Vitamin D and Bladder Cancer Risk: An Umbrella Review and Second Order Meta-Analysis.

Area of Science:

• Oncology
• Nutritional Science
• Epidemiology

Background:

• Bladder cancer is a prevalent malignancy with substantial recurrence rates.
• Vitamin D, known for bone health, is increasingly investigated for its potential role in cancer risk, including bladder cancer.

Purpose of the Study:

• To assess the relationship between serum vitamin D levels, dietary vitamin D intake, and supplementation with bladder cancer risk.

Main Methods:

• An umbrella review synthesized findings from systematic reviews and meta-analyses on vitamin D and bladder cancer.
• Included studies focused on serum vitamin D levels or dietary intake.
• Quality was assessed using the JBI Critical Appraisal Tool; quantitative synthesis involved two second-order meta-analyses.

Main Results:

• Low serum vitamin D (below 30 nmol/L) showed a significant association with increased bladder cancer risk (RR=1.32).
• Higher serum vitamin D levels suggested a non-significant reduction in risk (RR=0.86).
• Data on dietary vitamin D intake provided inconsistent results, with some indications of a modest protective effect.

Conclusions:

• Low serum vitamin D is consistently linked to a higher risk of bladder cancer.
• Maintaining serum vitamin D levels above 30 nmol/L may offer protective benefits.
• Further research is needed to clarify the roles of dietary intake, supplementation, and standardized measurement methods.