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: Soy Makes Your Red Blood Cells Clump Together
Soy, as well as many other types of plant-based foods, contains proteins called lectins. These proteins were discovered over a century ago. Lectins can cause red blood cells to agglutinate, or clump together, so they are also given the name haemagglutinins. As such, some people put stock in this myth and fear soy and soyfoods because of it.
Clumping red blood cells sounds pretty omininous, which is why the fear-mongers make this soy-myth sound so scary. But solid research shows the fears of lectin activity from soy to be unfounded. The research shows the lectins in soy don't cause any health problems. Dr. Messina describes one study done by Dr. Irvin E. Liener, from the University of Minnesota, and says that "unlike a number of other lectins, soybean lectins were found to be essentially harmless." In his research paper, which is now classic, Liener says:
"More definite proof for the relatively innocuous effect of the soybean agglutinin on (rat) growth came from a much later experiment in which we showed that a crude soybean extract, from which the soybean agglutinin had been removed by affinity chromatography, supported no better growth than the untreated extract. The failure of the soybean agglutinin to inhibit the growth of rats upon oral ingestion may perhaps be explained by the observation that it is readily inactivated by pepsin and by the hydrolases of the brush border membrane of the intestines."
While rats aren't identical to humans, they are often used in research to determine toxicity. No evidence of problems in rat development or growth after use of very large amounts of a substance (like agglutinin, in this case) can be reassuring when there is no data to confirm its effect in humans.
So to boil it down, when you eat soy and soyfoods, the lectins are destroyed by your digestive system -- they don't do anything to your blood cells. Actually, most of the lectins are destroyed by heat, cooking or processing long before you eat soyfoods.
Often, the fear-mongers cling to results from research studies that were performed by exposing cells to lectins in a lab dish or by injecting soy lectins into the body and not actually feeding soy to lab animals. As Dr. Messina concludes, "Citing reports of soybean lectin toxicity that involve the effect of lectins on cells in the lab and/or other than oral administration have little relevance to in vivo(in the body) findings."
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.
