Regular physical activity dramatically reduces the risk of developing 13 types of cancer, according to research published in JAMA Internal Medicine.
The study pooled data from 12 US and European studies carried out between 1987 and 2004. It compared physical activity levels with the incidence rates of 26 different cancers.
Regular exercisers were 42 per cent less likely to develop oesophageal cancer, 26 per cent less likely to develop lung cancer, and 16 per cent less likely to develop colon cancer than people who did very little exercise.
These figures were reached by comparing the 10th percentile to the 90th percentile of participants grouped according to the amount of time they spent exercising.
Seven of the 12 studies focused on moderate exercise like brisk walking, dancing and gardening. Four of the studies concentrated on high-intensity exercise, such as running and competitive sports.
Researchers found that the link between inactivity and cancer remained regardless of body mass index or other lifestyle factors such as tobacco and alcohol consumption.
During an 11-year period, 186,932 incidences of cancer were identified among the 1.4 million people in the study.
The research also reveals that 31 per cent of people worldwide are not meeting recommended levels of exercise, and that higher levels of physical activity reduce the risk of developing any cancer by seven per cent.
Dr Steven Moore, the study’s lead author, said: ‘These findings support promoting physical activity as a key component of population-wide cancer prevention and control efforts.’
Dr Marilie Gammon, who reviewed the study, said it showed that ‘high v low levels of physical activity engagement are associated with reduced risk of 13 cancer types (including three of the top four leading cancers among men and women worldwide).
‘The widespread generalisability of these findings is reinforced by the suggestion the associations persist regardless of BMI or smoking status.’
This study puts forward a wider association between exercise rates and cancer than had previously been found — in the past exercise had only been linked to a decreased risk of endometrial cancer, colon and breast cancer. (Melanoma is the anomaly here, as exercise raises your risk. This is probably related to the amount of time spent outdoors.)
What causes this association is open to debate. The paper suggests the answer may lie in cell biology, pointing to a change in how our cells mediate stress, secrete hormones and control fat. Other possible factors are the reduction of inflammation, the improvement of immune function and a change in gastrointestinal transit time.
The study notes that there may be a significant amount of confounders, despite attempts to adjust for all known factors in cancer development. Self-reporting of exercise is also liable to bias.
All things noted, this is a study that states the bleeding obvious. Our bodies are designed to move: immobility kills. This paper extends what we already know about the positive health effects of regular exercise.
Research score: 3/5