Patients with colorectal cancer who used 10 or more multivitamin tablets per week had a higher risk of death, according to research.
For patients with colorectal cancer (CRC), moderate multivitamin use was associated with a decreased risk of death from the disease. However, researchers also found that high-dose multivitamin use had the opposite effect and was associated with increased CRC-specific mortality.
These findings, which were published in the journal, Cancer, may give reason for patients with CRC to discuss multivitamin use with their cancer care team, explained study author Dr. Mingyang Song, associate professor of Clinical Epidemiology and Nutrition at the Harvard T.H. Chan School of Public Health and assistant professor of Medicine at Massachusetts General Hospital, Harvard Medical School.
“There has been a lot of controversy regarding whether multivitamin use is beneficial or not,” Song said in an interview with CURE®. “So we wanted to take advantage of our data to say whether multivitamins may be beneficial for [patients with] colon cancer.”
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Song and his team collected and analyzed data from 2,424 patients with stages 1 to 3 colon cancer and provided information about their multivitamin use through the Nurses’ Health Study and Health Professionals Follow-Up Study, which is a large database of patient information regarding specific health behaviors and outcomes.
At a median follow-up of 11 years, a total of 1,512 patient deaths occurred — 343 of which were related to CRC.
Compared with patients who reported that they did not use multivitamins at all, those who reported either 3 to 5 tablets tended to have lower CRC-specific mortality. Additionally, patients who reported 3 to 5 or 6 to 9 tablets per week also had lower all-cause mortality. However, patients who started taking multivitamins after their diagnosis and reported taking 10 or more tablets per week had a higher risk of death.
“That means people who take multivitamins at a dose of three to nine tablets per week at a lower risk of dying from colon cancer or dying from all causes compared to non-users,” Song explained. “In contrast, patients who took at least 10 tablets per week actually had a higher risk of dying compared to the now users, so there’s a nonlinear relationship in our analysis.”
The research team did not inquire about any specific type of vitamin, so any type of multivitamin use was applicable — including non-prescription versions that can be purchased at the drugstore.
Results from prior research on multivitamin use and cancer outcomes are mixed. For example, a 2023 study published in the British Journal of Cancer found that multivitamin use was not associated with lower all-cause death risk in cancer survivors, although there was an observed decreased risk of cardiovascular-related death in female survivors of reproductive cancers who used multivitamins, as well as male survivors of non-reproductive cancer types and survivors, of any gender with skin and breast cancer.
Song also emphasized that patients and clinicians alike should be “cautious when interpreting [his team’s] results,” because this study was observational, which, according to the National Cancer Institute, is “a type of study in which individuals are observed or certain outcomes are measured. No attempt is made to affect the treatment outcome (for example, no treatment is given).”
A randomized, controlled trial, which assigns participants to certain treatments or behaviors, such as supplement use, would better be able to assess if there is a causal relationship between multivitamin use and CRC outcomes, according to Song, noting that with the current data, he and his team determined that while patients who took a moderate amount of multivitamins per week tended to have better outcomes, they cannot say for sure if the multivitamins caused this.
“This kind of study is quite doable because we have a very large population of cancer survivors who are really eager to find out whether this kind of supplement is beneficial or not,” Song said. “I think that there is certainly both public and scientific interest in this topic, and I would want to see more research in this area before we can make a clinical recommendation.”
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