Nearly Half of Colorectal Cancer Survivors Change Their Supplement Use Within Five Years

More than half of colorectal cancer survivors were taking dietary supplements five years after their diagnosis, and nearly half of those tracked over the full period changed their supplement habits at least once along the way, according to a prospective cohort study published in Supportive Care in Cancer. The findings document how supplement use evolves across the colorectal cancer disease trajectory, from diagnosis through long-term survivorship.

Researchers drew on data from the COLON study, a prospective cohort of participants diagnosed with stage I to IV colorectal cancer. A total of 1,934 participants completed a dietary supplement questionnaire at diagnosis, with follow-up questionnaires at 6 months (1,769 participants), 2 years (1,533), and 5 years (1,198) post-diagnosis. The questionnaires captured the type, brand, frequency, and doses of the supplements each participant used. Participants were classed as regular users if they took at least one supplement at least once a week.

Supplement use was common at every stage of the trajectory. Forty-three percent of participants reported using supplements at diagnosis, a figure that dipped slightly to 42 percent at 6 months post-diagnosis, rose to 45 percent at 2 years, and reached 53 percent at 5 years. Multivitamins, vitamin D, and vitamin C were the products most frequently reported across all timepoints.

The longitudinal data revealed that supplement habits are far from fixed. Among the 1,146 participants with data at all four timepoints, 48 percent changed their supplement use at least once during the five years after diagnosis. Only 26 percent were consistent users throughout, taking supplements at every measurement, while an equal 26 percent were consistent non-users.

Doses mattered as well as prevalence. The researchers compared reported intakes against tolerable upper intake levels. Between 1 and 2 percent of vitamin D users exceeded the limit, as did 7 to 13 percent of vitamin B6 users and 4 to 5 percent of folic acid users. The proportions were higher for some minerals: 14 to 32 percent of magnesium users and 6 to 23 percent of iron users exceeded the tolerable upper intake level at some point.

Supplement use was not evenly distributed across the cohort. Across all timepoints, women and participants with higher education were more likely to be regular users than men and participants with lower levels of education.

Participants diagnosed with stage III or IV colorectal cancer were less likely to use supplements at 6 months and 2 years post-diagnosis than those diagnosed with stage I or II disease. The same held true for patients receiving adjuvant treatment compared with those who did not receive it.

The study’s design carries both strengths and limitations. As a prospective cohort, it followed the same individuals over time rather than asking them to recall past behavior. However, the participant numbers declined at each follow-up wave, from 1,934 at diagnosis to 1,198 at 5 years, and the observational design cannot establish why people started, stopped, or switched supplements.

The researchers conclude that dietary supplement use is common among colorectal cancer survivors and that, given how regularly supplements are taken, the potential impact of high-dose supplement use on clinical outcomes warrants further investigation. For now, the study documents a behavior rather than an effect: it establishes who takes what, when, and at what doses.

Subject of Research: Dietary supplement use patterns among colorectal cancer survivors over five years post-diagnosis

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

Article References: Zwart, N. R. K., Verstraete, F. F., Wesselink, E., Winkels, R. M., van Duijnhoven, F. J. B., de Wilt, J. H. W., Kampman, E., & Kok, D. E. (2026). Dietary supplement use throughout the colorectal cancer disease trajectory: a prospective cohort study. Supportive Care in Cancer, 34(11), Article 1145. https://doi.org/10.1007/s00520-026-11390-7

Image Credits: AI Generated

DOI: 10.1007/s00520-026-11390-7

Keywords: colorectal cancer, dietary supplements, prospective cohort, cancer survivors, vitamin D, multivitamins, vitamin B6, tolerable upper intake level, adjuvant treatment, survivorship, nutrition, Dietary