But they did conclude there was enough scientific evidence to suggest the existence of a subgroup of healthy individuals in the general population who may respond badly to large doses of MSG, usually within an hour of exposure. But these reactions were observed in studies where they were given three grams or more of MSG delivered in water, without food; a scenario unlikely to occur in the real world where, according to the FDA, most people will get around 0.55 grams per day of added MSG in their diet.

A study in 2000 tried to explore this further with 130 people who described themselves as being reactive to MSG. These otherwise healthy people were first given a dose of MSG without food, or given a placebo. If anyone scored above a certain level on a list of 10 symptoms, they were tested again with the same dose (or placebo) to see if their response was consistent. They were also tested with higher doses to see if this increased their symptoms. After another round of retests, only two of the original 130 had shown consistent reactions to MSG and not the placebo. But then, when they were tested again with MSG in food, their reactions differed – which cast doubt on the validity of self-described MSG sensitivity.