Multiple double-blind, placebo-controlled crossover trials have failed to consistently demonstrate MSG as a headache trigger. The 'MSG symptom complex' (headache, flushing, numbness) reported in open-label challenges disappears when subjects are properly blinded. This is one of the most well-documented nocebo effects in food science. Some individuals may have idiosyncratic sensitivity at very high single doses (>3 g on empty stomach), but this does not apply to typical dietary or supplement exposure [1].

L-glutamic acid is one of the most abundant amino acids in nature — found in breast milk, tomatoes, Parmesan, mushrooms, and virtually all protein-containing foods. Commercial MSG is produced by bacterial fermentation (Corynebacterium glutamicum), the same process used to make yogurt and vinegar. The glutamate molecule is identical regardless of source [1].

MSG is used as a flavoring agent in chewable tablets, effervescent powders, and some protein supplements to improve taste. The amounts are small (10–100 mg per serving) — far less than a single serving of soy sauce. It is listed in Other Ingredients [1].

Glutamate is present in human breast milk (~20 mg/100 mL) and is essential for infant brain development. MSG in baby food was voluntarily removed by manufacturers in the 1970s due to public pressure, not scientific evidence of harm. The WHO, JECFA, and AAP have not identified MSG as a safety concern for children [1].