[Evgeny]

Actually, there is very little evidence of kidney damage from high protein intake in healthy individuals. This, for example

http://www.ncbi.nlm.nih.gov/pmc/articles/PMC1262767/

Although excessive protein intake remains a health concern in individuals with pre-existing renal disease, the literature lacks significant research demonstrating a link between protein intake and the initiation or progression of renal disease in healthy individuals.

or this

http://www.ncbi.nlm.nih.gov/pubmed/10722779

To conclude, it appears that protein intake under 2. 8 g.kg does not impair renal function in well-trained athletes as indicated by the measures of renal function used in this study