Quite interestingly, I had absolutely no problem w/ NutraSweet or MSG ’till I consciously went w/o them for 8 months or so. I did it because NutraSweet can cause intestinal spasms (amongst other things)–the last thing I needed when my gut hurt all the time anyway. Also, I found all carbonation (even Perrier) to be irritating when I was in die-off. MSG was giving me headaches so I decided to hold off on it for a while too. I looked at it as an experiment. As my above Diet Coke episode indicates, I recently tried to have NutraSweet and I reacted. And I react worse to MSG than ever before.
My naturopath says that the body’s immune system can get worn down so much that it doesn’t send off red flags for some harmful things. Once we give the body a rest and heal the immune system, then it has the energy to set off red flags for harmful substances. I think this is what happened for me.