/MS) techniques have been lacking, yet there is need for such a technique to provide more information on 7DHC concentration and its UVB responses in human skin.

OBJECTIVES

To develop and validate a reliable method to measure 7DHC concentration in skin.

METHODS

Human skin punch biopsies of 5 mm diameter obtained through the Manchester Skin Health Biobank were utilised. 7DHC was extracted with ethyl acetate:methanol 1:1 (v/v) and derivatised using 4-phenyl-1,2,4-triazoline-3,5-dione (PTAD), to allow for improved ionisation of 7DHC through Electrospray Ionisation Mass Spectrometry (ESI-MS). Solid supported liquid extraction (SLE) was also employed to allow the removal of larger lipids from 7DHC and minimise potential matrix effects.

RESULTS

The LC-MS/MS assay satisfied International Council for Harmonisation research standards for method validation. Calibration curve was linear with a typical r² of 0.997, coefficient of variation was 11.1% and 4.32% for inter-assay and intra-assay imprecision, respectively. Lower limit of quantification was 1.6 µg/g and upper limit of quantification was 100 µg/g, SLE recovery of 7DHC was on average 91.4%.

CONCLUSIONS

We have developed a robust, precise and accurate assay for the detection and quantification of 7DHC in small samples of human skin (0.2 cm² surface area). This novel method of extraction and quantification will be valuable to future vitamin D photobiology research.

Role of distinct fibroblast lineages and immune cells in dermal repair following UV radiation induced tissue damage

Solar ultraviolet radiation (UVR) is a major source of skin damage, resulting in inflammation, premature ageing, and cancer. While several UVR-induced changes, including extracellular matrix reorganisation and epidermal DNA damage, have been documented, the role of different fibroblast lineages and their communication with immune cells has not been explored. We show that acute and chronic UVR exposure led to selective loss of fibroblasts from the upper dermis in human and mouse skin. Lineage tracing and in vivo live imaging revealed that repair following acute UVR is predominantly mediated by papillary fibroblast proliferation and fibroblast reorganisation occurs with minimal migration. In contrast, chronic UVR exposure led to a permanent loss of papillary fibroblasts, with expansion of fibroblast membrane protrusions partially compensating for the reduction in cell number. Although UVR strongly activated Wnt signalling in skin, stimulation of fibroblast proliferation by epidermal β-catenin stabilisation did not enhance papillary dermis repair. Acute UVR triggered an infiltrate of neutrophils and T cell subpopulations and increased pro-inflammatory prostaglandin signalling in skin. Depletion of CD4- and CD8-positive cells resulted in increased papillary fibroblast depletion, which correlated with an increase in DNA damage, pro-inflammatory prostaglandins, and reduction in fibroblast proliferation. Conversely, topical COX-2 inhibition prevented fibroblast depletion and neutrophil infiltration after UVR. We conclude that loss of papillary fibroblasts is primarily induced by a deregulated inflammatory response, with infiltrating T cells supporting fibroblast survival upon UVR-induced environmental stress.

100 YEARS OF VITAMIN D: Dose-response for change in 25-hydroxyvitamin D after UV exposure: outcome of a systematic review

A systematic review of publications addressing change in vitamin D status (25-hydroxyvitamin D (25OHD)) after exposure to UV radiation identified 2001 independent peer-reviewed publications. Of these, 21 used artificial sources of UV radiation, met all inclusion criteria and were quality assured; 13 publications used solar radiation and met sufficient inclusion criteria to be retained as supporting evidence; 1 further included publication used both solar and artificial sources. The review consistently identified that low dose, sub-erythemal doses are more effective for vitamin D synthesis than doses close to a minimum erythema dose; increasing skin area exposed increases the amount of vitamin D synthesised although not necessarily in a linear manner; constant dosing leads to a dose-dependent plateau in 25OHD, and dose-response is greatest at the start of a dosing regime; there is a large interpersonal variation in response to UV exposure. Fourteen of the studies using artificial sources of radiation were used to determine a dose-response relationship for change in 25OHD on whole-body exposure to repeated sub-erythemal doses of UV radiation, taking the form Δ25OHD (nmol/L) = A ln(standard vitamin D dose) + B. This helps quantify our understanding of UV as a source of vitamin D and enables exposure regimes for safe synthesis of vitamin D to be assessed. Specific studies of people with pigmented skin (Fitzpatrick skin types 5 and 6) were rare, and this dose-response relationship is only applicable to white-skinned individuals as skin type is a determinant of response to UV radiation. Findings provide information for vitamin D guidance updates.

