Aspartame was discovered in 1965. It was first authorized to enter the market in the United States in 1974. This authorization was suspended a few months later on the grounds that the first studies had not properly evaluated if aspartame could be toxic to the brain or cause brain cancer. A new assessment of those studies led to a marketing authorization for solid food in 1981 and for soft drinks in 1983. Aspartame was finally authorized as general sweetener in 1996. Up to now, the safety of aspartame has been assessed by a number of national and international organizations.

Aspartame is approximately 200 times sweeter than sugar. Though aspartame has a caloric value similar to that of carbohydrate or protein (4 calories per gram), its intense sweetening capacity allows for only small amounts to be used. As a result, the amount of calories actually provided is negligible. Because aspartame may lose its sweetening power upon prolonged exposure to heat, it is not recommended for use in recipes requiring lengthy cooking or baking. Aspartame is found in soft drinks, which account for more than 70 percent of aspartame consumption. Aspartame is marketed under the brand name NutraSweet.

Evidence indicates that long-term consumption of aspartame does not cause health problems. However, information for people with phenylketonuria (PKU) is required on the label of all products that contain aspartame. People with PKU cannot utilize phenylalanine, and harmful by-products build up in their bodies. For this reason, large amounts of aspartame are not recommended for people with PKU.

Additional Resources:

ttp://rd411.com/index.php?option=com_content&view=article&id=1068:sugar-substitutes-are-they-safe&catid=136:weight-control&Itemid=424
http://tuftshealthletter.com/ShowArticle.aspx?rowId=347