Aspartame

Aspartame is a sugar-free, low energy sweetener, 200 times sweeter than sugar.   It has been used in a variety of foods and drinks, usually in place of sugar, for more than 25 years. Having a sweet taste, whilst low in energy, makes aspartame useful for those who wish to decrease their sugar intake.
Aspartame is made up of the amino acids phenylalanine and aspartic acid as well as a small amount of methanol.  Aspartame is broken down, in the body, to these three compounds, all of which occur naturally in many common foods.   The body uses phenylalanine, aspartic acid and methanol in exactly the same way whether it comes from aspartame or another food.   Aspartame does not enter the bloodstream or accumulate in the body.  (N.B. Because aspartame contains phenylalanine, it should not be consumed by those with phenylketonuria (PKU). PKU is a rare genetic disease diagnosed soon after birth and treated through avoidance of foods high in phenylalanine.)
Foods which may contain aspartame include diet soft drinks, yoghurt, chewing gums, low calorie sweetners and calorie-reduced foods. When used, aspartame will appear in the list of ingredients as aspartame or as E951. 
Aspartame has attracted a high level of interest over the last few years, due to concerns raised by a few individuals over its safety.   One concern regards the production of methanol when aspartame is broken down in the body. The amount of methanol produced, however, is small and often less than from foods in which methanol occurs naturally, e.g. bananas, citrus fruit and some vegetables.  
An ‘acceptable daily intake (ADI)’ is set for all food additives. A woman would have to consume 14-15 cans of a sugar-free drink containing aspartame every day before reaching aspartame’s ADI; men even more. A 2003 survey by Food Standards Australia New Zealand (FSANZ) showed, on average, New Zealanders reach only 4% of the ADI, while those taking in higher amounts of aspartame, reached only 13% of the ADI.
 
Aspartame is one of the most extensively tested food ingredients. It has been deemed safe by independent regulatory authorities in more than 100 countries including the New Zealand Food Safety Authority (NZFSA), the U.S. Food and Drug Administration (FDA) and the European Food Safety Authority.   The NZFSA has a fact sheet available: Aspartame: What it is and why it’s used in our food.