A revised action spectrum for vitamin D synthesis by suberythemal UV radiation exposure in humans in vivo

Solar UV radiation (UVR) causes sunburn but initiates the first step of vitamin D synthesis, which is the formation of previtamin D₃ (pre-D₃) in skin. The gold standard for assessing vitamin D is serum 25-hydroxyvitamin D₃ [25(OH)D₃]. Public health advice for optimal solar exposure requires UVR wavelength-dependence (action spectrum) data on risks and benefits. An action spectrum for pre-D₃ in human ex vivo skin was established over 30 y ago, but its validity has been questioned. We tested this action spectrum in healthy volunteers using serum 25(OH)D₃ as the endpoint. Our analysis shows that the pre-D₃ action spectrum can be improved with a systematic correction. This will result in better risk–benefit calculations for public health advice on solar exposure.

Action spectra are important biological weighting functions for risk/benefit analyses of ultraviolet (UV) radiation (UVR) exposure. One important human benefit of exposure to terrestrial solar UVB radiation (∼295 to 315 nm) is the cutaneous synthesis of vitamin D₃ that is initiated by the photoconversion of 7-dehydrocholesterol to previtamin D₃. An action spectrum for this process that is followed by other nonphotochemical steps to achieve biologically active vitamin D₃ has been established from ex vivo data and is widely used, although its validity has been questioned. We tested this action spectrum in vivo by full- or partial-body suberythemal irradiation of 75 healthy young volunteers with five different polychromatic UVR spectra on five serial occasions. Serum 25-hydroxyvitamin D₃ [25(OH)D₃] levels, as the most accurate measure of vitamin D₃ status, were assessed before, during, and after the exposures. These were then used to generate linear dose–response curves that were different for each UVR spectrum. It was established that the previtamin D₃ action spectrum was not valid when related to the serum 25(OH)D₃ levels, as weighting the UVR doses with this action spectrum did not result in a common regression line unless it was adjusted by a blue shift, with 5 nm giving the best fit. Such a blue shift is in accord with the published in vitro action spectra for vitamin D₃ synthesis. Thus, calculations regarding the risk (typically erythema) versus the benefit of exposure to solar UVR based on the ex vivo previtamin D₃ action spectrum require revision.

UVB mutagenesis differs in Nras- and Braf-mutant mouse models of melanoma

BRAF-mutant melanomas are more likely than NRAS-mutant melanomas to arise in anatomical locations protected from chronic sun damage. We hypothesized that this discrepancy in tumor location is a consequence of the differential sensitivity of BRAF and NRAS-mutant melanocytes to ultraviolet light (UV)-mediated carcinogenesis. We tested this hypothesis by comparing the mutagenic consequences of a single neonatal, ultraviolet-AI (UVA; 340-400 nm) or ultraviolet-B (UVB; 280-390 nm) exposure in mouse models heterozygous for mutant Braf or homozygous for mutant Nras Tumor onset was accelerated by UVB, but not UVA, and the resulting melanomas contained recurrent mutations affecting the RING domain of MAP3K1 and Actin-binding domain of Filamin A. Melanomas from UVB-irradiated, Braf-mutant mice averaged twice as many single-nucleotide variants and five times as many dipyrimidine variants than tumors from similarly irradiated Nras-mutant mice. A mutational signature discovered in UVB-accelerated tumors mirrored COSMIC signatures associated with human skin cancer and was more prominent in Braf- than Nras-mutant murine melanomas. These data show that a single UVB exposure yields a greater burden of mutations in murine tumors driven by oncogenic Braf.

