Soy and soy foods are rich in protein, fiber, phytochemicals and other nutrients. Soy and soy foods are popular in the United States, however there are some myths that effect consumers' opinion of soy. I asked Dr. Mark Messina, adjunct associate professor of nutrition at Loma Linda University and an expert on soy and nutrition, to help me dispel the myths surrounding soy.
Myth: Trypsin Inhibitors Destroy Your Pancreas
Your pancreas is well-known for producing insulin, which is important for regulating blood sugar, but it also produces digestive enzymes that break down carbohydrates and proteins. The protein-digesting enzymes are called protease. Raw soybeans contain compounds called protease inhibitors that are at the base of the myth. Some fear-mongers call these compounds anti-nutrients and claim that eating soyfoods will damage your pancreas by destroying the enzymes. Apparently, protease inhibitors will destroy protein-digesting enzymes, which will cause your pancreas to work too hard and increase in size, rendering it vulnerable to diseases like cancer.
The protease inhibitors found in soybeans (and other foods such as legumes and whole-grains) could only effect the activity of protein-digesting enzymes in the foods you eat, but only in very large amounts. And this is where the myth gets soyfoods wrong. While raw soybeans contain a large amount of protease inhibitors, we don't eat them when they're raw. We cook them or process them into tofu, tempeh or soy milk. According to Messina, "Raw soybeans have a high protease inhibitor content but the heat and processing of the soybeans destroys 80% to 95% of the protease inhibior activity. The amount remaining in properly processed soy products is likely far too small to cause any untoward effects on the pancreas."
Trypsin inhibitors are frequently blamed for the damage in these myths, but that's not true either. The processing and cooking of soybeans removes almost all of the trypsin inhibitor, and even if it didn't, laboratory research suggests it wouldn't matter. Messina explains, "Research in the male miniature swine –- which is considered to be the ideal animal for studying the effects of protease inhibitors because their digestive physiology and anatomy is similar to humans –- found there were essentially no adverse effects in response to the consumption of diets containing very high amounts of trypsin inhibitors."
Messina also points out that if these protease inhibitors were so active, they would prevent your body from absorbing the proteins found in soy. But, in fact, your body absorbs soy proteins very well. "Throughout the 1980s, Vernon Young and colleagues from the Massachusetts Institute of Technology showed in long-term human-feeding studies that the quality of soy protein is quite high – essentially similar to that of animal protein."
Ironically, some of the protease inhibitors blamed by the fear-mongers, may actually be beneficial. There's a lot of interest in the disease preventative properties of protease inhibitors called Bowman-Birk inhibitors that are found in soybeans. They may prove to be beneficial for treatment of benign prostatic hyerplasia and for prevention of prostate cancer.
Mark Messina, Ph.D. is a Health and Wellness Expert for The United Soybean Board.
Source:
Email interview with Mark Messina, PhD. April 2009. The Soy Connection.
