What causes colon cancer? And how do you prevent it?

USA Today

16-07-2025

Colon cancer is one of the most preventable cancers in the U.S., but each year it claims more than 50,000 lives – in part because early symptoms can be mild and easily missed.
'Colon cancer is the deadliest cancer for men under 50 and second deadliest for women under 50,' says Dr. Heinz-Josef Lenz, professor of medicine at the University of Southern California Keck School of Medicine.
The good news is that when it is caught early, colon cancer is highly treatable. Even better, it's largely preventable through routine screening and healthy dietary and lifestyle habits.
Here's what colon cancer is, what increases your risk and how you can take steps to prevent it.
What is colon cancer?
Colon cancer (also sometimes referred to as colorectal cancer because it often spreads to the rectum) is a disease that begins with the formation of benign polyps in the body's large intestine, also known as the colon. Over time, these polyps can become cancerous (malignant) and spread to other areas of the body.
Symptoms of more advanced stages of colon cancer usually include "abdominal pain, bloody stool, a change in bowel habits (such as constipation or diarrhea), anemia due to blood loss and unexplained weight loss," explains Dr. Xavier Llor, a gastroenterologist at Yale Medicine, who specializes in colon cancer prevention. "But early on," he says, "symptoms can be mild or even absent.'
While individual risk factors vary, the average risk of developing colorectal cancer over one's lifetime is about one in 24 for men and about one in 26 for women, per the American Cancer Society.
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What causes colon cancer?
While exact causes can't always be known and vary widely from patient to patient, a family history of colon cancer is known to dramatically increase one's risk, says Llor. Ditto for associated inherited conditions such as Lynch syndrome or familial adenomatous polyposis (FAP). Inflammatory bowel diseases like Crohn's or ulcerative colitis also increase risk due to ongoing inflammation in the digestive tract, explains Lenz, and type 2 diabetes may play a role as well.
Age is a factor, too, as most cases of colon cancer occur in individuals over 50, but incidence among younger adults is rising.
Many of the most common causes of colon cancer are thought to be related to lifestyle behaviors and dietary choices. "Diets rich in red meat such as beef, and pork – particularly if it's fried or broiled – and eating processed meats such as hot dogs and deli meat have been shown to cause colon cancer," says LLor. A lack of physical activity, obesity, smoking and excessive alcohol consumption can also all contribute, says Lenz.
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How to prevent colon cancer
Understanding how these factors can cause colon cancer goes a long way in helping prevent it. But even more people avoid the worst outcomes of colon cancer by getting screened early and as often as is recommended.
Here are the most commonly recommended suggestions that help colon cancer be one of today's most preventable cancers.
No matter how you and your doctor choose for you to get screened, what matters is doing so as soon as you reach the recommended age and then keeping up with screenings every five to 10 years, as advised by your doctor. 'If caught early,' Llor says, 'your chances of surviving colon cancer are excellent at around 90%.'