Wait, what?

A plain old can of soda is now too much for my system to handle.

I was feeling a little sleepy in the middle of the afternoon, so I had a Coke. Now I feel jittery and, I kid you not, nauseous. I can drink the equivalent of a whole bottle of wine without really ever feeling too drunk or headache-y afterwards, but not even a whole can of Coca-Cola, and I think I'm gonna yak?

Is this what "getting old" is like? Because it's weird.