Food Additives and Health: The Case Against MSG
While I was in medical school, I did research under a March of Dimes grant on MSG (monosodium glutamate), a common food additive. Back then, then damage we saw in rats was reversable IF you stopped giving it to them.
However the case against its use in man is mounting, including one that strongly suggest it has negative metabolic effects and leads to thyroid dysfunction and obesity.