The Lowdown On The Sweet Stuff
Source: Portions of this article also taken from contributors to MSNBC.com.

There are four FDA approved artificial sweeteners now on the market, along with one "dietary supplement" and one recently FDA approved sweetener, that hasn't yet hit the market. Here's the scoop on all of them:
 
Saccharin
Saccharin is made from methyl anthranilate, derived from petroleum, but which is also found in many fruits, including grapes.
How Sweet It Is: 300 times as sweet as sucrose (table sugar).
The Lowdown: Produces no rise in blood sugar levels. Ban proposed several years ago because of cancer in lab rats, but the amount given to the rats was equal to the amount in hundreds of cans of soda, drunk daily from birth, so the FDA withdrew the proposal. Warning label dropped in December 2000.
Aceulfame-K (Sunette, Sweet One)
Aceulfame-K was approved by the FDA as a tabletop sweetener and as an additive in a variety of desserts, candy, and alcoholic beverages.
How Sweet It Is: 200 times sweeter than sucrose.
The Lowdown: Is not metabolized in the body and is excreted unchanged, producing no rise in blood sugar. The body does not absorb any calories from it. Is not considered cancer causing.
Sucralose (Splenda)
Sucralose starts out as a cane sugar molecule, then three hydrogen-oxygen groups are substituted with three tightly bound chlorine atoms.
How Sweet It Is: 600 times sweeter than sucrose. It can be used in baking and heating without reducing its sweetening power.
The Lowdown: Inert and is not broken down by the body. Has no calories, and about 15 percent of it is passively absorbed; the rest is excreted unchanged. The small amount that is absorbed is eliminated within 24 hours, according to studies. The FDA says it does not pose a risk for cancer, reproductive health problems, or neurologic cancers.
Aspartame (Nutrasweet, Equal)
Aspartame is a product of two amino acids combined with methanol.
How Sweet It Is: 180 to 200 times sweeter than sucrose, so the small amount needed to sweeten products does not actually contribute a significant number of calories to your diet. Has the same calorie level as protein--4 calories per gram.
The Lowdown: Required to carry a warning label about the content phenylalanine and the possibility of phenylketonuria, a genetic disease where the body cannot produce the enzyme necessary to use phenylalanine. The FDA has set the acceptable daily intake at 50mg per kilogram of body weight. That’s 17 cans of Aspartame-sweetened soft drinks per day.
Neotame
Neotame, the newest FDA-approved artificial sweetener (July 2002), is made from amino acids, aspartic acid, and phenylalanine.
How Sweet It Is: The most intense sweetener to date--7,000 to 13,000 times sweeter than sucrose.
The Lowdown: Quickly metabolized and fully eliminated from the body through normal biological processes. Made by the same company that makes Aspartame; does not require any warning label. There are no products yet on the market that contain Neotame.
Stevia
Stevia is made from the material between the veins of the leaves of Stevia rebaudiana (stevia), a South American shrub that’s a member of the daisy family.
How Sweet It Is: 250 to 300 times as sweet as sucrose.
The Lowdown: Has not been approved by the FDA as GRAS (generally regarded as safe), but it is sold in the U.S. as a dietary supplement. A study in 1985, conducted by the College of Pharmacy at the University of Illinois, found that when stevioside (stevia) was exposed to a testing bacterium, the DNA of the bacteria was altered. The FDA’s position is that Stevia’s safety has not been adequately demonstrated.