Calcium homeostasis and body composition in patients with palmoplantar pustulosis: a case-control study

Background Palmoplantar pustulosis (PPP) is a common disease strongly associated with smoking, autoimmune comorbidities and a deranged calcium homeostasis. It is unclear whether these changes in calcium homeostasis are a consequence of vitamin D status, abnormal dermal vitamin D synthesis or whether they are substantiated in effects on bone mineral density (BMD). Objectives To study the vitamin D status and BMD in patients with PPP. Methods In comparisons with two sets of controls (n = 101 for serum analyses and n = 5123 for BMD analyses), we therefore aimed to investigate whether PPP (59 cases) was associated with serum levels of 25‐hydroxyvitamin D and 1,25‐dihydroxyvitamin D, whether patients with PPP had decreased BMD and finally if the dermal expression of 25‐hydroxyvitamin D₃‐1α‐hydroxylase (CYP27B1) and the vitamin D receptor (VDR) were affected in PPP skin lesions. Results We found no differences in mean serum 25‐hydroxyvitamin D levels between cases and controls, whereas PPP cases displayed 17·8 pmol L^?1 lower (P = 0·04) values in 1,25‐dihydroxyvitamin D. BMD at the hip, lumbar spine or of total body did not differ substantially between cases and controls. Finally, patients with PPP had lower dermal expression of CYP27B1 and VDR in affected skin lesions. Conclusions The increase in serum calcium levels and suppressed parathyroid hormone in patients with PPP were not attributable to derangements in vitamin D status and these patients did not have lower BMD.     

High plasma 25‐hydroxyvitamin D and high risk of nonmelanoma skin cancer: a Mendelian randomization study of 97 849 individuals

In this study from Denmark, we investigate whether vitamin D status, usually measured by 25‐hydroxyvitamin D in blood samples, is associated with development of non‐melanoma skin cancer (NMSC). Previously, it has proven difficult to answer this particular question. If you simply divide everyone into two groups, i.e. those with a high and those with low measured 25‐hydroxyvitamin D, a higher incidence rate of NMSC would be observed in the group with high 25‐hydroxyvitamin D. However, this simple observation is susceptible to misinterpretation, e.g. sunlight's UV radiation causes damage to the skin that starts the development of skin cancer, as well as inducing vitamin D synthesis in the skin (i.e. helping the body to create vitamin D). On average, people who have higher high 25‐hydroxyvitamin D levels will therefore also have been exposed to more sunlight and UV radiation and be at higher risk of developing skin cancer. For this reason, we could observe a potentially false association between 25‐hydroxyvitamin D and cancer if we base our conclusions on just raw data alone. In this study, we used a method called Mendelian randomisation that is not susceptible to these potential errors, and we found that genetic variants affecting vitamin D neither increase nor decrease the risk of getting skin cancer. The implications of this study are that the association of 25‐hydroxyvitamin D with skin cancer cannot be taken at face value and similar studies are required for other types of cancer.     

The relation between sunscreen layer thickness and vitamin D production after ultraviolet B exposure: a randomized clinical trial

Background Sunscreens absorb ultraviolet B (UVB) and it is a major concern that sunscreen use may lead to vitamin D deficiency. Objectives To investigate the relation between the amount of sunscreen applied and the vitamin D serum level in humans after UVB exposure under controlled conditions. Methods Thirty‐seven healthy volunteers with fair skin types were randomized to receive an inorganic sunscreen with sun protection factor (SPF) 8 of 0 mg cm^?2, 0·5 mg cm^?2, 1 mg cm^?2, 1·5 mg cm^?2, or 2 mg cm^?2 thickness on the upper body, approximately 25% of the body area. Participants were irradiated with a fixed UVB dose of 3 standard erythema doses 20 min after sunscreen application. This procedure was repeated four times with a 2‐ to 3‐day interval. Blood samples were drawn before the first irradiation and 3 days after the last to determine the serum vitamin D level expressed as 25‐hydroxyvitamin D₃ [25(OH)D]. Results The vitamin D serum level increased in an exponential manner with decreasing thickness of sunscreen layer in response to UVB exposure. For all thicknesses of sunscreen, the level of 25(OH)D increased significantly after irradiation (P < 0·05), except for the group treated with 2 mg cm^?2, in which the increase in 25(OH)D was not statistically significant (P = 0·16). Conclusions Vitamin D production increases exponentially when thinner sunscreen layers than recommended are applied (< 2 mg cm^?2). When the amount of sunscreen and SPF advised by the World Health Organization are used, vitamin D production may be abolished. Re‐evaluation of sun‐protection strategies could be warranted.     

