Words: Dr. Juliet McGrattan
Cancer Research UK tells us that every two minutes someone in the UK is diagnosed with cancer. Also one in two people born after 1960 will be diagnosed with some form of cancer during their lifetime.
These are scary statistics and it’s unlikely that any of you reading this haven’t been affected by cancer in some way. I don’t need to tell you that the consequences can be devastating. Anyone who has been told they have cancer will be seeking ways to improve their chances of survival and others will be wondering what they can do to reduce their risk of developing it.
While I’m in no way suggesting you can definitely avoid cancer through running, I think it’s important that the benefits of exercise in cancer prevention and treatment are more widely known and, quite honestly, shouted about. When the very word cancer can strike fear into our hearts, it’s great to have something with an evidence-base for benefit, something we can all do and share with others. Let’s look at the relationship between cancer and running.
The cells in our body contain DNA, which is the genetic code for the cell and gives it instructions about how to behave. If the DNA is damaged or changed (known as a mutation) then the cell’s behaviour alters. The usually ordered cell division and reproduction gets out of control, with the mutated cells over-multiplying and forming clumps and lumps called tumours. The triggers for DNA damage are varied and include smoking and UV exposure, but they can be spontaneous, happening by chance. Some mutations are inherited which is why many cancers run in families. Cells do quite a bit of housekeeping, tidying up and repairing damaged DNA, but sometimes the damage is too severe.
Cancer Research UK advises that 42 per cent of cancers in the UK each year are linked to lifestyle factors – and keeping active could help to prevent 3,400 cases of cancer annually. So how does being active reduce the risk of developing cancer? Well, like all medical things, it’s complicated and we don’t fully understand all the mechanisms yet, but some of them are becoming clearer.
DNA damage can be triggered by stress inside a cell. A type of stress, called oxidative stress, builds up when we don’t use the energy that cells are generating for us. If we’re sedentary, a charge builds up across the cell wall, which is released in the form of free radicals. They damage the DNA and can cause the cell to die early. Early cell death causes inflammation. Cancer is, in part, due to a low grade, long-term inflammation in our bodies and reducing this inflammation is one way we can lower our risk of cancer.
Physical activity, such as running, acts as an anti-inflammatory. When we move frequently, less oxidative stress builds up in the cells, resulting in less DNA damage, less early cell death and therefore less inflammation. Our harmful, internal fat stores, called visceral fat, also cause inflammation and regular exercise is a really effective way to reduce visceral fat.
While obese people have higher risks of certain cancers and losing weight can help to reduce them, the benefits of exercise are not purely about weight loss. There are separate, independent benefits and risk reductions too. Exercise is good for all, regardless of weight.
When muscles are activated they release substances called myokines which zoom around in our circulation and have an anti- inflammatory action, this can last for several hours after exercise.
The immune system springs into action when viruses or other invading cells, such as cancer cells, are discovered in the body. Cells called natural killer cells form part of the arsenal of weapons the body uses to protect itself. When cancer cells are discovered the natural killer cells recognise them as abnormal and try to destroy them.
Moderate exercise has been shown to increase the number and activity of natural killer cells. More research is needed in the area though, particularly into what effect strenuous endurance exercise has on natural killer cell levels. Some studies have shown a reduction in their numbers.
Certain hormones have also been linked to cancer. Oestrogen is the main female hormone and some breast and womb cancers are stimulated by oestrogen. Exercise lowers oestrogen levels and women who exercise regularly throughout their life can have a 20 to 30 per cent reduced risk of developing breast cancer compared to inactive women. For women who’ve had breast cancer, regular exercise can help to reduce the risk of recurrence by 20 per cent.
Bowel cancer is the third most common cancer in women in the UK. The evidence for the benefit of regular exercise as a preventative measure is strong. A woman running regularly could be reducing their risk of developing cancer of the colon by as much as 40 to 50 per cent. If you’ve been treated for bowel cancer, exercising regularly can help lower the chances of it recurring by up to 50 per cent too. As well as exercise helping reduce inflammation in the body, it helps the passage of faeces through the gut, reducing the contact of carcinogens (cancer forming substances) with the bowel wall.
As the benefits of exercise are becoming better known, doctors, nurses and health care professionals are advising patients to be as physically active as they can, to help prevent cancer but also to treat it.
Sarah Russell is an exercise specialist and qualified L4 cancer rehabilitation specialist, coach and runner. She trains nurses and works with bowel cancer patients, teaching them how to rehabilitate after bowel surgery. She told me, “Patients are often surprised to learn they can exercise when they have cancer, especially during treatment. Cancer treatments such as chemotherapy, radiotherapy and surgery all wreak havoc on the body. Patients talk about a deep, overwhelming fatigue that doesn’t get better with rest. However, research has shown ‘cancer-related fatigue’ is best treated with low-to-moderate intensity exercise. Brisk walking is ideal, it can energise patients and they’re often surprised to find it doesn’t make them more tired. In fact it helps them feel better and gives them energy.”
It isn’t easy to find the energy or motivation to exercise when you’re undergoing cancer treatment. But, as Russell points out, “There are many physical benefits, including preventing muscle loss and weight changes, maintaining cardiovascular fitness and being fitter, which can help the patient withstand the treatment and make a faster recovery. However, I think the main role is a psychological one, the sense of control it gives patients, at a time when they can feel as if everything is out of their control.”
For many cancers, the survival rates are better in those that are physically active. “Patients are always telling me how frustrated they are when friends and family tell them to rest and come round to mow the lawn or walk the dog,” says Russell. “While the offer of help is caring, it can be disempowering. The most loving thing you can do for them is take them out for a walk, encourage them to be active and help them do as much as they can for themselves.”
However, during cancer treatment you’re unlikely to be able to continue with your normal exercise regime. So how do you know how much is too much? Russell advises, “You can’t say ‘listen to your body’, because if patients did that, they would rest. Sometimes you have to push through the fatigue a little, try it and see how you feel. It’s a fine line. Too much will leave you feeling shattered for days. So use a fatigue scale of some sort (such as on macmillan. org.uk) to monitor your fatigue levels, and only try short sessions of low-intensity exercise to begin with; walking, cycling or swimming are all great. Monitor the reaction and see how you feel. Exercise during cancer treatment is about keeping moving. Some days will be better than others. The focus needs to be on mental wellbeing and general physical health… just keep moving as much as you can. If you’ve been a runner before, it’s OK to pack the sports watch away for now and just go out to walk and listen to the birds instead.”