MSG

MSG is the sodium salt of glutamic acid, an amino acid that occurs naturally in tomatoes, aged cheese (especially parmesan), mushrooms, fermented sauces, breast milk, and many other foods. The free glutamate in a teaspoon of MSG behaves the same way in the body as the free glutamate in a serving of parmesan. It produces umami — the "savory" taste — and has been used in cooking for over a century.

The reputation comes from a 1968 letter to the New England Journal of Medicine coining "Chinese restaurant syndrome" to describe self-reported symptoms (headache, flushing, palpitations) after MSG-containing meals. The framing was unfortunate — Chinese food is no more likely to use MSG than processed snacks, canned soup, deli meats, or fast-food seasonings — and the term has since been formally retired by Merriam-Webster as outdated and racially loaded.

What the evidence shows

In double-blind, placebo-controlled trials, the vast majority of people who report MSG sensitivity cannot reliably distinguish MSG-containing meals from MSG-free ones. The FDA classifies MSG as "generally recognized as safe" (GRAS), and the same conclusion has been reached by the WHO, EFSA, and most other regulators. Large doses on an empty stomach occasionally produce mild, transient symptoms in some individuals, but it does not behave like an allergen, and there is no strong evidence for chronic harm at typical dietary intakes.

When people still report symptoms

A small subset of people do appear to react reproducibly to MSG-heavy meals — and that's worth taking seriously as a personal pattern even if the mechanism isn't classical. The complicating factor is that MSG-heavy foods (chips, restaurant takeout, processed snacks) often share other features: high sodium, high fat, refined carbs, sometimes histamine. A blinded self-experiment — buying plain MSG and adding small amounts to home-cooked food — is a cleaner way to test reactivity than blaming a restaurant meal.