Computer Modeling Indicates Dramatically Less DNA Damage from Far-UVC Krypton Chloride Lamps (222 nm) than from Sunlight Exposure

This study aims to investigate, with computer modeling, the DNA damage (assessed by cyclobutane pyrimidine dimer (CPD) formation) from far-ultraviolet C (far-UVC) in comparison with sunlight exposure in both a temperate (Harwell, England) and Mediterranean (Thessaloniki, Greece) climate. The research utilizes the published results from Barnard et al. [Barnard, I.R.M (2020) Photodermatol. Photoimmunol. Photomed. 36, 476-477] to determine the relative CPD yield of unfiltered and filtered far-UVC and sunlight exposure. Under current American Conference of Governmental Industrial Hygienists (ACGIH) exposure limits, 10 min of sunlight at an ultraviolet (UV) Index of 4-typical throughout the day in a temperate climate from Spring to Autumn-produces equivalent numbers of CPD as 700 h of unfiltered far-UVC or more than 30 000 h of filtered far-UVC at the basal layer. At the top of the epidermis, these values are reduced to 30 and 300 h, respectively. In terms of DNA damage induction, as assessed by CPD formation, the risk from sunlight exposure greatly exceeds the risk from far-UVC. However, the photochemistry that will occur in the stratum corneum from absorption of the vast majority of the high-energy far-UVC photons is unknown, as are the consequences.

Visible light and human skin pigmentation: The importance of skin phototype

Melanin is synthesised within melanocytes and transferred to keratinocytes in human skin, thereby regulating skin colour and protecting skin cells against UVR-induced damage. We commonly divide human skin into six phototypes (SPT)-I to -VI (Fitzpatrick scale) according to the skin's tanning response to UVR. In this pilot study, we investigated the impact of UVR (maximum 311nm), blue (peak 450nm) and green visible light (peak 530nm) on melanin production and type in healthy human skin histocultures (SPT-I, -II and -III). UVR, blue and green light stimulated a surface tanning response in SPT-II and -III, but not SPT-I. Using the Warthin-Starry stain for sensitive melanin detection, all three light treatments induced melanogenesis in SPT-II and -III skin. Surprisingly, blue and green light (but not UVR) stimulated melanin synthesis in SPT-I skin. Moreover, melanin synthesis induced by blue and green visible light in SPT-I, SPT-II, and SPT-III skin was not associated with a detectable increase in DNA damage or cell apoptosis. By contrast, both responses were detected after UVR. These data suggest that blue and green visible light can stimulate melanin production in fair-skinned individuals without, at least some of, the harmful consequences of UVR-induced pigmentation. We are currently examining the molecular basis of UVR-independent melanogenesis in fair skin.

Older Adults Who Spend More Time Outdoors in Summer and Have Higher Dietary Vitamin D Than Younger Adults Can Present at Least as High Vitamin D Status: A Pilot Study

Vitamin D₃ can be produced by exposing skin to UVB radiation or sourced through dietary products. It is often stated that vitamin D status declines in older adults, yet little is known about differences in current-day lifestyle and dietary behaviours influencing vitamin D outcomes in younger (18–40 years old) and older adults (65–89 years old). Our objectives were to perform a pilot study to compare sun exposure behaviours, i.e., time spent outdoors, holiday behaviour and use of sunscreen/clothing, and dietary vitamin D intake, in young and older adults in the UK, together with assessment of their vitamin D status. A total of 13 young and 11 older volunteers completed a four-page questionnaire to assess sun exposure and photoprotective behaviour and an eleven-page one-week vitamin D diet diary, alongside their plasma 25(OH)D measurement. It was found that the older group tended to spend more time outdoors during the working week in summer, to take more summer and winter holidays each year, take longer winter holidays and have similar sunscreen use when compared to younger adults. Older adults had a significantly higher daily dietary intake of vitamin D (4.0 μg) than young adults (2.4 μg). Mean winter 25(OH)D concentration was higher in older (56.9 nmol/L) than in young adults (43.2 nmol/L), but there was no statistical difference between the groups. Contrary to common assumptions, in this study, older adults had sun exposure and dietary behaviours conferring a vitamin D status at least as good as that of younger adults.

