Why is your pee yellow

One of the many curiosities of the human body is the fact that no matter what you drink, to a certain extent at least, your pee will always be some shade of yellow — from almost clear to dark muddy yellow-orange. There have been cases of urine color changing from the consumption of excessive amounts of a particular food or drink (such as beets), or due to some medical condition (most famously England’s “mad” King George III, who passed urine tinged with a blue-indigo color). But why exactly is pee nearly always yellow? What makes it that color? The answer is urobilins.

Urobilins are a chemical product of breaking down the bile pigment bilirubin, which is itself produced when the body breaks down worn out red blood cells. In particular, bilirubin comes from breaking down the heme part of hemoglobin. This happens primarily in the liver and intestines and is what gives both the brown color to your poop and the yellow color to your pee. It is also these chemicals that give jaundice and bruises their color, as the breaking down of blood cells outpaces the livers ability to process the waste.

It is easier to understand this process when you think of the reason we pee in the first place. Many people mistakenly think that we are simply passing excess water and such out of the body, but this isn’t the case. Water is vital to the body and we are constantly needing to take in more to replace what is lost through bodily processes, such as sweating and urinating. The real reason we pee is to expel harmful toxins from the body before they can do any damage.

One of the most toxic substances that our bodies produce naturally is ammonia. This is produced when the body breaks down amino acids. Due to the fact that even a tiny amount of ammonia can be lethal, our body quickly processes the ammonia in the liver and produces urea, which is not as harmful and can then be passed as urine. This ensures that no harmful ammonia is left to build up in the system, and keeps the body healthy like a natural detox.

Urine isn’t all “bad” though. Over the years, scientists have found many uses for pee based on the urea it contains. For example, urea can be used as a fertilizer, since it provides nitrogen that plants need. The nitrates that can be processed and refined from urea have also resulted in urine being used together with other organic matter as a source of potassium nitrate which is used in the manufacture of gunpowder and smoke bombs. Although by far this is not the quickest method of obtaining potassium nitrate, it has still proven extremely valuable in certain circumstances. Today, urea is actually manufactured through industrial processes and is used in many applications, including as a flavor additive in cigarettes! This might make you think twice before you light up your next cigarette, or at least allow you to more fully appreciate the filter.