Why is it that food that was once red or green or yellow, et cetera, comes out one color when it comes out of the human body?

Why is it that food that was once red or green or yellow, et cetera, comes out one color when it comes out of the human body?

And we know what color she is referring to and the answer actually is that the food itself doesn’t necessarily contribute very much to the color of what comes out the back end. The reason being that the dominant determinant of the color of what comes out the back end is bile and bile salts, what your liver squirts into your small intestine to help you to absorb fat. And the reason for that is that there is a chemical which is called bilirubin which is a breakdown product of hemoglobin, the stuff that makes your red blood cells red, that goes into your intestines and it gets modified by a bacteria in the small bowel and as a result of that modification, it gets oxidized into a chemical first called urobilinogen which is what gets reabsorbed into your blood stream and makes your wee go yellow but then it also ends up back in your gut and gets turned into an even browner chemical called stercobilin and stercobilin is the brown stuff that it makes pooh a brown color. And if you have a blockage in the supply of bile into your intestines from the liver, what that does is actually prevent you from getting any of this stercobilin being made and you actually do very pale colored poohs and so, you can use that as a way to diagnose people who have gall stones or liver problems.

Why is urine yellow? Is it usually yellow in most species, just mammals? It’s mostly water so why is it yellow?

Why is urine yellow? Is it usually yellow in most species, just mammals? It’s mostly water so why is it yellow?

The yellow colour is because of the stuff that makes your blood red. When we break down red blood cells which last about 120 days the haemoglobin makes a protein which has a iron atom at the centre. That protein gets broken down into something called bilirubin. Bilirubin is dumped out of the body by the liver. The liver metabolises the bilirubin bit by adding sugar to make it dissolve in water, puts in bile and your bile then gets squirted into your small intestine to help it reabsorbs fats. The bilirubin, because it has sugars stuck on it becomes broken down by bacteria. The bacteria metabolise the molecule and they turn it into something which is called urobilinogen. Urobilinogen gets reabsorbed further down the small intestine. Unlike bilirubin, which is not very soluble in water urobilinogen is very soluble but it’s a brown colour. The urobilinogen goes round the blood stream again but when it goes round in your blood stream again but when it goes through you kidney, because it’s soluble in water, it moves out through the kidney in the same way as the other things that go into urine do and it goes into your urine. Because your urine is a concentrate of plasma you take water back but leave the products that have got filtered behind and it builds up in the urine and adds this brown colour. So urine goes darker and darker. The more dehydrated you are the darker it is because the concentration is higher.
It may be a bit of it’s riboflavin as well because if you take a lot of B vitamins you just wee them out. I think, riboflavin, when it’s dissolved in water is very yellow as well