Scientists based at Washington University School of Medicine in St. Louis pooled data from all 20 studies that have previously looked at this association, to produce the most accurate figures yet showing low exercise levels are linked to bowel polyps.
The researchers found that people who took regular exercise were 16 per cent less likely to develop bowel polyps, and 30 per cent less likely to develop large or advanced polyps – which are more likely to develop into cancer.
The finding supports an earlier analysis by the same group, showing people who are physically active can reduce their risk of bowel cancer by a quarter.
Bowel cancer is the third most common cancer in the UK after breast and lung cancer. In the UK more than 38,000 people are diagnosed with the disease each year.
Lead author Professor Kathleen Wolin, based at Washington University School of Medicine in St Louis, US, said: “We’ve long known that an active lifestyle can protect against bowel cancer, but this study is the first to look at all the available evidence and show that a reduction in bowel polyps is the most likely explanation for this.
“Exercise has many benefits, including boosting the immune system, decreasing inflammation in the bowel and helping to reduce insulin levels – all factors which we know are likely to have an effect on bowel polyp risk.
“We hope these results will encourage more people to enjoy the many benefits of regular exercise as part of a healthy lifestyle, including a reduction in bowel cancer risk.”
Sara Hiom, director of health information at Cancer Research UK, said: “Evidence shows that keeping active could help to prevent thousands of cases of cancer every year and this study adds weight to evidence showing regular exercise can substantially cut the risk of bowel cancer.
“We’d recommend doing at least half an hour’s moderate exercise a day – such as brisk walking or anything that leaves you slightly out of breath. Getting enough physical activity will also help you keep a healthy weight, which is one of the most important ways of reducing the risk of cancer.”
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Wolin K., et al, Physical activity and risk of colon adenoma: a meta-analysis (2011), British Journal of Cancer, doi: 10.1038/sj.bjc.6606045