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Longevity Library · Lab reference

Written by Daniel Tagge, MD
Updated October 23, 2026
Reviewed October 24, 2026
35 sources · Measured in enzyme activity units per gram of stool

System: Gut-Immune Health

Fecal beta-glucuronidaseBeta-glucuronidase · Stool beta-glucuronidase · Faecal beta-glucuronidase · GUS enzymes

Beta-glucuronidase is a bacterial enzyme in the colon that cuts the glucuronic acid tag the liver attaches to estrogens, bilirubin and many drugs, which releases those molecules back into the gut in their active form; 279 different versions of it were found across 139 people's microbiomes, and its one proven clinical consequence in humans is drug toxicity, where blocking it protected mice from the diarrhea caused by a chemotherapy drug and an oral antibiotic that abolished the activity relieved that diarrhea in six of seven patients. The stool activity measurement sold on gut panels has no outcome evidence behind it at any value: no study has taken a healthy adult's fecal beta-glucuronidase, raised or lowered it, and shown that anything happened, and in the one study that measured both, higher fecal activity went with lower, not higher, fecal estrogens.

Beta-glucuronidase reverses one of the liver's main disposal steps inside the colon, so it governs how much of what the body has already packaged for excretion gets reabsorbed. The biology is well mapped and the drug story is real. The stool test is not: there is no outcome-derived reference range, no agreed unit, and no study linking a value in a healthy person to a disease or a symptom. The popular claim that a high value causes estrogen excess is a hypothesis with cross-sectional support at most, and the human data point the other way as often as not.

01 · The scale

Where the laboratory range and the evidence sit.

No outcome evidence ties a stool beta-glucuronidase value to anything. Nobody has taken a healthy adult's value, moved it, and shown that a symptom, a hormone level or a disease changed. What is established is narrower and mostly not about stool testing: the enzyme reactivates a chemotherapy drug's inactive metabolite in the gut, where an inhibitor protected mice from the drug's toxicity and an oral antibiotic that drove fecal activity to undetectable levels relieved the diarrhea in six of seven patients; a bacterial version of the enzyme was needed for a cooked-meat carcinogen to damage colon cells in rats, where its presence tripled the genotoxicity; one small series found activity 1.7 times higher in people with colon cancer than in controls; and in the one human study that measured both, higher fecal activity went with lower fecal estrogens, not higher.

0255075100

  1. One laboratory's own distribution is the only frame a value has; the scale here is a percentile of that distribution, not a unit, because no two assays share one and no boundary anywhere is outcome-derived

    0 and above enzyme activity units per gram of stool · This entry, 2026; Flores 2012 (methods)

  2. No evidence band exists anywhere on this scale: no study ties any value in a person without a disease, or on no relevant drug, to any outcome

    0 and above enzyme activity units per gram of stool · This entry, 2026

  • Laboratory range
  • Guideline goal or unstudied
Scale in enzyme activity units per gram of stool. There is no common unit. Published work reports activity as µg per hour per mg of protein, nmol per hour per gram of stool, or kinetic units per gram, each on its own assay, and no reference interval anywhere is derived from an outcome, so a value on one laboratory's report cannot be compared with a value on another's or with any number in the literature. Bands show where studies found something, not a recommendation for any one person.

02 · What it is

What Fecal beta-glucuronidase measures.

The liver inactivates hormones, bile pigments and drugs by attaching glucuronic acid to them, which makes them water-soluble and sends them out in bile or urine. Gut bacteria express beta-glucuronidase enzymes that strip that sugar off to use it as a carbon source, and in doing so they hand the original molecule back to the body in its active form. The enzymes are not one protein: an atlas built from the Human Microbiome Project found 3,013 total and 279 unique microbiome-encoded versions in 139 people, grouped into six structural categories, with wide differences between individuals.1,2Grade C

The bacterial enzyme and the human one are different proteins. Humans carry their own beta-glucuronidase, a lysosomal enzyme encoded by the GUSB gene, and losing it causes a rare inherited storage disease affecting fewer than 1 in 1,000,000 people, with skeletal changes, enlarged liver and spleen and cognitive impairment. The inhibitors designed to block the bacterial enzyme were chosen because they have no effect on the equivalent mammalian enzyme, a selectivity that rests on a loop found only in the bacterial versions. A stool test is measuring the bacteria's enzyme, not the body's.3,4Grade C

Only some gut bacteria make it. Screening 40 strains representative of the dominant groups in human stool found beta-glucuronidase activity confined to certain Firmicutes within two clostridial clusters, with a matching gene detected in 10 of the 40 isolates including all 9 that tested positive for activity, and the activity was inducible by its own substrate in at least one strain. Mining the metagenomes of 60 healthy people found 4 to 70 different versions per person, and the share of gut bacteria carrying at least one copy of the gene ranged from 0.7 to 82.2 percent, averaging 25.7 percent. One person's value is partly a readout of which species happen to be abundant and partly of what those species have been fed.5,6Grade C

03 · Origins

Where it came from, and where it sits in the network.

