Reactions video series. More than 6,000 food and beverage products contain aspartame, which was discovered in the mid-60s. The chemical has actually been very well-studied for its effects on human health, but many consumers are still skeptical about its safety. As the video explains, this could be because, when we digest aspartame, it gets partially broken down into a compound called methanol, which is then metabolized into formaldehyde, a carcinogen. Of course, if this was where aspartame's journey through your body ended, it wouldn't be unreasonable to have qualms about eating it. But it's not that simple — for one thing, the formaldehyde never actually builds up or gets stored in your body.
Aspartame isn't safe for everyone, however. It needs to be avoided by people who have a very real but relatively rare condition called phenylketonuria — they can't break down a compound in aspartame known as phenylalanine.
So, it looks like Pepsi didn't need to make the switch for any dire medical or scientific reasons. But seeing as how aspartame has been met with public resistance since its initial FDA approval, it probably won't shake its bad reputation any time soon.
Check out the video below for more info on how exactly aspartame breaks down and just how many cans of diet soda you'd have to drink to see any adverse effects.