Soy is high in phytic acid, a substance that binds iron, zinc, calcium, and magnesium in the digestive tract. Your body absorbs less of those key minerals because phytic acid essentially sticks to them and escorts them into your stool. In many foods, the phytate content is reduced by soaking, sprouting, fermenting, and ultimately cooking. However, phytic acid in soybeans is difficult to remove – you can soak and soak your soybeans and still retain high levels of this anti-nutrient.
Home cooks are faced with a key question: Is there an effective way to reduce phytates in soybeans? Can we benefit in any way from the mineral content of soybeans?
A 1985 study in the Journal of Applied Bacteriology, Sutardi and Buckle tested the level of phytic acid in soybeans after different stages of preparation. After soaking and boiling the soybeans, the researchers found that they retained almost 100% of this mineral inhibitor. They proceeded to steam the beans and found a 15% reduction. The levels were only significantly reduced when the researchers fermented the soybeans in the form of tempeh.
Keep these results in mind when buying soy milk and tofu. The soybeans in soy milk are soaked, strained, and cooked. Tofu has an additional step: a coagulant is added. Both products retain almost 100% of the phytates according to the 1985 study. When you look at your can of tofu and see that one of those 12-ounce cans has about 100 milligrams of magnesium, keep in mind that it will only absorb about 10% of it. that magnesium. Probably triple that absorption in a fermented soy product.
Home cooks benefit best if they learn fermentation techniques to prepare their soy foods. Soy milk can be fermented by diligent home cooks. Traditionally fermented tempeh and miso are available in many health food stores. These soy preparations will allow you to benefit from the mineral-rich soybeans.
