Recent human clinical trials in the US, Europe and Australia have shown that consumption of soy protein high in isoflavones contributes heavily to these health differences. The Japanese ingest substantial amounts of soy isoflavones because they typically eat 5 or more servings of soy protein per day. In comparison, the American diet contains almost no soy protein or soy isoflavones. Asian women and men excrete 100 - 1000 times more soy isoflavones in their urine than Americans. Japanese women also have much lower rates of heart disease, osteoporosis and many cancers including breast and endometrial cancers compared to their American counterparts.
Japanese men have much lower rates of heart disease and death from prostate cancer.
The key to soy's benefits is eating enough of it on a daily basis to make a real health difference. The traditional Japanese eat 4 - 6 servings of soy per day giving them a large amount of soy isoflavones. Our diet contains almost no soy. Unless we grow up eating soy, it simply tastes bad. New food technologies have allowed us to eliminate the bad taste and chalky texture of soy.