The role of multivitamins: an investigation into the association with colorectal cancer survival

Nutritional supplements are used by over half of United States adults, and many patients use supplements for their perceived anti-cancer benefit. Current evidence for the relationship between multivitamin use and colorectal cancer (CRC) survival is sparse. Some studies suggest that multivitamins may divert attention from healthful food-based diets or multivitamin use may be reflected in an effort to live a healthier lifestyle consequently impacting CRC survival. In this study, we examined the association of pre-diagnostic multivitamin use with CRC survival, while accounting for differences by fruit and vegetable consumption and smoking status. Methods: This study uses data from two large prospective patient cohorts; the Colon Cancer Family Registry (C-CFR) and the Advanced Colorectal Cancer of Serrated Subtype (ACCESS) study. A Cox Proportional Hazards regression was used to assess the relationship between pre-diagnostic multivitamin use and CRC-specific survival (reported as hazard ratios (HR) and 95% confidence intervals (CI)). We also examined effect modification by fruit and vegetable consumption and smoking status. Results: The estimated HR of CRC death for individuals who use multivitamins is 1.05 (95% CI: 0.94-1.18, p=0.4) compared to individuals who do not use multivitamins, suggesting no statistically significant evidence of an association between pre-diagnostic multivitamin use and CRC-specific survival. Users of multivitamins were less likely to have a history of smoking and consumed higher levels of fruits and vegetables; however, there was no evidence of effect modification by these variables in the relationship of multivitamin use with CRC survival. Conclusion: We found no evidence of an association between pre-diagnostic multivitamin use and CRC survival, regardless of stratification by smoking status and fruit and vegetable consumption. Clinicians should discuss a variety of approaches for healthful activities individualized to the patient post CRC diagnosis in addition to multivitamin use advice.