Aspartame is a dipeptide, built from asparagine acid and phenylalanine - amino acids which naturally occur in food. The doubts come from the fact that aspartame is a source of methanol, but the amounts are too small to pose a threat to the health. Aspartame is one of the best researches synthetic chemical sweetening substances when it comes to safety of use. Scientific research do not confirm the cancerogenic properties of aspartame, nor most of the attributed negative effects. It doesn't mean, though, that you should consume this sweetener in unlimited quantities.
Does the cancer and death scare have any rational basis?
There are scientific studies which prove that high consumption of aspartame can induce headaches. Similarly, there is information about the link between aspartame use and certain neurological problems, connected to the impaired relation between the neurotransmitters. Especially people with diagnosed neurological problems should steer away from aspartame-sweetened foods.
Foods with aspartame shouldn't be heated. A question in need of precise answers is also the neurohormonal response of the body when provided with sweet taste without the calories.
The established ADI (safe daily allowance) for aspartame is 40mg for each kilogram of body weight per day. This sweetener is 150-200 times sweeter than sugar. Although the amount of sweetener isn't usually mentioned on the labels of products containing it, it can be grossly calculated. If in 2 liters of soda there is about a 100g of sugar, then soda light will have 1-1,4g. Whereas the safe amount for a man weighting 80kg is 3,2 g per day. By drinking a couple of liters of aspartame-sweetened drinks you can easily not only get close to the limit, but also exceed it.
So despite the fact that the dramatic messages recommending strictly avoiding the "sweet death" aren't a voice of reason, equally unjustified is the excess optimism concerning aspartame. You need to approach artificial sweeteners with caution and try not to overindulge in them. Nevertheless, when used in moderation, they do not pose a threat to the health.