Protein slows down the release of that sugar though, giving a more level energy supply [1], important for a runner that likes to carbo-load before races. I'd usually try to get some chicken in the pasta, or in my rice and beans as well (The actual effectiveness of carbo-loading is debatable, yes)
How does that work? You get twice as much sugar (lactose) than protein from milk. http://www.wolframalpha.com/input/?i=milk