Influence of multiple UV exposures on serum cobalamin and vitamin D levels in healthy females.

AIMS: Ultraviolet (UV) radiation is a major source for vitamin D production. Furthermore, UV destroys cobalamins (also called vitamin B12) in solution. However, data from humans are scarce. The aim of the present study was to clarify if UV exposure has any effect on serum cobalamins, as compared to vitamin D levels, in healthy volunteers. METHODS: This single-center, open observational study was conducted in a research institute: 23 non-pregnant, non-lactating, healthy, fair-skinned female subjects had their serum cobalamin and 25-hydroxyvitamin D (25(OH)D, the marker for vitamin D status) levels measured before and after exposure to UV. RESULTS: UV exposure increased serum 25(OH)D levels from 61.6 nmol/L to 88.5 nmol/L (44%; p < 0.001). A statistically insignificant decay in serum cobalamin levels from 300 pmol/L to 260 pmol/L (13%; p = 0.142) was observed in the volunteers after the first UV exposure; however, no additional decline of statistical significance was seen after subsequent exposures. CONCLUSIONS: Multiple exposure to UV radiation give a significant increase in 25(OH)D levels, but has no detrimental effect on cobalamin concentrations.

Vitamin D levels and dietary intake among patients with benign soft tissue tumors and sarcomas.

BACKGROUND: Calcitriol [1,25(OH)2D] is hypothesized to lower the risk of cancer via binding to the vitamin D receptor (VDR). VDRs are also found in benign and malignant cells of mesenchymal origin. To our knowledge, vitamin D levels and dietary intake have not been previously evaluated in patients newly diagnosed with benign and malignant mesenchymal tumors. PATIENTS AND METHODS: Forty-eight patients with benign soft tissue tumors and 25 patients with sarcoma had their serum 25-hydroxyvitamin D [25(OH)D], 1,25(OH)2D and parathyroid hormone levels measured, vitamin D intake scored and body mass index [BMI] calculated. RESULTS: Vitamin D deficiency [25(OH)D level<50 nmol/l] was observed in 19% and 28% of patients with benign tumor and sarcoma, respectively. CONCLUSION: Serum 25(OH)D, 1,25(OH)2D and parathyroid hormone concentrations, BMI and daily vitamin D intake did not differ significantly between the two groups of patients. Higher vitamin D intake or UV exposure is needed to ensure that all patients achieve sufficient vitamin D levels.

The relationship between UV exposure and incidence of skin cancer.

BACKGROUND: The incidence rates of skin cancer increase with decreasing latitude in most western countries. Ultraviolet (UV) radiation is a main risk factor for skin cancer. METHODS: We have studied the relationship between UV exposure and skin cancer incidence rates of squamous cell carcinoma (SCC), basal cell carcinoma (BCC), and cutaneous melanoma (CM), and tried to fit different mathematical models to the experimental data. RESULTS: The incidence-UV exposure relationship for all three cancers is best described by the power law: ln(RTD) = Ab ·ln(annual UVEry dose), with relative tumor density (RTD) being age-adjusted incidence rate per unit area of skin, and the power parameter Ab being the biological amplification factor. For SCC, the RTD is a factor of 16-19 times larger on the head than on the trunk. For BCC, this factor is 7 and for CM it is 0.9-1.3. Ab for CM has remained almost unchanged from the 1960s until recently. CONCLUSIONS: The incidence-sun exposure relationship for all three cancers is well described by the power law. SCC is dependent on total UV exposures, while BCC, and even more CM, is dependent also on exposure patterns, with intermittent exposures being most carcinogenic.

Ultraviolet radiation and cutaneous malignant melanoma.

Essential features of the epidemiology and photobiology of cutaneous malignant melanoma (CMM) in Norway were studied in comparison with data from countries at lower latitudes. Arguments for and against a relationship between ultraviolet radiation (UV) from sun and artificial light and CMM are discussed. Our data indicate that UV is a carcinogen for CMM and that intermittent exposures are notably melanomagenic. This hypothesis was supported both by latitude gradients, by time trends and by changing patterns of tumor density on different body localizations. However, even though UV radiation generates CMM, it may also have a protective action and/or an action that improves prognosis. There appears to be no, or even an inverse latitude gradient for CMM arising on non-UV exposed body localizations (uveal melanoma, CMMs arising in the vulva, perianal/anorectal regions, etc.). Furthermore, CMM prognosis was gradually improved over all years of increasing incidence (up to 1990), but during the past 20 years, incidence rates stabilized and prognosis was not improved significantly. Comparisons of skin cancer data from Norway, Australia and New Zealand indicate that squamous cell carcinoma and basal cell carcinoma are mainly related to annual solar UVB fluences, while UVA fluences play a larger role of CMM.

Sun exposure and melanomas on sun-shielded and sun-exposed body areas.

