How much do sunlight and vitamin D help to prevent prostate cancer? In 2005, Dr. Esther John and colleagues reported on research in which they compared the lifetime sun exposure of 450 men with advanced prostate cancer with that of 455 men who did not have cancer. The men were divided into five groups (quintiles) according to the amount of sun exposure they had received. The results were impressive. The men in the highest quintile (fifth) of sun exposure had only 51% of the risk of prostate cancer as did those in the lowest quintile.
Several other studies have shown that high sun exposure over a lifetime relates to a considerably lower rate of death from prostate cancer.    The last study showed that those who were born in a state with high solar radiation had a reduced risk of 49%.
Perhaps the most impressive research studies were done by Dr. S Moon and colleagues where they compared sunlight exposure and prostate cancer risk. The subjects in two of studies were divided into four groups (quartiles) according to the lifetime sunlight exposure they had received. Those in the lowest quartile of sunlight exposure had more than three times the risk of developing prostate cancer as those in the highest quartile.
Dr. Moon’s group noted that when sunbathing was compared with prostate cancer, men in the lowest exposure quartile (fourth) of sunbathing had 5.33 times the risk of prostate cancer as those in the highest quartile. Sunbathing is obviously a great habit for men, provided it isn’t overdone. Other research has indicated that “higher levels of cumulative exposure, adult sunbathing, childhood sunburning and regular holidays in hot climates were each independently and significantly associated with a reduced risk of this cancer.” Nevertheless, it is always best to avoid sunburn.
Can there be any doubt that sunlight and vitamin D are essential to a good prostate health?
 John, E. et al. sun exposure, vitamin D receptor polymorphisms and risk of advanced prostate cancer. Cancer Res 2005;65:5479.
 Freedman, D. et al. sunlight and mortality from breast, ovarian, colon, prostate and non-melanoma skin cancer: a composite death certificate based case-control study. Occup environ Med 2002;59:257-62.
Hanchette, C. et al. Geographic patterns of prostate cancer mortality: Evidence for a protective effect of ultraviolet radiation. Cancer 1992;70:2861-69
 Schwartz, G. et al. Is vitamin D deficiency a risk factor for prostate cancer? [hypothesis] Anticancer Res 1990;10:1307-11.
 John, E. et al. Residential sunlight exposure is associated with a decreased risk of prostate cancer. J Steroid Biochem Mol Biol 2004;89:-90.
 Moon, S. et al. Ultraviolet radiation: effects on risks of prostate and other internal cancers. Mutat Res 2005; 571:207–219.
 Bodiwala, D. et al. Prostate cancer risk and exposure to ultraviolet radiation: further support for the protective effect of sunlight. Cancer Lett 2003;192:145-49.