Biomarkers of nucleic acid oxidation - A summary state-of-the-art

Oxidatively generated damage to DNA has been implicated in the pathogenesis of a wide variety of diseases. Increasingly, interest is also focusing upon the effects of damage to the other nucleic acids, RNA and the (2′-deoxy-)ribonucleotide pools, and evidence is growing that these too may have an important role in disease. LC-MS/MS has the ability to provide absolute quantification of specific biomarkers, such as 8-oxo-7,8-dihydro-2′-deoxyGuo (8-oxodG), in both nuclear and mitochondrial DNA, and 8-oxoGuo in RNA. However, significant quantities of tissue are needed, limiting its use in human biomonitoring studies. In contrast, the comet assay requires much less material, and as little as 5 μL of blood may be used, offering a minimally invasive means of assessing oxidative stress in vivo, but this is restricted to nuclear DNA damage only. Urine is an ideal matrix in which to non-invasively study nucleic acid-derived biomarkers of oxidative stress, and considerable progress has been made towards robustly validating these measurements, not least through the efforts of the European Standards Committee on Urinary (DNA) Lesion Analysis. For urine, LC-MS/MS is considered the gold standard approach, and although there have been improvements to the ELISA methodology, this is largely limited to 8-oxodG. Emerging DNA adductomics approaches, which either comprehensively assess the totality of adducts in DNA, or map DNA damage across the nuclear and mitochondrial genomes, offer the potential to considerably advance our understanding of the mechanistic role of oxidatively damaged nucleic acids in disease.

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Oxidatively damaged nucleic acids are implicated in the pathogenesis of disease.

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LC-MS/MS, comet assay and ELISA are often used to study oxidatively damaged DNA.

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Urinary oxidatively damaged nucleic acids non-invasively reflect oxidative stress.

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DNA adductomics will aid understanding the role of ROS damaged DNA in disease.

Physical Determinants of Vitamin D Photosynthesis: A Review

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

Cyclobutane pyrimidine dimers from UVB exposure induce a hypermetabolic state in keratinocytes via mitochondrial oxidative stress

Ultraviolet B radiation (UVB) is an environmental complete carcinogen, which induces and promotes keratinocyte carcinomas, the most common human malignancies. UVB induces the formation of cyclobutane pyrimidine dimers (CPDs). Repairing CPDs through nucleotide excision repair is slow and error-prone in placental mammals. In addition to the mutagenic and malignancy-inducing effects, UVB also elicits poorly understood complex metabolic changes in keratinocytes, possibly through CPDs. To determine the effects of CPDs, CPD-photolyase was overexpressed in keratinocytes using an N1-methyl pseudouridine-containing in vitro-transcribed mRNA. CPD-photolyase, which is normally not present in placental mammals, can efficiently and rapidly repair CPDs to block signaling pathways elicited by CPDs. Keratinocytes surviving UVB irradiation turn hypermetabolic. We show that CPD-evoked mitochondrial reactive oxygen species production, followed by the activation of several energy sensor enzymes, including sirtuins, AMPK, mTORC1, mTORC2, p53, and ATM, is responsible for the compensatory metabolic adaptations in keratinocytes surviving UVB irradiation. Compensatory metabolic changes consist of enhanced glycolytic flux, Szent-Györgyi-Krebs cycle, and terminal oxidation. Furthermore, mitochondrial fusion, mitochondrial biogenesis, and lipophagy characterize compensatory hypermetabolism in UVB-exposed keratinocytes. These properties not only support the survival of keratinocytes, but also contribute to UVB-induced differentiation of keratinocytes. Our results indicate that CPD-dependent signaling acutely maintains skin integrity by supporting cellular energy metabolism.

Influence of skin melanisation and ultraviolet radiation on biomarkers of systemic oxidative stress

Skin melanisation ranges widely across human populations. Melanin has antioxidant properties and also acts as a filter to solar ultraviolet radiation (UVR) incident upon the skin. In this study we firstly examined whether melanin level might influence baseline levels of systemic oxidative stress, in 65 humans in vivo from the same geographical area ranging from the lightest to darkest skin type (phototype I-VI). This was examined in winter-time (latitude 53.5°N). Remarkably, we found that urinary biomarkers of oxidatively-generated DNA damage (8-oxodG) and RNA damage (8-oxoGuo) were significantly correlated with skin lightness (L*), such that 14-15% of the variation in their baseline levels could be explained by skin colour. Next we exposed 15 humans at the extremes of skin melanisation to a simulated summer-time exposure of solar UVR (95% UVA, 5% UVB; dose standardised to sunburn threshold), following which they provided a sample of every urine void over the next five days. We found that UVR induced a small but significant increase in urinary 8-oxodG and 8-oxoGuo, with differing kinetics between skin types. Thus greater melanisation is associated with protection against systemic oxidative stress, which may reflect melanin's antioxidant properties, and solar UVR exposure also influences systemic oxidative stress levels in humans. These novel findings may have profound implications for human physiology and health.

