In the 1980s Common Cause did an extensive investigation into Aspartame (NutraSweet). I’ll look for my copy of the articles, but you might want to contact them directly. The state psychiatric hospital where I worked in quality assurance the psychiatrists charted that patients exhibiting Parkinson tremors should not receive any food or beverage containing NutraSweet as it increased the tremors.
Common Cause noted that NutraSweet was approved for use in foods three months after Reagan came into office. Scientist who had studied Aspartame did not recommend it for use in foods because when heated it breaks down into toxic elements.
I will try to find the Common Cause article so I can give you the date of the publication. But the quickest thing to do is to get the phone # for Common Cause and ask them for a copy of their study.
Good luck. I NEVER use Aspartame (NutraSweet) or any food or beverage containing it due to what I have seen as side effects in patients with Parkinson tremors.