I’ve also heard that there’s a connection between MSG sensitive people and people who are Aspartame (NutraSweet) intolerant. When NutraSweet first hit the market, I tried diet soda sweetened with it, and every time I did, I’d end up with a splitting headache. After the fourth time or so, I gave up on the artificially sweetened beverages and stayed with sugared ones.
Several years later, I read an article that made the MSG/NutraSweet connection.