It's funny with the MSG thing. I don't pretend to know the how or why of it, but on occasion I have had some weird symptoms after eating (cheap) Chinese food. Not a migraine, but a feeling of stiffness/achiness in my hands and cheeks. The first time this happened I was very weirded out and that makes me think there's something to it, because it's not like I was *expecting* it and therefore made myself ill in some placebo manner.
So I don't know what it is, but there is something to it. Obviously avoiding all MSG would mean I was eating very simply, but maybe some people are sensitive to large amounts of MSG. I know it's in almost every stock, so it's hard to avoid.