TUDCA and Gut Health: SIBO and the Microbiome

Bile acids help keep bacterial numbers in check in the small intestine, which is why TUDCA comes up in conversations about SIBO and the gut microbiome. But we found no study of TUDCA for SIBO, and in the one placebo-controlled trial that looked at gut bacteria, TUDCA didn't change their overall diversity, although the mix of species differed.

---

Gut health forums often link bile, SIBO and gallbladder removal. The reasoning goes that without a gallbladder, bile no longer arrives in strong bursts with meals, bacteria get the upper hand in the small intestine, and a bile acid such as TUDCA might help. Each step sounds plausible, but the evidence for each is different.

This guide sets out what SIBO is and how it is diagnosed and treated, what bile acids do to gut bacteria, what is known about SIBO after gallbladder removal, and what the TUDCA studies found. It also covers probiotics.

What Is SIBO?

SIBO is the presence of too many bacteria in the small intestine, causing digestive symptoms [1]. The most common symptom is bloating, and abdominal pain, gas, distension and diarrhea are also common, but according to the American College of Gastroenterology, no single symptom points to SIBO on its own [1]. In most cases, SIBO is a result of something else, such as slow gut movement or a past operation on the intestine, and the guideline says treating the underlying cause is the main way to prevent it [1].

How is SIBO diagnosed?

Doctors usually use a breath test, in which you drink a sugar solution and breathe into a bag at intervals, to measure gases made by bacteria [1]. A sample of fluid from the small intestine is another option. The guideline suggests breath testing for people with symptoms in certain situations, such as irritable bowel syndrome, but these are conditional recommendations based on very low-quality evidence [1].

How is SIBO treated?

The guideline suggests antibiotics for people with symptoms, a conditional recommendation based on low-quality evidence from small trials [1]. Rifaximin is the antibiotic studied most, but SIBO isn't among its approved uses, so prescribing it for SIBO is off-label and is a decision for your doctor [2]. Two of the guideline's authors reported ties to the company that makes rifaximin [1].

How Do Bile Acids Affect Gut Bacteria?

Bile acids act as detergents, and they can affect the membranes of bacteria. The ACG guideline lists them among the small intestine's defenses against overgrowth, alongside stomach acid, digestive enzymes, the movement of the small intestine and the immune system [1]. Lower bile acid levels in the gut are associated with bacterial overgrowth and inflammation [3].

The relationship works both ways. Gut bacteria in the colon change bile acids chemically, turning the ones the liver makes into different forms [4]. And when a diet changes, the mix of bile acids reaching the colon changes with it: in a two-week diet swap, secondary bile acids in the colon fell 70% on a high-fiber, low-fat diet and rose 400% on the reverse [5].

Does Gallbladder Removal Cause SIBO?

The studies disagree, so it isn't known. All used breath tests, mostly in people referred for testing because they had symptoms:

• In a Korean study, 47% of people with symptoms after gallbladder removal tested positive, more than in people with other gut complaints or healthy volunteers [6].
• Later studies from the same group found positive tests in 17% to 41% after gallbladder removal, and one found SIBO more linked to having gallstones than to having had the operation [7, 8, 9].
• In a US study of people referred for testing, a positive test was less common in those who had had their gallbladder removed, 33% vs 52% [10].
• In a larger US study of 1,461 breath tests, gallbladder removal was associated with one type of positive result [11].

Breath tests are an indirect measure [1], and these figures come from people who already had symptoms, so they aren't rates for everyone after surgery. If you have bloating, gas or diarrhea after gallbladder removal, SIBO is one of several possible causes; our guide to bloating after gallbladder surgery covers the others.

Does TUDCA Help With SIBO?

We found no study of TUDCA for SIBO. The study often quoted online for bile acids and SIBO tested ursodiol (UDCA), a long-established prescription medicine and a different bile acid, in 24 people with indigestion and SIBO, with an untreated comparison group rather than a placebo; symptoms and methane on the breath test fell on ursodiol, and the authors called it a preliminary study [12]. Its results can't be applied to TUDCA. The idea also comes from the role bile acids play in keeping bacteria in check [1, 3], but that is general biology, not a test of TUDCA.

Online SIBO forums are split. Some people describe feeling better after starting TUDCA, while others describe more bloating or a change in bowel habits. These are personal experiences, often with several changes made at once, and they can't show whether TUDCA had any effect on bacteria. Our guide to TUDCA and bowel changes covers what the trials recorded.

Does TUDCA Change the Gut Microbiome?

Three reports in people have looked at this. In a 16-week trial in people with progressive multiple sclerosis, those taking 2 g of TUDCA a day had no change in the overall diversity of their gut bacteria compared with placebo, although the mix of species differed [13]. In a six-week open-label study of 14 people with ulcerative colitis, published as a preprint, diversity was also unchanged [14]. One case report described changes in one woman's gut bacteria on long-term TUDCA, but she was also taking an antibiotic during that time [15].

A different mix of species isn't necessarily better or worse, and the trial didn't measure whether it affected digestion. Our review of the human research covers these studies in more detail.

Does TUDCA Heal a Leaky Gut?

"Leaky gut" is a popular term for a gut lining that lets more through than it should; doctors call it increased intestinal permeability. Claims that TUDCA seals the gut lining rest on animal studies, such as mice with fatty liver or with experimentally induced colitis [16, 17]. We found no study in people that measured gut permeability on TUDCA, so those results can't be assumed to carry over.

What About Probiotics?

Probiotics are often suggested for gut health after gallbladder removal, but we found no controlled trial of probiotics after the operation. Their effects differ by strain: if one kind of Lactobacillus helps with something, that doesn't mean another kind would [18]. The ACG guideline found no consistent data to recommend specific probiotics for SIBO [1].

One study combined TUDCA with a probiotic. In 96 people with gallstones awaiting surgery, TUDCA, a Lactobacillus probiotic, both or neither were given for two weeks, and the combination didn't enhance the effect of either on blood fats or bile composition [19]. It recorded no symptoms and wasn't in people without a gallbladder.

Where Does TUDCA Fit After Gallbladder Removal?

After gallbladder removal, bile flows directly from the liver into the small intestine instead of being stored for meals [20]. Dr.Primal's TUDCA is made for life after gallbladder removal and taken with meals, to support healthy bile flow and fat digestion when richer meals feel heavy. It isn't a treatment for SIBO. Our guide to digestive problems after gallbladder removal covers the common causes of symptoms.

When Should You See a Doctor?

If bloating, diarrhea or abdominal pain persists, see a doctor, who can work out whether SIBO, bile acid diarrhea or something else is the cause and test for it. Talk with a doctor right away for diarrhea that lasts more than two days, six or more loose stools a day, a high fever, or black, tarry or bloody stools [21].

In Summary: TUDCA and Gut Health

Bile acids help keep bacteria in check in the small intestine, but we found no study of TUDCA for SIBO, and studies disagree on whether SIBO is more common after gallbladder removal. In the one placebo-controlled trial that looked, TUDCA didn't change overall diversity, though the mix of species differed, and SIBO is diagnosed with a breath test.

If you are working out what is behind your symptoms after meals, our digestion quiz is a quick way to put your symptoms and habits in order.

This article is for general education and is not a substitute for advice from your doctor. TUDCA is sold as a dietary supplement. These statements have not been evaluated by the Food and Drug Administration. This product is not intended to diagnose, treat, cure, or prevent any disease.