Shephard R J
School of Physical and Health Education, University of Toronto, Ontario.
Crit Rev Food Sci Nutr. 1996 Apr;36(4):321-39. doi: 10.1080/10408399609527728.
This review examines possible protection against various types of tumors from both occupational and leisure-time physical activity. A growing number of well-controlled studies suggest that both hard physical work and an active leisure reduce the overall incidence of cancer. Benefit is demonstrated most clearly for colonic tumors; here, benefit persists after control of the data for body mass index, and a likely mechanism is the speeding of colonic transit, with a resulting decrease in exposure to carcinogens. There are occasional reports of protection against tumors of the breast, reproductive tract, and other body organs. In some of these latter sites, potential mechanisms of protection include a suppression of sex hormone secretion and reduction of body fat depots, where androgens are converted to toxic estrogen derivatives. While vigorous athletic participation may well modulate hormone output, a reduction of body fat is a more likely explanation of any benefit from more moderate physical activity. Protection against cancer is unlikely to become a major argument for an active lifestyle, but it is nevertheless a useful byproduct of physical activity undertaken with other health objectives.
本综述探讨了职业性体力活动和休闲性体力活动对各类肿瘤可能的预防作用。越来越多严格对照的研究表明，高强度体力工作和积极的休闲活动都能降低总体癌症发病率。结肠癌方面的获益最为明显；在此，在控制体重指数数据后这种获益依然存在，一种可能的机制是结肠运输速度加快，从而减少致癌物暴露。偶尔也有关于预防乳腺、生殖道及其他身体器官肿瘤的报道。在其中一些部位，潜在的预防机制包括抑制性激素分泌和减少身体脂肪储存，雄激素在脂肪储存部位会转化为有毒的雌激素衍生物。虽然积极参加剧烈运动很可能调节激素分泌，但身体脂肪减少更有可能解释适度体力活动带来的任何益处。预防癌症不太可能成为倡导积极生活方式的主要理由，但它仍是出于其他健康目标进行体力活动的一个有益副产品。
