Kathy,
I'm not a doctor and am a heavy diet coke drinker. Re aspertame, to the best of my knowledge, there is no "official" research / conclusion that it is harmful. Most of the sites on the net are from vested interests that will want your $. My mother is now 74, has been taking sacharin since it was on the market and for the last 30 odd years, pumping nutra-sweet down her at an alarming rate of 40-50 tablets a day (heavy coffee drinker). She has not got any tumours and apart from being over weight is perfectly healthy. I am not endorsing the product, I am just saying, be careful in views about products that we still don't fully understand. Tell your work colleagues to provide one piece of research endorsed by the FDA or has been published by the british journal of medicine.
It's like the horrible AN's we have all had/have. They truly suck and have changed my life significantly and hopefully one day, some research will reveal that AN's are caused by ..... Till that day.
Larry