There are studies that argue either side of this case. I think the stronger arguments lie with the studies asserting that artificial sweeteners are damaging to the body and may cause cancer. My recommendation is steer clear from using artificial sweeteners, or anything artificial when you can help it. Here is the low down on some of the most common artificial sweeteners.
Saccharin (aka Sweet N' Low) Saccharin was first developed in 1878 and Sweet N' Low has been around since 1957. People who were heavy saccharin users (six or more servings of saccharin or two or more 8-ounce servings of diet drink daily) had "some evidence of an increased risk of bladder cancer, particularly for those who heavily ingested the sweetener as a tabletop sweetener or through diet sodas.
Aspartame (aka NutraSweet, Equal, NatraSweet, Canderel, Spoonfuls, DiabetiSweet) Aspartame, discovered in 1965 and has possible side effects like hallucinations, seizures and brain tumors. Aspartame is blamed for a number of health problems, including headaches, seizures, chronic fatigue syndrome, memory loss, and dizziness. It has also been associated with an increase in multiple sclerosis, Alzheimer's disease, and cancer. According to How Stuff Works, when digested, aspartame breaks down into three components: aspartic acid, phenylalanine, and methanol (wood alcohol). 10% aspartame is absorbed into the bloodstream as methanol. The EPA recommends a limit of 7.8 milligrams per day of methanol. One liter of a diet soda with aspartame contains about 56 milligrams!
Sucralose (aka Splenda) Sucralose is a synthetic compound created in 1976. Recent studies found that Splenda can enlarge both the liver and kidneys and shrink the thymus glands. Sucralose breaks down into small amounts of dichlorofructose, which has not been tested adequately tested in humans. Splenda reportedly can cause skin rashes, panic, diarrhea, headaches, bladder issues and stomach pain. Splenda claims that it is all natural because it is comprised of sucrose (sugar) — however three of the hydroxyl groups in the molecule have been replaced by three chlorine atoms. So while some claim sucralose is molecularly similar to table salt or sugar, others say it is more structurally like a pesticide because the bonds holding the carbon and chlorine atoms together are more characteristic of a chlorocarbon than a salt — and most pesticides are chlorocarbons. Pesticide-like structure doesn't sound very natural to me.
There is an all-natural alternatives sold at places like Whole Foods called Stevia, which is an extract from the Stevia plant. Truvia and Purevia are two new brand name products based on the Stevia plant.
Just to paint a picture on how much pull the artificial sweetener companies may have over the FDA, check out this information from WikipediaIn 1991, the FDA labeled stevia as an "unsafe food additive" and restricted its import. This ruling was controversial. This ruling was controversial, as stevia proponents pointed out that this designation violated the FDA's own guidelines under which natural substances used prior to 1958, with no reported adverse effects, should be generally recognized as safe (GRAS). Stevia occurs naturally, requiring no patent to produce it. Since the import ban in 1991, marketers and consumers of stevia have shared a belief that the FDA acted in response to [artificial sweetener] industry pressure. Further proof came in December 2008 when the FDA gave a "no objection" approval for GRAS status to Truvia (developed by The Coca-Cola Company) and PureVia (developed by PepsiCo), both of which are wholly-derived from the Stevia plant.
The safest bet is to generally reduce your sugar intake. This will also help keep your weight at a healthy level, which is known to help prevent cancer.
Limit your coffee and tea to have either no sugar or only 1 teaspoon (you can do this, believe me I went from 4 teaspoons of sugar to none).
Stop drinking soda or limit your soda intake. Seltzer is a good substitute as it can help satisfy a carbonation craving.
Use raw sugar, honey or all-natural maple syrup as alternatives to refined sugar, which is more difficult for the body to process.
Don't get lured in by the "Sugar-free" call out on some food products - check the ingredients, chances are one of the above chemicals will be listed