Prospective cohort study of the association between post-diagnostic multivitamin supplement use and colorectal cancer survival

Use of multivitamin supplements has been associated with lower incidence of colorectal cancer (CRC). However, its influence on CRC survival remains unknown. Among 2424 patients with stage 1-3 CRC who provided detailed information about multivitamin use in the Nurses’ Health Study and the Health Professionals Follow-up study, the multivariable HRs of multivitamin supplements for all-cause and CRC-specific mortality according to postdiagnostic use and dose of multivitamin supplements were calculated. During a median follow-up of 11 years, there were 1512 deaths, among which 343 were of CRC. Compared to non-users, postdiagnostic users of multivitamin supplements at a dose of 3-5 tablets per week had lower CRC-specific mortality (HR 0.55; p=0.005) and users of 3-5 and 6-9 tablets per week had lower all-cause mortality (0.81; p=0.04 and 0.79; p<0.001, respectively). The dose-response analysis showed a curvilinear relationship for both CRC-specific and all-cause mortality, with a maximum risk reduction at 3-5 tablets per week and no further reduction at higher doses. New users (after diagnosis) at a dose of ≥ 10 tablets per week had a higher risk of CRC-specific mortality (HR 1.58; 95% CI 1.07-2.33). The authors conclude that use of multivitamin supplements at a moderate dose after diagnosis of nonmetastatic CRC is associated with lower CRC-specific and overall mortality, whereas high dose use was associated with higher CRC-specific mortality.