Saccharine (often mis-typed as saccharine with an E) is an artificial sweetener that has been around for over 100 years, since 1879. Saccharin is 300 times sweeter than sugar. It was banned as early as 1911, but the bans were lifted during the sugar rationing of WWI.
Nowadays, saccharin is best known in the pink packet form of Sweet 'N Low.
The FDA began researching saccharin Benzoate sufinide - in the 70s, to ensure it really WAS safe. A series of studies were done and saccharin was found to cause bladder cancers. Some felt it was impurities in the saccharin, and not the saccharin itself, that caused the trouble, so nothing was done. However, in 1977, Canadians proved conclusively that it WAS the saccharin itself causing the cancer. As a result, the FDA required that any saccharin products carry a warning label about cancer.
The actual warning reads:
"Use of this product may be hazardous to your health. This product contains saccharin, which has been determined to cause cancer in laboratory animals."
Note that this warning was removed in 2000 by the US Congress (not by the FDA) after heavy lobbying by the saccharin industry :)
Further research was then done on saccharin, because the FDA wished to ban saccharin outright but the food companies fought this (successfully). The National Cancer Institute ran studies in the next 2 years and found that saccharin was indeed connected with bladder cancer. People who drank only 2 cans or more a day of diet soda had an increased risk.
Studies show that the average teenager drinks over 2 cans of soda a day. One in 10 teenage boys drink EIGHT servings of soda a day. The average American drinks over a gallon of soda each week. With more people turning to diet sodas to control obesity, these levels can cause serious problems.
Pregnant mothers are especially cautioned to stay away from saccharin, because even small usage of saccharin could overwhelm the developing fetus' defenses and cause damage to the developing bladder area.
Congress continues to keep prolonging the "ban moratorium", that is, refusing to allow the FDA to ban saccharin because it is so popular in products. Saccharin is cheap and stable, so diet food makers find it perfect for use in sodas, candies, and many other products. This commercial interest has outweighed the proven cancer risks since 1977, and shows no sign of letting up.
My recommendation is, if you MUST have sweet foods, to consume products with Splenda in it, and stay away from saccharin. Even better, wean yourself off the sweet tooth and enjoy water, iced tea and wine for drinking, and natural foods for eating. There's no reason to go with ANY artificial sweetener, and the less sweets you crave, the less likely you'll end up with health problems from ANY form of sweetener - natural or unnatural.
NOTE: Some people ask why I do not recommend buying products with stevia in them. Simple answer - they rarely exist. We can argue about why this is, but in reality there simply are not many stevia-sweetened processed foods out there to choose from. Anyway, as mentioned above, your goal should be to wean yourself off of all sweets, not to find a new one to latch onto :)
NOTE 2: Some people write to ask where they can read the NCI research online. It's not a big surprise that they have chosen NOT to put it online, given the great power of the soda industry. However, there are many, many books on this topic which go over the sequence of events in great detail.
NOTE 3: Even more oddly, occasionally someone will write to me claiming that saccharin has NEVER been used in ANY food or beverage product. This simply is false. Saccharin is on the shelves right now - walk into any store and you can find a variety of products that use saccharin as an ingredient.
Soda Consumption and Obesity
If you're interested in the Canadian study on saccharin, here is the text -
Canadian Study about Cancer and Saccharin