Does bowel cancer screening really help (fewer deaths)?
For people between 45 and 75 with an average risk, bowel cancer screening is worthwhile and widely recommended. It demonstrably lowers the chance of developing bowel cancer, although the evidence for reducing deaths in the short term is less definitive than previously thought.
Yes, bowel cancer screening works. Many studies and international guidelines confirm that screening reduces both the number of new cases and deaths from bowel cancer. The American health guideline recommends screening for everyone between the ages of 45 and 75 with an average risk. Between 76 and 85, the decision is weighed individually; above 85, screening is no longer recommended.
The strongest direct evidence comes from the NordICC study, the largest study in people in this field. People who received an invitation for a one-time colonoscopy (a camera examination of the bowel) had an 18% lower chance of developing bowel cancer after ten years: the risk fell from 1.20% to 0.98%. It took 455 invitations to prevent one case. An important detail: only 42% of those invited actually went through with the colonoscopy. This means the figure underestimates the benefit for people who did participate.
The death figures from that same study are more nuanced. After ten years, the difference in deaths from bowel cancer was small and not clearly measurable: 0.28% versus 0.31%. Overall deaths were also nearly identical. This does not mean that screening does not help. Ten years may simply be too short a period for a slowly developing disease, and the low participation rate blurs the picture. Even so, these results temper earlier expectations.
Colonoscopy also carries risks. In the NordICC study, fifteen participants experienced a serious bleed after the removal of polyps. No perforations or deaths caused by the procedure occurred. The chance of complications is small, but it does factor into your personal decision.
The choice between methods makes a big difference for uptake. When people can choose from a stool test, colonoscopy, a CT scan of the bowel, or sigmoidoscopy, or are offered an alternative if they decline the first option, far more people take part. The best test is simply the test you actually do. Finally, bowel cancer is rising in people under 50, which is partly why the recommended starting age has been lowered to 45, although this change has not yet been adopted everywhere.
The claims are based on several large reviews, major guidelines, and one large European study (NordICC). The general agreement among experts is strong, but the direct evidence for a reduction in deaths from the only large study of this kind is not yet clear enough to be conclusive after 10 years of follow-up.
Is a colonoscopy the only way to detect bowel cancer early?
A colonoscopy is not the only way to detect bowel cancer early. Stool-based tests, CT scans and sigmoidoscopy are recognised alternatives. Choose the method you will actually use together with your doctor, and start from the age of 45.
Does eating a high-fibre diet help protect against colorectal cancer?
Eating more fibre, especially through whole grains, is consistently associated with a lower risk of colorectal cancer. Whether fibre itself is the cause has not been proven, but the association is large, consistent and has a sound biological explanation.
Which cancer screenings are worthwhile, and from what age?
Colorectal cancer screening from age 50 and mammography from age 40 have the best evidence base for the average person; lung cancer screening is only relevant if you have a heavy smoking history. Other screenings are only worthwhile in the presence of specific risk factors or inherited conditions.
Does eating processed meat such as sausage and ham give me colorectal cancer?
Eating a lot of processed meat measurably raises your risk of colorectal cancer by around 18-21%. Eating less sausage and ham, combined with more fibre, is the most evidence-backed step you can take yourself.
Does aspirin or ibuprofen protect against bowel cancer?
Aspirin demonstrably protects against bowel cancer in people with a hereditary elevated risk (Lynch syndrome) and in people under 60 with an unhealthy lifestyle, but for older adults or people with a low baseline risk the bleeding risks likely outweigh the benefits. Discuss it with your GP if you want to know whether this makes sense for you.
Does fasting or intermittent fasting help prevent cancer?
There is no evidence that fasting prevents cancer in people. Results from animal studies are promising but contradictory. If you want to address excess weight as a way to reduce risk, intermittent fasting can be a useful tool for that, but do not expect a direct effect on cancer risk itself.