|MadSci Network: Medicine|
Even though urine is mostly water, it contains many other chemicals.
Some of these chemicals are volatile (they mix with the air when urine leaves our body).
Because they mix with air, we can smell them.
Some of these volatile chemicals can have a sweet smell.
For people with an inherited disease called "Maple Syrup Urine Disease", their urine contains a volatile chemical called 4,5-dimethyl-3-hydroxy-2 [5H]-furanone, or sotolone. This makes their urine have a sweet smell, just like (you guessed it) maple syrup. Here is a reference if you would like more information about this condition:
Podebrad F, Heil M, Reichert S, Mosandl A, Sewell AC, Bohles H. 4,5-dimethyl-3-hydroxy-2[5H]-furanone (sotolone)--the odour of maple syrup urine disease. Journal of Inherited Metabolic Diseases. 1999 Apr;22 (2):107-14.
There are many other volatile chemicals that have a sweet smell, so depending on what people eat and how their bodies use the foods that they have eaten, they may also experience "sweet-smelling" urine from time to time.
I hope that this helps!
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