Vitamin D metabolism in psoriasis before and after phototherapy

Epidermis plays a major role in vitamin D synthesis and is a target tissue for 1,25 (OH)2 vitamin D, which could be involved in abnormal proliferation and differentiation of psoriatic keratinocytes. We investigated plasma calcium, phosphorus, alkaline phosphatases, parathyroid hormone, 25 (OH) D, 24,25 (OH)2 D and 1,25 (OH)2 D in 15 control subjects and 20 psoriatic patients before and after 3 weeks of phototherapy (UVB or PUVA). Before irradiation, all parameters were similar in psoriatics and controls, except for serum phosphorus (lower in psoriasis p less than 0.01). After phototherapy, P rose to normal values in psoriatic patients; 25 (OH) D and 24,25 (OH)2 D were dramatically increased by UVB (but not by PUVA) in psoriatic patients as well as in controls; 1,25 (OH)2 D was unmodified in controls but was significantly increased in psoriasis. Since 1,25 (OH)2 D has been reported to be an effective treatment for psoriasis, the UV-induced increase in 1,25 (OH)2 D could account for the beneficial effect of phototherapy in psoriasis.     

Vitamin D deficiency in patients with cutaneous lupus erythematosus is prevalent throughout the year

Background Vitamin D mediates immunomodulatory functions and its deficiency has been associated with an increased prevalence of immunological diseases including systemic lupus erythematosus (SLE). Chronic discoid or subacute cutaneous lupus erythematosus (CLE) are ultraviolet (UV)‐triggered skin diseases. As vitamin D is mostly UV‐derived and not from nutrition, its deficiency is frequent especially during the UV‐deprived winter months. Objective To compare the vitamin D status of patients with CLE with patients with type I allergy and healthy individuals during the summer or winter months. Methods The vitamin D status of patients with CLE (n = 41) was compared with patients with type I allergy (n = 24), healthy individuals (n = 25) and a reference pool (n = 1951) by means of concentrations of circulating storage metabolite 25‐hydroxyvitamin D in the summer and winter. Results Serum 25‐hydroxyvitamin D concentrations were lower during the winter in the reference population, and type I allergic and healthy individuals (29·2–35·5 nmol L^?1) compared with the summer months (56·3–89·8 nmol L^?1) and paralleled by the prevalence of vitamin D deficiency (serum 25‐hydroxyvitamin D < 50 nmol L^?1; winter: 70·8–73·4%, summer: 34·9–39·4%). In contrast, vitamin D deficiency in patients with CLE was prevalent throughout the year (summer: 85·7%, winter: 97·1%). In patients with CLE with concomitant prednisolone treatment, the 25‐hydroxyvitamin D serum levels were comparable with (mean daily intake 877 IU) or without vitamin D supplementation during summer or winter (P = 0·75 and P = 0·14, respectively). Conclusions  Our data identify vitamin D deficiency in patients with CLE throughout the year and indicate that monitoring and correcting the vitamin D status should be considered to prevent bone demineralization and fractures and to modulate beneficially immunological dysfunction.     

