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

Impact of surface ultraviolet radiation intensity on hospital admissions for ischemic and hemorrhagic stroke: A large-scale database study using distributed lag nonlinear analysis, 2015-2022, in Harbin, China

OBJECTIVES

Our aim is to evaluate the impact of surface ultraviolet radiation intensity on hospital admissions for stroke and to compare the correlation and differences among different subtypes of strokes.

MATERIALS AND METHODS

We collected daily data on surface ultraviolet radiation intensity, temperature, air pollution, and hospital admissions for stroke in Harbin from 2015 to 2022. Using a distributed lag non-linear model, we determined the correlation between daily surface ultraviolet radiation intensity and the stroke admission rate. Relative risks (RR) with 95% confidence intervals (CI) and attributable fractions (AF) with 95% CI were calculated based on stroke subtypes, gender, and age groups.

RESULTS

A total of 132,952 hospitalized stroke cases (including hemorrhagic and ischemic strokes) were included in the study. We assessed the non-linear effects of ultraviolet intensity on hospitalized patients with ischemic and hemorrhagic strokes. Compared to the maximum morbidity benchmark ultraviolet intensity (19.2 × 10^5 for ischemic stroke and 20.25 for hemorrhagic stroke), over the 0-10 day lag period, the RR for extreme low radiation (1st percentile) was 0.86 (95% CI: 0.77, 0.96), and the RR for extreme high radiation (99th percentile) was 0.86 (95% CI: 0.77, 0.96). In summary, -4.842% (95% CI: -7.721%, -2.167%) and -1.668% (95% CI: -3.061%, -0.33%) of ischemic strokes were attributed to extreme low radiation intensity with a lag of 0 to 10 days and extreme high radiation intensity with a lag of 0 to 5 days, respectively. The reduction in stroke hospitalization rates due to low or high ultraviolet intensity was more pronounced in females and younger individuals compared to males and older individuals. None of the mentioned ultraviolet intensity intensities and lag days had a statistically significant impact on hemorrhagic stroke.

CONCLUSIONS

Our study fundamentally suggests that both lower and higher levels of surface ultraviolet radiation intensity in Harbin, China, contribute to a reduced incidence of ischemic stroke, with this effect lasting approximately 10 days. This finding holds significant potential for public health and clinical relevance.

Serum 25-hydroxyvitamin D levels and dermatomyositis: A 2-sample mendelian randomization study

BACKGROUND

Previous studies have reported low serum 25-hydroxyvitamin D [25(OH)D] levels in dermatomyositis (DM) patients, but the exact causal relationship between them remains elusive. Our aim is to confirm the causal relationship between 25(OH)D and DM risk through a Mendelian randomization study.

METHODS

Retrieve genome-wide association study (GWAS) data on 25(OH)D (n = 441 291) and DM (n cases = 201, n controls = 172 834) from the GWAS database (https://gwas.mrcieu.ac.uk/). Select single-nucleotide polymorphisms (SNPs) strongly correlated with 25(OH)D as instrumental variables (IVs). The primary analytical approach involves the use of the inverse-variance weighted method (IVW), supplemented by MR-Egger regression and weighted median methods to enhance the reliability of the results. Heterogeneity and sensitivity analyses were conducted using Cochran's Q and leave-one-out approaches, respectively.

RESULTS

The IVW analysis confirmed a positive causal relationship between genetic variation in 25(OH)D levels and DM (OR = 2.36, 95% CI = 1.01-5.52, p = .048). Although not statistically significant (all p > .05), the other methods also suggested a protective effect of 25(OH)D on DM. Based on MR-Egger intercepts and Cochran's Q analysis, the selected SNPs showed no horizontal pleiotropy and heterogeneity. Sensitivity analysis demonstrated the robustness of the results against individual SNPs.

CONCLUSION

We provide the first evidence of a causal relationship between 25(OH)D levels and DM. Our findings support the importance of measuring serum 25(OH)D levels and considering vitamin D supplementation in clinical practice for patients with DM.

Diet, physical activity, and UV protection comprehensively influenced vitamin D status in college students: a cross-section study from China

BACKGROUND

Vitamin D deficiency is one of the most prevalent health problems worldwide in all age groups, whereas vitamin D status of Chinese college students was seldom studied in China. The purpose of this study was to explore the vitamin D status in Chinese college freshmen and its influencing factors, providing evidence for nutrition strategy application.

