While I’m not a fan of Monsanto or synthetic sweeteners, Monsanto sold the rights to aspartame in 2000. A 165 pound person who drinks 21 12 ounce cans of diet soda a day is approaching the maximum amount of dietary aspartame. While it does metabolize into phenylalanine, aspartic acid, and methanol primarily, maximum consumption of aspartame results in 1%-2% of the daily production and consumption aspartic acid which is an amino acid. Phenylalanine is an essential amino acid found in milk products and eggs, and the while methanol itself is toxic, the amounts resulting from aspartame metabolites is very small. While aspartame is certainly not a vitamin, and gluttonous habits probably cause some people to overindulge, I believe it to not be cause for alarm ingested in small reasonable amounts. Check out Ajinomoto, the world’s largest producer of Aspartame. 😉 As with everything, toxicity is a function of concentration and time.