Development and preliminary validation of the PC‐SAD5, a screener‐derived short depression severity measure

Background The prevalence of depressive disorders is high among patients with skin disease. The PC‐SAD is a 37‐item self‐administered depression screening questionnaire that has been validated in dermatological patients. Objective The aim of this study was to develop and validate a brief depression severity instrument derived from the PC‐SAD that can be used to assess severity and monitor ongoing clinical course. Methods Two patient samples participated in the study: 72 adult dermatological inpatients and 73 adults attending six primary care practices. Psychiatric assessment included the Structured Clinical Interview for DSM‐IV and an 18‐item version of the PC‐SAD; moreover, dermatological patients completed the Patient Health Questionnaire depression scale (PHQ‐9), while primary care patients were administered the Montgomery‐Asberg Depression Rating Scale (MADRS). A subset of five PC‐SAD items showing the best psychometric properties were selected, and the reliability and validity of the resulting instrument (PC‐SAD5) were examined. Results The PC‐SAD5 showed satisfactory internal consistency in both samples. There was a high correlation between PC‐SAD5 and PHQ‐9 and MADRS scores. Multiple regression analysis revealed a gradient of PC‐SAD5 scores from patients with no mental disorder, those with milder forms of depression, to those with Major Depressive Disorder. Similar results were observed for the 18‐item version of the PC‐SAD. Conclusion The availability of valid and reliable continuous measures of depression severity derived from the PC‐SAD extends its field of application from depression screening to use as a follow‐up measure of depression severity in routine clinical practice. A validated very short instrument such as the PC‐SAD5 may have substantial clinical value.     

In vitro evaluation of a novel topical cream for vitiligo and psoriasis that selectively delivers NB‐UVB therapy when exposed to sunlight

Ultraviolet‐B (UVB) phototherapy is a well‐established mode of treatment for several types of dermatological disease. For psoriasis and vitiligo, narrow band UVB (NB‐UVB) phototherapy is an effective therapy, demonstrating greater efficacy and safety compared to broadband UVB or psoralen plus UVA treatments. While the treatment efficacy of NB‐UVB artificial light sources is well documented, the long term time and cost commitment of the therapy remains a barrier to treatment adherence. Natural sunlight is an ideal source of accessible UVB radiation; however, exposure to natural sunlight generally results in erythema prior to the accumulation of sufficient dosage of therapeutic wavelengths of UVB. This communication describes a novel topical cream designed to selectively deliver NB‐UVB therapy when exposed to sunlight. The topical cream when combined with natural sunlight could offer patients a more convenient phototherapy option for psoriasis and vitiligo, potentially increasing patient compliance.     

Narrowband ultraviolet B course improves vitamin D balance in women in winter

Background Vitamin D insufficiency is common in winter in the Nordic countries. Objectives  To examine whether a short course of narrowband ultraviolet B (NB‐UVB) improves vitamin D balance. Methods Fifty‐six healthy, white women (mean age 41 years) volunteered and 53 completed the study. NB‐UVB exposures were given on seven consecutive days either on the whole body (n = 19), on the head and arms (n = 9) or on the abdomen (n = 14). Similarly, seven solar simulator exposures were given on the face and arms (n = 11). The cumulative UVB dose was 13 standard erythema doses in all regimens. Serum calcidiol (25‐hydroxyvitamin D) concentration was measured by radioimmunoassay before and after the NB‐UVB exposures. Follow‐up samples were taken from the whole‐body NB‐UVB group at 2 months. Results At onset 41 women (77%) had vitamin D insufficiency (calcidiol < 50 nmol L^?1) and six (11%) had vitamin D deficiency (calcidiol < 25 nmol L^?1). Calcidiol concentration increased significantly, by a mean of 11·4 nmol L^?1 when NB‐UVB was given on the whole body, by 11·0 nmol L^?1 when given on the head and arms and by 4·0 nmol L^?1 when given on the abdomen. Solar simulator exposures given on the face and arms increased calcidiol by 3·8 nmol L^?1. After 2 months serum calcidiol was still higher than initially in the group who received NB‐UVB exposures on the whole body. Conclusions NB‐UVB exposures given on seven consecutive days on different skin areas of healthy women significantly improved serum calcidiol concentration. A short low‐dose NB‐UVB course can improve vitamin D balance in winter.     