The enzyme is a bacterial housekeeping tool that happens to intersect with human physiology. Its substrate, glucuronic acid, is a sugar, and from the bacterium's point of view a glucuronide arriving in bile is food with a handle on it; the review that framed this calls the arrangement a sugar-driven symbiosis, in which the mammal inactivates a compound by linking it to glucuronic acid for excretion and the microbe removes that sugar as a carbon source, reversing the mammal's own inactivation. A functional screen of human gut metagenomic libraries found a previously undescribed type of bacterial beta-glucuronidase present in the published microbiome of every healthy adult and child examined and specific to the human gut, which its authors read as part of a functional core evolved to fit that environment.1,7Grade C

Where the enzyme sits taxonomically has been mapped twice over. Two distinct gene families encode the activity in human colonic bacteria: in one survey, Firmicutes accounted for 96 percent of amplified sequences of the first family, while 59 percent of the second family's sequences belonged to Bacteroidetes and 41 percent to Firmicutes, and isolates carrying only the second gene gave relatively low activity that its substrate did not induce. The structural atlas sorted 279 unique proteins into six categories that differ in how they handle small glucuronides against larger carbohydrates, and the metagenome study found the categories most active on small molecules, including drugs, were often carried by scarce organisms, so a small shift in a few species can change the functional total.8,2,6Grade C

The reason this matters for hormones is enterohepatic recycling, which is older than any of the clinical questions asked about it. Estrogens leave the liver as glucuronides and sulfates in bile; bacteria deconjugate them in the gut and some are reabsorbed rather than excreted. The classic demonstration is pharmacological: giving pregnant women an antibiotic that reduces bacterial steroid metabolism caused a large increase in the fecal excretion of conjugated estrogens, and in a parallel study total urinary estrogen excretion fell to 67 percent of control by the second day of the antibiotic, consistent with interrupted enterohepatic circulation. Those experiments, from the 1970s, are the foundation under everything later written about gut bacteria and estrogens.9,10Grade C

The same recycling loop carries bile pigment and drugs, which is the part of the biology with the firmest modern evidence. Bilirubin is conjugated in the liver, deconjugated by bacterial beta-glucuronidase in the gut and then reduced to urobilinogen by a separate bacterial enzyme identified in 2024, which is nearly universal in healthy adults and less prevalent in newborns and in people with inflammatory bowel disease. The drug side is the same chemistry: the microbiome's reactivation of a transplant immunosuppressant's glucuronide correlated strongly with how much of that drug was recycled through the gut in 21 kidney transplant recipients compared with 15 healthy people, and particular gene variants in one common gut species drove the conversion. This is where the word estrobolome came from: the collection of bacterial genes capable of metabolizing estrogens, proposed as a model for distant microbial effects and developed as a possible influence on estrogen receptor-positive breast cancer risk.11,12,13,14Grade C

04 · The laboratory range

What a laboratory calls normal.

There is no standard reference interval. Reference ranges printed on stool panel reports are laboratory-specific, set from the distribution of that laboratory's own samples on its own assay and units, and none is outcome-derived.

No unit or method is shared across laboratories or papers, so the numbers cannot be lined up. Published human work reports fecal activity as µg per hour per mg of protein in one pharmacology series, as nmol per hour per gram in a transplant cohort where kidney recipients averaged 8.48 and stem cell recipients 3.50, and as kinetic colorimetric units in the National Cancer Institute's methods work. A value is interpretable only against the same laboratory's own distribution, and even then as a percentile among that laboratory's samples, not as a risk estimate.15,16,17Grade C

The measurement itself can be done well, which is a separate question from whether it means anything. In the one formal reproducibility study, 51 volunteers used two devices to self-collect four replicates of a stool; reproducibility between paired replicates was excellent for beta-glucuronidase with both devices (intraclass correlation 0.92). The same work found the result depends on handling: activity decayed by about 20 percent within 2 hours and about 40 percent within 4 hours at room temperature, and detection was best at neutral pH with snap freezing and rapid thawing before protein extraction. A sample mailed warm is not the sample that was produced.17Grade C

What a value is not is a measure of one thing. Fecal beta-glucuronidase activity correlated directly with microbiome richness and overall diversity and with the abundance of four clostridial genera, and inversely with two other genera, in 51 healthy volunteers; in the same group it was higher in people who had recently lost at least five pounds. Diversity is usually read on the same report as a favorable finding. A number that rises with diversity cannot also be read as a marker of a disordered gut without saying which reading is being used and why.18Grade C

05 · The evidence

What the studies support.

The one clinical application of the enzyme is drug toxicity, and it was built from the chemistry up. The dose-limiting side effect of a common colon cancer chemotherapy drug is severe diarrhea, caused by bacterial beta-glucuronidases reactivating the drug's inactivated metabolite in the gut. High-throughput screening found potent bacterial beta-glucuronidase inhibitors with no effect on the equivalent mammalian enzyme; crystal structures traced the selectivity to a loop unique to the bacterial enzymes; the inhibitors blocked the target inside living bacteria without killing them or harming mammalian cells; and oral administration of one protected mice from the drug's toxicity. Later structural work found that representative enzymes from four different bacterial groups differ markedly in catalytic properties and in how readily they are inhibited, and that inhibition did not change the drug's serum pharmacokinetics in mice, so the effect is local to the gut.4,19Grade C

In humans the same mechanism has been shown pharmacologically, in very small numbers. Seven patients who had developed diarrhea of grade 2 or worse on that chemotherapy drug received the same dose with an oral antibiotic in their next course. The antibiotic did not change the systemic exposure to the drug or its major metabolites, but it took fecal beta-glucuronidase activity from 7.03 µg per hour per mg to undetectable and lowered the fecal concentration of the active metabolite; diarrhea improved in six of the seven. This is the clearest human evidence that the enzyme does something that matters, and it is a seven-patient pharmacology study in people taking a specific drug, not a finding about healthy people's stool values.15Grade C

The estrogen claim is a hypothesis, and the direct human measurement did not support the version that is sold. In 51 participants, 25 men, 7 postmenopausal women and 19 premenopausal women, urinary and fecal estrogens were measured by mass spectrometry alongside fecal enzyme activity and microbiome sequencing. In men and postmenopausal women, urinary estrogens were strongly associated with microbiome richness and diversity, but of 15 estrogen measures only urinary estrone correlated significantly with fecal beta-glucuronidase activity (R = 0.36, P = 0.04), and fecal beta-glucuronidase correlated inversely with fecal total estrogens, both conjugated and deconjugated (R of minus 0.47 or lower, P of 0.01 or lower). Premenopausal women's estrogens were unrelated to any microbiome or enzyme measure. The authors' conclusion was that microbial richness and functions, including but not limited to beta-glucuronidase, influence non-ovarian estrogen levels, which is a statement about the community, not about one enzyme's value.20Grade C

