(By the way, there are all kinds of protein — including egg white, various grades of whey, casein,
even beef protein powder!
Three, collagen, or
hydrolyzed beef protein powder sourced from pasture raised, antibiotic and hormone free beef, may be a good option for some, but it's often hard to find one that tastes palatable enough to actually drink, and some people find they do not digest it well.
Consuming ≥ 3 g / kg / day from whole foods is pretty difficult so the participants on the high protein diet were able to consume commercially available whey or
beef protein powder.