Malignant melanoma is a tumor that arises from melanocytes and accounts for around 4% of all malignancies in Europe and Northern America and for about 11% in Australia and New Zealand. About 10% of primary melanomas arise from sites not exposed to sun. Acral lentiginous melanoma, mucosal melanoma (in the oral cavities, nasal sinuses, genital tract and rectum) and uveal melanoma are all on non-sun-exposed tissues. Epidemiologic aspects ofmelanomas on non-sun-exposed areas in comparison with melanomas in sun-exposed areas have been reviewed. We focus on the relationship between melanoma incidence, geographic latitude of residence, race/ethnicity and host factors as well as time trends.

Ultraviolet-radiation and health: optimal time for sun exposure.

Positive as well as negative health effects of exposure of human skin to UV radiation depend on spectra and fluence rates, both of which being dependent on latitude, time of the day and several other factors. The major positive effects are related to vitamin D photosynthesis and the major negative effect is skin cancer development. The action spectra for these effects are different. This lead us to conclude that for optimal vitamin D synthesis at minimal risk of cutaneous malignant melanoma (CMM), the best time for sun exposure is between 10 a.m. and 1 p.m. Thus, the common health recommendation (that sun exposure should be avoided between the hours of 10 a.m. and 4 p.m. and postponed to the afternoon) may be wrong.

Minimal and maximal incidence rates of skin cancer in Caucasians estimated by use of sigmoidal UV dose-incidence curves.

BACKGROUND: Sigmoidal (S-shaped) dose-cancer incidence relationships are often observed in animal bioassays for carcinogenicity. Ultraviolet (UV) radiation is an established skin carcinogen. The aim of this study is to examine if S-shaped curves describe the relationship between solar UV doses and skin cancer incidences, and if such relationships can be used to estimate threshold levels of non-carcinogenic UV exposure, as well as maximal incidence rates. METHODS: We studied the incidence rate-annual erythema-effective UV dose relationship for squamous cell carcinoma (SCC), basal cell carcinoma (BCC) and cutaneous melanoma (CM) among different Caucasian populations in Europe, Australia and New Zealand. RESULTS: Our analysis indicates that S-shaped associations describe the data well (P < 0.0001). The age-adjusted incidence rates for cases expected to be due to other causes than solar UV exposure (at zero UV dose) were found to be around 0.6, 9.7 and 4.0 per 100,000 for women in 1997-2007 for SCC, BCC and CM, respectively, and around 1.2, 14.3 and 2.6 per 100,000 for men. The analysis indicates that SCC, BCC and CM have maximal incidence of 361 ± 24, 1544 ± 49 and 36 ± 4 per 100,000 for women, and 592 ± 35, 2204 ± 109 and 50 ± 4 per 100,000 for men. CONCLUSIONS: Between 89 and 95% of the annual CM cases, around 99.8% SCC and 99.4% BCC cases are caused by solar UV exposure. The analysis did not identify any "safe" UV dose below which the risk for skin cancer was absent. Avoidance of UV radiation has a potential to reduce the incidence of skin cancer in fair-skinned population.

Sunbed use and cutaneous melanoma in Norway.

AIMS: Incidence rates of cutaneous melanoma (CM) in light skinned people in Norway are among the highest in the world. Sunbed use has increased in Norway since 1980. We will try to elucidate whether there is any correlation between the increase in sunbed use and the CM incidence rates, whether the increase in CM risk is similar for all age groups, and whether the possible difference between young and old persons can inform future healthcare strategies. METHODS: The frequency of sunbed use by different age groups in the time period 1980-2011 and incidence rates (1980-2009) of CM at different age groups in Norway were studied. Time in minutes per day spent in front of screen of computers or TVs for boys and girls was also analysed. RESULTS: The number of sunbed sessions per year in Norway increased throughout the entire period. The number of men and women diagnosed with CM per year, all ages combined, also increased. Sunbed use increased at a similar rate for three age groups (0-19, 20-50, and >50 years old), while the age-adjusted CM incidence rate increased only for the oldest group. Time spent in front of the screen of computers or TVs increased from 1985 to 2005 and is still increasing. CONCLUSIONS: CM incidence is decreasing while sunbed use is increasing in younger age groups. The present data indicate that more work needs to be done before one can know whether the overall health effects of sunbed exposure are positive or negative.

Cutaneous malignant melanoma incidence rates in Norway.

AIMS: The incidence rates of cutaneous malignant melanoma (CMM) increase throughout the world, in spite of introduction of strategies for prevention. However, a decrease in incidence rates is observed in some countries. If the reason for this could be found, it might be useful to transfer the knowledge to other fields of medicine. METHODS: CMM age-standardized incidence rates in different age groups in Norway were obtained from NORDCAN for the years 1970-1989 and 1990-2009. RESULTS: Until 1990, the CMM rates increased, but after that time a stabilization or a decrease was observed for young age groups (15-54 years old), while in older generations (>55 years old) the rates continued to increase. CONCLUSIONS: The decreasing CMM pattern in young age groups may be due to changing patterns to sunlight in sunbathing and use of sunbeds.

Biologically efficient solar radiation: Vitamin D production and induction of cutaneous malignant melanoma.

