Regular use of vitamin D supplements linked to lower risk of skin cancer.

Regular use of vitamin D supplements may reduce the risk of melanoma and other skin cancers, according to a study published in Melanoma Research.

Researchers found a lower rate of melanoma and other skin cancers among patients who reported taking vitamin D supplements regularly. However, the researchers could not confirm a causal link between vitamin D supplementation and skin cancer risk.

The study included 402 immunocompetent patients — 99 who did not take vitamin D supplements, 126 who occasionally took vitamin D, and 177 who took vitamin D regularly.

Researchers measured the serum concentration of 25(OH)-D3 in 207 patients total, or about half of the patients in each group. The concentration of 25(OH)-D3 increased significantly in a dose-dependent manner from the group that did not take vitamin D to the group that took vitamin D regularly.

Compared with the patients who did not take vitamin D, those who took vitamin D regularly had higher educational attainment (P =.032), were less likely to work outdoors (P =.003), had fewer tobacco pack years (P =.001), and had more frequent solarium exposures (P =.002).

However, there were no significant differences between the regular vitamin D users and the non-users for self-estimated lifetime exposure to sunlight, lifetime sunburns, Fitzpatrick skin type or score, UV light treatments, Photoaging Area and Severity Index score, facial photoaging score, number of actinic keratosis, number of nevi, incidence of extracutaneous cancers, neutrophil-to-lymphocyte ratio, age, body mass index, or family history of melanoma.

The patients who reported regular vitamin D supplementation had significantly fewer past or present melanomas (P =.007) and skin cancers of any type (P =.033), compared with patients who did not take vitamin D.

In a multivariate regression analysis, patients with a history of melanoma were less likely to report regular vitamin D use (odds ratio [OR], 0.447; 95% CI, 0.231-0.862; P =.016) than patients who had no melanoma history.

In a stepwise variable omission analysis, only regular vitamin D supplementation remained significantly associated with melanoma risk (P ≤.025).

The researchers noted that, although these results show an association between skin cancer risk and vitamin D supplementation, “the temporal and causal connection between the self-reported use of oral vitamin D and the history of past or present skin cancer should be interpreted with caution.”

The team noted that patients may have changed their use of vitamin D supplements because of a skin cancer diagnosis. Patients may have started taking vitamin D because they reduced their sun exposure after diagnosis.

The study had other limitations as well, including that the cohort does not represent the general population because patients were recruited based on their risk of developing skin cancer.