Egg whites are a complete protein source, containing all essential amino acids, providing your system can handle digesting egg (some are intolerant) then nutritionaly they are spot on for lean tissue growth/maintenance.
Sure, they dont have the same level of absorbtion that you would find in double micro filtered cassein powder supplements, nor the chocolatey taste of ripfast whey protein shake, but eggs work out a fraction of the cost of nicely packaged and marketed protein supplements.
Vince Gironda, Steve Reeves, John Grimek, Arnie, Sergio (the list goes on) all built physiques with milk and egg protein as the cornerstone of their diets/supplementation.

Thats how little nutrition egg whites have.

I think CanuckMA is part correct in that other than protein, egg whites actually contain very little minerals and vitamins or any other goodness. Depending on the main meal dumbell tucks into it is important that he gets enough of vitamins and minerals as well as protein, but that goes without saying.

Fair comment, it is always best not to assume the obvious.
As with any protein source, it should be complemented with good quality foods from all other groups to maintain a balanced diet.

6 eggs a day...alright, but you won't be pleased for what comes after. If you're lucky, you will digest the eggs. However, stay away loved ones for it will give you the worst smelling odor, great in matches. You opponent will steer clear from your backside.
I can't eat eggs because they always get me sick. I can't even eat one. I throw it up and I don't know what it is. I like the taist of eggs, but I just think it might be an issue with just me. No matter how I prep them, I get sick.
Good luck,
Gar

EEEK! You are still growing! Eat well and regular!