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If you live in the United States or Canada and you see the "natural flavoring" or "natural flavorings" on a food product label, the item contains monosodium glutamate, also known as MSG.

What Is MSG?

Sometimes MSG really is a "natural" product, but eating too many foods that contain MSG can cause problems.
Monosodium glutamate is a chemical first discovered in 1908 by a Japanese chemist named Kikunae Ikeda, who isolated it from seaweed. Dr. Ikeda had observed that certain Japanese foods had a taste that was neither salty, bitter, sour, or sweet. In Japanese, this fifth flavor came to be known as umami, or savory. Dr. Ikeda's isolation of monosodium glutamate from kombu seaweed made it possible to give a savory flavor to foods without the metallic aftertaste of other similar compounds.

Is MSG Really Natural?

The MSG extracted from kombu seaweed can be classified as a natural product. Most of the MSG used in food processing today, however, is made by fermenting cornyeform (acne) bacteria in a mixture of ammonia (the same chemical used in household cleaners) and fibers and sugars left over from processing sugar cane, tapioca, or molasses. MSG can also be made by mixing wheat gluten with hydrochloric acid, or by chemical synthesis from acrylonitrile, which is also used to make synthetic rubber for tires. These days, natural flavorings really aren't natural.

Where Is MSG Used?

The short answer to the question of where MSG is used is "everywhere." Food manufacturers all over the world use MSG to flavor just about any food mixture that comes from a box, a can, a mix, or a fast food restaurant. MSG is third-listed ingredient, for example, in "natural" hamburger buns. It's common in almost brands of soup and broth. It's even added to candy, and MSG is used to flavor many Asian dishes served in restaurants.

What Does MSG Do in the Human Body?

MSG is primarily an excitotoxin, increasing the speed at which nerve impulses are transmitted in the body and in the brain. Consumption of MSG:

  • Accelerates the emptying of the stomach, so that there is a greater "sugar surge" from the digestion of carbohydrates and also a greater risk of food allergies due to the incomplete digestion of food.
  • Accelerates death of nerve cells in the brain and peripheral nervous system during stress. It does not cause nerve tissue stress when production of stress hormones is low.
  • Increases the release of the pleasure chemical dopamine in the brain after the consumption of alcohol.
  • Seems to cause obesity without overeating in mice due to changes in the way intestinal enzymes work, but a similar effect has not been shown in studies of obesity in China.

There is some doubt that you can blame MSG for making you fat. But MSG can definitely cause stomach upset (nausea, vomiting, and diarrhea) and headaches, usually about 45 minutes after eating a food that contains MSG. Not everyone is equally sensitive to MSG, but some people have bad reactions after consuming just a tiny amount.

There actually are some people, however, who benefit from MSG. Long-term diabetics who have nerve damage in their gastrointestinal tracts and the elderly sometimes have better digestion when they eat high-calorie foods that are flavored with MSG. For most of us, however, natural foods that are cooked at home without MSG are healthier.

  • Behrens M, Meyerhof W, Hellfritsch C, Hofmann T. Sweet and umami taste: natural products, their chemosensory targets, and beyond. Angew Chem Int Ed Engl. 2011 Mar 1
  • 50(10):2220-42. doi: 10.1002/anie.201002094. Epub 2011 Feb 17. Review.
  • Photo courtesy of thai-food-blog on Flickr: