Soya intake and cancer risk
The interest in soy originates from geographic epidemiology: the observation that populations consuming a lot of soy, particularly those in eastern Asia, have a significant lower incidence of cancer (1). For example, when incidence rates of cancers of the colon, rectum, female breast, and prostate are compared among native Chinese (Shanghai), Chinese-American, and American populations, it was noted that Americans had fourfold higher age-adjusted rates of colon cancer, and twofold higher rates of rectal cancer than Chinese (2). Incidence rates of colon and rectal cancers in Chinese-Americans were nearly equal to the American rates, suggesting that the risk for tumour development in the lower intestinal tract is rapidly increased with transition to the US diet. Rates of prostate cancer and postmenopausal breast cancer were 26-fold and 10-fold higher in Americans than in native Chinese, whereas the rates for Chinese-Americans were intermediate (2). Thus health advantages are notably reduced when Asians adopt a Western lifestyle and eating habits. Another study reported age-adjusted prostate cancer incidence rates for Japanese men born in the US to be four times higher than for native Japanese men (3). There is much evidence to suggest that diets containing large amounts of soybean products are associated with overall low cancer mortality rates, particularly for cancers of the colon, breast and prostate. It is believed that supplementation of human diets with certain soybean products, shown to suppress carcinogenesis in animals, could markedly reduce human cancer mortality rates (4). Not only in hormone-dependent cancers (breast cancer and prostate cancer), but also in many other cancers, isoflavones could be interesting. Isoflavones have an inhibiting action on a certain number of enzymes which intervene in the cancerous processes. Genistein is a powerful inhibitor of the protein tyrosin-kinase and DNA topo-isomerases (important in the control of cell multiplication). Moreover genistein has not only a direct effect on the proliferation of the tumours but also an indirect effect by inhibition of the angiogenesis.
Please choose one of the links below to learn more about soya and cancers :
References :
- Adlercreutz H. Phytoestrogens: epidemiology and a possible role in cancer protection. Environ Health Perspect 1995;103 Suppl 7:103-12.:103-12.
- Yu H, Harris RE, Gao YT, Gao R, Wynder EL. Comparative epidemiology of cancers of the colon, rectum, prostate and breast in Shanghai, China versus the United States. Int J Epidemiol 1991;20:76-81.
- Shimizu H, Ross RK, Bernstein L. Possible underestimation of the incidence rate of prostate cancer in Japan. Jpn J Cancer Res 1991;82:483-5.
- Kennedy AR. The evidence for soybean products as cancer preventive agents. J Nutr 1995;125:733S-43S.