The later estrogen work moved further away from the enzyme, not closer. In 60 healthy postmenopausal women not using antibiotics or hormone therapy, the ratio of urinary estrogen metabolites to parent estrogens was directly associated with microbiome diversity (R = 0.35, P = 0.01) and with the abundance of one bacterial order and one genus, independent of age and body mass index. Fecal beta-glucuronidase activity was not the exposure measured in that study at all: the finding is about the community's diversity. It is cross-sectional, it is small, and it does not show that a stool enzyme value predicts anything.21Grade C

Laboratory work does establish that these enzymes can reactivate estrogens, which is why the hypothesis is worth taking seriously and not worth acting on. The first direct test examined 35 human gut microbial beta-glucuronidases against two estrogen glucuronides and found that members of three structural classes reactivated estrone and estradiol from their inactive conjugates; the authors mapped the key molecular interactions and solved two new structures. In the same paper, an inhibitor selective for one of those classes blocked reactivation in purified enzyme and in mixed fecal preparations, yet did not reduce tumor development in a mouse model of breast cancer. Their reading is that these enzymes do participate in the estrobolome and that the estrobolome is a many-enzyme, multidimensional set of processes, so no single measurement stands for it.22Grade C

The colon cancer hypothesis, which is where the stool test originally came from, rests on animal work and one small human comparison. In gnotobiotic rats colonized with either a normal bacterial strain or an isogenic mutant lacking the enzyme, the presence of bacterial beta-glucuronidase in the gut lumen tripled the genotoxicity of a carcinogen formed in meat and fish during cooking, measured in colon cells; this was the first in vivo demonstration of that role. In humans, a 2001 series found fecal activity 1.7 times higher in patients with colon cancer than in healthy controls, rising to 12.1 times higher when the specimens were sonicated, and its authors proposed the enzyme as a prime factor in the etiology of colon cancer. That is a small cross-sectional comparison in people who already had cancer, with no prospective cohort behind it, and no screening or prevention use has followed in the twenty-five years since.23,24Grade C

Where fecal activity has been measured in patients, high is not uniformly the worrying direction. Among kidney transplant recipients with diarrhea after transplant, those with higher fecal beta-glucuronidase activity more often had a prolonged course of 7 days or more (91 percent against 40 percent, P = 0.02), consistent with more reactivation of an immunosuppressant in the gut. In irritable bowel syndrome after infection, the finding runs the other way: patients with high gut proteolytic activity had lower fecal beta-glucuronidase activity and fewer end-products of bilirubin deconjugation, germ-free mice had tenfold higher proteolytic activity than conventional mice, and treating mice with unconjugated bilirubin or with bacteria overexpressing the enzyme reduced proteolytic activity while inhibiting the enzyme increased it. In that disease the enzyme looks protective. A single stool number, read without the clinical context, does not know which story it is in.25,26Grade C

The inhibitor literature is pharmaceutical, not nutritional. A 2020 review of beta-glucuronidase inhibitors describes the enzyme as a viable molecular target, notes that its activity level in body fluids is deemed a potential biomarker for diagnosing some conditions, and concludes that although natural products and synthetic compounds have been identified as inhibitors, only a few have found clinical utility and those with moderate to poor pharmacokinetic profiles. No inhibitor is in routine use for any condition, and nothing in that literature licenses taking a supplement to push a stool number down.27Grade D

06 · What moves it

The levers with evidence behind them.

What is listed here has been tested. The size of each effect, and the size of the study, are in the sentence, so a small effect reads as a small effect.

  • Fiber, and which kind

    wheat and oat bran lowered it; it depends on the fiber

    In premenopausal women who added 13 to 15 g a day of wheat, oat or corn bran to their usual diet for 8 weeks, wheat bran lowered the activities of all the bacterial enzymes measured including beta-glucuronidase, and oat bran lowered beta-glucuronidase, nitroreductase and azoreductase without affecting bile acids. The authors' conclusion was that the effect depends on the type of fiber. An earlier study was less encouraging: adding bran or wheat germ to omnivores' diets for 30 days had no effect on beta-glucuronidase at all, though it did lower a bile acid enzyme, and a later survey found most fecal glycosidase activities changed little across a fivefold range of fiber intake. Fiber is worth eating for reasons that have their own evidence; moving this enzyme is not a reliable one of them.28,29,8Grade C

  • Meat and a Western dietary pattern

    raised it in the older feeding studies

    This is the oldest observation about the enzyme and the one that gave it its reputation. In 1974, fecal beta-glucuronidase activity was significantly higher in volunteers eating a mixed Western high-meat diet than on a non-meat regimen. In humans, omnivores eating a Western-type diet had higher fecal beta-glucuronidase than vegetarians, although removing red meat from the omnivores' diets for 30 days did not lower it. A later study found fecal beta-glucuronidase activity increased in obese volunteers on a high-protein, moderate-carbohydrate weight-loss diet compared with a weight-maintenance diet. The direction is consistent; what a shift in the number does to a person is not known.30,29,8Grade C

