Protein shakes definitely work, for me at least. My hair grows average pace, but I started drinking protein smoothies recently, and I have noticed the change. My nails grow a lot faster and stronger, and my hair has sped up in growth too.
I can see newer waves at my roots at a faster rate than I'm used to, and It definitely looks longer than I would have expected it to be. I used to do the length pictures and even measure inches but I wish I had.
The only thing with protein shakes is that if you are not active and working out you will gain weight. I gained some weight in my thighs because I started slacking while I was stil having the shakes. I would never want to be walking around with cute hair and an ugly body, so now I have the shakes only before or after I workout.