When NutraSweet first came out, I used it a lot (i.e. I drank gallons of Diet Coke).
I began to get headaches, dizziness, and a buzzing in my head. After a while, I noticed that it only happened after drinking something with NutraSweet in it.
Everyone said that it was the “most thoroughly tested product in the history of mankind” and that there were no reports of adverse effects. However, since I gave up NutraSweet, I have never had those symptoms again (and it’s been about 9 years now). Go figure.