Public Awareness and Behaviour in Great Britain in the Context of Sunlight Exposure and Vitamin D: Results from the First Large-Scale and Representative Survey

In recent years, UK public health messages about the risks of sunlight exposure (skin cancer) have been increasingly balanced by messages about its benefits (vitamin D production). Currently, data about the effects of this shift on public knowledge, awareness, and behaviour are scant. Thus, the objective of this paper is to report the findings of the first large-scale and representative survey of the awareness, knowledge, and behaviour of adults in Great Britain (England, Scotland, and Wales) (n = 2024) with respect to sunlight exposure, vitamin D, and sunburn and skin cancer. The findings suggest that the public in Great Britain is much more aware of public promotion of the risks of sunlight exposure than its benefits. That said, knowledge about sunlight exposure and vitamin D is fairly strong, though not with respect to the detail of the 'little and often' approach. However, the survey also suggests that levels of sunlight exposure among the public are often excessive. The survey indicates that knowledge and behaviour are both less satisfactory among men and people in lower socio-economic groups. The paper concludes with recommendations for public health communications and for research in this area.

Skin colour and vitamin D: An update

Homo sapiens evolved in East Africa and had dark skin, hair, and eyes, in order to protect against deleterious consequences of intensive UV radiation at equatorial latitudes. Intensive skin pigmentation was thought to bear the risk of inefficient vitamin D3 synthesis in the skin. This initiated the hypothesis that within the past 75 000 years, in which humans migrated to higher latitudes in Asia and Europe, the need for vitamin D3 synthesis served as an evolutionary driver for skin lightening. In this review, we summarize the recent archeogenomic reconstruction of population admixture in Europe and demonstrate that skin lightening happened as late as 5000 years ago through immigration of lighter pigmented populations from western Anatolia and the Russian steppe but not primarily via evolutionary pressure for vitamin D3 synthesis. We show that variations in genes encoding for proteins being responsible for the transport, metabolism and signalling of vitamin D provide alternative mechanisms of adaptation to a life in northern latitudes without suffering from consequences of vitamin D deficiency. This includes hypotheses explaining differences in the vitamin D status and response index of European populations.

Prevalence and correlates of sun protections with sunburn and vitamin D deficiency in sun-sensitive individuals

BACKGROUND

Sun sensitivity is an inherent risk factor for skin cancer. Sun protection is important in sun-sensitive individuals to reduce sunburns for skin cancer prevention. However, concerns have arose regarding the possible impact of sun protection on vitamin D deficiency.

OBJECTIVE

To examine the prevalence and correlates of sun-protective behaviours (staying in the shade, using sunscreen and wearing long sleeves) with sunburn and vitamin D deficiency in sun-sensitive individuals.

METHODS

This was a cross-sectional study of 2390 US non-Hispanic white adults aged 20-59 years in the National Health and Nutrition Examination Survey 2011-2014. Sun sensitivity was defined as self-reported tendency to severe sunburn when exposed to the sun for half an hour after months of non-sun exposure, and single serum 25(OH)D levels less than 50 nmol/L was determined as vitamin D deficiency. We calculated adjusted odds ratios (aORs) and 95% confidence intervals (95% CIs) using multivariable logistic regression taking into account the complex survey design.

RESULTS

Sun-sensitive individuals had higher odds of frequently staying in the shade (aOR = 3.08; 95% CI 2.19-4.33) and using sunscreen (aOR = 1.93; 1.44-2.59) but not associated with sun exposure time (aOR = 0.91; 0.62-1.32). Yet, sun-sensitive individuals had significantly higher likelihood of sunburns (aOR = 1.93; 1.45-2.55), and no increased likelihood of vitamin D deficiency (aOR = 1.15; 0.84-1.58). Among sun-sensitive individuals, being younger, male and spending more time outdoors were associated with increased odds of sunburns and the risk of sunburn was reduced with frequently staying in the shade and engaging in multimodal sun protections.

