Soy proponents like to point to low rates of breast cancer in Asian countries as proof that consumption of soy can protect against cancer. They fail to mention that Asians have high rates of other types of cancer compared to westerners. A new study conducted in Singapore found that consumption of soyfood was associated with higher rates of bladder cancer, and the relationship was statistically significant. Similar results were obtained for soy protein and soy isoflavones. The soy-cancer relationship became stronger when the analysis was restricted to subjects with longer duration of follow-up (Cancer Epidemiol Biomarkers Prev 2002 Dec;11(12):1674-7).
Soy and Breast Cancer
The only food associated with protection against breast cancer is miso, according to a recent study performed in Japan. Women who consumed three or more bowls of miso soup containing about 25 mg genistein daily had approximately half the risk of breast cancer. Consumption of other foods containing soy, such as soybeans, tofu, deep-fried tofu or other fermented soybean products was not associated with reduced risk of breast cancer (J Natl Cancer Inst 2003;95:906-913). What this means is that Japanese women on a traditional diet eating small amounts of soy in a nourishing soup (probably fish broth) have lower rates of breast cancer. Eating large amounts of modern soy foods will not protect against breast cancer.
Soy and Migraine
A recently published case report details the onset of migraine associated with the use of soy isoflavone supplements (Neurology 2002 Oct 22;59(8):1289-90).
Soy and the Amazon
Youâ€™ve all seen the t-shirts about saving the Amazon by avoiding beef. Now we find out the biggest threat to the Amazon jungles is not cattle raising but soy production. Cultivation of soybeans has lead to a 40 percent increase in deforestation last year, to nearly 10,000 square miles. Even the pastures where cows grazed until recently are being converted to soy. (New York Times, September 17, 2003)