Does UVR reduces the risk of cancer?

rescent study by Soerjomataram I et al :

Ultraviolet exposure may reduce the risk of colorectal and breast cancer as the result of rising vitamin D levels. Because skin cancer is positively related to sun exposure, the authors hypothesized a lower incidence of breast and colorectal cancer after skin cancer diagnosis. They analyzed the incidence of colorectal and breast cancer diagnosed from 1972 to 2002 among 26,916 Netherlands skin cancer patients (4,089 squamous cell carcinoma (SCC), 19,319 basal cell carcinoma (BCC), and 3,508 cutaneous malignant melanoma (CMM)). Patients with CMM exhibited an increased risk of breast cancer, especially advanced breast cancer (SIR = 2.20, 95% CI: 1.10, 3.94) and older patients at CMM diagnosis (SIR = 1.87, 95% CI: 1.14, 2.89). Study results suggest a beneficial effect of continuous sun exposure against colorectal cancer. The higher risk of breast cancer among CMM patients may be related to socioeconomic class, both being more common in the affluent group.

comment: vitamine D seems to have anti cancer propreties(colon, prostate, breast and probably melanoma), cumulative sun expsosure has been documtend to be a major risk factor for Squamus Cell carcinoma, but the evidene for cutaeous melanoma is still controversial. the amount of sun exposure needed to induce skin cancer is not known and therefore recommendations regarding outdoor activities (to replensih vitamin D) cant be determined. if in doubt regrading vitamin D defeciency it should always be supplemented especially for indvisulas with ligher skin types who avoid the sun for extended times.