Two of the three artificial sweeteners approved for use in the United States have been linked to cancer in laboratory animals fed many times the amount human beings would consume. One, cyclamate, was banned in 1969 because of this finding. The other, saccharin, is still in use today. Saccharin has been linked to bladder cancer in women, particularly those who smoke, but the findings are inconclusive.
Aspartame, also known by its trade name Nutrasweet, was approved for use as an artificial sweetener in 1981. It is a combination of two amino acids the body digests as it does other proteins. One of the amino acids - phenylalanine - cannot be metabolized by people with a disease called phenylketonuria (PKU). This is the reason for the warning on cans of diet soda. There is at present no scientific evidence of any side effects associated with the consumption of aspartame, although there have been some anecdotal reports of headache, depression, dizziness, blurred vision, and confusion in some persons. If you experience any of these symptoms, it may be a good idea to limit your intake of artificial sweeteners by consuming no more than one or two diet sodas a day.