Final answer:
Excessive intake of proteins can damage the kidneys, particularly the glomerular capillaries, leading to nephrotic syndrome or kidney failure.
Step-by-step explanation:
The organ that may be damaged by excessive protein intake is the kidneys. When the glomerular capillaries are damaged, it allows protein to leak into the filtrate, leading to conditions such as nephrotic syndrome, which are characterized by symptoms like swelling, low serum albumin, and high cholesterol. In severe cases, this can lead to kidney failure. It is important to monitor protein intake and kidney function to prevent damage, especially in those with pre-existing kidney issues or diseases that might predispose them to renal problems.