一项大规模的日本人研究发现，大豆异黄醇无法对抗末期的摄护腺癌。
在这项最大型的研究中，审查日本传统富含大豆的饮食与日本人摄护腺癌发生率的相关性，结果得到了矛盾的结论：异黄醇的摄取量可减少局部的摄护腺癌风险，但是反而会增加末期摄护腺癌的风险。
这项共包含43,509名男性的前瞻性研究，发表于3月号的Cancer Epidemiology, Biomarkers & Prevention中，研究结果异黄醇对于摄护腺癌发展的影响，可能会依不同的疾病阶段而异。
其中一种可能的解释是，异黄醇可能会延迟潜伏的摄护腺癌发生，一旦肿瘤不再表现雌性激素受体且发展至末期，异黄醇就无法保护男性免于末期的摄护腺癌，甚至可能会增加恶化的风险，因为异黄醇会减少血清中的睪固酮。
另外一种可能是，末期和局部化的摄护腺癌可能属于不同的肿瘤亚型，所以对于异黄醇的反应不同。
目前的研究结果还无法理解末期和局部化的摄护腺癌对于异黄醇的反应为何不一样，因此研究人员建议，日本男性还是可以继续依照原本的饮食习惯，但是尽量避免服用异黄醇补充剂。
(资料来源 : Bio.com)
部分英文原文：
Cancer Epidemiology Biomarkers & Prevention 16, 538-545, March 1, 2007. Published Online First March 2, 2007;
doi: 10.1158/1055-9965.EPI-06-0517
Soy Product and Isoflavone Consumption in Relation to Prostate Cancer in Japanese Men
Norie Kurahashi, Motoki Iwasaki, Shizuka Sasazuki, Tetsuya Otani, Manami Inoue, Shoichiro Tsugane Japan Public Health Center–Based Prospective Study Group
Epidemiology and Prevention Division, Research Center for Cancer Prevention and Screening, National Cancer Center, Tokyo, Japan
Requests for reprints: Shoichiro Tsugane, Epidemiology and Prevention Division, Research Center for Cancer Prevention and Screening, National Cancer Center, 5-1-1 Tsukiji, Chuo-ku, Tokyo 104-0045 Japan. Phone: 81-3-3542-2511; Fax: 81-3-3547-8578. E-mail: stsugane@ncc.go.jp
The incidence of prostate cancer is much lower in Asian than Western populations. Environmental factors, such as dietary habits, may play a major role in the causation of prostate cancer. Although isoflavones have been suggested to show a preventive effect against prostate cancer in animal experiments, the results of epidemiologic studies are inconsistent. Here, we conducted a population-based prospective study in 43,509 Japanese men ages 45 to 74 years who generally have a high intake of isoflavones and low incidence of prostate cancer. Participants responded to a validated questionnaire, which included 147 food items. During follow-up from 1995 through 2004, 307 men were newly diagnosed with prostate cancer, of which 74 cases were advanced, 220 cases were organ localized, and 13 cases were of an undetermined stage. Intakes of genistein, daidzein, miso soup, and soy food were not associated with total prostate cancer. However, these four items decreased the risk of localized prostate cancer. In contrast, positive associations were seen between isoflavones and advanced prostate cancer. These results were strengthened when analysis was confined to men ages >60 years, in whom isoflavones and soy food were associated with a dose-dependent decrease in the risk of localized cancer, with relative risks for men in the highest quartile of genistein, daidzein, and soy food consumption compared with the lowest of 0.52 [95% confidence interval (95% CI), 0.30-0.90], 0.50 (95% CI, 0.28-0.88), and 0.52 (95% CI, 0.29-0.90), respectively. In conclusion, we found that isoflavone intake was associated with a decreased risk of localized prostate cancer. (Cancer Epidemiol Biomarkers Prev 2007;16(3):538–45)
