flajice said:
Because it has been proven, over and over again. Your body will digest whatever macro-nutrients your put into your body. The argument is risk/reward with protein intake.
Hypothetically speaking, high protein intake is great for a variety of reasons. For bodybuilding purposes, it almost ensures that you will have a positive nitrogen balance. Further, gram for gram, protein is more thermogenic than any other macro nutrient in that it takes more energy to digest protein than it does carbs or fat.
Any two dollar trainer that states "your body can only absorb X amount of protein" should be kicked in the balls. This is ignorance on par with "steroids make your dick smaller" statement that is still being sprayed.
The facts are these:
1. Your body will digest almost everything you ingest.
2. Excess nitrogen will be excreted through the urine.
3. The ignorance of the general public is astounding.
So, knowing all of this, from a bodybuilding perspective the argument becomes:
Should I take in a level of protein that might put me in a positive nitrogen balance, or should I eat enough protein to ensure that I am in a positive nitrogen balance?
The worst thing that can happen is you excrete the excess nitrogen. Whoopy-doo. High protein intake can be correlated with increased liver and kidney values that are indicators of abnormal function, but "normal" does not necessarily mean pathological. Bodybuilders are not "normal" humans, and I don't know of one case where high protein intake caused renal failure, or cirrohis of the liver etc.
This is the information age people, lets get it right. If anyone has any scientific proof to the contrary bring it, but I have never seen it, and I have looked and looked.