Case of thymoma‐associated cutaneous graft‐versus‐host disease‐like disease successfully improved by narrowband ultraviolet B phototherapy

Thymoma‐associated graft‐versus‐host disease (GVHD)‐like disease is a rare paraneoplastic disease seen in patients with thymoma. Here, we describe the first case of thymoma‐associated GVHD‐like disease localized to the skin that was successfully improved by a combination of systemic corticosteroids and whole‐body narrowband ultraviolet (UV)‐B phototherapy. The patient had developed toxic epidermal necrolysis‐like erosive skin lesions over the whole body. Although systemic corticosteroids were effective up to a point, we were unable to begin the steroid taper. The addition of systemic narrowband UV‐B phototherapy improved the skin manifestation of this disease, allowing corticosteroids to be reduced to a third of the original dose. Histopathologically, it was confirmed that the proportion of Foxp3‐positive lymphocytes in the skin increased after narrowband UV‐B irradiation. We propose that whole‐body narrowband UV‐B phototherapy is a good therapeutic option for the skin manifestation of thymoma‐associated GVHD‐like disease.     

A global phase III randomized controlled trial of etanercept in psoriasis: safety, efficacy, and effect of dose reduction

BACKGROUND: In previous studies, etanercept significantly improved plaque psoriasis and was well tolerated. OBJECTIVES: To examine further the efficacy and safety of etanercept and to assess maintenance of treatment effect after dose reduction of etanercept. METHODS: In this multicentre 24-week study in the U.S.A., Canada and Western Europe, patients were at least 18 years old; had active, clinically stable plaque psoriasis involving at least 10% of body surface area; had a minimum Psoriasis Area and Severity Index (PASI) of 10 at screening; and had received or were a candidate to receive systemic psoriasis therapy or phototherapy. During the first 12 weeks of the study, patients were randomly assigned to receive by subcutaneous injection etanercept twice weekly (BIW) at a dose of 50 mg or 25 mg, or placebo BIW in a double-blind fashion. During the second 12 weeks, all patients received etanercept 25 mg BIW. The primary endpoint was a 75% or greater improvement from baseline in PASI (PASI 75) at 12 weeks. RESULTS: Five hundred and eighty-three subjects were randomized and received at least one dose of study drug. At week 12, a PASI 75 was achieved by 49% of patients in the etanercept 50 mg BIW group, 34% in the 25 mg BIW group, and 3% in the placebo group (P < 0.0001 for each etanercept group compared with placebo). At week 24 (after 12 weeks of open-label 25 mg etanercept BIW), a PASI 75 was achieved by 54% of patients whose dose was reduced from 50 mg BIW to 25 mg BIW, by 45% of patients in the continuous 25 mg BIW group, and by 28% in the group that received placebo followed by etanercept 25 mg BIW. Etanercept was well tolerated throughout the study. CONCLUSIONS: Etanercept provided clinically meaningful benefit to patients with chronic plaque psoriasis, with no apparent decrease in efficacy after dose reduction.     

Vitamin D status in patients with chronic plaque psoriasis

Background Vitamin D could have important immunomodulatory effects in psoriasis. Objectives To measure 25‐hydroxyvitamin D [25(OH)D], parathyroid hormone (PTH) and calcium serum levels in patients with psoriasis and the associations with some relevant clinical features. Methods A cross‐sectional study was conducted over 1 year including 145 patients with chronic plaque psoriasis, 112 patients with rheumatoid arthritis (RA) and 141 healthy controls. 25(OH)D, PTH and calcium serum levels were measured in a centralized laboratory. Demography, comorbidities, disease severity and exposure time to sunlight (which was derived by questionnaire) were collected. Results The prevalence of vitamin D deficiency [25(OH)D levels < 20 ng mL^?1] in patients with psoriasis was 57·8% vs. 37·5% in patients with RA and 29·7% in healthy controls (P < 0·001). In winter, the prevalence of vitamin D deficiency rose to 80·9% in patients with psoriasis, to 41·3% in those with RA and to 30·3% in healthy controls (P < 0·001). Patients with psoriasis or psoriatic arthritis did not differ in 25(OH)D serum levels nor in the prevalence of vitamin D deficiency. In the logistic regression analysis, vitamin D deficiency was associated with psoriasis independently of age, sex, body mass index, calcium, PTH levels and season of blood sampling. A limitation is that the study design does not allow a causal or temporal relationship between vitamin D deficiency and psoriasis to be established. Conclusions Vitamin D deficiency may be common in patients with psoriasis, especially in winter.     

