Fewer cases of melanoma were observed among individuals who regularly took vitamin D supplements than among those who did not take the supplements, according to a new study published by Kanasuo et al in Melanoma Research. Researchers also found that individuals taking vitamin D supplements regularly had a considerably lower risk of other types of skin cancer.
Background
Vitamin D—which plays a key role in the normal function of the human body—may also play a role in many diseases. The link between vitamin D and skin cancers has been studied abundantly in the past, but these studies have mainly focused on serum levels of the vitamin D metabolite calcidiol 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 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.
Study Methods and Findings
In the new study, researchers recruited 498 patients estimated to have an increased risk of developing skin cancers such as basal cell carcinoma, squamous cell carcinoma, or melanoma. They then carefully analyzed the patients’ background information and medical history; conducted skin examinations; and classified the patients into low-risk, moderate-risk, and high-risk skin cancer classes. Based on their use of oral vitamin D supplements, the patients were divided into three groups: nonusers, occasional users, and regular users. Serum calcidiol levels were analyzed in half of the patients and found to correspond to their self-reported use of vitamin D.
After conducting the analyses, the researchers discovered that there were considerably fewer cases of melanoma among regular users of vitamin D than among nonusers, and that the skin cancer risk classification of regular users was considerably better than the risk classification of nonusers. Logistic regression analysis showed that the risk for melanoma among regular users was considerably reduced—less than half the risk discovered among nonusers.
Conclusions
The findings suggested that even occasional users of vitamin D may have a lower risk for melanoma than nonusers. However, there was no statistically significant association between the use of vitamin D and the severity of photoaging, facial photoaging, 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 analyses were cross-sectional, the researchers were unable to demonstrate a causal correlation.
Other relatively recent studies 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 in order for it to have beneficial effects remains to be answered. Until we know more, national intake recommendations should be followed,” noted Ilkka T. Harvima, MD, PhD, Professor in the Department of Dermatology and Allergology at the University of Eastern Finland School of Medicine and the Kuopio University Hospital.
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 [of] this region,” Dr. Harvima concluded.
Disclosure: For full disclosures of the study authors, visit journals.lww.com.
