Exercise Reduces Risk for Premature Death from Cancer

A study from Finland has shown that men who exercised for at least 30 minutes a day at moderate to high intensity halved their risk of dying prematurely from cancer, mainly gastrointestinal and lung cancer. The results were published online July 28, 2009 in the British Journal of Sports Medicine. Physical inactivity over a person's lifespan might be a "key factor in the initiation of cancer development," the authors note.
"We found a 50% reduction in the risk of dying prematurely from cancer," Dr. Kurl pointed out. Exercise also improves well being and confidence, and leads to better sleep and weight control, he added.
The study was carried out in men, but Dr. Kurl said he expects to see similar results in women.

Intensity of Physical Activity Was Important

The reduction in the risk for premature death from cancer was seen in men who exercised for more than 30 minutes every day, and with an intensity that was moderate to high, Dr. Kurl noted. The activities they performed included jogging, swimming, cycling to work, and gardening or yard work, he said
Exercise intensity was measured in metabolic equivalents of oxygen consumption (METs). The average intensity of jogging was 10.1 MET, of skiing was 9.6 MET, of ball games was 6.7 MET, of swimming was 5.4 MET, of rowing was 5.4 MET, of cycling was 5.1 MET, of gardening/farming/yard work was 4.3 MET, and of walking was 4.2 MET.
"Anything above an average of 4 MET can be considered [to be] moderate-intensity exercise," Dr. Kurl told Medscape Oncology.
"The intensity of leisure-time physical activity should be at least moderate so that the beneficial effect of physical activity for reducing overall cancer mortality can be achieved," the authors write.
The results show that at least moderate-intensity physical activity is more beneficial than low-intensity physical activity in the prevention of cancer, the authors note. This finding is consistent with American consensus statements suggesting that at least moderate-intensity physical activity is needed to prevent chronic diseases caused mainly by cardiovascular disease, they add.

Several Mechanisms Involved

"Our results indicate that those with an active lifestyle have a decreased risk of gastrointestinal cancers," the researchers note. This finding may be due to changes in energy balance, which includes body mass, which is particularly important for colon cancer, they note. In addition, the increased gut motility with exercise training decreases gastrointestinal transit time, thereby reducing the contact time between fecal carcinogens and the colonic mucosa, as well as allowing less opportunity for the initiation of carcinogenesis and colonic cell division and proliferation. There may also be an affect on insulin and fat metabolism, they add.
Medscape Medical News, July 27, 2009.