CONCLUSION

Sun-sensitive individuals more frequently used sun protection methods yet they still were significantly more likely to experience sunburns and the risk of vitamin D deficiency was not increased. Education on proper application of sunscreen combined with other sun-protective techniques is important to reduce sunburn in sun-sensitive populations.

Oxidative Stress and Genotoxicity in Melanoma Induction: Impact on Repair Rather Than Formation of DNA Damage?

Keratinocytes and melanocytes, two cutaneous cell types located within the epidermis, are the origin of most skin cancers, namely carcinomas and melanomas. These two types of tumors differ in many ways. First, carcinomas are almost 10 times more frequent than melanomas. In addition, the affected cellular pathways, the mutated genes and the metastatic properties of the tumors are not the same. This review addresses another specificity of melanomas: the role of photo-oxidative stress. UVA efficiently produces reactive oxygen species in melanocytes, which results in more frequent oxidatively generated DNA lesions than in other cell types. The question of the respective contribution of UVB-induced pyrimidine dimers and UVA-mediated oxidatively generated lesions to mutagenesis in melanoma remains open. Recent results based on next-generation sequencing techniques strongly suggest that the mutational signature associated with pyrimidine dimers is overwhelming in melanomas like in skin carcinomas. UVA-induced oxidative stress may yet be indirectly linked to the genotoxic pathways involved in melanoma through its ability to hamper DNA repair activities.

Food-based strategies for prevention of vitamin D deficiency as informed by vitamin D dietary guidelines, and consideration of minimal-risk UVB radiation exposure in future guidelines

There is widespread acknowledgement of the presence of vitamin D deficiency in the community and the pressing need to address this. From a public health perspective, emphasis has been placed on addressing vitamin D deficiency through dietary means. However, naturally rich food sources of vitamin D are few and infrequently consumed, and nutrition survey data from various countries have indicated that habitual vitamin D intakes in the community are much lower than the current vitamin D dietary guidelines. This review will briefly overview the extent of vitamin D deficiency within the community, its causes, and how our food chain, once its embraces the evidence-based practise of food fortification and potentially biofortification, can cater for meeting the dietary vitamin D needs of the community. Finally, international authorities, briefed with establishing vitamin D dietary guidelines over the past decade, have struggled with uncertainties and gaps in our understanding of the relative contribution of sunshine and diet to vitamin D status and vitamin D requirements for health maintenance. The review will also consider how emerging evidence of a possible minimal-risk UVB radiation exposure relative to skin cancer that also enables vitamin D production could greatly inform future vitamin D dietary guidelines.

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

Purpose

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

Methods

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

Results

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

Conclusion

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

Clinical trial registry number

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

Electronic supplementary material

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

The Paleolithic Nutrition Model in Relation to Ultraviolet Light and Vitamin D

The biology of every species has been optimized for life in the environment in which that species evolved. Humans originated in the tropics, and while some natural selection took place in response to behaviors and environments that decreased exposure to ultraviolet light, there has never been a species-wide biological accommodation. Paleolithic nutrition advocates argue that risk of disease is higher because modern diets differ from what was consumed by early humans. Early humans were the naked ape living in the tropics, exposed to high levels of ultraviolet light and vitamin D nutrition (serum 25-hydroxyvitamin D; 25(OH)D) averaging 115 nmol/L, as compared to today's population averages that are well below 70 nmol/L. Natural selection from an available gene pool cannot compensate fully to an environmental change away from the one within which the species originally evolved. Vitamin D nutrition remains a contentious area. The epidemiological evidence consistently relates lower 25(OH)D to higher disease risk. However, evidence from double-blind clinical trials looking at preventing new disease in healthy volunteers has been disappointing. But such negative trials have been the case for all nutrients except for folic acid which lowers risk of spina bifida. The Paleolithic nutrition model is based on fundamental biological concepts, but it has overlooked the environmental effects of ultraviolet light and vitamin D nutrition. This paper presents evolutionary and Paleolithic aspects of ultraviolet light and vitamin D with the aim to support pertinent research and, ultimately, public policy regarding nutrition and light exposure.

