Two major wastes :
- Urea : Urea is the major waste resulting from protein metabolism, accounting for about half of total urinary wastes. Most of the urea is eliminated through urine, and thus the amount of urea in the urine is often used as a marker of protein intake.
- Sodium : Sodium is an essential mineral, coming exclusively from food. It has a key role in maintaining body fluid volume. Sodium can also be eliminated through perspiration or bowel elimination, but the major part is through urination. The kidneys can adapt sodium elimination to a wide range of intakes, from virtually 0 to about 25g per day
›› In a modern diet comprising many processed foods sodium intake largely exceeds our daily requirements, and most dietary sodium must be excreted in urine. That’s why it is sometimes used as an indicator of excess sodium intake !