A new study has found that individuals who regularly take vitamin D supplements are significantly less likely to have a history of malignant melanoma, or any type of skin cancer, than non-users. They also found a trend for benefit with occasional use.
The study was conducted in collaboration with researchers from the University of Eastern Finland and Kuopio University Hospital, and has been published in the journal Melanoma Research. It involved almost 500 individuals attending a dermatology clinic who reported on their use of vitamin D supplements.
Vitamin D plays a key role in the normal function of the human body and it may also play a role in preventing many diseases. The link between vitamin D and skin cancers has been studied abundantly in the past; but these studies have been focused mainly on serum levels of calcidiol, which is a metabolite of vitamin D, and its association with skin cancers.
Findings from most such studies have been inconclusive and even contradictory, at times, as serum calcidiol levels have been associated with a slightly higher as well as 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.
This new study, conducted under the ‘North Savo Skin Cancer Programme’, took a different approach. A total of 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 carefully analysed the patients’ background information, medical history and examined their skin. Patients were also classified into different skin cancer risk classes, namely, low-risk, moderate-risk and high-risk. Further, 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 were found to correspond to their self-reported use of vitamin D.
Regular users had a significant 55% reduction in the odds of having a past or present melanoma diagnosis, while occasional use was associated with a non-significant 46% reduction. The reduction was similar for all skin cancer types. Logistic regression analysis showed that the risk for melanoma among regular users was considerably reduced, more than halved, compared to non-users.
The study reports 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 photo-ageing, facial photo-ageing, 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.
“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,” said Prof Harvima.