METHODS

Information including demographic status, diet habit, physical activity, and ultraviolet ray (UV) protection was collected by online questionnaire. Serum 25(OH)D₃ concentrations were measured using a liquid chromatograph mass spectrometer. Multivariate linear regression analyses were used to explore the comprehensive influence of diet, physical activity and UV protection on serum 25(OH)D₃ levels.

RESULTS

Totally 1667 freshmen from 26 provinces, autonomous districts or municipalities, were recruited, with a mean age of 18.6 ± 0.9 years. The mean serum 25(OH)D₃ levels were 18.1 ± 6.3 ng/mL and the proportion of vitamin D deficiency and insufficiency was 67.5% and 27.8%, respectively. Multivariate linear regression indicated that higher intake of milk and yogurt, calcium or vitamin D supplementation, and longer time of outdoor activity were positively linked to higher serum 25(OH)D₃, while higher intake of candy and higher UV protection index were negatively associated with serum 25(OH)D₃, after adjusted for age, gender, region of original residence, latitudes, longitude and BMI.

CONCLUSIONS

Vitamin D deficiency is very common in Chinese college students. Milk and yogurt intake and outdoor activity should be encouraged while candy intake should be limited for preventing vitamin D deficiency. Public health policies should focus on these changeable lifestyles and consider well-balanced guidelines on UV protection and vitamin D supplementation.

Estimation of Inactivation time for the SARS-CoV-2 virus from the UV biometer in South Korea

The coronavirus disease 2019 (COVID-19) is a result of the infection by "severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2), and has caused various social and economic effects over the globe. As the SARS-CoV-2 is effectively inactivated by the exposure to the UV-B radiation (shorter than 315 nm), the exposure time for inactivation of the SARS-CoV-2 was estimated using the broadband UV observation instrument over 11 observation sites in South Korea. For the limitation of the UV biometer, which has limited spectral information, the coefficient for conversion from the erythemal UV (EUV) to the radiation for virus inactivation was adopted before estimating the inactivation time. The inactivation time of SARS-CoV-2 is significantly dependent on seasonal and diurnal variations due to the temporal variations of surface incident UV irradiance. The inactivation times in summer and winter were around 10 and 50 min, respectively. The inactivation time was unidentified during winter afternoons due to the weak spectral UV solar radiation in winter. As the estimation of inactivation time using broadband observation includes the uncertainty due to the conversion coefficient and the error due to the solar irradiance, the sensitivity analysis of the inactivation time estimation was also conducted by changing the UV irradiance.

Sun Exposure Score and Vitamin D Levels in Moroccan Women of Childbearing Age

Sunlight exposure is an essential source of vitamin D for many humans. However, hypovitaminosis D is a global public health problem. This study aimed to develop and validate a sun exposure score (SES) and correlate it with serum 25-hydroxyvitamin D levels in women of childbearing age. One hundred and sixty women aged 18 to 45 years residing in Meknes, Morocco, were included. A questionnaire estimating the sun exposure score and blood analysis of serum 25-OHD concentration were performed. The questionnaire's reliability and construct validity were evaluated using Cronbach's alpha and factor analysis. Spearman's test was used to assess the correlation between SES and 25-OHD levels. The score's reliability and construct validity were good, with Cronbach's alpha values >0.70 and factorial saturation ranging from 0.696 to 0.948. Serum 25-OHD levels were significantly associated with the total sun exposure score, and all SES domains (Rho was 0.615 (p < 0.0001), 0.307 (p < 0.0001), 0.605 (p < 0.0001), and 0.424 (p < 0.0001) for total SES, indoor exposure domain, outdoor exposure domain, and sun protection practice domain, respectively). In addition, median 25-OHD levels increased significantly when sun exposure was changed from insufficient to sufficient (p < 0.0001). The results suggest that the sun exposure score could be used as a clinical tool to assess vitamin D levels in women of childbearing age.

Vitamin D status and COVID-19 prevention in a worker subgroup in Italy

BACKGROUND

Low levels of vitamin D are widespread in the world's population and associated with sun exposure, genetics, and lifestyles. Office workers in different occupational sectors seem more vulnerable than others. Scientific evidence reports a contribution of vitamin D in resistance to infections, opening to supplementation as a preventive action against pathogens, including SARS-CoV-2.