Combination treatment by 10 600 nm ablative fractional carbon dioxide laser and narrowband ultraviolet B in refractory nonsegmental vitiligo: a prospective, randomized half-body comparative study

Background Vitiligo is a common acquired depigmentation disorder caused by the loss of melanocytes. Despite the numerous treatment modalities available for vitiligo, responses to treatment are still unsatisfactory. For this reason, new treatment modalities and approaches are needed. Objectives To investigate the effects of fractional carbon dioxide (CO₂) laser therapy followed by systemic narrowband ultraviolet B (NB‐UVB) phototherapy on nonsegmental vitiligo (NSV) as a prospective and randomized left‐right comparative study. Methods Ten patients with NSV who presented symmetrical vitiligo lesions with no further improvement despite more than 1 year of conventional treatment were enrolled. Two sessions of half‐body fractional CO₂ laser therapy were performed at a 2‐month interval. NB‐UVB phototherapy was then administered to the entire body 5 days after each fractional laser treatment twice a week, increasing the dose incrementally by 15% at each session. Objective clinical assessments were made by two blinded dermatologists using a quartile grading scale, and the patients’ overall satisfaction was evaluated using a 10‐point visual analogue scale. Results Two months after the last treatment, mean improvement scores, assessed by physicians, were significantly higher for those treated with half‐body fractional CO₂ laser therapy followed by NB‐UVB phototherapy, compared with those treated with NB‐UVB alone (P = 0·034). In addition, according to subjective assessment, the half‐body laser treatment followed by NB‐UVB showed significantly higher improvements compared with NB‐UVB treatment alone (P = 0·023). Noticeable adverse events, such as infection, scarring and Koebner phenomenon, were not found in any patient. Conclusions This study suggests that fractional CO₂ laser therapy followed by NB‐UVB phototherapy could be used effectively and safely as an alternative modality for the treatment of refractory vitiligo.     

Effect of narrowband ultraviolet B therapy on inflammatory markers and body fat composition in moderate to severe psoriasis

Background Previous studies have shown increased prevalence of metabolic syndrome in patients with psoriasis. Objectives To characterize the anthropometric and metabolic profile of Spanish patients with moderate to severe psoriasis compared with controls without psoriasis matched for gender, age and body mass index (BMI), and to evaluate the impact of narrowband ultraviolet B (NB‐UVB) therapy on patient profiles. Methods Baseline waist circumference, body fat composition, lipid, carbohydrate and calcium metabolism profile, inflammation markers, homocysteine, vitamins D, B₆ and B₁₂ and folic acid of 50 patients with psoriasis and 50 matched controls were recorded then evaluated after NB‐UVB in patients with psoriasis and correlated with clinical outcome. Results Despite very similar BMIs, 54% of patients met International Diabetes Foundation criteria for metabolic syndrome compared with 42% of controls (P = 0·01); body fat was 29·9% in patients and 28·0% in controls (P = 0·037), correlating with waist circumference; while patient atherogenic profiles were less favourable, with higher apolipoprotein B and low density lipoprotein cholesterol than controls, and both patients and controls showed insufficient vitamin D serum levels (< 20 ng mL^?1). Mean improvement of Psoriasis Area and Severity Index (PASI) after NB‐UVB was 78·2%. Ferritin, B₁₂ and C‐reactive protein decreased significantly after NB‐UVB therapy. Vitamin D levels reached adequate levels after phototherapy; however, no relationship with PASI improvement was observed. Conclusions We characterized inflammatory and atherogenic profiles of Spanish patients with psoriasis compared with matched controls. After NB‐UVB therapy we demonstrated improvement in psoriasis and some systemic inflammation markers, which were not mediated by enhancement of vitamin D synthesis.     

