Colon cancer is common because it develops slowly from small growths in a very long, heavily used organ, and many widespread lifestyle and genetic factors increase the risk over decades.

What colon cancer is

  • Colon cancer starts in the large intestine (colon) or rectum, usually from small growths called polyps that gradually turn into cancer over years.
  • It is among the most frequently diagnosed cancers worldwide and a leading cause of cancer‑related death in both men and women.

Why colon cancer is so common

1. The colon’s biology and “polyp to cancer” pathway

  • Most cases follow an “adenoma–carcinoma sequence,” where normal lining cells accumulate DNA damage, form polyps, then progress to cancer over many years.
  • Because this process is slow, there is a long time window in which many people can develop precancerous polyps without symptoms, making the overall disease more common.

2. Ageing and long exposure time

  • Risk rises with age because DNA damage, inflammation, and cumulative exposure to diet, toxins, and lifestyle factors build up over decades.
  • Historically, most cases occurred after age 50, though rates are now rising in younger adults as well, which further increases how often it appears in the population.

3. Lifestyle and environment

Many very common habits in modern life raise colon cancer risk:

  • Low‑fiber, high‑fat, “Western” diets, especially high in red and processed meat and low in fruits, vegetables, and whole grains.
  • Obesity, physical inactivity, and sedentary lifestyles, which are now widespread in many countries.
  • Smoking and heavy alcohol use, both clearly linked to higher colorectal cancer risk.
  • Long‑term insulin resistance or diabetes, which are increasingly common and associated with higher colon cancer risk.

Because these factors are so prevalent, they push population‑level risk up, making colon cancer more common than many other cancers.

4. Genetics and family history

  • Around 3–5% of cases are caused by inherited syndromes such as Lynch syndrome and familial adenomatous polyposis, which sharply raise lifetime risk.
  • Another 20–25% of people with colon cancer have a strong family history without a clearly identifiable single gene mutation, suggesting shared genes and environments.

5. Inflammation, microbiome, and chemicals

Researchers are increasingly focusing on “why now” and “why younger people”:

  • Unhealthy diets, obesity, and some drugs (like frequent antibiotics) can disturb gut bacteria, promote chronic inflammation, and may encourage tumor growth in the colon.
  • Chronic inflammatory conditions of the gut, such as Crohn’s disease and ulcerative colitis, significantly raise colon cancer risk over time.
  • Scientists are also studying environmental chemicals (pollution, pesticides, industrial compounds) that cause intestinal tumors in animals and may damage human colon cell DNA.

Is colon cancer becoming more common?

  • Overall, in older adults, screening (like colonoscopy) has actually reduced incidence by catching and removing polyps before they turn cancerous.
  • At the same time, diagnoses are rising in people under 50, which has become a major topic in recent news and expert forums since the early 2020s.

What you can do about it

Even though no one can eliminate risk completely, you can lower it:

  • Eat more fiber‑rich foods (fruits, vegetables, whole grains) and limit processed and red meats.
  • Exercise regularly, maintain a healthy weight, avoid smoking, and limit alcohol.
  • Follow screening recommendations for your age and risk level, because removing polyps is one of the most effective ways to prevent colon cancer.

If you are asking “why is colon cancer” because of personal symptoms (blood in stool, changes in bowel habits, unexplained weight loss, persistent abdominal pain), you should contact a doctor or urgent care promptly to be evaluated.

Information gathered from public forums or data available on the internet and portrayed here.