A recent study, involving nearly 500 people with an increased risk of skin cancer, like basal cell carcinoma and squamous cell carcinoma, found that the risk of melanoma was more than halved by regular users of vitamin D supplements compared with non-users.
The study was a collaboration between the University of Eastern Finland and Kuopio University Hospital and published in Melanoma Research.
While links between vitamin D and skin cancers has been studied abundantly in the past, the research mainly focused on serum levels of calcidiol, a metabolite of vitamin D, and its association with skin cancers.
Findings from these studies have been inconclusive and even contradictory at times, as serum calcidiol levels have been associated with both a slightly higher and with a slightly lower risk of different skin cancers. This may, in part, be explained by the fact that serum calcidiol analyses do not provide information on the metabolism of vitamin D in the human skin, which can express enzymes that generate biologically active vitamin D metabolites or inactivate them.
The latest study, conducted under the North Savo Skin Cancer Programme, took a different approach: 498 adult patients estimated to have an increased risk of a skin cancer, such as basal cell carcinoma, squamous cell carcinoma or melanoma, were recruited at the dermatological outpatient clinic of Kuopio University Hospital. Experienced dermatologists at the University of Eastern Finland analysed their background information and medical history and examined their skin.
The dermatologists also classified the patients into different skin cancer risk classes, namely low risk, moderate risk and high risk.
Based on their use of oral vitamin D supplements, the patients were divided into three groups: non-users, occasional users and regular users. Serum calcidiol levels were analysed in half of the patients and found to correspond to their self-reported use of vitamin D.
A key finding was that there were considerably fewer cases of melanoma among regular users of vitamin D than among non-users, and that the skin cancer risk classification of regular users was considerably better than non-users’. Logistic regression analysis showed that the risk for melanoma among regular users was considerably reduced, more than halved, compared with non-users.
The findings suggest that even occasional users of vitamin D may have a lower risk for melanoma than non-users. However, there was no statistically significant association between the use of vitamin D and the severity of photoageing, facial photoageing, actinic keratoses, nevus count, basal cell carcinoma and squamous cell carcinoma. Serum calcidiol levels were not significantly associated with these skin changes, either. Since the research design was cross-sectional, the researchers were unable to demonstrate a causal relationship.
Other relatively recent studies, too, have provided evidence of the benefits of vitamin D in melanoma, such as of the association of vitamin D with a less aggressive melanoma.
“These earlier studies back our new findings from the North Savo region here in Finland. However, the question about the optimal dose of oral vitamin D for it to have beneficial effects remains to be answered. Until we know more, national intake recommendations should be followed,” said professor of dermatology and allergology Ilkka Harvima of the University of Eastern Finland.
Researchers at the University of Eastern Finland and Kuopio University Hospital have previously reported that the melanoma mortality rate in North Savo is relatively high in relation to its incidence.
“For this reason, too, it is worth paying attention to sufficient intake of vitamin D in the population in this region,” Harvima said.
Study details
Regular use of vitamin D supplement is associated with fewer melanoma cases compared to non-use: a cross-sectional study in 498 adult subjects at risk of skin cancers.
Emilia Kanasuo, Hanna Siiskonen, Salla Haimakainen, Jenni Komulainen, Ilkka T. Harvima.
Published in Melanoma Research on 28 December 2022.
Abstract
There are conflicting results on the role of vitamin D system in cutaneous carcinogenesis. Therefore, it was investigated whether the use of oral vitamin D supplements associates with photoageing, actinic keratoses, pigment cell nevi, and skin cancers. In this cross-sectional study, 498 adults (aged 21–79 years, 253 males, 245 females, 96 with immunosuppression) subjects at risk of any type of skin cancer were examined, and possible confounding factors were evaluated. The subjects were divided into three groups based on their self-reported use of oral vitamin D supplements: non-use, occasional use, or regular use. The serum level of 25-hydroxyvitamin-D3 was analysed in 260 subjects. In 402 immunocompetent subjects, vitamin D use did not associate with photoaging, actinic keratoses, nevi, basal, and squamous cell carcinoma. In contrast, there were lower percentages of subjects with a history of past or present melanoma (32/177, 18.1% versus 32/99, 32.3%, P = 0.021) or any type of skin cancer (110/177, 62.1% versus 74/99, 74.7%, P = 0.027) among regular users compared to non-users. In the logistic regression analysis, the odds ratio for melanoma was 0.447 (P = 0.016, 95% confidence interval, 0.231–0.862) among regular users. Furthermore, the investigator-estimated risk class of skin cancers was significantly lower among regular users. Serum 25-hydroxyvitamin-D3 did not show marked associations with skin-related parameters. The results on 96 immunosuppressed subjects were somewhat similar, although the number of subjects was low. In conclusion, regular use of vitamin D associates with fewer melanoma cases, when compared to non-use, but the causality between them is obscure.
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