  • Fermented foods and probiotics

    lowered it in several trials, for as long as they were taken

    Live lactobacilli lower the measured activity reproducibly, and the effect goes away when they stop. Adding viable supplements to omnivores' diets significantly lowered fecal beta-glucuronidase and nitroreductase, and 30 days after stopping, activities returned to baseline. In 21 subjects through a sequence of control, plain milk, control, lactobacillus-containing milk and control periods, activities of three enzymes fell 2- to 4-fold only during the lactobacillus period, in all subjects, and returned to baseline within 4 weeks of stopping. In 64 women aged 20 to 41 randomized to a yogurt containing a live strain, that yogurt with or without added rye fiber significantly lowered fecal beta-glucuronidase, with values returning to baseline during follow-up and added fiber making no difference. A randomized crossover study in 53 healthy volunteers found two prebiotics significantly lowered the activity and two probiotic organisms tended to. A fermented dairy product containing two organisms, taken for 3 weeks by 9 volunteers, did not change it. In none of these trials was the endpoint connected to a symptom, a hormone level or a disease: the enzyme was the outcome measured, and nothing downstream was.29,31,32,33,34Grade C

  • Calcium D-glucarate

    lowered it in animals; no human outcome trial exists

    The supplement sold for this purpose has animal data and nothing else. Glucarate is in equilibrium with a natural inhibitor of beta-glucuronidase, and in rats a single dose of calcium glucarate inhibited the enzyme in serum, liver, lung and intestinal microsomes by 57, 44, 37 and 39 percent, while a 4 percent dietary supplement inhibited the activity of the bacterial flora from the small intestine by 70 percent and from the colon by 54 percent. The same paper measured glucaric acid in foods, from 1.12 to 1.73 mg per 100 g in broccoli and potatoes up to 4.53 mg per 100 g in oranges. These are rat experiments. No human trial has given calcium D-glucarate and measured a hormone-related or cancer-related outcome, so taking it to correct a stool number is acting on a mechanism alone.35Grade D

  • Antibiotics

    lower it sharply, and that is a side effect, not a treatment

    An oral antibiotic took fecal beta-glucuronidase activity to undetectable levels in patients on a chemotherapy drug, and the 1970s estrogen experiments used an antibiotic to interrupt the same chemistry: during treatment, fecal excretion of conjugated estrogens rose sharply and total urinary estrogen excretion fell to 67 percent of control. Antibiotics also change the whole community, which is why this is a demonstration of mechanism and not a lever anyone should pull for a laboratory value.15,9,10Grade C

07 · Reading it well

Caveats, and what belongs with a physician.

There is no outcome-derived reference interval, so a flagged result is a position in one laboratory's distribution. No study has established what value in a person without a disease carries more risk of anything than another value, and the enzyme is not one protein but a family of at least 279 variants with different activities, carried by between 0.7 and 82.2 percent of a person's gut bacteria. A report that prints a range and an arrow is describing its own sample population, not a target.2,6Grade C

Handling moves the number. Activity fell by about 20 percent within 2 hours and about 40 percent within 4 hours at room temperature in the one methods study, detection was best with neutral pH, snap freezing and rapid thawing, and the two collection devices compared gave significantly different mean activities for the same enzyme. Reproducibility between replicates of a well-handled stool was excellent (intraclass correlation 0.92), so the problem is not the assay's precision; it is everything between the bathroom and the bench.17Grade C

A high value is not a direction on its own, because the direction depends on which story the person is in. Higher fecal activity went with a longer course of diarrhea in kidney transplant recipients on an immunosuppressant that the enzyme reactivates, while in irritable bowel syndrome after infection lower activity went with the high gut proteolytic activity that drives symptoms, and animal work in that model pointed to the enzyme's product as protective. The same number carries opposite meanings in those two settings.25,26Grade C

The estrogen inference is not supported in the direction it is usually stated. The one human study that measured fecal enzyme activity and estrogens together found only urinary estrone significantly correlated with the enzyme, and found fecal estrogens correlated inversely with it, while nothing at all was related in premenopausal women, whose samples spanned the menstrual cycle. The laboratory work shows these enzymes can reactivate estrogens; an inhibitor that blocked reactivation in purified enzyme and in fecal preparations did not reduce tumors in a mouse breast cancer model, and the authors concluded that the estrobolome involves many enzymes. Diagnosing an estrogen problem from a stool enzyme is not something the literature supports.20,22Grade C

Reading the number as a marker of a disordered gut conflicts with the rest of the report. Fecal beta-glucuronidase correlated directly with microbiome richness and diversity in 51 healthy volunteers and directly with the abundance of four clostridial genera, and in 60 postmenopausal women greater microbiome diversity went with a higher urinary metabolite-to-parent estrogen ratio. Diversity is normally presented as favorable. Anyone interpreting a high enzyme value as harmful on the same page that presents high diversity as good owes an explanation.18,21Grade C

The drug evidence does not transfer to people who are not taking those drugs. The toxicity work involves a chemotherapy drug, a transplant immunosuppressant and a cancer drug whose glucuronides the enzyme reactivates in the gut; its human demonstrations are a seven-patient pharmacology study and transplant cohorts. Even there, inhibition did not change the drug's blood levels in mice, so the question is local gut exposure in a person on a specific medicine, which belongs to the prescriber.15,19,12Grade C

See a physician

  • Blood in the stool, black stools, unexplained weight loss, a persistent change in bowel habit, iron deficiency, or new bowel symptoms after about age 45, none of which a stool enzyme value addresses and all of which belong in a colorectal evaluation.
  • Diarrhea while taking a chemotherapy drug or a transplant immunosuppressant, which is the one setting where this enzyme's activity has a demonstrated clinical consequence and where the decision belongs to the prescribing oncologist or transplant team, not to a supplement.
  • Abnormal uterine bleeding, new breast symptoms, a breast lump, or postmenopausal bleeding, which need their own evaluation and are never explained by a stool enzyme result.
  • A plan to start calcium D-glucarate, a high-dose supplement regimen or a course of antibiotics on the strength of a stool panel, which is worth discussing with a physician first, since the supplement evidence is in rats and antibiotics change the whole gut community.
  • Persistent diarrhea, abdominal pain, fever, or symptoms that began after an infection or a course of antibiotics, which is a clinical picture to work up rather than a number to correct.

