Higher vitamin D levels associated with lower risk of bladder cancer

November 2, 2010

An article published online on October 26, 2010 in the journal Cancer Research reveals an association between higher levels of serum vitamin D and a lower risk of bladder cancer in men. The finding adds another cancer to the list of those for which vitamin D appears to have a protective benefit.

The current study involved 500 participants in the Alpha-Tocopherol, Beta-Carotene Cancer Prevention Study, a randomized, double-blinded trial of Finnish male smokers conducted to determine the effects of alpha-tocopherol and beta-carotene supplementation on cancer risk. Participants were cancer-free at the beginning of the study. Blood samples drawn upon enrollment between 1985 and 1988 were analyzed for serum 25-hydroxyvitamin D levels and other factors.

The National Cancer Institute researchers compared 250 subjects who were diagnosed with bladder cancer through April, 2005 and an equal number of participants who did not have the disease. Cases and controls were matched for age and date of blood draw. A low level of vitamin D was associated with a significantly greater risk of bladder cancer. Men whose vitamin D level was less than 25 nanomoles per liter experienced a 73 percent greater adjusted risk of the disease than those whose levels were at least 50 nanomoles per liter. Similar risks were observed for those whose levels fell between 25 and less than 37.5, and from 37.5 to less than 50 nanomoles per liter.

"These findings are consistent with previous cell culture, in vivo, and genetic evidence suggesting that greater exposure to vitamin D could have a role in protecting against bladder cancer," Alison M. Mondul and coauthors write. "Higher serum 25-hydroxyvitamin D may be associated with greater urinary excretion and concentration of free and conjugated vitamin D metabolites. Increased exposure of the bladder mucosa to these metabolites could promote transitional cell differentiation and apoptosis and, thus, reduce epithelial proliferation and neoplasia."

"Future studies should examine the association in other populations, especially nonsmokers and women, and evaluate possible effect modification by season of blood draw, physical activity, and intake of other nutrients, including vitamin E," they recommend.