Ursodeoxycholic acid (UDCA) is a secondary bile acid that acts in our gut to help us digest fats. Phew, that's enough physiology for today.

Therapeutically, UDCA is the mainstay of treatment in primary biliary cholangitis, and is also used to dissolve cholesterol gallstones and treat itching in obstetric cholestasis. In fact, it has been used in China and Japan to treat digestive problems for centuries (its use was first recorded in 659 AD), but Western medicine only caught on to its potential in the second half of the 20th century.

Ursodeoxycholic acid derives its name from the Latin ursus, meaning “bear”, because it is found in bear bile. Yep, you read that right, at some point someone looked at a bear's gallbladder and thought “I'm going to drink the contents of that and see what happens”. You're probably familiar with the constellations Ursa Minor and Ursa Major, so named because they supposedly resemble bears (although if you ask me, the guys who named them must have been tripping as hard as the anatomist who thought the navicular bone looks like a boat). They have the same linguistic root as UDCA, as do lots of European words for “bear” including ours (French), osso (Spanish) and urs (Romanian).

Sadly, there's a dark side to this word origin, because although the UDCA that you might prescribe to an itchy pregnant lady is synthetic, in traditional Chinese medicine there is still demand for its original source, bear bile. This has led to certain species of bears being hunted to the brink of extinction, and to the establishment of brutal “bear farms”, where bears are kept in tiny cages to have their bile extracted using crude and painful methods. The good news is, thanks to animal rights campaigners, it looks as though this practice won't be around much longer.

There you have it – ursodeoxycholic acid: the bilious substance that shares its name with stars and has been used for centuries to make life more bearable.

(Sorry.) 

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