Increased 25(OH)D3 level in redheaded people: Could redheadedness be an adaptation to temperate climate?

About 1-2% of European population are redheaded, meaning they synthesize more pheomelanin than eumelanin, the main melanin pigment in humans. Several mutations could be responsible for this phenotype. It has been suggested that corresponding mutations spread in Europe due to a founder effect shaped either by a relaxation of selection for dark, UV-protective phenotypes or by sexual selection in favour of rare phenotypes. In our study, we investigated the levels of vitamin D precursor 25(OH)D3 (calcidiol) and folic acid in the blood serum of 73 redheaded and 130 non-redheaded individuals. In redheaded individuals, we found higher 25(OH)D3 concentrations and approximately the same folic acid concentrations as in non-redheaded subjects. 25(OH)D3 concentrations correlated with the intensity of hair redness measured by two spectrophotometric methods and estimated by participants themselves and by independent observers. In non-redheaded individuals, 25(OH)D3 levels covaried with the amount of sun exposure and intensity of suntan while in redheaded individuals, this was not the case. It suggests that increased 25(OH)D3 levels in redheaded individuals are due to differences in physiology rather than in behaviour. We also found that folic acid levels increased with age and the intensity of baldness and decreased with the frequency of visiting tanning salons. Our results suggest that the redheaded phenotype could be an evolutionary adaptation for sufficient photosynthesis of provitamin D in conditions of low intensity of UVB radiation in central and northern parts of Europe.

Assessment of Predictors of Sun Sensitivity as Defined by Fitzpatrick Skin Phototype in an Ecuadorian Population and Its Correlation with Skin Damage.

BACKGROUND: The Fitzpatrick skin phototype scale (FSPTS) is a widely used instrument to assess skin type. METHODS: A cross-sectional survey collected responses from 254 subjects from Quito regarding self-reported FSPTS, gender, age, education, and tobacco and alcohol consumption. Univariate and multivariate logistic regression analyses were performed to determine if ethnicity, hair color, and eye color significantly predict FSPTS. In addition, we studied the correlation between FSPTS and the SCINEXA scale with Pearson's correlation coefficient. RESULTS: Ethnicity, eye color, and hair color are significant independent predictors of FSPTS (p < 0.0001). CONCLUSIONS: Patient self-reported race and pigmentary phenotypes are inaccurate predictors of sun sensitivity as defined by Fitzpatrick skin phototype. Our study does not fully represent the population of the country. There are limitations to using patient-reported race and appearance in predicting individual sunburn risk.

The dynamics of pigment reactions of human skin to ultraviolet A radiation.

The pigment responses of human skin to broadband UVA radiation (320-400 nm) occur in three distinct phases. The first phase includes immediate pigment darkening (IPD), the pigment that appears immediately after irradiation. The second phase involves an intermediate step, termed persistent pigment darkening (PPD), which leads to the third phase of neomelanogenesis or delayed tanning (DT). Since DT results from synthesis of new melanin, it persists beyond 5-7 days. We conducted studies on human subjects to investigate the dynamic responses of the IPD and PPD reactions to broadband UVA radiation at threshold and superthreshold doses. The threshold doses for IPD, PPD, and DT were found to be approximately 1, 11, and 18 J/cm2 , respectively. The colorimetry ΔL* value corresponding to minimal clinically perceptible pigmentation was found to be 0.8 ± 0.1. IPD appeared immediately and had an associated decay constant of approximately 1.4 minutes. At doses greater than PPD threshold, IPD reaction decayed while PPD developed indicating toward IPD being used as a substrate in the formation of PPD.

Dihydroxyacetone: A Review.

The sunless tanning industry has experienced rapid growth due to public education on the dangers of ultraviolet radiation on skin and improvements in products. Dihydroxyacetone (DHA) is a 3-carbon sugar allowed by the Food and Drug Administration (FDA) as a color additive in sunless tanning products. Bronzers, a product removed with soap and water, may also contain DHA. We aim to review the literature on DHA. DHA is intended for external application, not including the mucous membranes or in or around the eye area. DHA has been used in spray-tan booths and by airbrushing it onto consumers, although these are unapproved uses, as contact with the color additive is not restricted to the external part of the body. Consequently, the FDA recommends customers shield their eyes, lips, and mucous membranes, as well as refrain from ingestion or inhalation of DHA. Unlike sunscreens, products that protect against ultraviolet radiation and are regulated by the FDA as non-prescription drugs, sunless tanning products are regulated as cosmetics and cannot provide any protection from exposure to ultraviolet radiation. There are reports of non-cosmetic uses of DHA that are not FDA approved. With the wide-spread use of DHA, additional studies on its safety are warranted.

J Drugs Dermatol. 2018;17(4):387-391.

Sunbed use in Germany: trends, user histories and factors associated with cessation and readiness to change.

BACKGROUND: Sunbed use is considered carcinogenic in humans. Studies that examine behavioural patterns related to sunbed use over time are needed for developing skin cancer prevention strategies. OBJECTIVES: To explore age-related trends in the initiation age, to investigate individual histories of sunbed use and to identify characteristics associated with cessation. METHODS: We analysed cross-sectional data of 4851 sunbed users and nonusers from a representative sample of Germans, aged 14-45 years, interviewed in 2011/2012. Biographical data were reconstructed based on reported tanning frequency/duration and changes in sunbed use over time. We used survival analysis to model the initiation age and created birth cohorts to assess age-related trends. Characteristics associated with sunbed use cessation were identified using logistic regression. RESULTS: Among sunbed users, median sunbed exposure was 180 min per year. Annual exposure remained constant in 85·6% of this subgroup with no changes over time during periods of sunbed use. Age at initiation decreased significantly across birth cohorts from 25 to 19 years (25th percentile; cohorts 1966-75 to 1986-93). Characteristics associated with sunbed use cessation included educational level [odds ratios (OR) 1·53 and 1·71 for medium and high education, respectively], greater awareness of skin cancer risk (OR 2·41) and immigrant background (OR 0·54; all P < 0·01). CONCLUSIONS: Initiation of sunbed use at an increasingly younger age suggests the need for interventions targeted at young adults. Approaches that increase general skin cancer risk awareness and that are sensitive to participants' educational level and immigrant background may also be helpful.