This page is education, not individual medical advice, and reading it creates no physician-patient relationship.

08 · Open questions

What the literature does not settle.

  • No study has measured fecal beta-glucuronidase in healthy people and followed them for any outcome, so the test has no prognostic evidence at any value; whether the measurement carries information about health at all is unanswered.
  • No trial has moved a person's fecal beta-glucuronidase and measured a downstream outcome. The probiotic and fiber trials used the enzyme itself as the endpoint, so the central question, whether lowering it changes anything a person would notice, has never been tested.
  • There is no agreed unit, no shared assay and no outcome-derived reference interval, and no interlaboratory comparison has been published, so whether two laboratories' reports on the same stool would agree is unknown.
  • The enzyme is a family of at least 279 variants in six structural classes with different substrate preferences, and total activity measured on one synthetic substrate may not predict activity on estrogen glucuronides, bilirubin conjugates or a particular drug; which measurement would matter for which question is unresolved.
  • Whether the estrobolome influences breast cancer risk through this enzyme is open. The human data are small and cross-sectional, the direct biochemical test showed reactivation but a selective inhibitor did not reduce tumors in one mouse model, and the authors of that work call the estrobolome a multidimensional set of processes involving many enzymes.
  • The colon cancer hypothesis, built from a rat genotoxicity experiment and a small case-control comparison, has had no prospective cohort test in the twenty-five years since, and whether the activity precedes the cancer or follows it is unknown.
  • In irritable bowel syndrome after infection, low rather than high activity accompanied the symptom-driving mechanism, and whether raising the enzyme or its bilirubin product helps anyone has not been tested in humans.

09 · In practice

How Dr. Tagge reads it in his own practice.

I see this one on the stool panels I order, and I read it as a single line in a longer story rather than a finding. What it sits beside matters more than what it says: the rest of the microbiome report, how much fiber and fermented food someone actually eats, estradiol and SHBG in a woman and whether she is on hormone therapy, her bowel habit, and how much she drinks. One marker is a clue, three are a story, and I read markers against each other, never alone. I want to be plain about the limits. There is no validated cutoff for the stool activity, no shared unit between laboratories, and no study that ties a value in a healthy person to an outcome, so I do not have a target for it and I am not going to invent one. I do not diagnose estrogen dominance from it; if I am asking a question about estrogen, I ask it with estradiol, FSH, symptoms and the person's history. I do not sell a supplement against it either, because the evidence for the one that gets sold for this is in rats. What the result does earn is a good conversation about fiber, fermented food and alcohol, and those three have their own evidence, which is the reason I am willing to have the conversation at all. Where I am ahead of the evidence, I say so: the biology of this enzyme is real and well described, and I still cannot tell a person what their number means for them.

A practice judgment, labeled as one (Grade D): it is how one physician reads the number for the people he cares for, not a recommendation for you.

10

Questions

11 · Sources

35 sources, read in full.

Numbered in the order they appear. Each line says what this page relies on from the paper; the link opens the record at PubMed or the publisher.

  1. 1.

    Pellock SJ, Redinbo MR. Glucuronides in the gut: Sugar-driven symbioses between microbe and host. Journal of Biological Chemistry. 2017. PMID 28389557. DOI 10.1074/jbc.R116.767434.

    Review · Mammals inactivate endobiotic and xenobiotic compounds by linking them to a glucuronic acid sugar for gastrointestinal excretion; in the gut, microbiota express beta-glucuronidase enzymes that remove the glucuronic acid as a carbon source, effectively reversing mammalian inactivation.

  2. 2.

    Pollet RM, D'Agostino EH, Walton WG, Xu Y, Little MS, Biernat KA, et al.. An Atlas of β-Glucuronidases in the Human Intestinal Microbiome. Structure. 2017. PMID 28578872. DOI 10.1016/j.str.2017.05.003.

    Laboratory method study · An atlas comprehensive for the Human Microbiome Project gastrointestinal database identified 3,013 total and 279 unique microbiome-encoded beta-glucuronidase proteins in six structural categories across 139 individuals, with inter-individual variability and differential processing of smaller glucuronides against larger carbohydrates; 112 enzymes were novel.

  3. 3.

    Grant CL, López-Valdez J, Marsden D, Ezgü F. Mucopolysaccharidosis type VII (Sly syndrome) - What do we know?. Molecular Genetics and Metabolism. 2024. PMID 38301529. DOI 10.1016/j.ymgme.2024.108145.

    Review · The human lysosomal beta-glucuronidase is encoded by the GUSB gene; its deficiency causes mucopolysaccharidosis type VII, with an estimated prevalence under 1 in 1,000,000, presenting with skeletal deformities, hepatosplenomegaly, coarse facies and cognitive impairment.

  4. 4.

    Wallace BD, Wang H, Lane KT, Scott JE, Orans J, Koo JS, et al.. Alleviating cancer drug toxicity by inhibiting a bacterial enzyme. Science. 2010. PMID 21051639. DOI 10.1126/science.1191175.

    Laboratory method study · The dose-limiting diarrhea of a common colon cancer chemotherapeutic is caused by symbiotic bacterial beta-glucuronidases that reactivate the drug in the gut; inhibitors found by high-throughput screening had no effect on the orthologous mammalian enzyme, with selectivity based on a loop unique to bacterial beta-glucuronidases, were effective inside living bacteria without killing them, and protected mice from the drug's toxicity when given orally.

  5. 5.

    Dabek M, McCrae SI, Stevens VJ, Duncan SH, Louis P. Distribution of beta-glucosidase and beta-glucuronidase activity and of beta-glucuronidase gene gus in human colonic bacteria. FEMS Microbiology Ecology. 2008. PMID 18537837. DOI 10.1111/j.1574-6941.2008.00520.x.

