Providing new information related to glutamate science, the April 2000 supplement to the
Journal of Nutrition contains a thorough scientific update on glutamate from the Second International Conference on Glutamate, held October 1998 in Bergamo, Italy, focusing on four areas: glutamate's role in taste and flavoring as monosodium glutamate (MSG), glutamate as a neurotransmitter, its role in carbohydrate and amino acid metabolism, and its safety in the food supply.
Although most people are aware of glutamate only as MSG, a common flavor enhancer, glutamate is also produced by the body and is essential for important physiological functions.
"Few biological molecules have the importance to such a wide range of body functions as glutamate," stated John D. Fernstrom, Ph.D., conference co-chair and professor of psychiatry, pharmacology, and neuroscience at the University of Pittsburgh School of Medicine. "When the first international conference was held, we knew quite a lot about glutamate safety as a food component, but little about functions of glutamate in the human body. Today, our knowledge base has expanded substantially with information on benefits to human health."
The symposium proceedings add to the significant body of scientific evidence that MSG does not cause adverse reactions, food allergy, or asthma, and is safe for the public. Glutamate is a naturally occurring amino acid found in virtually all protein-containing foods. MSG is one of several forms of glutamate. The human body does not distinguish between glutamate in natural foods like tomatoes, mushrooms or Parmesan cheese and glutamate in MSG. The average American consumes about 11 grams of glutamate per day from food and less than 1 gram per day from MSG, an amount similar to 1 to 1.5 ounces of Parmesan cheese.
At the Bergamo conference, evolving research on taste over the past 25 years has fully defined the basic taste of glutamate called "umami"-the fifth taste beyond sweet, sour, salty, and bitter. Resent research has provided the definitive identification of glutamate receptors on the tongue. Umami is what provides the savory or meaty taste in many foods. This fifth taste is important because of the pleasant taste that it provides.
Knowledge about glutamate in the brain has also expanded substantially. Research on glutamate receptors in the brain shows that they are different from those found on the tongue. A vast quantity of glutamate is produced in the brain for normal functions, and important transport systems are present to protect the neural cells from harm. "While it was earlier thought that circulating glutamate in the body might enter the brain and cause damage, it is now clearer than ever that circulating glutamate is kept strictly separate from the glutamate inside the brain that is used for normal neural function," added Dr. Fernstrom.
There are also important new findings related to glutamate metabolism in the digestive tract. Research shows that dietary glutamate (from foods or from MSG) serves as a major source of energy for the intestine. "It now appears that most of the glutamate consumed from foods is used in the gut to fuel digestion," remarked Peter J. Reeds, Ph.D., professor of pediatrics, Baylor College of Medicine, and the U.S. Department of Agriculture's Children's Nutrition Research Center, Houston. "Glutamate is vital and beneficial for normal functioning of the digestive tract and digestion."
Between 1993 and the present, many well-controlled studies examined both the general population and individuals who identified themselves as sensitive to MSG. Any reactions to MSG were benign and short-lived. All of these food allergy and asthma studies conclude that any perceived adverse reactions to MSG—including food allergy or asthma—cannot be reproduced in clinically controlled studies.
An often-asked question is whether glutamate or MSG can trigger or exacerbate asthma. Dr. Donald Stevenson of the Division of Allergy, Asthma and Immunology at the Scripps Clinic and Research Foundation, La Jolla, California, summarized current research on glutamate, MSG, and asthma. "We now know from numerous well-designed clinical studies that MSG or glutamate cannot trigger or exacerbate asthma, even among individuals who believe their asthma is caused by MSG."
Results from a multicenter study conducted by Harvard University in Boston; Northwestern University in Chicago; and the University of California in Los Angeles were also presented at the conference. The study included 130 individuals who believed that they were sensitive to MSG and used double-blind, placebo-controlled testing conditions. When challenged, reactions could not be reproduced with either placebo or MSG in the presence of food. Any observed reactions were mild, transient, and not life threatening.
In the United States, the Food and Drug Administration (FDA) categorizes MSG as "generally recognized as safe" or GRAS, along with other food ingredients like baking powder, table salt, and black pepper. In addition, a comprehensive scientific review commissioned by FDA published by the Federation of American Societies for Experimental Biology in 1995 reaffirmed the safety of MSG.
The research presented at the Second International Conference on Glutamate indicates that glutamate is more essential than was previously thought for health and well-being and support for its safety is reinforced.
More information about glutamate and MSG safety, food allergy, and asthma can be found on the IFIC Foundation Online at http://ific.org.
