In a recent meta-analysis, researchers found that sufficient vitamin D status is linked with a 60% reduced risk of bladder cancer.
Bladder cancer is the 4th most common form of cancer in the United States, with nearly 80,000 new cases diagnosed annually. Bladder cancer typically occurs in individuals over the age of 55 years, affecting men three to four times more frequently than women.
Past research has determined that vitamin D may exert anti-cancer properties. Preventing cellular proliferation, promoting programmed-cell death and decreasing inflammation in the body are just a few of the mechanisms by which vitamin D may act in the presence of cancer cells. Furthermore, current evidence suggests that vitamin D status is inversely associated with several types of cancer, including prostate, lung and breast cancer.
In an effort to more conclusively define the relationship between vitamin D status and bladder cancer, researchers recently conducted a systematic review and network meta-analysis. The network meta-analysis provides an additional benefit to the current research as it combines all of the relative treatment effects gathered from past studies on vitamin D and bladder cancer, thereby providing a cohesive cohort analysis of all of the current clinical research.
Studies were included in the analysis if the following criteria were met:
- The studies were either a prospective cohort, case control or nested case control design.
- The researchers focused on multiple vitamin D concentrations on bladder cancer risk.
- Odds ratios or hazard ratios were estimated by quintile of serum vitamin D status on bladder cancer.
- Bladder cancer outcome, disease progression or mortality were evaluated.
A total of 7 studies (2 prospective cohorts and 5 case control studies) with 90,757 participants, 2509 of which had bladder cancer met this criterion and were included in the analysis. The researchers analyzed the data provided from the previous studies, here is what they found:Vitamin D levels 30 ng/ml (75 nmol/l) or greater were associated with a decreased incidence of bladder cancer.
- Vitamin D levels > 30 ng/ml were associated with:
- a 32% decreased odds of developing bladder cancer compared to severely deficient individuals (< 10 ng/ml, <25 nmol/L)
- a 35% decreased odds of developing the disease when compared with moderately deficient individuals (10–15 ng/ml; 25–37.5 nmol/l)
- a 39% decreased odds when compared to those who were slightly deficient (15–20 ng/ml; 37.5–50 nmol/l)
- and a 35% decreased likelihood when compared to vitamin D insufficient individuals (20—30 ng/ml; 50– 75 nmol/l).
- Adjustment for age and BMI did not alter the relationship between vitamin D and bladder cancer.
- Maintaining a vitamin D status of 30 ng/ml (74 nmol/L) or greater was associated with a 60% reduced risk of developing bladder cancer (p = 0.007).
Dose-response curve for bladder cancer based off of 25(OH)D concentration. The five points are the odds ratios for each quintile of 25(OH)D from the combined data of the seven studies.
The researchers concluded,
“Ensuring sufficient serum 25-hydroxyvitamin D concentrations might play an important role in decreasing the risk of bladder cancer. The serum 25-hydroxyvitamin D concentration 74 nmol/L (~30ng/ml) was associated with a 60% lower risk of bladder cancer incidence.”
The findings from this network meta-analysis are consistent with the most recent research, providing further validity to the current evidence supporting the relationship between vitamin D status and bladder cancer risk. In addition, the unique study design allowed the researchers to rank the effects of multiple ranges of vitamin D levels on bladder cancer risk. However, due to the lack of randomized controlled trials, the results of this study prove correlation only.
Therefore, the researchers call for large scaled, randomized controlled trials to confirm the role of vitamin D in the prevention or treatment of bladder cancer.
Sturges, M. & Cannell, JJ. Meta-analysis finds healthy vitamin D status may help reduce the risk for bladder cancer. The Vitamin D Council Blog & Newsletter, 2016.