Monosodium glutamate (MSG) is a flavor enhancer often used in Asian dishes as well as in a wide range of commercially prepared foods. Chemically, it is a salt of glutamic acid, one of the amino-acid building blocks of protein. Glutamic acid and its salts, including MSG, stimulate a particular taste receptor, the one responsible for the so-called "fifth taste" or umami (a Japanese word meaning "meaty" or "savory").
MSG is often suspected of causing health concerns such as flushing, general weakness, and heart palpitations, but studies have produced no evidence linking consumption of moderate amounts of MSG with any serious reactions, and have found no links to short- or long-term health problems, including Alzheimer's disease, Huntington's disease or neurodegenerative diseases. However, people who eat large amounts of MSG (three grams or more per meal) on an empty stomach and people with severe and poorly controlled asthma can develop such symptoms as numbness, burning sensation, tingling, facial pressure or tightness, chest pain, headache, nausea, rapid heartbeat, drowsiness and weakness. (Note that three grams is a lot of MSG - the amount in a typical serving of food to which MSG is added is less than 0.5 grams.)
If you find that you react to foods containing MSG or glutamate, check labels when shopping, and when dining in Asian restaurants, ask that your food be prepared without MSG.
If you want to boost the umami component of foods naturally, try using seaweeds such as kombu and mushrooms such as shiitake in soups and stocks and sauces, or add other foods naturally containing free glutamates: fresh tomatoes, tomato paste and Parmesan cheese.
Try these natural umami recipes using one of my favorite foods - mushrooms - and skip the MSG!