Phytic Acid in Soy - Can We Reduce It?

In many foods, the phytate content is reduced by soaking, sprouting, fermentation, and ultimately, cooking. However, the phytic acid in soy 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 soy? Can we benefit somehow from the mineral content of the soybean?

A 1985 study in the Journal of Applied Bacteriology, Sutardi and Buckle tested the level of phytic acid in soy after different stages of preparation. After soaking and boiling the soy beans, the researchers found that they retained nearly 100% of this mineral-inhibitor. They proceeded to steam the beans and found a 15% reduction. The levels were only reduced significantly when researchers fermented the soybeans in the form of tempeh.

Keep these results in mind as you shop for soy milk and tofu. Soybeans in soy milk are soaked, strained, and cooked. Tofu has an additional step - a coagulant is added. Both of these products retain nearly 100% of the phytates according to the 1985 study. When you look at your tub of tofu and see that one of those 12 ounce tubs has 100 milligrams or so of magnesium, keep in mind that you will only absorb about 10% of that magnesium. You would likely triple that absorption in a fermented soy product.

Home cooks are best served by learning fermentation techniques to prepare their soy foods. Soy milk can be fermented by diligent home cooks. Traditionally fermented tempeh and miso are both available in many health food stores. These soy preparations will allow you to benefit from the mineral-rich soybean.