It wasn’t one of the truly earth-shattering unsolved questions, but it affects us all: Why is urine yellow anyway? You would think that the answer has been known for a long time, but that is not the case: research has been trying to solve the mystery for over 100 years – so far in vain. But now it seems that scientists have managed to figure out the reason for the color of this body fluid. At the beginning of January, a study was published in the journal ‘Nature Microbiology’ that addresses and ultimately answers the question.
To find an explanation for the yellowish color of urine, a team of researchers from the University of Maryland and the National Institutes of Health led by biologist Brantley Hall investigated how the pigment bilirubin is broken down in the intestine. Bilirubin is a bright red-yellowish pigment that is formed as a byproduct of the breakdown of hemoglobin in red blood cells in the spleen, liver, and bone marrow. Bilirubin then travels to the liver and is excreted into the intestines via bile.
The dye is then excreted through the feces or further converted into other molecules by microorganisms in the intestine. At the end of this chain, the yellow dye urobilin is formed. This is also excreted in the feces or absorbed from the intestine into the blood. This way it reaches the kidneys and is excreted through the urine.
It has long been known that urobilin is responsible for the yellowish color of urine. But until now it was unclear what physiological process led to its creation. “It is remarkable that such an everyday biological phenomenon could not be explained for so long,” Hall notes.
As the researchers have now discovered, an enzyme is responsible for the production of urobilin: Bilirubin reductase (BilR) plays an important role in the breakdown of bilirubin. This enzyme occurs in many bacteria in our intestinal flora; According to the study, mainly in lactobacilli and clostridia. “Gut microbes encode bilirubin reductase, which converts bilirubin into a colorless byproduct called urobilinogen,” Hall explained in a statement from the university. “Urobilinogen is then spontaneously broken down into a molecule called urobilin, which is responsible for the yellow color we all know.”
The enzyme bilirubin reductase is present in the intestines of virtually all healthy adults, the research team explains. In contrast, patients suffering from inflammatory bowel disease are often missing. BilR also often does not occur in newborns – and they are usually prone to jaundice in the first few months of life. Therefore, the researchers believe their findings could help better understand inflammatory bowel disease and jaundice.
In these diseases, the pigment bilirubin is not excreted properly, but is reabsorbed from the intestines into the blood, where it accumulates and leads to various complaints. For example, jaundice causes a yellowish discoloration of the skin and eyes. Patients with inflammatory bowel disease often suffer from gallstones, which can cause painful colic. Scientists believe that the lack of the enzyme may contribute to jaundice in newborns and the formation of gallstones in adults. (mr)
source: watson
I’m Maxine Reitz, a journalist and news writer at 24 Instant News. I specialize in health-related topics and have written hundreds of articles on the subject. My work has been featured in leading publications such as The New York Times, The Guardian, and Healthline. As an experienced professional in the industry, I have consistently demonstrated an ability to develop compelling stories that engage readers.