OBJECTIVE

A pilot campaign in the workplace during the coronavirus 2019 (COVID-19) pandemic was conducted based on the preliminary measurement of vitamin D amount and its integration.

METHODS

A preventive action to contrast the deficiency of vitamin D was offered to a population of 700 bank employees. Vitamin D supplementation was performed between April and June 2021, on workers (n = 139) and showed 25(OH)D serum levels ≤ 30 ng/ml. Demographic, anthropometric and lifestyle information were collected by survey and changes in the serum 25(OH)D amounts were monitored.

RESULTS

The adherence of the target population to the prevention campaign was 21%. 75% of the enrolled workers had low levels of vitamin D. After the intervention, serum vitamin D levels increased (1.28-fold;p = 0.0001) and 80% of the subjects reported optimal values > 30 ng/ml. Only 2.9% reported slight flu-like symptoms, but only 0.7% was confirmed as COVID-19, with respect to a ten-fold higher incidence in the general population.

CONCLUSIONS

Vitamin D supplementation can be achieved by simple and noninvasive approaches and can bring along further insights into health literacy on diet and lifestyles, representing an opportunity to protect the population by the widespread state of vitamin deficiency.

A prospective analysis of concentration of 25-OHD between northern and southern district in Japan in year-round study

Although osteoporotic patients have already been recognized as having a low-volume vitamin D status, the concentration of active vitamin D precursor has not been studied in detail. This trial aimed to clarify the concentration of 25-hydroxyvitamin D (25-OHD), which is a natural type of vitamin D and compare between 2 separate areas in Japan. To compare and clarify the concentration of 25-OHD between 2 separate areas, Japanese patients who were diagnosed as having osteoporosis based on bone mineral density were studied. We analyzed 2 different hospitals' patients whose residence is separated into a northern district (Akita city: north latitude 39" 43') and a southern district (Shizuoka city: north latitude 34" 58'). Both of them have completely different daylight hours. Three-hundred sixty eight patients (174 in Akita, 194 in Shizuoka) were enrolled in this trial to compare the differences of concentration of 25-OHD by Welch's t t-test. There were significant differences in the concentration of 25-OHD and age between them. Akita patients were significantly higher than that of Shizuoka patients despite Shizuoka having much daylight hours of Akita. In conclusion, there might be no relationship between the concentration of 25 OHD and exposure to sunlight.

Association of sunshine duration with acute myocardial infarction hospital admissions in Beijing, China: A time-series analysis within-summer

BACKGROUND

Over the years, various epidemiological studies found that acute myocardial infarction (AMI) often shows seasonal rhythm patterning, which is usually influenced by the variations of environmental factors, such as air pollution, ambient temperature, solar activity, relative humidity. However, there are few studies on the impact of sunlight-induced AMI especially in developing countries, and they had inconsistent results. This study aimed to examine within-summer variations in the temporal association between sun exposure and AMI.

METHODS

We obtained hospitalization data for AMI of Beijing during 2013-2019. We used a distributed lag non-linear model (DLNM) combined with a quasi-Poisson regression model to estimate the non-linear lag effects of sunshine duration on AMI incidences. We evaluated the overall effect of AMI admissions with exposure to sunshine duration in the lag 0-21 days.

RESULTS

A total of 45,301 AMI cases were enrolled in our study during summer (June-September). The minimum of the morbidity was during days with a sunshine duration of 3.9 h. We found significant and U-shaped associations between sunshine duration and AMI, and the overall estimated relative risk was 1.29 (95% CI: 1.02,1.62) and 1.69 (95% CI: 1.28,2.24) for short (1st percentile) and long (99th percentile) sunshine duration, respectively. The males and younger people (<65 years) were most susceptible to these effects.

CONCLUSION

Our results suggest that both short and long sunshine duration could increase the risk of AMI admissions, especially for males and younger people. We suggest that public health policymakers should fully consider the balance of the pros and cons of solar exposure, and provide appropriate public health recommendations accordingly to gain the greatest benefits from sunlight.

