The amino acids important to our well-being are a small set divided into two groups: essential and non-essential. The essential amino acids typically must be supplied in the diet. The normal body makes the non-essential amino acids from molecules harvested from the diet. Glutamic acid can be synthesized in the body and so falls into the non-essential group. It has two carboxylate groups and under physiological conditions travels as the half salt, aka, glutamate and hence the mono- in monosodium glutamate (MSG). Besides its key role in protein and energy metabolism, Glutamate serves as a neurotransmitter in the brain.
One would be hard pressed to find anything edible containing no MSG. It is so ubiquitous that it is one of the most intensely studied food ingredients. Human breast milk contains 10x more MSG than cow’s milk and nursing infants recognize its taste.
MSG has been valued in world cuisine for more than 2000 years. The unique taste was first described in print in 1866 and proposed as a distinct taste in 1908. In 2000, the L-Glutamate taste receptor was identified: taste mGluR4. This fifth taste receptor is named “umami.” When stimulated, the umami signal to the brain is extremely positive. It is variously translated from the Japanese as “yummy,” “delicious” and “wow.” Of the long list of translations, I prefer “savory.” The list of positives regarding MSG in one’s diet would be wearisome to enumerate.
So why in 1968, when Robert Ho Man Kwok, M.D. coined the phrase “Chinese restaurant syndrome” (CSR), did the rap get hung on MSG? The answer is that tough, leathery cuts of meat are often tenderized with blends containing the digestive enzyme papain. These blends do usually include MSG as a flavor enhancer. Since the tenderizing effect is shallow, it is usually only used with thinly sliced meat which is typical in a Chinese kitchen. Catabolic enzymes like papain facilitate hydrolysis of peptide bonds. The reactive stew also brews side reactions, among which is the possible conversion of the amino acid L-Histidine into histamine, which is well-known to allergy sufferers.
Can you eat parmesan cheese, peas, corn, tomatoes or spinach? MSG is everywhere, even if you don’t eat. Do you think you’re allergic to MSG? Check again, perhaps there is something else…