The yellow color of human urine is primarily due to a pigment called urochrome. Urochrome is a waste product resulting from the breakdown of hemoglobin, a protein in red blood cells. The varying shades of yellow in urine can be influenced by factors such as hydration levels, diet, and certain medications, but urochrome is the main pigment responsible for the typical yellow color of urine.

Vitamins A, D, E, and K are called the fat-soluble vitamins, because they are soluble in organic solvents and are absorbed and transported in a manner similar to that of fats. Vitamin E deficiency, which is rare and usually due to an underlying problem with digesting dietary fat rather than from a diet low in vitamin E, can cause nerve problems.