Monosodium glutamate (MSG) is a flavor enhancer commonly added to Chinese food, canned vegetables, soups and processed meats. The Food and Drug Administration (FDA) has classified MSG as a food ingredient that's "generally recognized as safe," but its use remains controversial. For this reason, when MSG is added to food, the FDA requires that it be listed on the label.

MSG has been used as a food additive for decades. Over the years, the FDA has received many anecdotal reports of adverse reactions to foods containing MSG. These reactions — known as MSG symptom complex — include:

• Headache
• Flushing
• Sweating
• Facial pressure or tightness
• Numbness, tingling or burning in the face, neck and other areas
• Rapid, fluttering heartbeats (heart palpitations)
• Chest pain
• Nausea
• Weakness

However, researchers have found no definitive evidence of a link between MSG and these symptoms. Researchers acknowledge, though, that a small percentage of people may have short-term reactions to MSG. Symptoms are usually mild and don't require treatment. The only way to prevent a reaction is to avoid foods containing MSG.