Oral vitamin D intake was not associated with any protective effect against skin cancer development including melanoma, despite findings of previous studies, according to data taken from two large population cohort studies. However, increased intake of vitamin D was associated with a greater risk for basal cell carcinoma (BCC) of the skin. The results of this latest study were published in PLOS One.
“Although we found a modest positive association between vitamin D intake and BCC risk, the major differences in BCC risk were largely found in lower vitamin D intake quintiles, while the risks were similar among higher quintiles of vitamin D intake,” wrote Sang Min Park, MD, of Brigham and Women’s Hospital and Harvard Medical School in Boston, and colleagues. “Therefore, the positive association was largely driven by the effect of low vitamin D intake.”
In addition, Park and colleagues noted that they “cannot exclude the possibility of reporting bias and misclassification of BCC, because the identification of BCC cases in this study was based on self-report.”
In the study, the researchers wanted to explore any association between vitamin D and risk for skin cancers. Some previous studies have shown a protective effect of vitamin D against ultraviolet damage and skin cancer development, but overall, results from epidemiologic studies have been inconsistent.
They prospectively evaluated whether total, dietary, and supplemental vitamin D intake was associated with skin cancer risk by looking at data from two large cohort studies: the Nurses’ Health Study (n = 63,760) and the Health Professionals Follow-Up Study (n = 41,530). In these studies, vitamin D intake was gathered every 2 to 4 years.
Of the study participants, there were 20,840 incident BCCs, 2,329 incident squamous cell carcinomas, and 1,320 melanomas. The researchers divided vitamin D intake into quintiles. The median intake for the lowest quintile was 124.8 IU/d for women and 156.0 IU/d for men; the median for the highest quintile was 638.2 IU/d for women and 775.3 IU/d for men.
After multivariable adjustment, total vitamin D intake was significantly associated with an increased risk for BCC. Increases in vitamin D intake from food and supplements were each associated with this increased risk. Comparing the lowest with the highest quintile for intake, the hazard ratio for BCC was 1.12 for women (Ptrend < .01) and 1.07 for men (Ptrend = .14). The pooled hazard ratio was 1.10 (Ptrend = .05).
“These trends remained despite strategies to minimize confounding by sun exposure,” the researchers wrote. “When we examined individual vitamin D-rich foods, intakes of fish, cereal, and skim milk were significantly associated with risk of BCC in both cohorts.”
In an age-adjusted analysis, vitamin D intake was also associated with increased risk for squamous cell carcinoma and melanoma, but after adjustment for other risk factors, the association was no longer significant.