HMMmmm... Interesting thread. This may seem off topic at first, but hang in there. I will get to the point somewhere down the road.

I quit smoking in 92. In the following 3 months I gained almost 30 pounds. So I switched to diet everything. I didn't have headaches but I could not think straight. I figured that I had some real good smoke that week. But when it ran out and I still had the same problem. I thought there was a new problem with me. I would forget where I was going and drive past my destinations and find myself wondering down the road forgetting why. One morning, I was out of my supply of diet soda & candies. It was pay day & had no cash to buy more yet. Somehow, I felt better. Maybe I was in recovery from whatever it was. Got paid at lunchtime. Went right out to buy more diet crap. By 2 PM I was in never never land again. I started to put 2 & 2 together and got 5. But I stopped with the diet stuff and went back to feeling normal.
To this day, I can immediately tell if something has diet anything in it. As soon as it touches my lips I get a feeling all over as if I'm allergic. I thought it was the artificial sweeteners till now. Thanks for the article Nod.