Protease inhibitors interfere with the action of trypsin and chymostrypsin, enzymes produced by the pancreas to break down ingested proteins. They are found to some extent in cereal grains (oats, barley, and maize), Brussels sprouts, onion, beetroot, wheat, finger millet, and peanuts. They have caused pancreatic hypertrophy in chicks and rats, but no ill effects have been observed in calves, pigs and dogs.2
Raw soybeans have high levels of trypsin inhibitors. Soybean fractions high in trypsin inhibitors depressed the growth of rats, chicks, and mice. Cooking heat largely destroys the trypsin inhibitors in soybeans, but 5 to 20% of the original trypsin inhibitor activity may be retained in commercially available soybean food products. For example, while raw soy flour contains 52.1 TI (trypsin inhibitor activity) per gram of sample, toasted soy flour contains 3.2-7.9 TI per g.3
Back to List of Endogenous Plant Toxins
Prepared Summer 1997 by Bernadene Magnuson, Ph.D.
University of Idaho, Dept. of Food Science and Toxicology - EXTOXNET FAQ Team.