“The evidence is fairly clear now that men and women who are physically active have a 30 to 40 percent lower risk of colon cancer compared to individuals who are not active,” says Harvard’s I-Min Lee, who examined dozens of studies.
Experts have several theories that might explain how physical activity protects the colon. ” It increases transit in the intestine, which makes food flow through fast,” says Lee. “So any carcinogens in the intestine have less contact with the cells that line the intestine.”
Another possibility is that regular exercise shores up the immune system. ” That would protect the body from any cancer, including colon,” she ads.
Than there’s the obvious: “Physical activity prevents weight gain, and the overweight have a higher risk of colon cancer,” says Lee.
How much movement is enough? “We don’t have precise data, but it looks like you need 30 to 60 minutes a day of moderate-intensity physical activity.” says Lee.
Regular exercise also appears to lower the risk of breast cancer by about 20 percent.
“We are not clear how much physical activity you need to reduce the risk of breast cancer,” says Lee. But it’s in the same ballpark as for colon cancer – between 30 and 60 minutes of moderate-intensity physical activity a day.”
As for some other cancers, she ads,”there’s some suggestive evidence, but it’s not as conclusive.”