Urea excretion is primarily related to which factor?

Urea excretion is primarily related to protein intake because urea is a byproduct of protein metabolism. When the body breaks down proteins, it deaminates amino acids, which results in the production of ammonia. The liver then converts ammonia into urea, which is less toxic and can be safely excreted through urine. Therefore, the more protein a person consumes, the more urea is produced and excreted by the kidneys.

While hydration level can influence the concentration of urea in urine, it does not directly impact the total amount of urea produced. Similarly, while fat and carbohydrates are important macronutrients, they do not significantly contribute to urea production as proteins do. Their metabolism does not produce urea in the same way that amino acid metabolism does. This makes protein intake the key factor determining urea excretion levels.