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

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

Remodelling of fibrillin-rich microfibrils by solar-simulated radiation: impact of skin ethnicity

Cutaneous fibrillin-rich microfibrils (FRMs) should be considered as two distinct populations that differentially accrue damage in response to SSR. Furthermore, FRMs derived from black African skin show greater change following UVR challenge.

Melanin has a Small Inhibitory Effect on Cutaneous Vitamin D Synthesis: A Comparison of Extreme Phenotypes

Epidemiology suggests that melanin inhibits cutaneous vitamin D₃ synthesis by UVR. Laboratory investigations assessing the impact of melanin on vitamin D production have produced contradictory results. We determined the effect of melanin on vitamin D₃ photosynthesis in healthy young volunteers (n = 102) of Fitzpatrick skin types II-VI (white to black). Participants, irrespective of skin type, were exposed to the same suberythemal UVR dose, to 85% body surface area, using solar simulated UVR or narrowband UVB (311 nm). This was repeated five times with intervals of 3-4 days between UVR exposures. Blood was taken before, during, and after the irradiation and assessed for serum 25-hydroxyvitamin D₃ (25[OH]D₃) as a marker of vitamin D₃ status. Linear UVR dose-dependent increases in 25(OH)D₃ were highly significant (P ≤ 7.7 x 10^-11). The ratios of regression slopes of the different skin type groups were compared, and only skin type II was significantly steeper than the other groups. Comparisons between extreme skin types II and VI showed melanin inhibition factors of approximately 1.3-1.4, depending on the UVR source. We conclude that the inhibitory effect of melanin on vitamin D₃ synthesis is small, compared with erythema, but that this difference may be sufficient to explain the epidemiological data.

Detection of the small oligonucleotide products of nucleotide excision repair in UVB-irradiated human skin

UVB radiation results in the formation of potentially mutagenic photoproducts in the DNA of epidermal skin cells. In vitro approaches have demonstrated that the nucleotide excision repair (NER) machinery removes UV photoproducts from DNA in the form of small (∼30-nt-long), excised, damage-containing DNA oligonucleotides (sedDNAs). Though this process presumably takes place in human skin exposed to UVB radiation, sedDNAs have not previously been detected in human skin. Using surgically discarded human skin, we have optimized the detection of the sedDNA products of NER from small amounts of human epidermal tissue ex vivo within minutes of UVB exposure and after UVB doses that normally lead to minimal erythema. Moreover, sedDNA generation was inhibited by treatment of skin explants with spironolactone, which depletes the epidermis of the essential NER protein XPB to mimic the skin of xeroderma pigmentosum patients. Time course experiments revealed that a partially degraded form of the sedDNAs could be readily detected even 12 hours following UVB exposure, which indicates that these repair products are relatively stable in human skin epidermis. Together, these data suggest that sedDNA detection may be a useful assay for determining how genetic, environmental, and other factors influence NER activity in human skin epidermis and whether abnormal sedDNA processing contributes to photosensitive skin disorders.

Sunscreen photoprotection and vitamin D status

Background

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

Objectives

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

Methods

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

Results

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

Conclusions

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

What's already known about this topic?

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

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

What does this study add?

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

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

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

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

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

The effect of sunscreen on vitamin D: a review

BACKGROUND

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

OBJECTIVES

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

METHODS

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

RESULTS

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

CONCLUSIONS

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

Optimal sunscreen use, during a sun holiday with a very high ultraviolet index, allows vitamin D synthesis without sunburn

Background

Sunlight contains ultraviolet (UV)A and UVB radiation. UVB is essential for vitamin D synthesis but is the main cause of sunburn and skin cancer. Sunscreen use is advocated to reduce the sun's adverse effects but may compromise vitamin D status.

Objectives

To assess the ability of two intervention sunscreens to inhibit vitamin D synthesis during a week‐long sun holiday.

Methods

The impact of sunscreens on vitamin D status was studied during a 1‐week sun holiday in Tenerife (28° N). Comparisons were made between two formulations, each with a sun protection factor (SPF) of 15. The UVA‐protection factor (PF) was low in one case and high in the other. Healthy Polish volunteers (n = 20 per group) were given the sunscreens and advised on the correct application. Comparisons were also made with discretionary sunscreen use (n = 22) and nonholiday groups (51·8° N, n = 17). Sunscreen use in the intervention groups was measured. Behaviour, UV radiation exposure, clothing cover and sunburn were monitored. Serum 25‐hydroxyvitamin D₃ [25(OH)D₃] was assessed by high‐performance liquid chromatography–tandem mass spectrometry.

