There are many things that were once thought safe that later on were found to be quite toxic to the human body. Asbestos is one that comes to mind, Thalidomide is another.
It's interesting to note that until several years ago, there was no disease clinically named fibromyalgia, and similarly no condition called chronic fatigue syndrome. It is also interesting to note that these maladys started to appear about the same time as aspartame was appearing on the market in appreciable amounts. Both of the afore mentioned conditions along with Lupus which has similar symptoms, are now being linked with aspartame consumption. My particular reaction was mild compared to other more serious heart rhythm problems that are related to interuptions in the electric impulses that control the heart rhythm. Formic acid is a known neurotoxin, and as such there is now interest in a possible link between aspartame and some heart related conditions. As seems to be usual in these cases, the evidence starts to accumulate slowly, then there is much debate over the validity of the evidence and arguments against by the vested interests, and then finally, acknowledgement that a problem may in fact exist. All of this can take years to develop.
A really good indicator of how the debate is being perceived elsewhere in the corporate world, as in The Coca-Cola company that has been using aspartame in it's soft drinks for many years now. Coca-Cola has been working with Cargil for a few years on creating a sweetner made from Stevia, a natural, non-caloric sweetner derived from a plant. Coca-Cola and Cargil are calling their new sweetner Rebiana and it's being developed for use in Coca-Colas's diet soft drinks (for starts). Pepsi-Cola apparently has expressed interest and possible support for this new sweetner as well. As the plant that produces Stevia is naturally occuring it can't be patented, however, a particular sweetner compound with Stevia as it's main ingredient apparently can, and that's what Cargil has created. Until recently, the FDA wouldn't consider approving Stevia as a natural sweetner despite the fact that there is ample evidence of it being used safely in South America and Asia for several decades. It's easy to understand if one follows the money trail. Monsanto stood to lose a great deal of business should a new, non-controversial and safe natural sweetner suddenly win approval by FDA. But, low and behold, now that another chemical giant Cargil was involved, FDA was suddenly receptive to hearing the case for Stevia. Again, follow the money trail. Well, all it takes is clout it seems (read MONEY). Cargil has won FDA approval for Rebiana and it's already in grocery stores in a sweetner product called Truvia. Look for it in Coca-Cola's Sprite soda soon in a grocery store near you. The larger corporate interests it appears, have shifted away from Monsanto's interests and towards Cargil, Coca-Cola, Pepsi, et al. But, it seems that Cargil, unlike Searle and Monsanto, has been a lot more cautious and responsible with Rebiana. And for Coca-Cola's and Pepsi-cola's parts, it seems they're looking for a way off the aspartame bandwagon before the wheels come off. A little ass saving before the big health impact of aspartame is suddenly revealed, perhaps. The conclusion here may be a bit speculative on my part, but the kind of speculation that is rarely very far off when it's based on big money interests.