Monosodium glutamate (MSG) is a flavor enhancer invented in 1908 that is the sodium salt of the naturally occurring amino acid glutamic acid. MSG is a white crystal that is highly soluble and can cause headaches, sweating, depression, nausea, vomiting and chest pain when consumed in excess. Studies have shown a potential link between obesity and MSG consumption. While MSG can enhance food flavors, it is unhealthy to consume in excessive amounts.