Tuesday, May 21, 2013

Diet sodas must be bad: They have a warning label!

My wife and I joined some friends for dinner tonight. It wasn't anything fancy - just pizza and some soda - but it was enjoyable nonetheless. During dinner our host started talking about the "dangers" of diet soda. I kept my mouth shut, not wanting to go on a Tim Minchin-esque Storm rant (warning: NSFW language), but eventually knowing I was a chemist I was asked to give an opinion on the nasty chemicals.

I quickly explained that aspartame was perfectly safe. I have wanted to write an article on it several times but frankly it's not interesting enough to hold my own attention. It's been studied for a long time and has been found to be safe for consumption. End of story.
"But what about the warning label?" the host replied
"What warning label? I don't know about a warning label." 
"Ya, every diet soda has to have a warning label because of how bad they are for you."
Luckily I have spent more time reading about aspartame than I care to, so after a few moments I realized what label she was talking about. I quickly explained the warning to her as I will to you:


No, this is not the label I'm talking about!

That's not it either.

No, the warning I'm talking about is much more simple. Here it is:

That's it. The only warning is: "Phenylketonurics: Contains Phenylalanine". What does this warning mean? Well, to tell you the truth if I have to explain what this warning means then it doesn't apply to you. 

You see, there is a specific genetic defect, called phenylketonuria, which (in short) messes with your liver and makes it impossible to correctly digest phenylalanine, a common amino acid. Phenylalaine is an essential amino acid that is used by your body to synthesize dopamine, a necessary neurotransmitter. An excess of phenylalanine, like you would see in phenylketonuria, can lead to serious problems including mental retardation and death. Phenylketonurics (those that suffer from phenylketonuria) must live on a diet that restricts intake of phenylalanine. Therefore, the warning is placed on diet sodas. 

But some would argue that if it's really bad for some people we should all avoid it. If the warning that diet soda contains phenylalanine prompts you to avoid phenylalanine, here's a list of other foods you should also avoid, as they also contain phenylalanine (and some in much higher doses):
  • Fish
  • Bacon (Nooo!!!!)
  • Beef
  • Chicken
  • Milk
  • Cheese
  • Walnuts
  • Almonds
  • Peanuts
  • Beans
  • Lentils
  • Crab
  • Oysters
  • Soy products
And this is by no means a comprehensive list. My point is this: Yes, there is a warning on diet sodas, but it's not because they will give you cancer, and the warning probably doesn't even apply to you. So go on, drink up. You know you want that Diet Coke.