I actually used to buy Equal which is an artificial sweetener containing aspartame for my coffee because I thought it was healthier...
On their site it says
Are Equal® and aspartame (the sweetening ingredient in Equal) safe?
Yes, Equal is safe.
Aspartame, the sweetening ingredient in Equal has been documented in more than 200 objective scientific studies. The safety of aspartame has been confirmed by regulatory authorities in more than 100 countries, including the U.S. Food and Drug Administration, Health Canada, and the European Commission's Scientific Committee on Food, as well as by experts with the United Nations' Food and Agricultural Organization and World Health Organization.
http://www.equal.com/faq/faq.html#1