Per Snopes, it’s absolute baloney:
To date, FDA has not determined any consistent pattern of symptoms that can be attributed to the use of aspartame, nor is the agency aware of any recent studies that clearly show safety problems.
Our research revealed over 6000 web sites that mention aspartame, with many hundreds alleging aspartame to be the cause of multiple sclerosis, lupus erythematosis, Gulf War Syndrome, chronic fatigue syndrome, brain tumours, and diabetes mellitus, among many others. Virtually all of the information offered is anecdotal, from anonymous sources and is scientifically implausible.
(American Council on Science and Health):
(Dr. Dean Edell):
A highly inaccurate “chain letter” is being circulated via e-mail warning the reader of the health dangers of aspartame (Nutrasweet) diet drinks.
Even daily large doses of the high-intensity sweetener aspartame, also known as NutraSweet, had no adverse effect on study subjects’ health and well-being, a visiting scientist at MIT reported in the American Journal of Clinical Nutrition last week.
“We conclude that aspartame is safe for the general population,” said Paul A. Spiers, visiting scientist in the Clinical Research Center (CRC).
A widely disseminated e-mail by a “Nancy Markle” links aspartame to Alzheimer’s, birth defects, brain cancer, diabetes, Gulf War syndrome, lupus, multiple sclerosis and seizures. Right away, the long list warrants skepticism. Just as no single chemical cures everything, none causes everything.