Is there a relationship between aspartame and neurological illnesses, such as multiple sclerosis, Parkinson’s disease and Alzheimer’s disease?

There is no relationship between aspartame and any neurological illnesses. It is accepted as safe by major heath organizations, including the Multiple Sclerosis Foundation, the American Diabetes Association, the American Dietetic Association and the Council on Scientific Affairs of the American Medical Association. The faulty premise behind these allegations is that consuming large amounts of aspartame causes aspartic acid to reach high levels in the blood. Critics claim that these high levels of aspartic acid circulate to the brain and kill nerve cells by over-stimulating them. Carefully conducted scientific research with aspartame shows that this is not possible. Consuming even extraordinarily large amounts of aspartame over a long period of time does not result in high blood levels of aspartic acid.

In one study published in the American Journal of Clinical Nutrition, human subjects who receive doses of aspartame as high as that found in about 12 liters of a diet soft drink (about 33 cans) did not show significant increases in the amount of aspartic acid in their blood. Blood levels of subjects who received 24 liters of diet soft drink (about 65 cans) at one time stayed well below toxic levels. Another study published in the Archives of Internal Medicine showed that aspartic acid did not build up in the blood, even after long-term, high-dose aspartame use. Researchers randomly divided 108 healthy adults into two groups. Every day for 6 months, half of the subjects took capsules containing as much aspartame as that found in about 10 liters (about 28 cans) of an aspartame-sweetened drink. The other half took placebo capsules that did not contain aspartame. The study was double blinded, meaning that neither the subjects nor the researchers knew who took aspartame and who took the placebo. Results showed that blood levels of aspartic acid did not change significantly in either group.