Dietary Supplement Use after Cancer Diagnosis in Relation to Total Mortality, Cancer Mortality and Recurrence: A Systematic Review and Meta-Analysis

Abstract

To study post-diagnosis dietary supplement use in relation to total mortality, cancer mortality and recurrence among cancer survivors. PubMed and Cochrane Library were searched until April 2019 for observational studies (OS) and randomized clinical trials (RCT). Pooled risk ratios (RR) were calculated using random-effects models. Compared to no supplementation, calcium supplementation was associated with lower total (RR = 0.88, 95% confidence interval (CI): 0.77-1.00, I²=0%, four OS) and cancer mortality (RR = 0.71, 95% CI: 0.53-0.95, I²=0%, three OS) among all cancer survivors, and cancer mortality among colorectal cancer survivors (RR = 0.66, 95% CI: 0.47-0.94, I²=0%, two OS). Vitamin D supplementation was associated with lower total mortality (RR = 0.86, 95% CI: 0.76-0.99, I²=0%, three OS and two RCT). Among breast cancer survivors, supplementation with vitamin C (RR = 0.79, 95% CI: 0.68-0.92, I²=0%, four OS), D (RR = 0.85, 95% CI: 0.72-0.99, I²=0%, two OS), and E (RR = 0.76, 95% CI: 0.64-0.90, I²=0%, three OS) was associated with lower total mortality, while multivitamins (RR = 0.79, 95% CI: 0.64-0.97, I²=0%, two OS), vitamin C (RR = 0.76, 95% CI: 0.64-0.91, I²=0%, two OS), and E (RR = 0.69, 95% CI: 0.55-0.85, I²=0%, two OS) with lower cancer recurrence. Conclusions: Findings are mostly based on OS. More RCTs are needed to justify any recommendation for use.

Acknowledgments

This study was part of a Master Thesis conducted in the context of the MSc Program in Biostatistics of the School of Medicine of the National and Kapodistrian University of Athens, Greece. The authors dedicate this manuscript to the memory of their dear colleague Christina Bamia.

Disclosure statement

There is no conflict of interest between the authors.