E621

MSG, aka E621, is a natural flavor even if the particular molecule you are consuming was made synthetically.

It’s found in tomatoes, mushrooms and a host of other foods but probably at lower concentrations than found in certain food products.

Even at super high concentrations the negative health effects apparently are greatly exaggerated;

“71 fasting participants were given 5g of MSG and then a standard breakfast. There was one reaction to the placebo, in a self-identified MSG-sensitive individual.”