Myth: Use of soy as a food dates back many thousands of years.
Truth: Soy was first used as a food during the late Chou dynasty (1134-246 BC), only after the Chinese learned to ferment soy beans to make foods like tempeh, natto and tamari.

Myth: Asians consume large amounts of soy foods.
Truth: Average consumption of soy foods in Japan and China is 10 grams (about 2 teaspoons) per day. Asians consume soy foods in small amounts as a condiment, and not as a replacement for animal foods.

Myth: Modern soy foods confer the same health benefits as traditionally fermented soy foods.
Truth: Most modern soy foods are not fermented to neutralize toxins in soybeans, and are processed in a way that denatures proteins and increases levels of carcinogens.

Myth: Soy foods provide complete protein.
Truth: Like all legumes, soy beans are deficient in sulfur-containing amino acids methionine and cystine. In addition, modern processing denatures fragile lysine.

Continue reading at: http://www.westonaprice.org/soy-alert/myths-and-truths-about-soy