Estimation of 1-km Resolution All-Sky Instantaneous Erythemal UV-B with MODIS Data Based on a Deep Learning Method

Although ultraviolet-B (UV-B) radiation reaching the ground represents a tiny fraction of the total solar radiant energy, it significantly affects human health and global ecosystems. Therefore, erythemal UV-B monitoring has recently attracted significant attention. However, traditional UV-B retrieval methods rely on empirical modeling and handcrafted features, which require expertise and fail to generalize to new environments. Furthermore, most traditional products have low spatial resolution. To address this, we propose a deep learning framework for retrieving all-sky, kilometer-level erythemal UV-B from Moderate Resolution Imaging Spectroradiometer (MODIS) data. We designed a deep neural network with a residual structure to cascade high-level representations from raw MODIS inputs, eliminating handcrafted features. We used an external random forest classifier to perform the final prediction based on refined deep features extracted from the residual network. Compared with basic parameters, extracted deep features more accurately bridge the semantic gap between the raw MODIS inputs, improving retrieval accuracy. We established a dataset from 7 Surface Radiation Budget Network (SURFRAD) stations and 1 from 30 UV-B Monitoring and Research Program (UVMRP) stations with MODIS top-of-atmosphere reflectance, solar and view zenith angle, surface reflectance, altitude, and ozone observations. A partial SURFRAD dataset from 2007–2016 trained the model, achieving an R2 of 0.9887, a mean bias error (MBE) of 0.19 mW/m2, and a root mean square error (RMSE) of 7.42 mW/m2. The model evaluated on 2017 SURFRAD data shows an R2 of 0.9376, an MBE of 1.24 mW/m2, and an RMSE of 17.45 mW/m2, indicating the proposed model accurately generalizes the temporal dimension. We evaluated the model at 30 UVMRP stations with different land cover from those of SURFRAD and found most stations had a relative RMSE of 25% and an MBE within ±5%, demonstrating generalization in the spatial dimension. This study demonstrates the potential of using MODIS data to accurately estimate all-sky erythemal UV-B with the proposed algorithm.

Vitamin D deficiency in primary health care users at risk in Spain

BACKGROUND AND OBJECTIVES

despite long hours of sunlight in Spain, vitamin D deficiency has been rising of late. We aimed to describe vitamin D deficiency and insufficiency in at-risk patients in La Rioja, a region in northern Spain.

METHODS

a retrospective, cross-sectional study involving 21,490 patients (74.3 % women) aged 14-105 years, who were primary health care (PHC) users in La Rioja, with an available 25-hidroxyvitamin D (25(OH)D) test result corresponding to the first request from January 2013 to October 2015. Vitamin D deficiency, insufficiency, and sufficiency were defined as 25(OH)D levels < 12 ng/mL, 12-20 ng/mL, and ≥ 20 ng/mL, respectively. Hypovitaminosis D was defined considering 2 cut-off points for 25(OH)D: < 20 ng/mL and < 30 ng/mL.

RESULTS

mean 25(OH)D levels were 18.3 (SD, 11.6) ng/mL in the whole sample, being lower in men than in women (17.6 vs 18.5 ng/mL, p < 0.001). Significantly higher 25(OH)D levels were found in the groups with 55-59, 60-64, 65-69, and 70-74 years of age (range, 19.4-20.4 ng/mL), and lower levels were found in the groups with 80-85 years and older (16.7 and 14.5 ng/mL), as compared to other groups. Two thirds of the population were vitamin D-deficient (< 12 ng/mL, 30.9 %) or insufficient (12-20 ng/mL, 32.8 %), and only 32.8 % of patients were found to be vitamin D-sufficient (> 20 ng/ml). Hypovitaminosis D rate was higher (89.7 %) when the 25(OH)D cut-off point was set at < 30 ng/mL. A higher hypovitaminosis D rate (< 20 ng/mL) was found in men (67.1 %) vs women (62.6 %) (p < 0.001), and it was more prevalent in patients over 75 years (72.6 %). The prevalence of hypovitaminosis D followed a seasonal pattern ranging from 51.8 % to 76.5 %; the lowest 25(OH)D levels were found in winter, and the highest in summer, with levels above 20 ng/mL in all age groups except for patients over 75 years (17.7 ng/mL). Patients over 75 years exhibited high rates of deficiency or insufficiency across all seasons of the year.