Sunbed use among subjects at high risk of melanoma: an Italian survey after the ban.

BACKGROUND: The World Health Organization classified the entire ultraviolet (UV) spectrum and artificial UV tanning devices as carcinogenic to humans. Italian law has prohibited the use of tanning equipment by children under 18 years of age and by high-risk populations. OBJECTIVES: The present large survey aimed to determine the prevalence of current sunbed use in Italy and to identify user characteristics. This study identifies starting points for future national interventions to reduce the health risks of exposure to artificial UV radiation. METHODS: In 2011 we conducted a survey of 4703 people in an area on the sunny Mediterranean coast in Italy. Through multivariate logistic models we investigated the associations of sunbed use with phenotypical factors. RESULTS: Overall prevalence of sunbed use was 20%, higher among women (22% vs. 16%; P < 0·0001), and young (22% vs. 17% for age < 35 years; P < 0·0001) and highly educated people (22% vs. 14%; P < 0·0001). Subjects at high risk of melanoma used sunbeds significantly more; i.e. people with freckles (25% vs. 18%; P < 0·0001), red hair (30% vs. 19%; P = 0·01) or fair eyes (22% vs. 19%; P = 0·006). Associations were confirmed in multivariate models. CONCLUSIONS: More skin cancer monitoring is needed at tanning centres, and educational campaigns should be promoted, especially for young women and subjects at high risk of melanoma.

The physiological and phenotypic determinants of human tanning measured as change in skin colour following a single dose of ultraviolet B radiation.

Experimental study of the in vivo kinetics of tanning in human skin has been limited by the difficulties in measuring changes in melanin pigmentation independent of the ultravioletinduced changes in erythema. The present study attempted to experimentally circumvent this issue. We have studied erythemal and tanning responses following a single exposure to a range of doses of ultraviolet B irradiation on the buttock and the lower back in 98 subjects. Erythema was assessed using reflectance techniques at 24 h and tanning measured as the L* spectrophotometric score at 7 days following noradrenaline iontophoresis. We show that dose (P < 0.0001), body site (P < 0.0001), skin colour (P < 0.0001), ancestry (P = 0.0074), phototype (P = 0.0019) and sex (P = 0.04) are all independent predictors of erythema. Quantitative estimates of the effects of these variables are reported, but the effects of ancestry and phototype do not appear solely explainable in terms of L* score. Dose (P < 0.0001), body site (P < 0.0001) and skin colour (P = 0.0365) or, as an alternative to skin colour, skin type (P = 0.0193) predict tanning, with those with lighter skin tanning slightly more to a defined UVB dose. If erythema is factored into the regression, then only dose and body site remain significant predictors of tanning: therefore neither phototype nor pigmentary factors, such as baseline skin colour, or eye or hair colour, predict change in skin colour to a unit erythemal response.

Telomere-mediated effects on melanogenesis and skin aging.

UV-induced melanogenesis (tanning) and "premature aging" or photoaging result in large part from DNA damage. This article reviews data tying both phenomena to telomere-based DNA damage signaling and develops a conceptual framework in which both responses may be understood as cancer-avoidance protective mechanisms.Journal of Investigative Dermatology Symposium Proceedings (2009) 14, 25-31; doi:10.1038/jidsymp.2009.9.

Association between quantitative measures of skin color and plasma 25-hydroxyvitamin D.

UNLABELLED: We examined the relationship between vitamin D and skin color measured by reflectance colorimetry at an exposed and un-exposed site in 321 people. Exposed but not unexposed skin color was associated with better vitamin D status. Sun-exposure was more important than natural skin color in determining vitamin D status in our population. INTRODUCTION: Vitamin D is obtained through UV synthesis in the skin where melanin limits its synthesis. Ethnicity is often used as a proxy for skin color, but skin color varies considerably. The relation between quantitative measures of skin color and plasma 25-hydroxyvitamin D (25OHD) concentration has not been well described. METHODS: The aim of this study was to determine the association between constitutive (natural) and sun-induced skin color and 25OHD in a group of Pacific People (n = 87) and Europeans (n = 255) living in NZ (46 degrees S) in summer. Plasma 25OHD was determined and sun-induced (outer fore-arm) and constitutive (upper inner-arm) measured by reflectance colorimetry. RESULTS: Mean (SD) 25OHD was significantly higher in Europeans than Pacific People, 88 (31) nmol/L vs. 75 (34) nmol/L, respectively. Based on constitutive skin color, 35% of participants were very light, 45% light, 16% intermediate, 4% tanned, and 0% brown or dark. Skin color at the forearm but not constitutive skin color was a significant predictor of 25OHD. Each 10 degrees lower skin color value at the forearm (more tanning) was associated with a 5 nmol/L higher 25OHD (P < 0.001). CONCLUSIONS: Tanning but not natural skin color was an important determinant of 25OHD. Further study is needed in a population with a higher proportion of darker skin people.