http://www.cancer.gov/cancertopics/factsheet/risk/aspartame . The NCI study concluded that aspartame consumption did NOT increase the risk of any cancers, including leukemias, lymphomas, and brain cancer. The FDA approved daily dose of aspartame is 50 mg/kg of body weight, or about 16 cans of diet soda for a 150-pound person.
So why all the controversy? Well, for one thing, did you know that laboratory research causes cancer in rats? Yes, that's right, if you feed or inject rats with enough of anything, they will get cancer. Furthermore, Rats do not equal People. We cure breast cancer in mice and rats all the time, but we cannot cure people yet. Just about anything is dangerous in high enough doses (even pure water!).
I'm sure the experts will continue to argue about aspartame for decades to come. The bottom line: aspartame probably isn't good for you (for this reason, and for others I will discuss in future posts), and you should limit your intake. If you drink a diet pop or two everyday, you're most likely going to be just fine. There is no need for panicking and all those zombie pictures all over the internet. I for one am going to try to reduce my Diet Pepsi consumption, and I already think that foods made with aspartame (like Yoplait light yogurts) taste positively awful. If you like to limit your calories in things like coffee or tea, I recommend trying Stevia, which is an all-natural plant-derived sweetener.