    Laboratory method study · Across 40 bacterial strains representative of dominant groups in human feces, beta-glucuronidase activity was found only in some Firmicutes within clostridial clusters XIVa and IV; a family 2 glycosyl hydrolase beta-glucuronidase gene was detected in 10 of 40 isolates, including all 9 that assayed positive for the activity, and activity was inducible by glucuronic acid or a glucuronide substrate in one strain.

  6. 6.

    Candeliere F, Raimondi S, Ranieri R, Musmeci E, Zambon A, Amaretti A, Rossi M. β-Glucuronidase Pattern Predicted From Gut Metagenomes Indicates Potentially Diversified Pharmacomicrobiomics. Frontiers in Microbiology. 2022. PMID 35308380. DOI 10.3389/fmicb.2022.826994.

    Cross-sectional study · In metagenomes of 60 healthy subjects from five cohorts, each harbored 4 to 70 different beta-glucuronidases (218 altogether); the share of intestinal bacteria with at least one gene ranged from 0.7 to 82.2 percent, averaging 25.7 percent; the categories most active on small molecules including drugs were often carried by scarcely abundant organisms, and geography, genetics, nutrition and lifestyle did not explain the profile.

  7. 7.

    Gloux K, Berteau O, El Oumami H, Béguet F, Leclerc M, Doré J. A metagenomic β-glucuronidase uncovers a core adaptive function of the human intestinal microbiome. Proceedings of the National Academy of Sciences. 2011. PMID 20615998. DOI 10.1073/pnas.1000066107.

    Laboratory method study · A functional metagenomic screen of intestinal libraries identified a previously undescribed type of bacterial beta-glucuronidase with 15 homologs in Firmicutes genomes; unlike previously known versions it was present in the published microbiome of every healthy adult and child investigated (n = 11) and was specific to the human gut ecosystem, suggesting a functional core evolved to that environment.

  8. 8.

    McIntosh FM, Maison N, Holtrop G, Young P, Stevens VJ, Ince J, et al.. Phylogenetic distribution of genes encoding β-glucuronidase activity in human colonic bacteria and the impact of diet on faecal glycosidase activities. Environmental Microbiology. 2012. PMID 22364273. DOI 10.1111/j.1462-2920.2012.02711.x.

    Laboratory method study · Faecal beta-glucuronidase activity increased in obese volunteers on a high-protein moderate-carbohydrate weight-loss diet compared with weight maintenance, with little or no change when the type of fermentable carbohydrate varied and little change in other glycosidases over a fivefold range of fiber intake; Firmicutes accounted for 96 percent of amplified gus sequences while 59 percent of BG sequences were Bacteroidetes and 41 percent Firmicutes, and isolates carrying only BG gave relatively low, non-inducible activity.

  9. 9.

    Adlercreutz H, Martin F, Pulkkinen M, Dencker H, Rimér U, Sjöberg NO, Tikkanen MJ. Intestinal metabolism of estrogens. Journal of Clinical Endocrinology and Metabolism. 1976. PMID 956337. DOI 10.1210/jcem-43-3-497.

    Laboratory method study · Most estrogens in normal late-pregnancy feces were unconjugated; administering an antibiotic that decreases intestinal bacterial steroid metabolism caused a large increase in the fecal excretion of conjugated estrogens, emphasizing the active role of the intestinal microflora in estrogen metabolism under normal conditions.

  10. 10.

    Adlercreutz H, Martin F, Tikkanen MJ, Pulkkinen M. Effect of ampicillin administration on the excretion of twelve oestrogens in pregnancy urine. Acta Endocrinologica. 1975. PMID 1242569. DOI 10.1530/acta.0.0800551.

    Laboratory method study · On the second day of antibiotic administration, total urinary estrogen excretion fell to 67 percent of the mean control value, estriol to 69 percent and the other eleven estrogens to an average of 62 percent, with the pattern consistent with interference with enterohepatic circulation.

  11. 11.

    Hall B, Levy S, Dufault-Thompson K, Arp G, Zhong A, Ndjite GM, et al.. BilR is a gut microbial enzyme that reduces bilirubin to urobilinogen. Nature Microbiology. 2024. PMID 38172624. DOI 10.1038/s41564-023-01549-x.

    Laboratory method study · BilR was identified as the gut-microbiota-derived bilirubin reductase that reduces bilirubin to urobilinogen; it is predominantly encoded by Firmicutes and is nearly ubiquitous in healthy adults, with reduced prevalence in neonates and in people with inflammatory bowel disease.

  12. 12.

    Drevland OM, de Muinck EJ, Trosvik P, Hammerstad M, Kvitne KE, Midtvedt K, Åsberg A, Robertsen I. Microbiome-derived reactivation of mycophenolate explains variations in enterohepatic recirculation in kidney transplant recipients. Microbiome. 2025. PMID 40707990. DOI 10.1186/s40168-025-02142-6.

    Prospective cohort · In 21 kidney transplant recipients compared with 15 healthy individuals, the individual microbiome-derived reactivation rate of the immunosuppressant's glucuronide correlated strongly and positively with the degree of its enterohepatic recirculation in vivo, and the reactivation rate was linked to specific beta-glucuronidase gene variants associated with one common gut species.

  13. 13.

    Plottel CS, Blaser MJ. Microbiome and malignancy. Cell Host and Microbe. 2011. PMID 22018233. DOI 10.1016/j.chom.2011.10.003.

    Review · Reviews principles of microbiome-related malignancy and presents the estrobolome model of distant effects of the microbiota, alongside local neoplasia and latent viral interactions.

  14. 14.

    Kwa M, Plottel CS, Blaser MJ, Adams S. The Intestinal Microbiome and Estrogen Receptor-Positive Female Breast Cancer. Journal of the National Cancer Institute. 2016. PMID 27107051. DOI 10.1093/jnci/djw029.

