In 1968, a biomedical researcher claimed to experience numbness and heart palpitations after eating at Chinese restaurants. The cause of his symptoms, he said, was a food additive called MSG, or monosodium glutamate, which is also found in processed meats, chips, and canned vegetables.
In the 1990s, the FDA commissioned a review of the additive and found that MSG was safe to consume. The review also found that people who experienced headache, numbness, or drowsiness were likely to have eaten large amounts of MSG on an empty stomach.
But the stigma surrounding MSG has carried on: Around 42% of Americans still try to avoid consuming the ingredient.