The concern with aspartame comes from the fact that it is a small protein. It consists of two amino acids, phenylalanine and glutamic acid (which is also called glutamate). Glutamate is a strange amino acid. When combined with phenylalanine, it tastes sweet. When used alone (typically as the sodium salt called monosodium glutamate) it doesn't taste like anything but intensifies other flavors. MSG has long been blamed for a number of ill-effects, but the interesting thing is what if you give people who say that they have bad reactions to MSG a placebo and tell them that it has MSG in it, they get the same side-effects.
Glutamate, on top of being an essential amino acid, is also a neurotransmitter that activates neurons in the brain. It is present naturally in the brain and is used as a neurotransmitter there under normal conditions.
So what happens if you eat a bunch of glutamate? Well, the body has a bunch of physiologic systems to prevent it from hurting you, including very strict regulation of what crosses the blood-brain barrier. The amount of aspartame in a typical soft drink is relatively small (on the order of 100mg, of which less than 50% is glutamate by weight). By contrast, you get a lot more glutamate from a steak.
Aspartame has long been the target of a conspiracy theory in which critics claim that since 1974 there has been a cover-up of the dangerous health-effects of aspartame. They forget that other chemicals and additives with relatively minor effects have been pulled off the market for very small/insiginificant effects and that if there were actually a demonstrable effect that someone would have blown a whistle after 36 years of use.
The three websites you cite are all anti-aspartame websites and they will grasp at any story to demonstrate that it is dangerous. They're exactly as trustworthy as anti-vaccine sites and anti-round earth sites. Aspartame in the quantities usually consumed by soda drinkers simply doesn't provide enough of any of the components to cause toxicity.
|Quoting AA737-823 (Reply 1):|
In regards to the topic, as a small child I had an unusual issue with migraine headaches, followed by extreme nausea and dizziness. They were eventually (after much suffering, sorry to say) traced back to aspartame.
But how? Because some doctor said so? If so he had no rational basis on which to make that assumption unless he did blinded placebo-controlled trial. The caffeine in the soda, on the other hand, can do exactly what you describe.