Solar ultraviolet (UV) radiation is the main source of vitamin D production and is also the most important environmental risk factor for cutaneous malignant melanoma (CMM) development. In the present study the relationships between daily or seasonal UV radiation doses and vitamin D status, dietary vitamin D intake and CMM incidence rates at different geographical latitudes were investigated. North-South gradients of 25-hydroxyvitamin D (25(OH)D) generation and CMM induction were calculated, based on known action spectra, and compared with measured vitamin D levels and incidence rates of CMM. The relative roles of UVA and UVB in CMM induction are discussed. Latitudinal dependencies of serum 25(OH)D levels and CMM incidence rates can only partly be explained by ambient UV doses. The UV sensitivity is different among populations with different skin color. This is well known for CMM, but seems also to be true for vitamin D status. The fact that UV-induced vitamin D may reduce the risk of CMM complicates the discussion. To some extent high dietary vitamin D intake seems to compensate low UV doses.

North-South gradients of melanomas and non-melanomas: A role of vitamin D?

Incidence rates of skin cancer increase with decreasing latitude in Norway, as in many other countries with white populations. The latitudinal trends of the incidence rates of skin cancer were studied and compared with data for vitamin D-induced by UV and for vitamin D intake. The north-south gradient for CMM incidence rates on sun exposed skin is much smaller than those for BCC and SCC, and that for BCC is smaller than that for SCC. This indicates that SCC and BCC are mainly due to solar UVB, while UVA may play a significant role for CMM and a smaller role for BCC, since the north-south gradient of annual UVB fluences is larger than that of UVA fluences. However, there is an inverse latitudinal gradient of skin cancer in central Europe. This is probably due to a gradient of skin color, since white skin is an important determinant of increased risk of skin cancer. The role of vitamin D for skin cancer risk is difficult to evaluate, since serum levels of 25-hydroxyvitamin D, as well as vitamin D intakes, are widely different from country to country. Still, epidemiological evidence indicates a role: for melanomas arising on non-sun exposed body localizations (uveal melanomas, melanomas arising in the vulva and perianal/anorectal regions) there appears to be no latitudinal gradient, or, a negative gradient, i.e., increasing rates with decreasing latitude as would be expected if UV-generated vitamin D plays a protective role. Both skin cancer risk and vitamin D photosynthesis decrease with increasing skin darkness.

Superficial-spreading and nodular melanomas in Norway: a comparison by body site distribution and latitude gradients.

Superficial-spreading melanoma (SSM) and nodular melanoma (NM) are the most common histological types of melanoma. These are seemingly distinct entities, on the basis of epidemiology, clinical behavior, tumor biological, and histological aspects as well as molecular characteristics. Intermittent sun exposure seems to play a major role in SSM, which has an increasing incidence rate during the last decades. However, relationship with sun exposure is more complex in the case of NM, as the latter may arise on any body part and has a more stable incidence rate. To obtain more information on the role of sun exposure in these two types of melanoma, we have compared body site distributions and latitude gradients for a period of 30 years in Norway. The study was based on official reports from the Cancer Registry of Norway, using melanoma incidence rates for a period of 30 years (1978-2007), by age, sex, anatomic site, and region of Norway. Our results show that in Norway, SSM is more strongly related to intermittent sun exposure than NM, as it arises mostly on the trunk as compared with the head and neck. Moreover, SSM has a higher incidence in the Southern regions of Norway, whereas for NM, the north-south gradient is not statistically significant. Differences in sun exposure at northern latitudes have a major impact on different types of melanoma. It seems that NM is less sun-induced than SSM, for which other etiological and pathogenetic factors may play important roles.

UVA, UVB and incidence of cutaneous malignant melanoma in Norway and Sweden.

Latitudinal dependencies of UVA and UVB were studied together with relevant epidemiological data for squamous cell carcinoma (SCC) and cutaneous malignant melanoma (CMM) in Norway and Sweden. Our data support the hypothesis that solar UVA radiation may play a role for CMM induction. The etiologies of SCC and CMM are different according to a latitudinal dependency and differences in age curves. Sun exposure patterns, age-related decay rates of repair of UV damage and sex hormones may play different roles for the two skin cancers. Also, UVB induction of vitamin D may be involved. CMM incidence rates among young people have decreased or been constant since about 1990 in Norway and Sweden. All reasons for UVA contributing to CMM will be discussed.

Vitamin D, sun, sunbeds and health.

OBJECTIVE: To review the health effects of solar radiation, sunbeds and vitamin D. DESIGN: The literature was searched in the electronic database MEDLINE to indentify published data between 1981 and 2011. Studies were included if they reported relative risk for cutaneous malignant melanoma (CMM) associated with sunbed use, vitamin D and UV effects on human health. SETTING: Data from different time periods for populations at different latitudes. SUBJECTS: Persons of different ages and ethnic groups. RESULTS: UV from sun and sunbeds is the main vitamin D source. Young people with white or pigmented skin in northern Europe have a low vitamin D status. A number of health benefits from sufficient levels of vitamin D have been identified. However, UV exposure has been suspected of causing skin cancer, notably CMM, and authorities warn against it. CONCLUSIONS: The overall health benefit of an improved vitamin D status may be more important than the possibly increased CMM risk resulting from carefully increasing UV exposure. Important scientific facts behind this judgement are given.