Physical activity and exercise protect against bowel cancer

Keeping active can reduce the risk of bowel cancer

Amidst the usual flurry of scare stories, it makes for a pleasant change of pace when we have a positive and scientifically strong study to report in the area of cancer prevention.

One such story appeared last week. A new study published in the British Journal of Cancer showed that keeping physically active – walking, running, taking part in sport, or manual work – can reduce the risk of bowel cancer.

By (quite literally) taking simple steps, both men and women could reduce their risk of colon cancer – the most common type of bowel cancer – by a quarter.

We’ve talked about this message elsewhere, but it’s worth restating here, especially because bowel cancer is the third most common cancer in the UK. It’s important for people to know what they can do to reduce their risk of developing it.

This new work was a comprehensive review of the existing scientific evidence, taking the results of 52 previous studies into account.

The researchers found that several different types of physical activity, from occupational activity like manual labour, to more traditional leisure-time activity such as running or going to the gym, can all reduce the risk of bowel cancer.

Cancer Research UK recommends that you try to take half an hour’s “moderate” physical activity a day, five days a week.

“Moderate” activity should be enough to leave you feeling warm and slightly out of breath.  It doesn’t have to be strenuous, time-consuming or expensive – it can even include housework, gardening or walking briskly. In fact, a couple of studies included in the review even suggested that brisk walking is enough to reduce the risk of bowel cancer.

Why does being active reduce the risk of bowel cancer?

There are a few possible explanations and it could be one or a combination of these.

• It leads to regular bowel movements. This means that cancer-causing substances in undigested food pass through the bowel more quickly. It’s possibly  the same reason that bowel cancer is less common in people who eat lots of fibre.
• It reduces the levels of insulin and other hormones. At high levels, these substances can encourage the growth of tumours.
• It can reduce chronic (low level) inflammation in the bowel, which might otherwise lead to bowel cancer.
• It leads to higher levels of vitamin D, possibly because active people tend to spend more time outdoors in the sun.

One or more of these theories could be correct. Perhaps all of them are. Either way, the benefits of physical activity are clear, and they have been established through a significant amount of research in large numbers of people.

The benefits of keeping active aren’t limited to bowel cancer either. We also know that breast cancer, and possibly womb cancer, are less common among physically active women.

So if you want some tips for becoming more active, have a look at our Exercise and activity pages. Alternatively, why not sign up for one of Cancer Research UK’s many running events, such as Race for Life or Run for Moore. You’ll be helping us to raise funds for vital research, while making a start at reducing your risk.

-Ed

K Y Wolin, Y Yan, G A Colditz, I-M Lee (2009). Physical activity and colon cancer prevention: a meta-analysis British Journal of Cancer, 100 (4), 611-616 DOI: 10.1038/sj.bjc.6604917