CONCLUSIONS

in La Rioja, Spain, hypovitaminosis D was highly prevalent among PHC users, and especially in older age groups and during the winter months.

Mobile Deep Learning System That Calculates UVI Using Illuminance Value of User's Location

Ultraviolet rays are closely related with human health and, recently, optimum exposure to the UV rays has been recommended, with growing importance being placed on correct UV information. However, many countries provide UV information services at a local level, which makes it impossible for individuals to acquire user-based, accurate UV information unless individuals operate UV measurement devices with expertise on the relevant field for interpretation of the measurement results. There is a limit in measuring ultraviolet rays’ information by the users at their respective locations. Research about how to utilize mobile devices such as smartphones to overcome such limitation is also lacking. This paper proposes a mobile deep learning system that calculates UVI based on the illuminance values at the user’s location obtained with mobile devices’ help. The proposed method analyzed the correlation between illuminance and UVI based on the natural light DB collected through the actual measurements, and the deep learning model’s data set was extracted. After the selection of the input variables to calculate the correct UVI, the deep learning model based on the TensorFlow set with the optimum number of layers and number of nodes was designed and implemented, and learning was executed via the data set. After the data set was converted to the mobile deep learning model to operate under the mobile environment, the converted data were loaded on the mobile device. The proposed method enabled providing UV information at the user’s location through a mobile device on which the illuminance sensors were loaded even in the environment without UVI measuring equipment. The comparison of the experiment results with the reference device (spectrometer) proved that the proposed method could provide UV information with an accuracy of 90–95% in the summers, as well as in winters.

Can Optimum Solar Radiation Exposure or Supplemented Vitamin D Intake Reduce the Severity of COVID-19 Symptoms?

The foremost mortality-causing symptom associated with COVID-19 is acute respiratory distress syndrome (ARDS). A significant correlation has been identified between the deficiency in vitamin D and the risk of developing ARDS. It has been suggested that if we can reduce or modify ARDS in COVID-19 patients, we may significantly reduce the severity of COVID-19 symptoms and associated mortality rates. The increased mortality of dark-skinned people, who have a reduced UV absorption capacity, may be consistent with diminished vitamin D status. The factors associated with COVID-19 mortality, such as old age, ethnicity, obesity, hypertension, cardiovascular diseases, and diabetes, are all found to be linked with vitamin D deficiency. Based on this review and as a precautionary measure, it is suggested that the adoption of appropriate and safe solar exposure and vitamin D enriched foods and supplements should be considered to reduce the possible severity of COVID-19 symptoms. Safe sun exposure is deemed beneficial globally, specifically in low and middle-income countries, as there is no cost involved. It is also noted that improved solar exposure and vitamin D levels can reduce the impact of other diseases as well, thus assisting in maintaining general human well-being.

Wearable Bracelet Monitoring the Solar Ultraviolet Radiation for Skin Health Based on Hybrid IPN Hydrogels

The risk of extensive exposure of the human epidermis to solar ultraviolet radiation is significantly increased nowadays. It not only induces skin aging and solar erythema but also increases the possibility of skin cancer. Therefore, a simply prepared, highly sensitive, and optically readable device for monitoring the solar ultraviolet radiation is highly desired for the skin health management. Because of the photoinitiated polymerization triggered by graphene-carbon nitride (g-C₃N₄) under ultraviolet radiation, g-C₃N₄ is homogeneously distributed in the hybrid hydrogels containing N-isopropylacrymide (NIPAM), poly(ethylene glycol) methyl ether methacrylate (OEGMA₃₀₀), and sodium alginate (SA). By further immersing the hybrid hydrogels into calcium chloride solution, hybrid alginate-Ca²⁺/P(NIPAM-co-OEGMA₃₀₀)/g-C₃N₄ interpenetrating polymeric network (IPN) hydrogels are obtained. Due to the homogeneous distribution of g-C₃N₄ and the existence of thermoresponsive polymers, the hybrid IPN hydrogels present good adsorption capability and high degradation efficiency for methylene blue (MB) especially at high temperature under ultraviolet radiation. Based on this unique property, the bracelet monitoring skin health is prepared by simply immersing the hybrid IPN hydrogels into the MB solution and then wrapping it with PET foil. Because the immersion time for the top, middle, and bottom parts of the hybrid IPN hydrogels is gradually increased, their colors vary from light to dark blue. A longer time is required for the discoloration of the darker part under solar ultraviolet radiation. Thus, the bracelet can be used to conveniently monitor the dose of solar ultraviolet radiation by simply checking the discoloration in the bracelet under sunshine. Due to the facile preparation and low cost of the bracelet, it is a promising candidate for wearable devices for skin health management.

