The sweet-tasting chemical in Splenda is sucralose which is identical to table sugar (sucrose) except that three of the hydroxyl groups are replaced by chlorine atoms. Sucralose can not be digested by the body so it does not contribute calories. However, it is also many times sweeter than sucrose so in Splenda, sucralose is diluted by adding carbohydrates to reduce the sweetness per volume. The added carbohydrates do add calories to Splenda, but a single serving still contains few enough calories that it can be labeled as a no-calorie food. The Food and Drug Administration (FDA) allows food to be labeled as zero-calorie if a single serving contains less than 5 calories.According to the National Cancer Institute, sucralose is not known to cause cancer. It has been approved by the FDA and over 100 safety studies were conducted. A study conducted independently of the FDA by researchers at Duke University showed some adverse health effects of sucralose on rats, but these effects did not include cancer.