Fiber-Based Laxatives Linked to Decreased Risk of Colorectal Cancer


Key Points

  • Use of fiber-based laxatives was associated with a decreased risk of colorectal cancer.
  • Use of nonfiber laxatives was associated with an increased risk of colorectal cancer.
  • No association was made between bowel-movement frequency/constipation and colorectal cancer risk.
  • More research is needed before clinical recommendations regarding laxative use can be made.

A large, prospective study involving more than 75,000 adults in western Washington has found that frequent use of fiber-based laxatives is associated with a decreased risk of colorectal cancer. The study also found that use of nonfiber laxatives is linked to significantly increased risk of colorectal cancer. The study, reported by Citronberg et al in The American Journal of Gastroenterology, found no association between bowel-movement frequency/constipation and colorectal cancer risk.

The findings are important because an estimated 20% of Americans use laxatives, according to the paper’s first and corresponding author, Jessica Citronberg, MPH, a predoctoral fellow in the Epidemiology Program of the Public Health Sciences Division at Fred Hutchinson Cancer Research Center and a doctoral student in epidemiology at the University of Washington School of Public Health.

While nonfiber laxatives—those most commonly used in the United States—work by forcing the colon to contract, fiber-based laxatives rely on increasing the water content and bulk of the stool to move it through the colon.

Study Details

The investigators found that people who use nonfiber laxatives five or more times a year had a 49% increased risk of colorectal cancer, while those who used fiber-based laxatives at least 4 days a week for 4 years had a 56% lower risk of the disease compared to those who did not use them.

The analysis, which assessed frequency of bowel movements, constipation, and 10-year laxative use, was based on data from 75,214 men and women aged 50 to 76 years in western Washington who were part of a larger study to investigate the association between vitamins, minerals, and other dietary supplements on cancer risk. The study participants were surveyed initially between 2000 and 2002 and followed until 2008, during which time 558 of the study participants were diagnosed with colorectal cancer. People with a history of colorectal cancer, Crohn’s disease, and intestinal polyps were excluded from the study.

While previous research in laboratories and in animals has found stimulant laxatives to have carcinogenic and gene-mutating effects, prior cohort studies on laxative use have produced inconsistent results regarding colon cancer risk.

“Given that we found [colorectal cancer] risk to be dependent on laxative type, findings from the current study would help to explain the inconsistencies in previous studies that grouped all laxative types together,” the authors reported.

The authors hypothesize that soluble-fiber laxatives may possess some of the protective effects postulated for dietary fiber. Consuming dietary fiber is thought to reduce colorectal cancer risk by diluting carcinogens in the stool, encouraging growth of healthy bacteria in the colon, and, by increasing stool transit time, decreasing the duration by which carcinogens are in contact with the colon.  

More Research Needed

More research is needed before clinical recommendations regarding laxative use can be made, Ms. Citronberg noted. “[T]he takeaway is [there was] no association between bowel-movement frequency, constipation, and colorectal cancer risk [in this study], but [there was an] association with laxative use [and colorectal cancer risk],” Ms. Citronberg said. “While the study results suggest that nonfiber laxatives increase your risk and fiber laxatives decrease your risk of colorectal cancer, more research is needed. I wouldn’t necessarily say because of this study people should stop taking stimulant laxatives,” she said. “I think the better route would be to have a healthy diet.”

Ms. Citronberg is the corresponding author of the The American Journal of Gastroenterology article. Study collaborators included senior author Emily White, PhD, of the Fred Hutch Public Health Sciences Division and John Potter, PhD, of Massey University in Wellington, New Zealand.

The National Cancer Institute and the Office of Dietary Supplements, both branches of the National Institutes of Health, funded the research.

The content in this post has not been reviewed by the American Society of Clinical Oncology, Inc. (ASCO®) and does not necessarily reflect the ideas and opinions of ASCO®.