TUDCA

What it is

Bile acids help digest fats in the gut and circulate between the liver and the gut. Ursodeoxycholic acid, UDCA for short, is a particularly water-soluble and therefore gentle bile acid. When the body attaches taurine to it, TUDCA is formed. In the circulation between liver and gut, part of it is converted back into UDCA and conjugated again.

In Italy, TUDCA is approved as a prescription medicine, for example as Tauro with 250 mg per capsule. It is used there to dissolve cholesterol gallstones and to improve impaired bile formation. The package leaflet states 5 to 10 mg per kilogram of body weight, that is, 250 to 750 mg daily. In Germany, TUDCA is sold as a food supplement.

How it is supposed to work

The first route runs via the bile. Taking TUDCA shifts the bile acid pool toward the hydrophilic, less aggressive bile acids. This has been measured in humans: in patients with primary biliary cholangitis, the proportion of ursodeoxycholic acid in the bile rose to 34.4, 32.8 and 41.6 percent under 500, 1000 and 1500 mg per day over 6 months. At the same time, the body’s own, more aggressive bile acids decreased.

The second route is more exciting and, for biohackers, the real reason. In cells, TUDCA acts as a so-called chemical chaperone, a folding aid for proteins. It relieves the endoplasmic reticulum, the cell’s protein factory, when too many proteins are misfolded there. This ER stress is regarded as a link between excess weight, insulin resistance and type 2 diabetes. In a much-cited 2006 paper in Science, TUDCA and 4-phenylbutyric acid normalized blood sugar in obese, diabetic mice, restored insulin action and resolved fatty liver.

For the same reason, TUDCA is being studied in nerve diseases: dying nerve cells in ALS also show signs of ER stress and misfolded proteins. In the laboratory, TUDCA protects cells from programmed cell death.

What users are looking for

In the strength sports scene, TUDCA is used as liver protection with oral anabolic steroids, and in the longevity scene as general liver and cell protection. These are user reports that can be taken seriously, because TUDCA does work in cholestasis. But there are no controlled studies on exactly these purposes.

What the studies show

The ALS pilot study

34 ALS patients on the standard drug riluzole were randomized after 3 months of observation to 1 g TUDCA twice daily or placebo and treated for 54 weeks. A responder was anyone whose disease progression slowed by at least 15 percent on the ALSFRS-R scale. That was 87 percent under TUDCA and 43 percent under placebo. Side effects did not differ. The authors cautiously spoke of preliminary data.

TUDCA-ALS, the phase III trial

The European consortium tested the result with 336 participants at 25 centers in 7 countries. In addition to riluzole, they received 1 g TUDCA twice daily or placebo for 18 months. In March 2024, the consortium reported that the primary endpoint had been missed. There was also no difference in survival or in the nerve damage marker neurofilament. TUDCA was well tolerated, with predominantly mild gastrointestinal complaints in both groups. A full publication with all figures was still pending at the time of writing.

The clamp study on insulin action

20 adults with obesity, with an average age of 48 years and a BMI around 37, received 1,750 mg TUDCA per day or placebo for 4 weeks. Afterwards, liver and muscle responded about 30 percent better to insulin. Surprisingly, the markers of ER stress in muscle and adipose tissue did not change, even though that is precisely the presumed mechanism.

Where the data stop

In ALS, the story is a textbook case. After the small pilot study with 34 patients, the large trial with 336 participants did not reach the same result. An Italian registry analysis found a median survival of 49.6 instead of 36.2 months in 86 treated patients, but it was retrospective and not randomized. The combination with sodium phenylbutyrate went similarly: in the phase 2 trial CENTAUR with 137 participants it slowed functional decline by 0.42 points per month; in the phase 3 trial PHOENIX nothing changed after 48 weeks, and the drug approved in the US in 2022 was withdrawn in 2024. A 2026 meta-analysis rates the evidence as very uncertain. On insulin action, everything rests on one study with 20 people over 4 weeks. Whether TUDCA lowers long-term blood sugar, prevents diabetes or helps with weight loss has not been studied. On liver protection, all human data come from cholestatic diseases. Whether TUDCA protects healthy livers from alcohol, medications or oral anabolic steroids has not been tested by anyone in a controlled way. In newborns on parenteral nutrition, it did not prevent cholestasis.

Status, approval and legal

In Italy, TUDCA is a prescription medicine for cholesterol gallstones, at 250 to 750 mg daily according to the package leaflet. No TUDCA medicine is approved in Germany; it is sold as a food supplement. An official classification, for example as a novel food, could not be reliably clarified for this page. There are no reference values or maximum amounts from EFSA or BfR, because TUDCA is not a nutrient. TUDCA is not on the World Anti-Doping Agency’s 2026 Prohibited List. The studies used 750 mg per day in bile diseases, 1,750 mg per day over 4 weeks in the insulin study and 1 g twice daily over up to 18 months in ALS.

Safety

In the controlled studies, TUDCA was well tolerated. The most common complaints are mild gastrointestinal ones; in the Italian registry study, 8.1 percent discontinued because of them. The Italian package leaflet lists as contraindications pregnancy, an active stomach ulcer, radiopaque gallstones, an inflamed gallbladder or bile ducts, bile duct obstruction and pancreatitis triggered by stones. Cholestyramine inhibits absorption; estrogens, hormonal contraceptives and some lipid-lowering drugs can weaken the effect on the bile. More is not automatically better: in primary sclerosing cholangitis, high-dose UDCA at 28 to 30 mg per kilogram worsened the course, and serious adverse events occurred in 63 instead of 37 percent. This concerns UDCA and this disease, but it calls for caution with high doses. Anyone with a liver or bile disease should clarify taking it with a physician.

Sources

• Elia et al., Eur J Neurol 2016 – TUDCA in ALS, pilot RCT
• Albanese et al., Front Neurol 2022 – protocol of the TUDCA-ALS trial
• TUDCA-ALS consortium 2024 – topline results (MND Association)
• Kars et al., Diabetes 2010 – insulin sensitivity in people with obesity
• Ma et al., Medicine 2016 – TUDCA vs. UDCA in primary biliary cholangitis
• Setchell et al., Gut 1996 – metabolism of oral TUDCA
• Özcan et al., Science 2006 – chemical chaperones and ER stress in mice
• Zucchi et al., EClinicalMedicine 2023 – ALS registry cohort
• Jomaa et al., Ann Indian Acad Neurol 2026 – meta-analysis of phenylbutyrate-taurursodiol
• Lindor et al., Hepatology 2009 – high-dose UDCA in PSC