Bowel Polyps Explained: Causes, Foods and Cancer Risk

What are bowel polyps?

A bowel polyp is a small lump that grows on the inner lining of the large bowel (colon) or rectum. They are very common — many adults will develop one or more in their lifetime, often without ever knowing, because polyps rarely cause symptoms.

There are a few main types. Hyperplastic polyps are usually harmless. Adenomas and sessile serrated lesions are the ones that matter most, because a small proportion can slowly change into bowel cancer if they are left in place for many years. The reassuring part: that change is slow, and removing the polyp stops it.

What causes bowel polyps?

There is rarely one single cause. Polyps form when cells lining the bowel divide a little too eagerly, and several things make that more likely:

• Age — risk climbs from around 45–50 onwards.
• Family history of polyps or bowel cancer, or an inherited condition such as familial adenomatous polyposis or Lynch syndrome.
• Lifestyle — smoking, heavier alcohol use, being overweight and physical inactivity.
• Type 2 diabetes and longstanding inflammatory bowel disease.
• Diet — low in fibre and high in red and processed meat (more on this below).

Having one or more of these does not mean you will get polyps — it simply means screening is worthwhile, because polyps found early are easy to remove.

What foods are linked to bowel polyps?

People often ask which foods “cause” polyps. The honest answer: no single food causes them, but your overall eating pattern shifts the odds in either direction.

Linked to higher risk: diets heavy in red meat (beef, lamb, pork) and especially processed meats (bacon, ham, sausages, salami), low fibre intake, and regular alcohol.

Linked to lower risk: plenty of fibre from wholegrains, vegetables, fruit and legumes; adequate calcium and dairy; and a generally Mediterranean-style pattern. Fibre keeps the bowel moving and feeds a healthier gut microbiome.

Are bowel polyps cancerous?

Most polyps are not cancer. But because adenomas and sessile serrated lesions can become cancerous over a long period, they are treated as a warning sign worth acting on. This step-by-step change — from a normal polyp, to an advanced one, to cancer — usually takes years, which is what makes screening so effective. Remove the polyp, and you remove the risk it carried.

How are polyps found and removed?

Polyps are found at colonoscopy — a day-procedure where a thin, flexible camera examines the whole colon while you are gently sedated. If a polyp is seen, it is almost always removed in the same sitting using fine instruments passed through the scope (a polypectomy), then sent to pathology to confirm the type. Most patients feel nothing and go home the same day.

Stool tests such as the national bowel-screening kit (FOBT) are a useful first filter, but they cannot remove a polyp — a colonoscopy is the only test that both finds and treats them in one step.

When should you see a specialist?

Most polyps cause no symptoms, so screening from age 45–50 (or earlier with a family history) is the key. See your GP or a specialist sooner if you have rectal bleeding, a change in bowel habit, unexplained weight loss, tiredness from low iron, or a family history of bowel cancer. Rectal bleeding should never simply be assumed to be haemorrhoids — particularly over 45, or with any of those other features — it deserves proper assessment.

Reviewed by Dr Goutham Sivasuthan, FRACS, GESA-accredited — June 2026.

Frequently asked questions

What causes bowel polyps?

Most bowel polyps form as we age, when cells lining the colon grow a little out of step. Risk is higher with a family history of polyps or bowel cancer, smoking, heavier alcohol use, being overweight, type 2 diabetes, and a diet low in fibre and high in red or processed meat. Often there is no single cause — it is a mix of age, genetics and lifestyle.

What foods cause polyps in the colon?

No single food directly causes polyps, but eating patterns matter. Diets high in red and processed meat and low in fibre are linked to more polyps and higher bowel-cancer risk, as is heavy alcohol. Plenty of fibre from wholegrains, vegetables, fruit and legumes, along with adequate calcium and dairy, is associated with lower risk. Think pattern over any single food.

Are bowel polyps cancerous?

Most polyps are not cancer. But one type — adenomas and sessile serrated lesions — can slowly turn into bowel cancer over years if left in place. That is exactly why colonoscopy matters: removing these polyps interrupts the process before cancer can develop.

Can polyps be removed during a colonoscopy?

Yes. In most cases polyps are removed painlessly during the same colonoscopy, while you are sedated, using fine instruments passed through the scope (a polypectomy). They are then sent to pathology to confirm the type. You usually go home the same day.

If I have had polyps, how often do I need a colonoscopy?

It depends on the number, size and type of polyps found and your family history. Dr Goutham will give you a personalised surveillance interval — often three to five years — based on Australian guidelines and your pathology results.