Excess protein intake can stress body systems when protein provides more than approximately what percent of daily calories?

• A. 20%
• B. 25%
• C. 30%
• D. 40%

Answer: (C)

Protein as a share of daily calories has limits. While protein supports tissue building and repair, it also carries a nitrogen load that the body must excrete as urea. When protein contributes a sizable portion of energy—around 30% of calories or more—the body shifts energy away from other macronutrients and the kidneys and liver work harder to handle the nitrogen waste. This is why, in many guidelines and exam contexts, 30% is cited as a practical threshold beyond which excess protein may stress body systems. The lower options stay well below this tipping point, and the highest option exceeds it, but 30% best captures the commonly cited approximate limit.