New research which shows that prescribing exercise to people recovering from cancer of the colon significantly reduces their risk of recurrence, improving survival rates by more than a third, could change the way the condition is treated. And not before time. The study, part funded by Cancer Research UK (CRUK) and presented at the weekend to the American Society of Clinical Oncology, may have made headlines, but oncologists have long understood that an active lifestyle can help to treat and prevent a number of different cancers.
A review of evidence in 2019 found that physically active women recovering from breast cancer were up to 40 per cent less likely to die from the disease than less active women, and there are early signs of a similar effect (30 per cent reduction) in men with prostate cancer.
Most of what is known about the relationship between cancer and exercise is based on observational studies which, in themselves, can’t prove a causal relationship. However, similar beneficial effects seen across multiple studies, and a number of plausible underlying mechanisms as to why exercise could help, suggest there is a direct link — and a powerful one.
• Exercise ‘better than drugs’ to stop colon cancer returning
Better still, being active reduces the chances of developing cancer in the first place. A 2016 meta-analysis of 126 studies found people who did the most exercise were about 20 per cent less likely to develop cancer of the colon than their sedentary peers. And other studies have shown a similar protective effect in breast, bladder, womb, stomach, oesophageal and kidney cancers. But how?
The first thing that springs to mind is that people who exercise regularly are more likely than their sedentary peers to lead healthier lifestyles, which is why researchers adjust their findings to allow for confounding factors such as smoking, weight and poor diet (although they can never completely exclude them). So there is more to it than that.
There are myriad other reasons that exercise might be both preventive and therapeutic. Being active can boost the immune system, it reduces inflammation, helps to maintain a healthy weight, and controls levels of hormones (see below) that can promote tumour growth, and it speeds up the transit of food through the gut (so exposure time to carcinogens in the bowel is reduced).
And if you do have cancer and need treatment like surgery or chemotherapy, the fitter you are the better you’re likely to fare — so much so that some cancer centres now offer their patients “prehab” diet and exercise programmes to try to improve both short-term recovery and longer-term outcomes.
• Read more expert advice on healthy living, fitness and wellbeing
Finally, there are the direct effects of being sedentary. Not only is exercise beneficial, but being inactive may be cancer promoting in itself through a range of metabolic and immune pathways. The human body is built to work and, like a car, tends to give fewer problems if it is used as intended.
So how much exercise is required? This isn’t clear yet, but most studies suggest the more the better, although you don’t have to start entering triathlons. For perspective, the active group of volunteers with cancer of the colon in this latest study undertook supervised activities that ranged from walking to circuit classes, aiming to do the equivalent in energy expenditure terms of a 30-minute jog or a 45-60 minute brisk walk, three to four times a week. So not that much really.
The take-home message is clear: stay as active as you can, for as long as you can. And it’s not just about cancer, of course; you will also reap all the other benefits, from stronger bones and muscles to reduced risk of heart attack, stroke and dementia. And while not the best way to shed excess weight in isolation (you have to do a lot of exercise to shift fat), it will also help you to maintain a healthier figure.
So here is a second take-home message: try to stay trim. I don’t need to spell out all the health consequences of carrying too much weight — everything from high blood pressure to type 2 diabetes — but I should end by highlighting the strength of the link with the risk of being diagnosed with a range of cancers. CRUK estimates that at least 1 in 20 new cancers in the UK are triggered by being overweight/obese, with fat around the midriff being the most dangerous type.
For more information on the study into the benefits of exercise in people with cancer of the colon visit news.cancerresearchuk.org.
Reasons to stay active
• Excess fat is thought to impair the immune system’s ability to recognise, attack and neutralise errant cells that have mutated and are turning, or have turned, into cancers. Being overweight also alters metabolic conditions in the body that may promote or nurture the growth of such cells.
• Fatty tissue in women can produce oestrogen, a sex hormone which may fuel the growth of some types of breast cancer. Lots of fat, particularly around the abdomen, also boosts the activity of insulin-like growth factor (IGF), which can encourage tumour growth.
• In post-menopausal women, the chance of developing breast cancer is 50 per cent higher for those with the highest waist-to-hip ratios (a measure of abdominal obesity) than those with the lowest, and 30 per cent higher in men (who get breast cancer too, albeit rarely).