UVB phototherapy of atopic dermatitis

UVB phototherapy of atopic dermatitis was investigated in two paired-comparison studies. In study I, 17 patients were treated for 8 weeks with ultraviolet B radiation (UVB) on one half of the body and with visible light (placebo) on the other. A severity score based on eight clinical variables was determined before, during and after treatment. The total score, pruritus score and overall evaluation score were significantly better on the UVB treated sides than on the placebo treated sides (P less than 0.001). In 13 patients the UVB treated side healed or improved considerably, while the placebo treated side improved considerably in one patient only. In study II, 25 patients were treated for 8 weeks with 0.8 of the minimal erythema dose (MED) of UVB on one half of the body and with 0.4 MED UVB on the other. No statistically significant differences between these dosage regimens were found.     

Methotrexate/narrowband UVB phototherapy combination vs. narrowband UVB phototherapy in the treatment of chronic plaque‐type psoriasis – a randomized single‐blinded placebo‐controlled study

Background Psoriasis is a chronic, recurring inflammatory disease affecting the skin, joints and nails that has a significant negative impact on the quality of life. Efficacy of combination of methotrexate/narrowband ultraviolet B (NBUVB) phototherapy in the treatment of psoriasis has been rarely assessed. Objectives To compare the efficacy of methotrexate/NBUVB phototherapy combination vs. NBUVB phototherapy in the treatment of chronic plaque psoriasis. Methods Forty patients with chronic plaque‐type psoriasis (body surface area involvement >10%) were randomized to receive either methotrexate/NBUVB phototherapy (group A) or placebo/NBUVB phototherapy (group B). End point of treatment was 75% reduction in Psoriasis Area and Severity Index (PASI) Score or upto 6 months, whichever was earlier. Patients were then followed up for a period of 12 weeks for assessment of relapse. Results Of 40 patients, 37 completed the treatment period and 29 both the treatment period and follow‐up. PASI 75 was achieved in 19/20 patients in group A and 14/20 patients in group B (P < 0.04). The mean number of weeks(P = 0.001), the mean cumulative dose of NBUVB (P = 0.001) and the mean number of phototherapy sessions (P = 0.0001) required to achieve PASI 75 were significantly less in group A compared with group B. There was no significant difference in the number of patients who relapsed during the follow‐up period (P = 0.68). Conclusion Combination of methotrexate and NBUVB phototherapy provides more rapid clinical improvement compared with NBUVB monotherapy in the treatment for chronic plaque‐type psoriasis.     

Vitamin D production in psoriasis patients increases less with narrowband than with broadband ultraviolet B phototherapy

Background: Phototherapy of psoriasis is an effective treatment. In addition to standard broadband ultraviolet radiation B (UVB), (280–320 nm), narrowband phototherapy (NBUVB) (monochromatic UV between 311 and 312 nm) has become an important treatment for psoriasis. The same wavelength range of UVB (290–315 nm) induces synthesis of vitamin D. The aim was to compare the effect of broadband with NBUVB therapy on vitamin D synthesis in patients with psoriasis.
Methods: Sixty-eight Caucasian patients (17 women and 51 men) mean age 54.1 ± 16.0 years, with active plaque psoriasis, were treated with broadband UVB ( n =26) or NBUVB ( n =42) two to three times/week for 8–12 weeks. The serum concentrations of 25-hydroxyvitamin D (25(OH)D3), 1,25-dihydroxyvitamin D (1,25(OH)₂D3), intact parathyroid hormone (PTH), calcium and creatinine were measured before the first exposure and after the last dose of radiation.
Results: In broadband UVB treated patients, 25(OH)D3 increased from 37.9 ± 16.9 to 69.4 ± 19.7 ng/ml ( P <0.0001) and in patients treated with NBUVB from 34.8 ± 11.9 to 55.3 ± 17.6 ng/ml ( P <0.0001) and P =0.008 between the treatment groups. PTH decreased on broadband UVB ( P <0.05). The serum concentrations of 1,25(OH)₂D3, calcium or creatinine remained unaltered.
Conclusion: Serum 25(OH)D3 in psoriasis patients increased less with NBUVB than with broadband UVB phototherapy. Psoriasis improved on both regimens.     

