More info: Soy isoflavones are phyto-endocrine disrupters. At dietary levels, they can prevent ovulation and stimulate the growth of cancer cells. Eating as little as 30 grams (about 4 tablespoons) of soy per day can result in hypothyroidism with symptoms of lethargy, constipation, weight gain and fatigue.
Interesting. Soy makes up about 12% of the diet of the elders on Okinawa. That's a lot of soy. These same people live longer than anyone else on the planet and have some of the lowest rates of cancer and Alzheimer's in the world. There have been several studies conducted on Okinawans and it's been shown that Okinawans are at extremely low risk for hormone–dependent cancers, including cancers of the breast, prostate, ovaries, and colon. Compared to North Americans, they have a 80 percent less breast cancer and prostate cancer, and less than half the ovarian cancer and colon cancer.
Is soy the reason for this? I don't know but don't you find it interesting that the lowest cancer rates in the industrialized world are found in an area that also has the highest per-capita consumption of soy?