According to a new review from China, an increased intake of vitamin A may result in a decreased risk for bladder cancer.
The meta-analysis included 25 epidemiological studies that measured blood vitamin A (retinol) concentrations and documented cases of bladder cancer among a total of 11,580 participants (1). The study results showed that a high blood level of retinol was significantly linked to a reduced risk for developing bladder cancer. Moreover, high blood levels of total carotenoids, such as beta-carotene, lutein and zeaxanthin, were asso- ciated with a significant reduction in risk for developing bladder cancer.
The researchers commented that vitamin A is hypothesized to reduce the risk of bladder cancer due to their roles in the regulation of cell differentiation and cell death (apoptosis) (2). Although vitamin A is found in a wide variety of foods, many people do not obtain an adequate intake of this nutrient. Therefore, the impact of vitamin A intake on bladder cancer risk has important public health implications, they added. However, given the heterogeneity of existing studies, it is premature to recommend higher dietary vitamin A for the primary prevention of bladder cancer. Further investigation using large samples and a rigorous methodology is warranted.
Bladder cancer is the fifth most common cancer among with an estimated 386,000 new cases and 150,000 deaths world-wide in 2008. It has the highest lifetime treatment cost for any cancer (3). Carcinogens or dietary chemo-preventive agents can be concentrated in urine and have prolonged exposure to the bladder epithelium, making it an ideal target for preventative strategies.