Debunking myths about colorectal cancer: expert clarifies misconceptions on constipation, polyps, and diet

Colorectal cancer, a cancer of the colon and rectum, is often misunderstood. Common myths include the belief that constipation causes colon cancer, that having a large number of colon polyps (benign tumors) significantly increases your risk, and that you should stop eating meat to prevent the disease from returning. But are these claims true?

“There are no studies that show severe constipation increases the risk of colorectal cancer,” said Kim Hye-young, a professor of hematology-oncology at Ulsan University Hospital, during an appearance on the hospital’s YouTube channel.

She noted, however, that constipation could be a symptom of colorectal cancer. “If you experience constipation due to a change in bowel habits, it may be a sign of colorectal cancer, so it is recommended to consult a specialist for necessary tests,” Kim advised.

Addressing the belief that bloody stools indicate colorectal cancer, Kim explained, “Bloody stools can also occur with hemorrhoids, ulcerative colitis, and severe enteritis. Therefore, bloody stools do not necessarily indicate colorectal cancer, but if you have persistent bright red or black stools, it is best to consult a specialist for appropriate tests.”

Also, Kim explained that while lactobacilli or probiotics may not directly prevent colorectal cancer, they can be beneficial for patients who have undergone colorectal cancer surgery. Since the removal of the colon alters the existing gut microbiome, taking lactobacilli can aid in the production and distribution of gut microbes, providing general benefits.

Addressing the myth that all colorectal polyps will become cancerous if left untreated, Kim clarified that the risk of developing colorectal cancer varies depending on the type of polyp. In general, high-risk polyps—those that are large or have severe dysplasia in the pre-cancerous stage—are more likely to develop into colorectal cancer and should be removed.

Professor Kim stated, “Having a large number of polyps does not necessarily increase the risk of colorectal cancer, but if more than 10 polyps are observed during a colonoscopy, it is recommended to have a colonoscopy every year.”

“Especially in young people under the age of 40, if there are more than 10 to 20 polyps, it may indicate 'hereditary colorectal polyposis,' a condition where the incidence of colorectal cancer is significantly higher compared to the general population, thus increasing the likelihood of cancer in such cases.”

Kim also debunked the myth that people should avoid eating meat after colon cancer treatment to prevent recurrence.

Kim explained that meat contains essential nutrients like fat, protein, and B vitamins, making it necessary to consume an appropriate amount. However, she noted that excessive meat consumption—such as more than 100 grams of red meat and 50 grams of processed meat per day—has been linked to an increased risk of colorectal cancer, so it is advisable to avoid excessive intake.

In general, colorectal cancer surgery involves removing 25 to 30 centimeters of the large intestine. This shortens the bowel, which can lead to diarrhea, frequent stools, or even constipation. Kim advised that at this point, taking medications tailored to your symptoms can be helpful.

In response to a question about whether colorectal cancer surgery results in a permanent ostomy, Kim explained that ostomies can be either temporary or permanent. She noted that a temporary ostomy may be created before or after surgery, but if the anus is removed entirely or if an intestinal obstruction does not resolve, a permanent ostomy may be required.