    Review · Defines the estrobolome as the aggregate of enteric bacterial genes capable of metabolizing estrogens and discusses how it might affect risk of postmenopausal estrogen receptor-positive breast cancer; exploring variation in its composition and activity may lead to biomarkers and targeted interventions, which are proposed rather than established.

  15. 15.

    Kehrer DF, Sparreboom A, Verweij J, de Bruijn P, Nierop CA, van de Schraaf J, Ruijgrok EJ, de Jonge MJ. Modulation of irinotecan-induced diarrhea by cotreatment with neomycin in cancer patients. Clinical Cancer Research. 2001. PMID 11350876.

    Randomized trial · In seven evaluable patients with diarrhea of grade 2 or worse on the chemotherapy drug, adding an oral antibiotic in the next course left systemic exposure to the drug and its metabolites unchanged but took fecal beta-glucuronidase activity from 7.03 µg/h/mg to undetectable and lowered fecal concentrations of the active metabolite; diarrhea improved in six of seven (P = 0.033).

  16. 16.

    Khan MH, Onyeaghala GC, Rashidi A, Holtan SG, Khoruts A, Israni A, Jacobson PA, Staley C. Fecal β-glucuronidase activity differs between hematopoietic cell and kidney transplantation and a possible mechanism for disparate dose requirements. Gut Microbes. 2022. PMID 35921529. DOI 10.1080/19490976.2022.2108279.

    Cross-sectional study · Fecal beta-glucuronidase activity was significantly greater in kidney transplant patients (8.48 ± 6.21 nmol/hr/g) than in allogeneic hematopoietic cell transplant patients (3.50 ± 3.29 nmol/hr/g; P = .001), proposed as a determinant of how much immunosuppressant enters the circulation.

  17. 17.

    Flores R, Shi J, Gail MH, Ravel J, Goedert JJ. Assessment of the human faecal microbiota: I. Measurement and reproducibility of selected enzymatic activities. European Journal of Clinical Investigation. 2012. PMID 22409163. DOI 10.1111/j.1365-2362.2012.02660.x.

    Laboratory method study · A colorimetric kinetic assay was optimal at neutral pH with snap freezing and rapid thawing; activity decayed about 20 percent within 2 hours and 40 percent within 4 hours at room temperature; among 51 volunteers (25 men, mean age 39) providing four replicates with two devices, reproducibility was excellent for beta-glucuronidase with both (intraclass correlation 0.92), and the larger device gave significantly higher mean activities.

  18. 18.

    Flores R, Shi J, Gail MH, Gajer P, Ravel J, Goedert JJ. Association of fecal microbial diversity and taxonomy with selected enzymatic functions. PLoS One. 2012. PMID 22761886. DOI 10.1371/journal.pone.0039745.

    Cross-sectional study · In 51 healthy volunteers (26 female, mean age 39), fecal beta-glucuronidase was elevated with weight loss of at least 5 lb (P = 0.03) and correlated directly with microbiome richness and alpha diversity and with the abundance of four Firmicutes Clostridia genera, and inversely with two other genera; the authors call for independent validation.

  19. 19.

    Wallace BD, Roberts AB, Pollet RM, Ingle JD, Biernat KA, Pellock SJ, et al.. Structure and Inhibition of Microbiome β-Glucuronidases Essential to the Alleviation of Cancer Drug Toxicity. Chemistry and Biology. 2015. PMID 26364932. DOI 10.1016/j.chembiol.2015.08.005.

    Laboratory method study · Representative beta-glucuronidases from two Firmicutes, a Proteobacterium and a Bacteroidetes were structurally similar but differed markedly in catalytic properties and propensity for inhibition, indicating functional diversity in orthologous enzymes; beta-glucuronidase inhibition did not alter the serum pharmacokinetics of the chemotherapy drug or its metabolites in mice.

  20. 20.

    Flores R, Shi J, Fuhrman B, Xu X, Veenstra TD, Gail MH, Gajer P, Ravel J, Goedert JJ. Fecal microbial determinants of fecal and systemic estrogens and estrogen metabolites: a cross-sectional study. Journal of Translational Medicine. 2012. PMID 23259758. DOI 10.1186/1479-5876-10-253.

    Cross-sectional study · Among 51 participants (25 men, 7 postmenopausal and 19 premenopausal women), urinary estrogens in men and postmenopausal women were strongly associated with fecal microbiome richness and diversity (R ≥ 0.50, P ≤ 0.003); only urinary estrone correlated significantly with fecal beta-glucuronidase activity (R = 0.36, P = 0.04), fecal beta-glucuronidase correlated inversely with fecal total estrogens (R ≤ -0.47, P ≤ 0.01), and premenopausal women's estrogens were unrelated to microbiome or enzyme measures (P ≥ 0.6).

  21. 21.

    Fuhrman BJ, Feigelson HS, Flores R, Gail MH, Xu X, Ravel J, Goedert JJ. Associations of the fecal microbiome with urinary estrogens and estrogen metabolites in postmenopausal women. Journal of Clinical Endocrinology and Metabolism. 2014. PMID 25211668. DOI 10.1210/jc.2014-2222.

    Cross-sectional study · In 60 healthy postmenopausal women aged 55 to 69 without recent antibiotics or hormone therapy, the ratio of urinary estrogen metabolites to parent estrogens was directly associated with whole-tree phylogenetic diversity (R = 0.35, P = .01), with Clostridiales abundance (R = 0.32, P = .02) and inversely with Bacteroides (R = -0.30, P = .03), independent of age and body mass index.

  22. 22.

    Ervin SM, Li H, Lim L, Roberts LR, Liang X, Mani S, Redinbo MR. Gut microbial β-glucuronidases reactivate estrogens as components of the estrobolome that reactivate estrogens. Journal of Biological Chemistry. 2019. PMID 31636122. DOI 10.1074/jbc.RA119.010950.

