Phytic acid in soy

On their face, soybeans appear to be loaded with nutrients. They are mineral rich and contain just about the cheapest protein you can find. However, soy is high in phytic acid, an anti-nutrient, a substance which binds to zinc, iron, calcium, and magnesium in your digestive system. Your body will actually absorb less of the mineral content because the phytic acid clings to the minerals and reduces your body's ability to absorb them. In the case of grains, you can reduce phytic acid fairly easily by using sourdough techniques, sprouting them, and soaking them. Soaking beans is fairly effective as well. However, there are exceptions: phytic acid in oats is one; soy is another. The phytic acid in soy is difficult to remove in the home kitchen.

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, food scientists Sutardi and Buckle tested the level of phytic acid in soy after progressive stages of preparation and cooking. Some of their results are displayed in the figure at right. Researchers soaked the beans and then they boiled them. After each of these stages they found that the soybeans retained nearly 100% of the native phytic acid content. The researchers then steamed the beans and found a 15% reduction in phytic acid. Finally, the phytic acid levels were reduced significantly when the soybeans were fermented in the form of tempeh. The results were improved still more when the tempeh was fried and stored, but the graph shows how important is the fermentation step.

Your take-home lesson: If you are consuming soy, consume a fermented version. Tempeh and miso are both great fermented soy options

A great option in consuming fermented soy is miso soup. You can purchase miso paste at any Asian grocery store, gourmet market, or health food store. Making the soup is fairly simple. Watch the video below for instructions. The ingredients are all easy to find and the process is simple. To boot, there are few things more satisfying than miso soup.

Tempeh is a good option as well and also easily found in Asian groceries or health food stores. It is a simple addition to any stir-fry dish. If you want to be hard-core, you can even make the tempeh yourself. Watch the video below for instructions.

Some people do not worry about phytic acid in their food: phytic acid does have anti-oxidant properties, after all. Binding to iron is a great thing if you are high in iron. If your diet does not contain a lot of soy, perhaps you need not worry about this issue at all and enjoy a soy latte on occasion.

In the phytic acid video below, listen to a short commentary.