I really do not like these articles that say "science says not to worry, you must be a very stupid and uneducated person to be worried about this." Any honest scientist will tell you that science does not know exactly how the human body processes food and there is no model which will exactly predict the effects of the human body ingesting a certain food. Saying that the experimental results are mixed does not make me…
Your last sentence is very troubling: You feel the negative effects when eating certain foods that you 'suspect' contain MSG. To me, that really sounds like you may psyche yourself out. ie. that you worry about MSG so much that it starts to cause you stress about it, and it's a self-fulfilling prophecy/placebo effect/whatever. Anyway, I can't tell you with 100% certainty that MSG is healthy or not, but I can tell you that there are cultures that consume it in large quantities that seem largely unaffected.