Can colon cancer be prevented?
Largely, yes. Most colon cancers start as a polyp that takes years to become malignant, and if it is removed first the cancer never develops. On top of that, lifestyle habits affect anyone's risk.
More information on what colon cancer is.
Which habits lower the risk?
The ones the Spanish Ministry of Health lists as risk factors people can act on: not smoking, limiting alcohol, avoiding excess weight, exercising regularly and eating more fiber, fruit and vegetables and less fat, red meat and processed meat.
- Fiber, fruit and vegetables: wholegrains, pulses, fruit and vegetables every day.
- Red and processed meat: in 2015 the International Agency for Research on Cancer (IARC) classified processed meat (cold cuts, sausages, bacon) as carcinogenic to humans and red meat as probably carcinogenic. It is worth eating less of both, especially processed meat.
- Exercise and weight: a sedentary lifestyle and obesity raise the risk.
- Alcohol and tobacco: both raise the risk.
Habits lower the risk but do not remove it. That is why they do not replace screening.
How is screening done?
In Spain, with a fecal occult blood test every two years between ages 50 and 74, for people with no symptoms and no family history. If the test is positive, a colonoscopy follows. The extension from age 69 dates from April 2026 and each region has five years to apply it. We explain it in colorectal cancer screening.
Colonoscopy is also a valid screening test. In the United States, the USPSTF recommends it every 10 years if it is normal. It shows the whole colon and allows polyps to be removed on the spot; in exchange, it needs bowel preparation and sedation.
Who needs to start earlier or have colonoscopies?
People at higher risk than the general population, who need their own assessment rather than the program:
- Close relatives with colorectal cancer, especially several relatives or relatives diagnosed young. The usual approach is to start before 50, with colonoscopy.
- Hereditary syndromes such as Lynch syndrome or familial adenomatous polyposis. For Lynch syndrome, the 2021 European guideline recommends colonoscopies from age 25 or 35 depending on the gene, every 2 to 3 years.
- Previous polyps or colorectal cancer.
- Inflammatory bowel disease (ulcerative colitis or Crohn's disease), which needs surveillance colonoscopies after some years of disease, as advised by the gastroenterologist.
Why does removing polyps prevent cancer?
Because most colorectal cancers start from an adenomatous polyp, and that change usually takes years. If the polyp is removed during colonoscopy, the cancer never forms.
The National Polyp Study, the classic study on this question, followed 1,418 patients who had adenomas removed and found 76% to 90% fewer cancers than expected when compared with reference groups. Types of polyps, how they are removed and how often to be checked afterwards: colon polyps.
Which symptoms should I report without waiting for screening?
Blood in the stool, red or black, a change in bowel habits lasting more than two or three weeks, persistent abdominal pain, unexplained weight loss or anemia with no clear cause. Screening is for people without symptoms; with symptoms you need to see a doctor. We explain it in blood in stool.
More on what we know about colon cancer.
Does aspirin help prevent it?
For people with Lynch syndrome, the European guideline says daily aspirin has a high probability of lowering cancer risk. Outside that group it is not recommended to take it on your own to prevent colorectal cancer, because it raises the risk of bleeding. It is a decision to make with your doctor.
Do you have a family history or risk factors? If you are not sure when to start check-ups or with which test, request an assessment with our team.
Frequently asked questions
Can colon cancer really be prevented?
Largely, yes. Removing polyps during colonoscopy stops them from turning into cancer: in the National Polyp Study there were 76% to 90% fewer cancers than expected in patients who had them removed. Lifestyle habits also lower the risk.
Which foods raise the risk?
Processed meat, which IARC classifies as carcinogenic, and red meat, which it classifies as probably carcinogenic. A diet low in fiber, fruit and vegetables is also linked to higher risk.
At what age should I start screening if I have no family history?
At 50, with a fecal occult blood test every two years up to 74. If it is positive, a colonoscopy is done.
When should I start screening earlier because of family history?
With close relatives who have had colorectal cancer, the usual approach is to start before 50 with colonoscopy; the age depends on how many relatives are affected and how old they were at diagnosis. For Lynch syndrome, the European guideline recommends colonoscopies from age 25 or 35 depending on the gene.
Does a preventive colonoscopy hurt?
It is done under sedation, so you do not feel it, and it does not require a hospital stay. For most people the hardest part is the bowel preparation in the days before.
Do smoking and alcohol affect colon cancer risk?
Yes, both raise the risk. Stopping smoking and limiting alcohol are part of prevention.
Which symptoms should make me see a doctor?
Blood in the stool, a change in bowel habits lasting more than two or three weeks, persistent abdominal pain, unexplained weight loss or anemia with no clear cause.
References
- Spanish Ministry of Health. Colorectal cancer screening program: frequently asked questions (in Spanish).
- Bouvard V, Loomis D, Guyton KZ, et al. Carcinogenicity of consumption of red and processed meat. Lancet Oncol. 2015;16:1599-1600. doi:10.1016/S1470-2045(15)00444-1.
- Winawer SJ, Zauber AG, Ho MN, et al. Prevention of colorectal cancer by colonoscopic polypectomy. N Engl J Med. 1993;329:1977-1981. doi:10.1056/NEJM199312303292701.
- U.S. Preventive Services Task Force. Colorectal Cancer: Screening (2021).