Dietary supplement use throughout the colorectal cancer disease trajectory: a prospective cohort study

Dietary supplement use is common in the general population, but literature addressing supplement use throughout the disease trajectory in colorectal cancer (CRC) survivors is limited.

Data from the COLON study, a prospective cohort among participants diagnosed with stage I-IV CRC, were used. Participants were asked to fill out a dietary supplement questionnaire at diagnosis (n = 1934), 6 months post-diagnosis (n = 1769), 2 years post-diagnosis (n = 1533), and 5 years post-diagnosis (n = 1198) containing questions on type, brand, frequency, and doses of supplements. Participants were considered regular supplement users if they used ≥ 1 supplement(s) at least once a week.

Supplement use was reported in 43% of participants at diagnosis, 42% at 6 months post-diagnosis, 45% at 2 years post-diagnosis, and 53% at 5 years post-diagnosis. Multivitamins, vitamin D, and vitamin C were most often reported. Almost half of the participants (48%) with data across all timepoints (n = 1146) changed their dietary supplement use at least once during the 5 years post-diagnosis, whereas 26% were consistent users and 26% consistent non-users. The tolerable upper intake level was exceeded for 1-2% of vitamin D users, 7-13% of vitamin B6 users, 4-5% of folic acid users, 14-32% of magnesium users, and 6-23% of iron users. Across all timepoints, female and higher educated participants were more likely to use supplements. Participants diagnosed with stage III/IV CRC (versus I/II) and those receiving adjuvant treatment (versus not receiving) were less likely to use supplements at 6 months and 2 years post-diagnosis.

Dietary supplement use is common among CRC survivors. Given the regular use of supplements, the potential impact of (high-dose) supplement use on clinical outcomes warrants further investigation.