Some population studies already associated physical activity with a reduced risk of cancer, but the specific quantity and intensity of physical activity needed to reduce premature overall mortality is based on a few prospective population-based studies.
According to study findings published in the British Journal of Sports Medicine, Men who exercise hard are less likely to die from cancer.
The autors assessed a population-based sample of 2560 men from Finland with no history of cancer at baseline. A total of 181 cancer-related deaths occurred during the average follow-up of 16.7 years.
Physical activity was measured in metabolic units (METs or metabolic equivalents of oxygen consumption).The 12-month leisure-time physical activity questionnaire was used to assess physical activity. Physical activity was reported as frequency per month, duration per session, and intensity of the activity — recreational, conditioning, or completive.
Mean age of the men at follow-up was 53.0 years. The subjects had a mean intensity of leisure-time physical activity of 4.5 MET and mean duration of physical activity of 462 minutes per week. 27% of the subjects exercised for less than 30 minutes per day.
An increase of 1.2 MET in the mean intensity of leisure-time physical activity was associated with a 0.85 decrease in the relative risk of cancer mortality, after adjusting for age, smoking, alcohol consumption, body mass index, and total caloric, fiber and fat intake. This was mainly due to decreased risks of lung and gastrointestinal cancers.
Compared with men with physical activity of less than 3.7 MET, those with physical activity of more than 5.2 MET had a lower cancer mortality (Relative risk 0.64).
The mean intensity of physical activity was related to cancer deaths only among those who exercise more than 30 minutes per day on average.
The mechanisms by which physical activity may prevent cancer include beneficial effects on energy balance and body mass, intestinal transit time, hormonal concentrations, prostaglandin levels, and antioxidant enzymes activities.
Other mechanisms that may protect against cancer are via immunological mechanisms, effects on insulin regulation and oxygen-free radicals.
Source : Br J Sports Med 2009.