International official documents recommend that concentration of methanol in food should not exceed 8 ppm (parts per million). Given the average annual food consumption of some 700 kg per person, this amounts to 15 mg of methanol deemed safe to ingest daily. On the other hand, safe daily intake of aspartame had been defined at about 50 mg/kg, or 3500 mg per 70 kg adult.
Now we go to the formula of aspartame, in order to deduce the amount of methanol that will be generated in our body by 3500 mg of aspartame. A simple stoichiometric calculation tells us that 3500 mg of aspartame, upon hydrolysis in our stomach and guts, will produce 380 mg of methanol. This value exceeds by 2500% the safe levels for methanol ingestion.
This simple calculation shows that the "safe" levels of aspartame consumption had been grossly overestimated, and should be reduced by at least a factor of 100. Note that we need no clinical tests to come to this conclusion, our knowledge of chemistry has been more than sufficient.
Baseline: if you care about your health, stay away from artificial sweeteners, "diet" drinks and such like. Otherwise, you are subjecting yourself to inadmissible levels of methanol.