There is no doubt in my mind that the more the hand of man interferes in a substance, the less likely it is to promote health.
Certainly the information that has come to light about Splenda should give everyone pause. Dr. Mercola (www.mercola.com) is a well-informed critic of the stuff - here is an entry in his web log that will interest you.
Today he has more information about this poisonous stuff - you can read it here. Do sign up for his newsletter while you are there: it is, in my opinion, one of the best out there for natural health afficionados.
For a list of foods containing Splenda, go here.
