Saccharin is an artificial, or non-nutritive, sweetener usually sold with the brand name Sweet'N Low or Sugar Twin. It's 200 to 700 times sweeter than table sugar so very little of it is needed to sweeten foods.
It was discovered in 1879 and was used early in the 20th century as a sugar replacement for diabetics. Today the most common use is as a sweetener for beverages. It's found in a few diet sodas, and you can find Sweet'N Low in pink packets at restaurants and coffee shops.
Saccharin isn't hazardous to your health and it hasn't been shown to cause cancer in humans, although large amounts of saccharin cause bladder tumors in male rats. The formation of the tumors is due to a protein found in male rats that doesn't appear in humans.
How to Use Saccharin
Saccharin is typically stirred into coffee or tea as a sweetener or it can be added to cold drinks. Although it's heat-stable, it's rarely used in cooking or baking. Saccharin has been mostly replaced by aspartame and sucralose due to its bitter metallic aftertaste.
Research and Safety
Saccharin has a long history of safe use by humans. However, studies on rats in the 1970s showed that consumption of large amounts caused bladder cancer in male rats. These findings resulted in the banning of saccharin in Canada and labeling regulations in the United States.
In 2000, saccharin was removed from the list of substances that cause cancer in humans after scientists determined the mechanism for bladder tumor formation in the male rats was not relative to human biology. In the United States, products that contain saccharin are no longer required to carry warning labels.
Other No-Calorie Sweeteners:
Academy of Nutrition and Dietetics. "Position of the Academy of Nutrition and Dietetics: use of nutritive and nonnutritive sweeteners." J Am Diet Assoc. 2004 Feb;104(2):255-75.
National Cancer Institute. "Artificial Sweeteners and Cancer: Questions and Answers." Updated October 2006.
US Food and Drug Administration. "Artificial Sweeteners: No Calories ... Sweet!" July 2006.