WEDNESDAY, June 15, 2005 (HealthDay News) -- Spending lots of time in the sun seems to increase a man's vitamin D levels and lower his risk for prostate cancer, a new study finds.
But because tanning and burning actually raise skin cancer risks, researchers suggest vitamin D in supplement form may be a safer option.
The findings appear in the June 15 issue of the journal Cancer Research.
Researchers from three cancer centers compared 450 men with advanced prostate cancer with a control group of 455 men without the disease. They found that the men with high sun exposure were at half the prostate cancer risk of men with low sun exposure.
The risk of prostate cancer was as much as 65 percent lower in men with certain gene variants plus high sun exposure.
"We believe that sunlight helps to reduce the risk of prostate cancer because the body manufactures the active form of vitamin D from exposure to sunlight," research team leader Esther John, of the Northern California Cancer Center, said in a prepared statement.
According to previous research, the prostate uses vitamin D to promote the normal growth of prostate cells and to impede the invasiveness and spread of prostate cancer cells to other areas of the body, the researchers said.
"The genes involved are those that determine the type of vitamin D receptors a person has," study co-author Gary G. Schwartz, of the Comprehensive Cancer Center at Wake Forest University, said in a prepared statement.
"These receptors, which function with vitamin D like a lock and key, vary in their ability to bind vitamin D and thus to influence cell behavior," Schwartz said.
He and his colleagues emphasized that sunlight isn't the only source of vitamin D and that men shouldn't start sunbathing to reduce their risk of prostate cancer. Too much sun exposure increases the risk of skin cancer.
"If future studies continue to show reductions in prostate cancer risk associated with sun exposure, increasing vitamin D intake from diet and supplements may be the safest solution to achieve adequate levels of vitamin D," the researchers wrote.
The U.S. National Cancer Institute has more about prostate cancer prevention.