Vitamin C and Multi’s Don’t Help Colorectal Cancer Survivors

A Cancer Prevention Study-II Nutrition Cohort

Taking multivitamins or vitamin C before or after a diagnosis of colorectal cancer didn’t affect survival. Use of vitamin E is still in question.

The Challenge

People who have survived colorectal cancer want reliable, research-proven information about diet and nutrition that could influence their prognosis and quality of life, positively and negatively. It’s common for these survivors to use multivitamins and other over-the-counter dietary supplements. If fact, they are more likely to use them than the general population.

The challenge is that there is limited data and evidence on the effect of dietary supplements on people with a personal history of colorectal cancer. Knowing more about this could help the almost 2 million colorectal cancer survivors worldwide.

The Research

Several American Cancer Society (ACS) Population Science researchers collaborated with Jane Figueiredo, PhD, at Cedar-Sinai Medical Center in Los Angeles to examine the association between taking multivitamins and vitamin C and vitamin E (both antioxidants) and dying from cancer.

The ACS Population Science team routinely sent surveys to every volunteer in the ACS Cancer Prevention Study-II (CPS-II) Nutrition Cohort for several decades, and some of the questions were about taking vitamins. 

"The survey responses let us know if and when cohort participants developed colorectal cancer," says Caroline Um, PhD, MPH, RD, an ACS researcher.  "The collected responses gave us a tremendous amount of data that allows us to examine how long they may live after a cancer diagnosis."

The researchers found that taking multivitamins before or after diagnosis of colorectal cancer does not seem to be linked with survival. 

They also looked for any connections between participants' use of vitamins and mortality.

Use of multivitamins. The researchers found that of the more than 3,100 colorectal cancer survivors who were followed for 26 years:

• Almost half took multivitamins before being diagnosed with cancer and 58% took them after being diagnosed.
• About 28% took vitamin C both before and after diagnosis.
• About 28% took vitamin E before diagnosis and about 29% took it after diagnosis.

The effect of vitamins. They found no statistically significant links between taking a multivitamin or vitamin C, before or after colorectal cancer diagnosis, with:

• Dying from colorectal cancer
• Dying from any cause

However, they found that taking vitamin E before a diagnosis of colorectal cancer was associated with a slightly significant (but not statistically significant) increased risk of death from any cause. To be cautious, colorectal cancer survivors should make efforts to get their nutrients from the foods they eat rather than to take high doses of individual vitamins or supplements.

While this study suggests that multivitamins and vitamin C are neither helpful nor harmful, the authors recommend future studies to examine the use of vitamin E and outcomes among colorectal cancer survivors to see if their findings are replicated.

"Colorectal cancer survivors should follow a healthy diet based on ACS recommendations for cancer survivors as much as possible and discuss with their healthcare team whether they need vitamins to supplement their diet," Um says.

These published results in JNCI Cancer Spectrum were co-authored by 4 ACS researchers: Christina Newton, MSPH, Marjorie McCullough, SCD, RD, Caroline Um, PhD, MPH, RD, Alpa Patel, PhD, and 2 former ACS researchers: and former Mark Guinter, PhD (now at Flatiron Health in New York), Peter Campbell, PhD, (now at Albert Einstein College of Medicine).

Why It Matters

Because many people with cancer take vitamins and other supplements, it is important to identify potential benefits or harms of these supplements with cancer survival. Plus, individual vitamins and supplements tend to be sold in a higher dose, and high-dose vitamins—including vitamin E—have been related to an increased risk of developing cancer in some clinical trials.