Spectral transmission of solar radiation by plastic and glass materials

It is well known that excessive exposure to solar ultraviolet (UV) radiation can have serious adverse effects. Many everyday materials influence the UV radiation received by humans, for example, those used in construction and on the exterior of buildings such as plastics and glass can reduce the UV exposure of persons exposed to solar radiation. In this paper we analyse the spectral transmission of solar radiation of widely used materials using the transmittance parameter. The measurements were performed on clear days, at 8 h and 12 solar hours, in July 2018 (five days) and in January 2019 (three days). The spectral transmittances of these materials and the integrated transmittances in the UVB from 300 nm, UVA, visible (VIS) and near infrared ranges (NIR) were calculated. In summer in the UVB range from 300 nm methacrylate and smoked glass have the highest transmittance values (56%) and polycarbonate present the lowest (30%). In the VIS and NIR ranges methacrylate (95%) and smoked glass (80%) have the highest transmittances and polycarbonate the lowest (45%). In general the 8 h transmittances are higher than those at 12 h and are also higher in winter than summer. For two biological functions (erythemal and DNA-damage) and for the UVB range from 300 nm, the transmittance for most materials (except fibreglass) is in the range 6-14%. The exposure times obtained show that erythemal damage could occur after long exposure to solar radiation through the materials studied, information which should be made available to the general public.

A Possible Antioxidant Role for Vitamin D in Soccer Players: A Retrospective Analysis of Psychophysical Stress Markers in a Professional Team

The health benefits of physical activity are recognized, however, high levels of exercise may lead to metabolic pathway imbalances that could evolve into pathological conditions like the increased risk of neurological disease observed in professional athletes. We analyzed the plasma/serum levels of 29 athletes from a professional soccer team playing in the Italian first league and tested the levels of psychophysical stress markers (vitamin D, creatine kinase, reactive oxygen species (ROS) and testosterone/cortisol ratio) during a period of 13 months. The testosterone/cortisol ratio was consistent with an appropriate training program. However, most of the athletes showed high levels of creatine kinase and ROS. Despite the large outdoor activity, vitamin D values were often below the sufficiency level and, during the "vitamin D winter", comparable with those of the general population. Interestingly, high vitamin D values seemed to be associated to low levels of ROS. Based on the results of our study we proposed a vitamin D supplementation as a general practice for people who perform high levels of physical exercise. Beside the known effect on calcium and phosphate homeostasis, vitamin D supplementation should mitigate the high reactivity of ROS which might be correlated to higher risk of neurodegenerative diseases observed in professional athletes.

Development and Effect Analysis of UVB-LED General Lighting to Support Vitamin D Synthesis

Ultraviolet rays from sunlight are involved in vitamin D synthesis, which is essential in maintaining health. Most in vivo vitamin D synthesis occurs via exposure to sunlight, whereas a small portion is obtained through diet. Therefore, appropriate exposure to sunlight is recommended to satisfy vitamin D requirement. However, vitamin D deficiency still poses a serious issue to numerous people. To resolve this problem, artificial lighting has been studied to provide rays of UV light with characteristics similar to that of sunlight. The present study introduced vitamin D synthesis stimulating UVB-LED light via the general diffusion lighting type to indoor dwellers. However, despite the strides of advancement made in this type of lighting, studies on UVB with relation to vitamin D synthesis are limited. This study aimed to suggest UVB-LED lighting for indoor dwellers and confirm the effectiveness of vitamin D stimulation through animal testing. For this, a UVB-LED providing safe UVB dosage was developed based on the photobiological safety (IEC 62471) of lighting. Next, a comparison study of the suggested lighting and general lighting was executed in an isolated system. The study continued for two weeks and the vitamin D levels within the animal test subject (Rat, Wistar, male) were measured. At this time, the lighting was turned on for 06:00~22:00 considering the sunrise timing and average lighting time for modern people, and blood was collected from the caudal veins of the rats and analyzed for the amount of 25-hydroxyvitamin D [25(OH)D]. Analysis results showed that the amount of 25-hydroxyvitamin D [25(OH)D] in blood was higher, on average, by 6.8% (0.97 ng/mL) and 7.3% (0.9 ng/ml) in rats reared under UVB-LED lighting on the seventh and fourteenth experimental days, respectively, than those under general lighting. It was, therefore, confirmed that vitamin D synthesis in the human body can be supported by the proposed lighting in this study.

