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.
Key Findings
Results
Regular dietary supplement use was reported by 42-53% of colorectal cancer participants across four timepoints, increasing at 5 years post-diagnosis.
Use was 43% at diagnosis (n = 1934), 42% at 6 months (n = 1769), 45% at 2 years (n = 1533), and 53% at 5 years (n = 1198).
Regular use was defined as ≥1 supplement used at least once a week.
Data came from the COLON study, a prospective cohort of participants with stage I-IV CRC, using a questionnaire on type, brand, frequency, and dose.
Results
Multivitamins, vitamin D, and vitamin C were the supplements most often reported.
The questionnaire captured type, brand, frequency, and doses of supplements.
These three were the most frequently reported across the follow-up.
Results
Nearly half of participants changed their supplement use at least once during the 5 years after diagnosis.
Among participants with data at all timepoints (n = 1146), 48% changed their use at least once.
26% were consistent users and 26% were consistent non-users.
Results
A subset of supplement users exceeded the tolerable upper intake level (UL) for several micronutrients.
UL exceeded by 1-2% of vitamin D users.
UL exceeded by 7-13% of vitamin B6 users and 4-5% of folic acid users.
UL exceeded by 14-32% of magnesium users and 6-23% of iron users.
Results
Female sex and higher education were associated with a greater likelihood of supplement use at all timepoints.
The association was seen across all four timepoints (diagnosis, 6 months, 2 years, 5 years).
Results
Stage III/IV disease and receipt of adjuvant treatment were associated with a lower likelihood of supplement use at 6 months and 2 years post-diagnosis.
Comparison was stage III/IV versus stage I/II CRC.
Comparison was receiving versus not receiving adjuvant treatment.
The lower likelihood was observed at 6 months and 2 years post-diagnosis.
What This Means
This study followed people diagnosed with colorectal cancer for five years and asked them about vitamin and mineral supplement use at diagnosis, 6 months, 2 years, and 5 years later. Between 42% and 53% reported regularly using supplements, with use highest at 5 years. Multivitamins, vitamin D, and vitamin C were the most common. Women and people with more education were more likely to take supplements, while those with more advanced cancer or who received adjuvant treatment (such as chemotherapy after surgery) were less likely to take them at 6 months and 2 years.
Supplement habits were not stable: almost half of people with complete data changed their use at least once over the five years, while about a quarter always used supplements and a quarter never did. A minority of users took amounts above the tolerable upper intake level, particularly for magnesium (14-32% of users) and iron (6-23%), and to a lesser extent vitamin B6, folic acid, and vitamin D.
This research suggests supplement use is common and changes over time in people living with colorectal cancer, and that some take high doses. The authors note that the potential effect of high-dose supplements on clinical outcomes needs further study. The study describes use patterns only and does not show whether supplements help or harm.
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Zwart N, Verstraete F, Wesselink E, Winkels R, van Duijnhoven F, de Wilt J, et al.. (2026). Dietary supplement use throughout the colorectal cancer disease trajectory: a prospective cohort study.. Supportive care in cancer : official journal of the Multinational Association of Supportive Care in Cancer. https://doi.org/10.1007/s00520-026-11390-7