Results

Use of intervention sunscreens was the same (P = 0·60), and both equally inhibited sunburn, which was present in the discretionary use group. There was an increase (P < 0·001) in mean ± SD 25(OH)D₃ (28·0 ± 16·5 nmol L⁻¹) in the discretionary use group. The high and low UVA‐PF sunscreen groups showed statistically significant increases (P < 0·001) of 19·0 ± 14·2 and 13·0 ± 11·4 nmol L⁻¹ 25(OH)D₃, respectively with P = 0·022 for difference between the intervention sunscreens. The nonholiday group showed a fall (P = 0·08) of 2·5 ± 5·6 nmol L⁻¹ 25(OH)D₃.

Conclusions

Sunscreens may be used to prevent sunburn yet allow vitamin D synthesis. A high UVA‐PF sunscreen enables significantly higher vitamin D synthesis than a low UVA‐PF sunscreen because the former, by default, transmits more UVB than the latter.

What's already known about this topic?

Action spectra (wavelength dependence) for erythema and the cutaneous formation of vitamin D overlap considerably in the ultraviolet (UV)B region.

Theoretically, sunscreens that inhibit erythema should also inhibit vitamin D synthesis.

To date, studies on the inhibitory effects of sunscreens on vitamin D synthesis have given conflicting results, possibly, in part, because people typically apply sunscreen suboptimally.

Many studies have design flaws.

What does this study add?

Sunscreens (sun protection factor, SPF 15) applied at sufficient thickness to inhibit sunburn during a week‐long holiday with a very high UV index still allow a highly significant improvement of serum 25‐hydroxyvitamin D₃ concentration.

An SPF 15 formulation with high UVA protection enables better vitamin D synthesis than a low UVA protection product. The former allows more UVB transmission.

Linked Editorial: https://doi.org/10.1111/bjd.18273.

https://doi.org/10.1111/bjd.18492 available online

https://www.bjdonline.com/article/optimal-sunscreen-use-during-a-sun-holiday-with-a-very-high-ultraviolet-index-allows-vitamin-d-synthesis-without-sunburn/

Human health in relation to exposure to solar ultraviolet radiation under changing stratospheric ozone and climate

The Montreal Protocol has limited increases in the UV-B (280-315 nm) radiation reaching the Earth's surface as a result of depletion of stratospheric ozone. Nevertheless, the incidence of skin cancers continues to increase in most light-skinned populations, probably due mainly to risky sun exposure behaviour. In locations with strong sun protection programs of long duration, incidence is now reducing in younger age groups. Changes in the epidemiology of UV-induced eye diseases are less clear, due to a lack of data. Exposure to UV radiation plays a role in the development of cataracts, pterygium and possibly age-related macular degeneration; these are major causes of visual impairment world-wide. Photodermatoses and phototoxic reactions to drugs are not uncommon; management of the latter includes recognition of the risks by the prescribing physician. Exposure to UV radiation has benefits for health through the production of vitamin D in the skin and modulation of immune function. The latter has benefits for skin diseases such as psoriasis and possibly for systemic autoimmune diseases such as multiple sclerosis. The health risks of sun exposure can be mitigated through appropriate sun protection, such as clothing with both good UV-blocking characteristics and adequate skin coverage, sunglasses, shade, and sunscreen. New sunscreen preparations provide protection against a broader spectrum of solar radiation, but it is not clear that this has benefits for health. Gaps in knowledge make it difficult to derive evidence-based sun protection advice that balances the risks and benefits of sun exposure.

Reassessing Impacts of Extended Daily Exposure to Low Level Solar UV Radiation

Currently, health agencies recommend that no sun-protection is required when the UV Index (UVI) is less than 3. We use high-quality data from spectroradiometers and model calculations to demonstrate that this simplification is seriously flawed, particularly for mid-latitude conditions. For days when the peak UVI is below the threshold for advising protection, the daily dose of sun-burning UV available frequently far exceeds the threshold for damage to fair skin. This may have important health consequences, as populations at mid latitudes include a significant proportion with fair skin that is susceptible to damage.