How can I reduce my risk of colon polyps and colon cancer?

Dr Alan Desmond, MB, BcH, BAO, MRCPI, FRCP

Many of the patients who come to see me are worried about colon cancer (also called bowel cancer or colorectal cancer). This may be due to recent bowel symptoms or due to their personal family history. In the vast majority of cases, such a serious diagnosis can be ruled out once the appropriate tests have been completed. However, it is always worth considering what you can do to reduce your personal risk of developing colon cancer in the future. This is especially important if you have ever had colon polyps removed, or if you have previously been treated for colon cancer.

Colon cancer is the fourth most common type of cancer diagnosed in the UK. Every year more than 41,000 people are diagnosed with this serious and life-changing condition (1). Cancer Research UK estimate that more than half of all cases of colon cancer in the UK can be prevented by a healthy diet and lifestyle. Most cancers start as benign polyps which can be come pre-cancerous over time. If you are concerned about your personal risk of developing colon polyps or colon cancer, then there are several things that you can do to reduce your risk.

Maintain a healthy body weight

Being overweight or obese increases your risk of developing colon cancer. The risk is 48% higher for men who are obese (body mass index >30) compared to men who are a healthy weight (2). The larger your waist circumference, the higher your risk (3). The keys to reaching and maintaining a healthy body weight are a healthy diet and physical activity. Public Health England’s “Eatwell Guide” is an incredibly useful place to start if you wish to improve your diet. When this evidence-based guide to healthy eating was published in 2016, it was estimated that if every adult in the UK followed its recommendations, seventeen thousand new cases of colon cancer would be prevented every year. See our guide "What is A Healthy Diet" .

If you are struggling to get daily physical exercise, aim to start gently. Even a brisk 30 minute walk each day can be beneficial. The NHS Couch to 5k App has been used successfully by thousands of people and will gradually guide you to a more active lifestyle. You can download it for free here.

Eat plenty of fibre (more than 30g per day)

Unfortunately, with modern eating habits our diets can easily fail to provide enough dietary fibre (also called "roughage"). We can increase our fibre intake by making sure that we eat plenty of whole grain breads, wholewheat pasta, brown rice and unprocessed cereals. The NHS Eatwell Guide suggests that these foods should form more than one-third of the foods that we eat each day. For every 10g of whole grain fibre you consume daily, you will reduce your risk of colon cancer by 10% (4). A good fibre-rich breakfast is a great start to your day. You can get 7.5g of fibre from a bowl of Branflakes breakfast cereal or 4.5g from two Shredded Wheats. One large banana adds another 4g of healthy fibre. You should aim to consume  a minimum of 30g of fibre each day (5).

Eat your beans and greens

Vitamin B6 (also called pyroxidine) and vitamin B9 (also called folic acid), are important nutrients that help our bodies to maintain DNA stability and prevent the DNA damage that leads to colon cancer (6 & 7). Having a high consumption of foods which are rich in B vitamins has been associated with a 20% reduction in colon cancer risk (8). In patients who have had colon polyps removed, bean consumption may significantly reduce the risk of new polyps forming over time. In the US National Cancer Institute's Polyp Prevention Trial, patients who had had colon polyps removed were place on a healthy diet and followed for three years. The study found that participants who increased their bean consumption by 70g a day (less than a quarter of a can of beans) reduced their risk of developing more polyps by up to 65% (9). You can ensure that you are getting these benefits by eating your "beans and greens"; include plenty of leafy green vegetables, beans and whole-grains as part of your daily menu.

Avoid red meat and processed meat

Red meat (beef, pork, lamb, venison etc.) and processed meat (bacon, sausages, meat pies, cured hams etc.) have been strongly linked to increasing the risk of developing colon cancer.  Cancer Research UK estimates that 21% of colon cancer cases in the UK are caused by eating red and processed meats alone (1). That adds up to a startling 41,700 new cases of colon cancer caused by meat consumption every five years. Eating just 350 gram of processed meat each week (the equivalent of four sausages and three strips of bacon per week) increases your risk of colon cancer by about 18%. Eating unprocessed red meat such as steak also increases your risk of colon cancer, by about 17% for every 100g (3.5oz) consumed on a daily basis (10). If you would like to significantly reduce your risk of developing colon cancer in your lifetime, then eliminating red and processed meats from your diet is a great place to start.

Don't smoke (and if you do smoke, quit now)

Everyone knows that smoking causes cancer and this is just as true for cancer of the colon.  Large medical studies show that smokers have an 18-25% increased risk of developing colon cancer (11). This is due to the multiple cancer-causing chemicals found in cigarette smoke. The longer you smoke, the larger the risk. It is never too late to benefit from quitting cigarettes. You can learn more about getting help to quit by speaking to to your GP or pharmacist. You can get free help to stop smoking from NHS Smokefree.

Keep alcohol consumption to a minimum

While people are generally very aware of the link between smoking and cancer, the public are often less well informed of the links between alcohol and cancer. Cancer Research UK have estimated that 10% of cases of colon cancer are caused by alcohol consumption (12). Even moderate alcohol use can increase your risk. Just 30g of alcohol per day (that's less than half a bottle of wine or one pint of a 5% abv beer) can significantly increase your risk of colon cancer.

However, it's not all bad new on the beverage front. The US Diet and Health Study (which followed 489,706 men and women for over 10.5 years) found that drinking four or more cups of coffee per day was associated with a 15-26% lower risk of colon cancer, when compared to people who did not drink coffee at all (13).

If you have worrying symptoms, see your doctor

If you develop an unexplained change in your usual bowel habit (noticeably more frequent or less frequent bowel movements) or if you see blood or mucus in or on your bowel movement, please make sure that you discuss this with your GP. A quick check by your doctor may reveal a simple cause and if further reassurance is needed, they can refer you to see a specialist.

In the U.K. we have an excellent national Bowel Cancer Screening Programme ("BCSP"). At the age of 55 years you will be invited to have a brief camera examination of the lower bowel (flexible sigmoidoscopy) and when you are 60 - 75 years old you will be invited to send off a stool sample every two years. Taking part in  these screening  programmes has been show to significantly reduce your risk of developing colon cancer. Prevention is better than cure, so remember to take part.