Study finds no constipation, colon cancer link

Long-term constipation doesn't raise risk for colon and rectal cancers according to a new analysis of the existing evidence.

Past studies had suggested a possible connection, but researchers said those results may have been skewed by poor study designs.

"Someone who's got chronic constipation is unlikely to be associated with colon cancer now or in the future," said study author Dr. Alexander Ford, senior lecturer at the St. James's University Hospital's Leeds Gastroenterology Institute in the UK.

Colorectal cancer is the second leading cause of cancer death in the U.S., with an estimated 51,000 Americans dying from it each year, according to the Centers for Disease Control and Prevention.

Established risk factors for the disease include a personal or family history of colorectal cancer, irritable bowel disease, certain syndromes that cause colon polyps, type 2 diabetes, obesity, heavy drinking, smoking and being over age 50, according to the American Cancer Society.

Some experts have hypothesized that chronic constipation, by causing prolonged contact between potentially carcinogenic substances in the stool and the lining of the colon, might also increase the risk of cancer.

Studies in recent decades have both supported and refuted that idea, so Ford and his colleagues reanalyzed data across 28 studies that examined the connection between constipation and colorectal cancer. In total, the data included over 250,000 participants from 1966 to 2011.

Ford's team found little support for a link between constipation and cancer risk, according to their findings published in the journal Gastroenterology.

Studies that showed an association typically included questionnaires for participants to recall bouts of constipation. Ford told Reuters Health those studies suffered from bias because the suggestion of constipation could lead people to misremember their symptoms.

However, in stronger studies that tracked people for both constipation and colorectal cancer over six to 12 years, the researchers found no connection.

"If they just have constipation in isolation then that does not seem to be a risk factor for colon cancer," said Ford, who received funding from Allmiral, makers of Linaclotide, a drug currently under testing for irritable bowel syndrome. The Spanish pharmaceutical company was not involved in the study's design or execution.

Symptoms of advanced colon cancer typically include diarrhea or looser stools, unintentional rapid weight loss, abdominal pain, anemia and rectal bleeding.

Ford's team also found that studies focused just on colorectal cancer patients did find a significantly higher rate of constipation in patients compared to people without colorectal cancer, but again, those studies had weaknesses.