Cancer researchers in the U.S. say that high exposure to the sun halved the risk of prostate cancer in men participating in a U.S. trial.
They say this is likely because of their body’s higher vitamin D stores.
The researchers led by Esther John of the Northern California Cancer Center, say that if future studies continue to show that sunlight lowers prostate cancer risk, men may be advised to increase their vitamin D intake from diet and supplements as a safer option to sunbathing.
They say that in men with certain gene variants, high sun exposure reduced prostate cancer risk by as much as 65 per cent.
Previous research had also shown that the prostate uses vitamin D to promote the normal growth of prostate cells and to inhibit the invasiveness and spread of prostate cancer cells to other parts of the body.
Co-author Gary Schwartz of Wake Forest University, says the genes involved are those that determine the type of vitamin D receptors a person has, and the receptors, which function with vitamin D like a lock and key, vary in their ability to bind vitamin D and thus to influence cell behaviour.
The researchers say that although the body manufactures the active form of vitamin D from exposure to sunlight, men should not try to reduce their risk of prostate cancer by sunbathing because that increases the risk of sun-induced skin cancer, especially melanoma.
In future, increasing vitamin D intake from diet and supplements may be the safest solution to achieve adequate levels of vitamin D.
In the trial, 450 non-Hispanic white patients in the San Francisco Bay, area who had advanced prostate cancer were compared with a matched control group of 455 men who did not have prostate cancer.
The scientists measured sun exposure by comparing pigmentation of underarm skin, which is usually not exposed to sunlight, with forehead pigmentation, which is, using a portable reflectometer.