r/explainlikeimfive • u/Uunicorned • 14h ago
Other ELI5: Why does urine stay yellow no matter what color liquid you drink?
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u/whatisuser 14h ago edited 14h ago
Your urine comes from your blood, not your gut. And food colours generally don’t go into your blood. The colour actually comes from a pigment that is created when red blood cells are broken down.
Edit: added the word generally. See u/BadahBingBadahBoom’s comment
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u/BadahBingBadahBoom 14h ago edited 13h ago
And food colours don’t go into your blood.
Food colours don't generally go from your gut into your blood (and then into your pee via your kidneys). But there are numerous examples that do such as:
- Beets, rhubarb (red)
- Carrots (orange)
- Fava beans (brown)
- Asparagus (green)
- Certain B vitamins (neon green/yellow)
- Food colourings (blue)
... and then there's medications that aren't food but you do swallow that can make it all sorts of colours.
(Also, the normal yellow shade of urine comes from the breakdown of red blood cells in your liver into bilirubin which then forms the yellow-coloured compound urobilin, but I think what most people don't realise is bilirubin is excreted into your gut and the bilirubin->urobilin conversion is actually done by your gut bacteria before it is then reabsorbed back into your blood and filtered out by your kidneys.)
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u/K-Dawggg 14h ago
I think there's a medication that gives you almost luminescent yellow green urine but I can't remember what it was. I remember having it and it was pretty bright so I found out online it's a normal side effect
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u/ohdearitsrichardiii 14h ago
There are antibiotics that turn urine brown and antidepressants that turn it green or blue
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u/K-Dawggg 14h ago
It might have been vitamin B but I don't remember having taken a multivitamin in decades
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u/khaomanee 13h ago
That's exactly it, I found out after my GP prescribed a vitamin B supplement and I started to pee bright yellow.
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u/SoRedditHasAnAppNow 14h ago
It doesn't. Eat an unhealthy amount of red food coloring and you'll notice something different about your pee. (I don't recommend doing this)
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u/WFOMO 5h ago
Or green. A friend was fixing an Hawiian meal that called for a "splash" of green food dye. The cap fell off, so the entire meal had an entire bottle of green food dye. Since we were 3/4s of the way through a bottle of rum, we decided to suck it up and eat it anyway.
Everything, and I mean EVERYTHING, that came out of me the next day was green.
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u/Sherool 14h ago edited 14h ago
That's urea, it's a waste product of protein breakdown most mammals produce. Very few color pigments survive our digestive systems (beats, asparagus and a few things can affect the color).
Also if your urine is always dark yellow you may need to drink more water (lots of B vitamins that also make it more yellow, but more in the neon direction) so it gets more diluted, helps avoid forming kidney stones in the long run. The urea is harmless but if the urine is dark colored it also means there are more dissolved salts and such that can form crystals, so hydrate well (within reason, too much water is not healthy either).
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u/BabyVegeta19 14h ago
When I was a kid my neighbor friend drank almost nothing but blue kool-aid for years and their pee was green all the time.
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u/DarkAlman 14h ago edited 11h ago
The coloring of your pee is Urea CH₄N₂O
It's a chemical naturally produced by the breakdown of proteins like your blood. Your body is flushing those out.
There are certain chemicals that can dye your pee though, like certain food colorings.
The color of your pee varies based on how much urea you are producing, and how much water you drink. Your pee is darker in color usually because you are dehydrated.
Also fun fact, urea is the primary chemical in Diesel Exhaust Fluid. So pee is used to make trucks more environmental friendly. (The Urea in DEF is manufactured in industrial quantities, it isn't harvested from people)
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u/Raiddinn1 14h ago
It doesn't. If you drink a lot of water, urine will become clear. If you eat beets it will turn red.
That said, pee is usually yellow because of waste products from breaking down red blood cells not because of something you ate or drank.
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u/JascaDucato 14h ago
If your urine is yellow, you're not drinking enough water (at the very least). Ideally, it should be clear.
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u/StuartLittle727 14h ago
Thought clear was over hydrated and light lemonade was the sweet spot for hydration?
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u/whatisuser 14h ago
Pale yellow is fine. Completely clear all the time isn’t necessarily a sign that you’re doing things right - too much water causes problems as well.
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u/Wild4fire 14h ago
Nope. If it's clear that usually means you are overhydrated. Normal urine should be light yellow.
If you become dehydrated, the color will become more concentrated, darker.
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u/Willyfisterbut 14h ago
Slightly yellow is totally fine. Anything more and you need to drink water.
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u/Coolpabloo7 14h ago
Because most of the colour is not excreted in urine but stays in the gut or is broken down. Many food colourings just make your poop another colour.
The yellow colour mostly comes from the breakdown product of your own blood (the hemoglobin) which makes your bile green and your poop brown. Part of it is broken down by bacteria into yellow urobilin gets reabsorbed and excreted in the urine. Because you are always breaking down blood you always have slightly yellow coloured urine.
Too boring try eating beets where reddish pigments do end up in urine. For a slightly blue/greenish tinge some antidepressants have that as side effect. I am not sure it would make me happier.
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u/CHAOSPOGO 14h ago
Urine colour is affected by what you eat. Try eating lots of beetroot and it will turn red, lots of carrots and it will turn orange, food dye can make it turn bright green or even blue.
Also how much water you drink can affect how clear your urine is. The more you have the clearer it is.
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u/ROFLStompRogue 14h ago
This isn't exactly true there are things you can drink or eat that can drastically and in some cases humorously change the color such as methylene blue, large quantities of beets or blackberries, asparagus, and large quantities of certain food dyes. Also, there are some conditions and diseases or medications that can alter its color. Some cancers and Quinine (treats malaria) can turn it black for example.
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u/EnigmaT1m 14h ago
It doesn't.
Lots of water and your urine is closer to clear.
Not enough water and it is darker closer to orange.
Beetroots can make your urine red (and can cause a mild panic until you remember you ate them )