And finally... we address that important question: what is it that makes your pee yellow? Now before we answer this, I have to say that this story genuinely takes me back to when I was seven, in 1977. We've been having a discussion at school about bodies, and one of the more mischievous friends, Jason Lang, asked this particular cheeky question of the teacher, a Mrs. Williams, and she was terrifying. I remember her answer, given in a tone that was designed to end any further debate, being "becau
se that's the colour your body makes it." I vividly recall my seven-year-old brain feeling that this was an unsatisfactory answer to a genuinely intriguing question that my mate Jason had asked. Well now, 47 years later, I can finally get the answer. Jason, or indeed Mrs. Williams, if you're watching, I hope it helps. Now, it's been known for more than 125 years that a compound called urobilin is responsible for urine's yellow colour, but it was unclear - until now - exactly how it's created. As
we all know, urine colour can change due to hydration, or medication, or indeed diet, as anyone who's eaten a lot of pickled beetroot can no doubt attest. However, for the average healthy person, it is a shade of yellow. According to a new study published in Nature Biology, researchers, Nature Microbiology, researchers have finally uncovered a long-standing mystery of what leads to that yellow colour. And as always, we've saved you the trouble of finding the journal and having to wade through i
t. We have extracted the key information here. So pay close attention, because there might be a test. This is a representation of the haem degradation pathway. Key human enzymes are labelled in grey text, and as red blood cells degrade, the pigment bilirubin is created as a by-product. Experts have known for decades that compounds in the gut turn bilirubin into the compound urobilin. But what they didn't know was what enzyme, or collection of enzymes, turned bilirubin into urobilin. Gut microbes
can be challenging to study, but with advancements in genome sequencing, we've now discovered a new enzyme: bilirubin reductase. Now, what they discovered was that bilirubin reductase is present in healthy adults, but not in newborns, and not in adults with inflammatory bowel disease. This graph is particularly fascinating. It shows that jaundice is highest in individuals who are missing bilirubin reductase. In some disease states, high levels of bilirubin may result in brain damage, and could
even lead to death, so these results will help us study the links between gut microbiome and conditions such as jaundice, and inflammatory bowel disease. This research is particularly fascinating for me, from a personal perspective, because I had a health check just before Christmas, and it confirmed that I have elevated levels of bilirubin in my blood. This is apparently not uncommon, and it's called Gilbert's Syndrome. It is apparently hereditary, so thank you parents. And I was told by my doc
tor that it simply means that my body is less able to break down the yellow pigments in my blood. The doctor told me with a jaunty smile that sometimes the whites of your eyes might be a little more yellow than white, which felt like something I could happily live with. Having read this paper, I feel now I should monitor my pee a little more closely, although looking again at this chart, I'm pleased to say that I've never managed to even get to orange.
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