People who lead an active lifestyle are up to a third less likely to develop polyps which can develop into bowel¹ cancer, according to a study.

一项研究显示，具有积极生活态度的人的身体有1/3的机会不会产生息肉，息肉可进一步发展至肠癌。

Regular exercise reduces the risk of developing polyps which can lead to bowel cancer
The report pulls together 20 previous studies looking at the link between exercise and the development of large polyps.

Bowel cancer is the third most common cancer in the UK.

More than 38,000 people are diagnosed with the disease each year.

The work was done by scientists from the Washington University School of Medicine in St Louis in the US.

Publishing their findings in the British Journal of Cancer, they say they have produced the most accurate figures yet that show low exercise levels are linked to bowel polyps.

They found that people who take regular exercise were 16% less likely to develop bowel polyps（息肉） and 35% less likely to develop large or advanced polyps.

Polyps - also known as adenomas（腺瘤） - are growths in the bowel and while they are not cancerous in themselves they can develop into cancer over a long period of time.

Cancer Research UK says most bowel cancers develop from a polyp and about 1 in 4 of us have one or more by the age of 50, while about half of us have them by the time we are 70.

But only a small fraction（部分） of polyps develop into cancer and it takes years for that to happen.

Exercise link

Professor Kathleen Wolin, one of the lead authors of the research, says the evidence now shows a clear link between exercise and a reduced risk of bowel cancer but it is not yet clear exactly why that link exists.

"There are a number of likely pathways but we don't know exactly. So for example exercise reduces inflammation in the bowel, which has been linked to bowel cancer.

"But exercise also reduces insulin levels and improves the body's response to hyperinsulinaemia (excess levels of insulin circulating in the blood), which again increases polyp risk.

"It also enhances the immune system and because people who exercise often do so outside, they get vitamin D, which is also important for bowel cancer.

"The reality is that exercise is acting² through more than one mechanism³. The upside is there are so many benefits all over the body, it is hard to pinpoint⁴."