For the last 40 years, it has been fairly common for Americans to blame vague post-prandial physical sensations (tingling, headaches, dizziness) on an over-exposure to the food additive monosodium glutamate (MSG). The blame was often assigned to Chinese food, or Chinese Restaurant Syndrome (CRS) dating back to a 1968 New England Journal of Medicine article.
There were some shady early experiments that confirmed CRS and got the ball rolling. For about 10 years, the reality of CRS and MSG-poisoning was respectable opinion, even among physicians.
By 1980, better designed studies were failing to reproduce earlier studies on MSG and CRS. Like this one that found that, compared with other common foods, MSG provoked fewer symptoms of distress in general, and none of the symptoms associated with CRS.
And for the next 30 years, we basically got more findings like this:
The present study led to the conclusion that ‘Chinese Restaurant Syndrome’ is an anecdote applied to a variety of postprandial illnesses; rigorous and realistic scientific evidence linking the syndrome to MSG could not be found.*
Public disinterest in decades of scientific findings on CRS and MSG persists, so it is still fairly common for people to worry and complain about CRS and MSG, even though popular press articles debunking any link between MSG and CRS-like symptoms are common.
In some corners, extreme opinion holds that MSG remains a significant “silent killer.”
Others believe it is probably not that bad because it can help people reduce their salt intake (…of course recent evidence suggests that dietary recommendations to reduce salt intake are a bad idea based on weak evidence generated by lousy science).
Still others are fairly certain that the whole thing was an episode of racist hysteria.
As an individual matter, who knows what this means? You can’t prove that, say, your coworker is faking his complaint that MSG gives him migraines.
The decades of careful studies don’t prove that NO ONE gets physical symptoms from consuming MSG. They just showed that the overwhelming majority of people who claim to have MSG sensitivity in fact don’t get symptoms from MSG consumption unless they KNOW in advance that they are consuming MSG. And if they think they are consuming MSG, they can get CRS from consuming a placebo.