2015考研英语阅读集中练Cancer and Staying Fit_大学英语阅读

2015考研英语阅读集中练Cancer and Staying Fit

　　Recently two large, carefully designed studies suggested exercise may work through more than just hormonal mechanisms linked to estrogen. In a study published last month in the Archives of Internal Medicine, researchers speculated that exercise might affect tumor aggressiveness. The researchers found that long-term moderate or strenuous activity over a lifetime cut risk for developing estrogen-negative invasive breast cancers . Since fewer therapies are effective against estrogen-negative cancers, that s heartening news. Some earlier research on exercise suggests it lowers risk for estrogen-positive cancers, too. Scientists are also looking beyond estrogen at the effects exercise has on insulin, leptin and certain growth factors.

　　Regular exercise early in life, particularly around puberty, and exercise vigorous enough to suppress other reproductive hormones may make a difference, too. A 2005 multicenter study on lifetime activity matched more than 4,000 white and black breast-cancer survivors with controls. Researchers found a 20 percent decrease in breast-cancer risk for the most versus least active women.

　　After a woman is diagnosed, exercise can dramatically lengthen survival and lower the odds of another tumor. For up to 14 years, the Nurses Health Study tracked nearly 3,000 participants diagnosed with breast cancer. Researchers found that recurrence rates and deaths from breast cancer dipped 26 to 40 percent among those who exercised most, compared with their sedentary peers. Brisk walking or equivalent energy-burning activity for three to five hours a week-about 30 minutes a day-netted the biggest benefits. But even being active for one to three hours a week reduced risk to some degree。