Aspartame

"In 1995, FDA Epidemiology Branch Chief Thomas Wilcox reported that aspartame complaints represented 75% of all reports of adverse reactions to substances in the food supply from 1981 to 1995.^[6] Concerns about aspartame frequently revolve around symptoms and health conditions that are allegedly caused by the sweetener. A total of 92 different symptoms and health conditions were reported by physicians and consumers."
source: http://en.wikipedia.org/wiki/Aspartame_controversy