Exercise can protect against cancer, new findings from two animal studies suggest.
One showed that physically active mice with 24-hour access to running wheels took longer to develop skin tumours. The other found that exercise and a restricted diet reduced the number of pre-cancerous bowel growths in mice.
In the first experiment, mice were exposed to ultraviolet B rays, one of the harmful components of sunlight. Professor Allan Conney, who led the research at Rutgers University, New Jersey, USA, suspects that exercise increases levels of cell suicide, or apoptosis.
The programmed death of defective cells is one way the body protects itself against cancer, reports Guardian.
The other found exercise and a restricted diet reduced the number of pre-cancerous bowel growths. In the first, mice were exposed to ultraviolet B rays, one of the harmful components of sunlight.
Professor Allan Conney, who led the research at Rutgers University, New Jersey, said the findings suggest exercise increases levels of "cell suicide" - the death of defective cells, informs Scotsman.
Her findings included some surprises, though. The exercising mice had a lower body weight but retained more fat during the study than the controls – perhaps because the other mice were so sick they were wasting away, Colbert suggests.
And, in addition to higher levels of corticosterone, the runners also showed raised levels of insulin-like growth factor-1 (IGF-1), a hormone associated with the onset of cancer, which perplexed the researchers. This may be a result of the exercising mice laying down more muscle, Colbert says.
The next step in the research is to see what effect exercise alone has on polyp number and development, by allowing the mice to eat as much as they like, she adds.
Although both studies appear to show that exercise has a positive effect on reducing cancers, the researchers point out that the exact biological mechanisms are still unclear. “It is not yet known whether exercise decreases the risk of sunlight-induced cancer in humans,” Conney points out, according to New Scientist.