Does high protein intake cause kidney damge?

This is an answer to a email I recently received. Here is the deal with high protein intake. In people with normal kidney function, increased protein intake has not been shown to harm the kidneys. However, if you have underlying kidney disease, increased protein can speed up the rate of kidney function decline. Increased amounts of protein, even at 1 gram/lb of bodyweight, causes hyperfiltration in the kidneys. This has been shown in studies including the one done by me. However, to my knowledge, no one has done any longterm trials in healthy people to show if this hyperfiltration leads to kidney decline. In diabetics, we have increased hyperfiltration early in the disease and their kidney function slowly declines. So hyperfiltration causing kidney damage is a possibility but I don’t have any actual data in normal patients to support this with. At this time I would limit myself to no more than 1-1.5 grams per kilogram of bodyweight.
Regards,
Sean Hashmi

References:

• Manninen AH. High-protein diets are not hazardous for the healthy kidneysNephrol. Dial. Transplant., March 1, 2005; 20(3): 657 – 658.
• Knight et al. The Effect of Dietary Protein Intake on Kidney Function in Women with Normal or Mildly Abnormal Kidneys. Annals of Internal Medicine 2003;138: I-51.