Two new studies appearing in the May 13 issue of the journal "Carcinogenesis" say that proper exercise could confer some protection from skin and bowel cancers. The two studies were conducted on laboratory animals, but the researchers claim to have honed in on the mechanism that could cause this protective effect.
The first study conducted at Rutgers University, New Jersey, focused on skin cancer in mice. The researchers exposed the mice to ultraviolet B light (UVB), which is a high-risk factor for causing skin cancer. They found that mice that had an uninterrupted access to running wheels took longer to develop the skin tumors. These mice also had reduced body fat as compared to the other mice that did not have access to the wheels.
Dr Allan Conney, Garbe Professor of Cancer and Leukemia Research and the lead researcher in the study suggested that exercise could actually increase the physiological cell-death process and hence these mice showed delayed development of tumors although they were at significant risk. "Our studies may be the first to suggest an apoptotic mechanism for the effect of voluntary exercise in the development of cancer. This effect may also play an important role in the mechanism and warrants further investigation, bearing in mind the growing rates of obesity in the Western world, particularly in the USA and UK," he said.
The second study at the University of Wisconsin-Madison showed that exercise coupled with a reduced calorie intake protected from the development of polyps, which are pre-cancerous conditions leading to the eventual development of bowel cancer. Lead researchers Dr Lisa Colbert theorized that a negative energy balance, which is produced by increasing energy output through exercise, could be the reason for the inhibition of polyps.
"These data suggest that voluntary exercise that induces a negative energy balance protects against the onset of cancer in these mice, but that the mechanism is unlikely to be related to body composition, IGF-1 or corticosterone," Dr Colbert said. "On average there were 16 polyps per mouse in the exercising mice compared to 22 polyps in the control mice, a decrease of 25%."
