The soybean also contains hemagglutinin, a clot promoting substance that causes red blood cells to clump together. Trypsin inhibitors and hemagglutinin have been rightly labeled growth depressant substances. Fortunately they are deactivated during the process of fermentation. However, in precipitated products, enzyme inhibitors concentrate in the soaking liquid rather than in the curd. Thus in tofu and bean curd, these enzyme inhibitors are reduced in quantity, but not completely eliminated.
Soybeans are also high in phytic acid or phytates.
Although not a household word, phytates have been extensively studied. Scientists are in general agreement that grain and legume based diets high in phytates contribute to widespread mineral deficiencies in third world countries. Analysis shows that calcium, magnesium, iron and zinc are present in the plant foods eaten in these areas, but the high phytate content of soy and rice based diets prevents their absorption. The soybean has a higher phytate content than any other grain or legume that has been studied. Furthermore, it seems to be highly resistant to many phytate reducing techniques such as long, slow cooking.