It is estimated that more than one third of all cancers can be easily prevented.
Other than quitting a pack-a-day smoking habit, regular physical activity is the single most effective thing you can do to reduce your risk of cancer. That statement is not based on opinion it is a quantifiable fact. Exercise is safe in overdose and has a lower side effect profile than any medication we know of. If it was a drug, we’d put it in the water supply. If it was a product it would out-sell smartphones.
We’ve always known that regular activity improves many health outcomes from heart health to mental health but its role in cancer prevention and even cancer treatment is only just being understood and it is nothing short of astounding.
Exercise Prevents Cancer Far More Effectively than we ever predicted
A study comparing the leisure time activity of 1.44 million adults to rates of cancer showed a significant inverse relationship between cancer rates and exercise in 18-20 of the 26 cancer types studied. It suggests that exercise plays a role in preventing the vast majority of cancers and it is thought that there may be an even stronger association if we look at higher rates of exercise. (There was only one cancer, melanoma, which had a significant increase with exercise presumably due to increased UV exposure in outdoor activities). Countless other studies have demonstrated this trend and many are summarised in the table on this page.
Exercise can shrink and kill cancer cells and improve the effectiveness of existing cancer treatment
This is the really exciting part. New research shows that exercise can kill early tumours when they are at their most vulnerable and can shrink and kill established cancers. One incredible study compared exercising and sedentary rats with established cancers and showed that the exercising rats destroyed tumour growth. We think this is mostly by stimulating a part of the immune system called natural killer (NK) cells but there are other hormones and chemical mediators that play a role. It was also demonstrated that blood taken from rats immediately after exercise was effective in shrinking tumours in the lab.
So, What type of exercise is best?
Research is still filling in the details here. Exercising above 70% of our aerobic threshold stimulates the release of adrenaline which plays a key role in mobilising NK cells. All we can say with certainty is that there appears to be a dose-response relationship. It seems that increasing activity reduces risk but with a gradually decreasing return on investment. That means that the biggest gain you can make is to go from nothing at all to the ‘bare minimum’ of averaging 22 minutes of physical activity a day. Why precisely 22minutes? Well, that’s where the risk seems to escalate. If you get less than that your overall health risks are akin to smoking a pack a day, drinking a carton a night or having an illicit drug habit.
Take home message?
Play the percentages.
If you want to avoid cancer hit the big percentage points first. If you don’t smoke and exercise daily you’ve cut your risk of most cancers from a third to a half. The next tier of proven risk reduction is maintaining a healthy weight range, moderating alcohol, eating a high fibre unprocessed diet, limit processed meats and salt, be sun smart and reduce your risk of infections like hepatitis B and C.
(Notice there is no mention of superfoods, powerlines or specific food additives in the list of main risk factors.)