on a diet of strictly beer and water, would you be able to survive? i'm not talking quality of life, just survival.
vegetables and salts are important, but i think it would take a while at least for those deficiencies to have an effect... i think you could survive a couple of months on (good) beer and water. things might get bad after that.
the brew i am sipping right now has carbs and proteins. i wasn't aware of the presence of protein in beer and that's what got me to thinking.