I've not heard that, so I can't speak to it. Just because it's naturally occurring, doesn't meant I want a big ol concentration of it though.
Idk, maybe I'm being overly cautious, but I feel a whole lot better physically since specifically switching away from msg and toward more natural whole foods. I'm not super religious on the whole foods, but I'm religious about the msg. @burntoblog turned me on to the movie Hungry for Change on Netflix. That's what set me against msg. It's the one thing that stuck, though there's a lot more info in the movie.