Estimation of exposure durations for vitamin D production and sunburn risk in Switzerland

Although overexposure to solar ultraviolet radiation (UVR) is responsible for cutaneous melanoma and epithelial skin cancer and can cause negative health effects such as sunburn, a "little and often" exposure regime is often suggested to produce naturally recommended vitamin D levels, being essential for skeletal health. This study aimed to quantify solar UV doses needed to trigger 1000 International Units (IU) vitamin D doses and, at the same time, producing sunburn in Switzerland. Solar UV erythema irradiance (in mW/m2) measured at four meteorological stations in Switzerland for the period 2005-2017 were used to evaluate effective solar UV radiation producing 1000 IU vitamin D doses in skin phototype II and III individuals. Daily solar UV exposure durations (in minutes) needed to produce vitamin D with limited sunburn risk were estimated while considering mean vitamin D food intake of the Swiss population and seasonal skin coverage. In summer and spring, with 22% of uncovered skin, 1000 IU vitamin D doses are synthesized in 10-15 min of sun exposure for adults. Exposure durations between erythema risk and 1000 IU vitamin D production vary between 9 and 46 min. In winter and autumn, the recommended vitamin D production without sunburn risks often unachievable, since up to 6.5 h of sun exposure might be necessary considering 8-10% of uncovered skin surface. The vitamin D food intake only represented 10% of the recommended vitamin D production and remained unchanged throughout the year. These findings might clarify why vitamin D deficiency is common in Switzerland. Moreover, exposure durations between recommended vitamin D and increased sunburn risk might only differ by few minutes. Without additional oral vitamin D supplementation, daily doses of vitamin D (1000 IU) are not reachable in autumn and winter months in Switzerland.

Association between solar ultraviolet doses and vitamin D clinical routine data in European mid-latitude population between 2006 and 2018

The major source of vitamin D in humans is the ultraviolet radiation-dependent cutaneous synthesis of cholecalciferol; however, low vitamin D status is common in Europe even at mid-latitudes. The UV-radiation that reached the Earth's surface near Milan between May 2006 and December 2018 was retrieved from the TEMIS database and matched with the serum vitamin D levels measured in 30 400 people living in the same area. The results showed a high percentage of insufficient vitamin D levels (measured as 25-hydroxy-vitamin D) throughout the years. During the "vitamin D winter" (November-March) up to 60-90% of the population shows deficient/insufficient (<20-30 ng mL^-1) levels of vitamin D and it is explained by the difficulty in obtaining the recommended UV vitamin D doses. In contrast, the warm season provides plenty of UV-radiation, but still 30-50% of the population shows deficient/insufficient vitamin D levels. The circannual vitamin D variations were less evident in the female groups which, in the cold season, show values higher than the corresponding male groups. An age group analysis explained this difference by the strongly recommended vitamin D intake for post-menopausal women. In conclusion, increasing the medical advice for vitamin D intake is strongly recommended to improve the vitamin D status at European mid-latitudes. Our findings suggest that UV availability alone cannot explain the vitamin D status of the population which instead is likely to be influenced by several other factors related to both the people's lifestyle and their personal characteristics. A desirable vitamin D range considering the time of the year and sun exposure, but also including factors not related to UV-radiation, would probably result in a more accurate diagnosis of the patients' vitamin D status. Despite the relatively large time interval, no evident effects due to climate changes were observed in the vitamin D levels during the almost 13 years of analysis.

