Tauroursodeoxycholic acid (TUDCA) is a naturally occurring, water-soluble bile acid derivative. Produced in small amounts by gut bacteria, TUDCA is primarily used as a dietary supplement to support liver health and optimize bile flow. Like any active compound, it can cause digestive side effects, the most common being diarrhea. This discomfort is a direct consequence of how this bile acid interacts with the intestines.
Understanding TUDCA and its Bile Acid Function
Bile acids are compounds synthesized in the liver from cholesterol and stored in the gallbladder, playing a central function in digestion. When released into the small intestine, they act like a detergent, emulsifying dietary fats into tiny droplets. This emulsification is necessary for the proper breakdown and absorption of lipids and fat-soluble vitamins (A, D, E, and K).
TUDCA is a hydrophilic (water-loving) bile acid that is conjugated with the amino acid taurine, making it highly soluble. As a supplement, it supports the body’s bile pool, promoting healthy liver function and detoxification pathways. Normally, approximately 95% of bile acids are efficiently reabsorbed in the lower small intestine (ileum) and cycled back to the liver via enterohepatic circulation.
The Mechanism Linking TUDCA to Digestive Upset
The occurrence of diarrhea from TUDCA supplementation is fundamentally linked to an overflow of unabsorbed bile acid reaching the colon. When a person takes a supplemental dose of TUDCA, especially a large one, the small intestine’s reabsorption capacity can become overwhelmed. This excess bile acid then passes into the large intestine, causing effects that result in loose, watery stools.
Once in the colon, bile acids exert a dual action on the intestinal lining. First, they act as secretagogues, prompting the colon to secrete water and electrolytes from the bloodstream into the bowel lumen. This influx creates an osmotic effect, significantly increasing the stool’s water content. Second, the unabsorbed bile acids interact with receptors on the colon wall, such as the G protein-coupled bile acid receptor 1 (GPBAR1 or TGR5).
Receptor activation stimulates muscle contractions in the colon, accelerating intestinal motility. This rapid movement reduces the transit time of waste through the large intestine, limiting the opportunity for water to be reabsorbed. The combined effect of increased fluid secretion and accelerated transit time results in the characteristic watery diarrhea associated with high doses of bile acid supplementation. This adverse reaction is dose-dependent; higher intake increases the likelihood of this mechanism being triggered.
Dosage Considerations and Management Strategies
Careful consideration of dosage is important for managing TUDCA supplementation and minimizing digestive upset. Most users begin with a low daily amount (250 to 500 milligrams) to assess individual tolerance. If no gastrointestinal issues occur, the dosage can then be slowly increased, or titrated, over time to the desired level.
A common strategy to minimize diarrhea risk is dividing the total daily dose into two or three smaller portions taken throughout the day. This split-dosing approach prevents a single large bolus of TUDCA from overwhelming the small intestine’s reabsorption capacity all at once. Taking TUDCA with a meal, particularly one containing fat, can also be beneficial.
Consuming the supplement alongside food slows its passage into the small intestine, promoting gradual absorption and reducing the unabsorbed bile acid reaching the colon. Maintaining adequate hydration is important when experiencing diarrhea, as watery stools cause a loss of water and electrolytes. If symptoms persist, become severe, or include fever or abdominal pain, discontinue use and consult a healthcare professional.