Aspartame is an artificial sweetener sold under the brand names Equal or Nutrasweet. It's about 200 times sweeter than sugar, so very little of it is needed to sweeten foods. Aspartame isn't poisonous, doesn't cause cancer, and it's not a pesticide.
Aspartame replaced saccharin as the sweetener of choice for diet sodas because it doesn't have the strong bitter aftertaste of saccharin. Aspartame is also found in powdered diet soft drinks, packaged desserts, yogurt and some vitamin and cold remedies.
It does not hold up to heat so you cannot use aspartame as a sugar replacement for baking or cooking. Sucralose is a better choice in the kitchen, because it is heat-stable.
The American Medical Association, the Academy of Nutrition and Dietetics, and the American Diabetes Association all consider aspartame safe when used as part of a healthy eating plan. But that doesn't prevent people from worrying about it's possible side effects.
Science Indicates Aspartame is Safe
Aspartame has been shown to be safe in more than 200 studies, but some people who suffer from migraines claim that it triggers their headaches.
The sweetener has been blamed for causing brain tumors, leukemia and many other ailments and has been the topic of urban legends for many years. No credible studies have found any relationships between aspartame and these diseases.
But -- Formaldehyde is Toxic!
Your body breaks aspartame down into phenylalanine and aspartic acid, and a very small amount of methanol. It's the part about methanol that scares people because, it's metabolized into formaldehyde in your body.
Formaldehyde is toxic in large amounts, but the metabolism of aspartame results in a very tiny amount of formaldehyde. You get more formaldehyde from the digestion and absorption of 100-percent fruit and vegetable juices. Your liver eliminates the little bit of formaldehyde quickly and safely.
Other No-Calorie and Reduced Calorie Sweeteners
Van den Eeden SK, Koepsell TD, Longstreth WT Jr, van Belle G, Daling JR, McKnight B. "Aspartame ingestion and headaches: a randomized crossover trial." Neurology. 1994 Oct;44(10):1787-93.
Magnuson BA, Burdock GA, Doull J, Kroes RM, Marsh GM, Pariza MW, Spencer PS, Waddell WJ, Walker R, Williams GM. "Aspartame: a safety evaluation based on current use levels, regulations, and toxicological and epidemiological studies." Crit Rev Toxicol. 2007;37(8):629-727.
Academy of Nutrition and Dietetics. "Straight Answers About Aspartame." 2006.