Aspartame consists of three molecules joined together. They are: (1) 50% phenyl alanine, an amino acid found in food, which can be neurotoxic in high quantities and can cause seizures in certain susceptible people; (2) 40% aspartic acid, also an amino acid found in food, which is a neuroexciter and neurotoxic in high concentrations; and (3) 10% methanol or methyl alcohol, which is also called wood alcohol. Free methanol is quite toxic even in relatively low concentrations.
The FDA and manufacturers response to the many expressed concerns of the damaging effects of methanol in aspartame is to point out that it occurs naturally in fruit juices and vegetables. They neglect to state that in these foods, the methanol is in a bound form and the human body does not have the digestive enzymes that breakdown the pectin and release the methanol into the bloodstream. In addition, natural methanol is always accompanied by ethanol in higher concentrations, which acts to protect the body against any damage. The methanol in aspartame is in free form and can be absorbed.
Some of the breakdown metabolic products of these substances are also toxic and carcinogenic. Thus, you can see that there are many possible mechanisms by which aspartame is potentially toxic and dangerous.
An additional concern about aspartame is that it tends to lower serotonin in the brain. Low brain serotonin levels are associated with depression. The FDA has banned the food supplement tryptophan, the essential amino acid responsible for making serotonin in the brain. With so much aspartame being used and no tryptophan available to increase brain serotonin levels, is it any wonder that the new anti-depressant serotonin reuptake inhibitor drugs, such as Prozac, have become so popular.
Who is at risk for experiencing aspartame toxicity? At least 30% of the population is sensitive to moderate doses of aspartame and may suffer from any of the symptoms that I've previously discussed. Women are 3 times more likely to suffer symptoms and pregnant women may put their unborn babies at risk. The undeveloped nervous systems of children are more vulnerable to even mild doses. An example of a subpopulation of adults who may be more susceptible to symptoms are phenyl ketonuria or PKU carriers.
Phenyl ketonuria or PKU is an inherited disease in which babies lack an enzyme necessary to convert phenyl alanine to tyrosine. If given foods containing phenyl alanine, they accumulate excessive phenyl alanine in the brain, which results in permanent brain damage and mental retardation. Their parents are carriers of the disease and also have some difficulty metabolizing phenyl alanine. These carriers of PKU, of which there are between four and twenty million in the United States, are among those most susceptible to the toxic effects of aspartame.
The FDA & manufacturers of aspartame claim that all of the adverse symptoms reported are "anecdotal". Because it is common that a person will not experience noticeable illness from a short term usage of aspartame, this is taken as proof that there is no problem with safety. Unfortunately, this position ignores the fact that the effects of aspartame poisoning are cumulative.
If an approved drug had as many complaints as aspartame, it would have been removed from the market long ago. But, aspartame has been approved as a safe food additive and not a drug. The manufacturer does not have to track adverse reactions once the food additive has been approved, as in the case of new drugs. Aspartame was approved for use in dry foods and as a sugar substitute in 1981 and for soft drinks in 1983.