Association of Serum 25-Hydroxyvitamin D Concentration with Pulmonary Function in Young Adults

The role of vitamin D on pulmonary function is unclear and is mostly studied in patients, smokers and elderly people. The aim of this paper was to evaluate the association between serum 25-hydroxyvitamin D [25(OH)D] concentration and pulmonary function in young adults. Cross-sectional analysis of 499 individuals that were evaluated at 21 years of age as part of the population-based cohort Epidemiological Health Investigation of Teenagers in Porto (EPITeen). Serum 25(OH)D was categorized according to the Institute of Medicine. Pulmonary function was evaluated using spirometry. Linear regression models were used to estimate the regression coefficients (β) and its 95% confidence intervals (95% CI), and were adjusted for confounders. Education, smoking, body mass index, and season of evaluation were determinants of serum 25(OH)D concentration. Prevalence of serum 25(OH)D concentration <50 nmol/L was 48.9%. A decrease in all pulmonary function parameters, with the decrease of serum 25(OH)D, was observed. The higher effect was found for peak expiratory flow (PEF). Having as reference participants with serum 25(OH)D concentration ≥50 nmol/L, PEF was significantly lower for those with a concentration of 30 to <50 nmol/L (β= −0.576; 95% CI: −0.943, −0.210), and for those with a concentration of <30 nmol/L (β= −0.650; 95% CI: −1.155, −0.146). Although only PEF attained statistical significance, the consistent results with the other parameters support the role of serum 25(OH)D to promote better pulmonary function in young adults.

No improvement in vitamin D status in German infants and adolescents between 2009 and 2014 despite public recommendations to increase vitamin D intake in 2012

Purpose

Vitamin D is a key component for the growth and development of children and adolescents, influencing a multitude of functions. Worldwide epidemiological studies have shown that minimum vitamin D blood levels of ≥ 20.0 ng/ml, often defined as vitamin D sufficiency by international and national nutrition and pediatric organizations, are often not met in practice. In 2012 the D–A–CH (Germany, Austria, Switzerland) nutrition societies increased their vitamin D intake recommendations fourfold from 200 IU (5 µg) to 800 IU (20 µg) per day. The outcome of this study will contribute to answering the question as to whether the new recommendations for increased vitamin D intake improve the highly prevalent vitamin D deficiency status in German children and adolescents.

Methods

For this 6-year study (January 2009–December 2014) carried out in Mülheim an der Ruhr, Germany, healthy children and adolescents (n = 1929, age range 1–17 years, median age 11.0 years, 46.9% female) consulting a pediatric group practice (KIDS4.0) were recruited. Serum 25(OH)D determinations were performed using a competitive chemoluminescence immunoassay (CLIA, DiaSorin).

Results

The median serum vitamin D values for each year from 2009 to 2014 were 18.4, 13.0, 20.8, 16.4, 19.4 and 14.9 ng/ml. The summarized median 25(OH)D serum concentrations between the two time periods 2009–2012 and 2013–2014 after increasing recommendations for vitamin D intake did not show a significant difference (17.0 versus 16.8 ng/ml).

Conclusions

The increased D–A–CH recommendations for vitamin D intake had no influence on vitamin D levels in children and adolescents. The prevalence of vitamin D deficiency has not changed compared to previous studies.

Electronic supplementary material

The online version of this article (10.1007/s00394-018-1717-y) contains supplementary material, which is available to authorized users.

Contribution of sun exposure to the vitamin D dose received by various groups of the Spanish population

Although the harmful effects of excessive exposure to solar ultraviolet (UV) radiation are well known, the recommended dose of UV radiation is beneficial for the synthesis of vitamin D by the skin, in addition to being useful in the treatment of various illnesses and mental problems. Numerous studies have shown that vitamin D performs important functions in the human organism, such as absorbing calcium and phosphorous and contributing to the immune system, among others. Several studies have found that a high percentage of various groups of the Spanish population suffer from vitamin D deficiency, and since very few natural foods contain vitamin D, it was considered important to determine whether groups such as schoolchildren, outdoor workers and athletes, receive enough solar radiation to produce adequate levels of vitamin D in their daily activities. It was found that the amount of vitamin D (in IU) produced by personal effective solar UV doses could exceed the recommended dose of 1000IU/day in spring and summer, while the winter estimate (about 220IU/day) is only one quarter of the recommended dose. These results suggest that most people would not receive the recommended daily vitamin D dose in winter from exposure to solar UV radiation, the main source of vitamin D.