The importance of stressful family events in psoriatic patients: a retrospective study

Background Psychosomatic stress events are believed to play an important role in psoriasis either by inducing or worsening the disease. Objective In this article, we compared the role of family stress events against other types of stress events on the psychological well being of patients and on their skin disease. We used our sample of psoriasis patients with said stress events. Method Patients underwent a dermatological examination which was evaluated through the PASI index. Simultaneously, they underwent interviews for psychological evaluations. The Hamilton scales were administered to assess anxiety and depression (Ham‐A scores significant >20, Ham‐D >15). Results It has been demonstrated that family stress influences the psychological well being more than other types of daily stress events. In fact, people with family stress events reported higher value HAM‐A (P = 0.03) and HAM‐D (P = 0.02) compared with those who reported other types of stress events. Women reported higher values of HAM‐A and HAM‐D than men. The value of PASI in the two groups (with family stress events and those with other stress events) was not statistically significant. Conclusion Results obtained from this analysis show the importance of family stress events on the quality of life and on psychiatric and dermatological status. For the psychological morbidity, a parallel approach of both bio‐psychiatric and skin care is recommended, especially for women.     

Modelling the seasonal variation of vitamin D due to sun exposure

Background The current interest in vitamin D as a preventive agent in many chronic diseases has led to a reappraisal of adequate sun exposure. Yet just what constitutes adequacy remains to be clearly defined and validated. To do this requires an understanding of how behaviour outdoors during the year translates into seasonal changes in vitamin D status. Objectives To develop a model for estimating the changes in serum 25‐hydroxyvitamin D [25(OH)D] levels as a consequence of sun exposure throughout the year. Methods A novel mathematical model is described that incorporates the changes in serum 25(OH)D following a single, whole‐body exposure to solar ultraviolet radiation with daily sun exposure in order to estimate the annual variation in serum 25(OH)D. Results The model yields results that agree closely with measured data from a large population‐based study. Application of the model showed that current advice about 10–20 min of daily sun exposure during the summer months does little in the way of boosting overall 25(OH)D levels, while sufficient sun exposure that could achieve a worthwhile benefit would compromise skin health. Conclusions There is little in the way of public health advice concerning the benefits of sun exposure that can be given as an effective means of maintaining adequate vitamin D levels throughout the year. Instead it would seem safer and more effective to fortify more foods with vitamin D and/or to consider the use of supplements during the winter months. Messages concerning sun exposure should remain focused on the detrimental effects of excessive sun exposure and should avoid giving specific advice on what might be ‘optimal’ sun exposure.     

Interdependence between body surface area and ultraviolet B dose in vitamin D production: a randomized controlled trial

Background Ultraviolet (UV) B radiation increases serum vitamin D level expressed as 25‐hydroxyvitamin‐D₃ [25(OH)D], but the relationship to body surface area and UVB dose needs investigation. Objective To investigate the importance of body surface area and UVB dose on vitamin D production after UVB exposure. Methods We randomized 92 participants to have 6%, 12% or 24% of their skin exposed to 0·75 (7·5 mJ cm^?2 at 298 nm using the CIE erythema action spectrum), 1·5 (15 mJ cm^?2) or 3·0 (30 mJ cm^?2) standard erythema doses (SED) of UVB. Each participant underwent four UVB exposures at intervals of 2–3 days. Skin pigmentation and 25(OH)D levels were measured before and 48 h after the final exposure. Results The increase in 25(OH)D after irradiation [Δ25(OH)D] was positively correlated with body surface area (P = 0·006; R² = 0·08) and UVB dose (P < 0·0001; R² = 0·28), and negatively correlated with baseline 25(OH)D (P < 0·0001; R² = 0·18), for the entire data sample. However, when analysing each body surface area separately, we found a significant UVB response correlation for 6% (P < 0·0001; R² = 0·48) and 12% (P = 0·0004; R² = 0·35), but not for 24%. We also found a significant skin area response correlation for 0·75 SED (P < 0·0001; R² = 0·56), but not for 1·5 and 3·0 SED when analysing each UVB dose separately. The relationships did not change significantly after adjustment of Δ25(OH)D for baseline 25(OH)D. Conclusion The increase in 25(OH)D depends mainly on the UVB dose; however, for small UVB doses the area of irradiated body surface is important.