    Laboratory method study · The first in vitro analysis of 35 human gut microbial beta-glucuronidases found that members of three structural classes reactivate estrone and estradiol from their glucuronides; a class-selective inhibitor blocked reactivation in purified enzymes and in mixed murine fecal preparations but did not reduce tumor development in a mouse breast cancer model, and the authors conclude the estrobolome is a multidimensional set of processes involving many enzymes.

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    Humblot C, Murkovic M, Rigottier-Gois L, Bensaada M, Bouclet A, Andrieux C, Anba J, Rabot S. Beta-glucuronidase in human intestinal microbiota is necessary for the colonic genotoxicity of the food-borne carcinogen 2-amino-3-methylimidazo[4,5-f]quinoline in rats. Carcinogenesis. 2007. PMID 17660508. DOI 10.1093/carcin/bgm170.

    Laboratory method study · Comparing gnotobiotic rats colonized with a wild-type bacterium or an isogenic beta-glucuronidase-deficient mutant, the presence of the enzyme in the digestive lumen increased the colonic genotoxicity of a carcinogen formed in meat and fish during cooking threefold; the first in vivo demonstration of this role.

  24. 24.

    Kim DH, Jin YH. Intestinal bacterial beta-glucuronidase activity of patients with colon cancer. Archives of Pharmacal Research. 2001. PMID 11794536. DOI 10.1007/BF02975166.

    Cross-sectional study · Fecal beta-glucuronidase activity in patients with colon cancer was 1.7 times higher than in healthy controls, and 12.1 times higher when specimens were sonicated; the activity was inducible by substrate and by bile from carcinogen-treated rats, leading the authors to propose the enzyme as a prime factor in colon cancer etiology.

  25. 25.

    Zhang LT, Westblade LF, Iqbal F, Taylor MR, Chung A, Satlin MJ, et al.. Gut microbiota profiles and fecal beta-glucuronidase activity in kidney transplant recipients with and without post-transplant diarrhea. Clinical Transplantation. 2021. PMID 33605497. DOI 10.1111/ctr.14260.

    Prospective cohort · Among 97 kidney transplant recipients with 273 fecal specimens, those with post-transplant diarrhea had lower microbial diversity; among those with diarrhea, higher fecal beta-glucuronidase activity went with a more prolonged course of 7 days or more (91 percent against 40 percent, P = .02).

  26. 26.

    Edwinson AL, Yang L, Peters S, Hanning N, Jeraldo P, Jagtap P, et al.. Gut microbial β-glucuronidases regulate host luminal proteases and are depleted in irritable bowel syndrome. Nature Microbiology. 2022. PMID 35484230. DOI 10.1038/s41564-022-01103-1.

    Cross-sectional study · In 52 patients with post-infection irritable bowel syndrome, high gut proteolytic activity went with lower fecal beta-glucuronidase activity and fewer end-products of bilirubin deconjugation; germ-free mice had tenfold higher proteolytic activity than conventional mice, and unconjugated bilirubin or beta-glucuronidase-overexpressing bacteria reduced proteolytic activity while inhibiting the enzyme increased it.

  27. 27.

    Awolade P, Cele N, Kerru N, Gummidi L, Oluwakemi E, Singh P. Therapeutic significance of β-glucuronidase activity and its inhibitors: A review. European Journal of Medicinal Chemistry. 2020. PMID 31835168. DOI 10.1016/j.ejmech.2019.111921.

    Review · Reviews beta-glucuronidase as a molecular target, notes its activity level in body fluids is deemed a potential biomarker for some conditions, and concludes that although natural products and synthetic scaffolds have been identified as inhibitors, only a few have found clinical utility, with moderate to poor pharmacokinetic profiles.

  28. 28.

    Reddy BS, Engle A, Simi B, Goldman M. Effect of dietary fiber on colonic bacterial enzymes and bile acids in relation to colon cancer. Gastroenterology. 1992. PMID 1314747. DOI 10.1016/0016-5085(92)91704-8.

    Randomized trial · Premenopausal women consuming 13 to 15 g a day of wheat, oat or corn bran for 8 weeks: wheat bran decreased the activities of all bacterial enzymes measured including beta-glucuronidase and lowered secondary bile acids; oat bran decreased beta-glucuronidase, nitroreductase and azoreductase without affecting bile acids; corn bran did not lower beta-glucuronidase; the effect depends on the type of fiber.

  29. 29.

    Goldin BR, Swenson L, Dwyer J, Sexton M, Gorbach SL. Effect of diet and Lactobacillus acidophilus supplements on human fecal bacterial enzymes. Journal of the National Cancer Institute. 1980. PMID 6766508. DOI 10.1093/jnci/64.2.255.

    Cross-sectional study · Omnivores eating a Western-type diet had higher fecal beta-glucuronidase, nitroreductase, azoreductase and steroid 7-alpha-dehydroxylase than vegetarians; removing red meat or adding bran or wheat germ for 30 days did not change beta-glucuronidase, nitroreductase or azoreductase but lowered 7-alpha-dehydroxylase; adding viable lactobacillus supplements significantly lowered fecal beta-glucuronidase and nitroreductase, which returned to baseline 30 days after stopping.

  30. 30.

    Reddy BS, Weisburger JH, Wynder EL. Fecal bacterial beta-glucuronidase: control by diet. Science. 1974. PMID 4808971. DOI 10.1126/science.183.4123.416.

    Cross-sectional study · In human volunteers, fecal bacterial beta-glucuronidase activity was significantly higher on a mixed Western high-meat diet than on a non-meat regimen, so the flora on the high-meat diet was more able to hydrolyze glucuronide conjugates.

  31. 31.

    Goldin BR, Gorbach SL. The effect of milk and lactobacillus feeding on human intestinal bacterial enzyme activity. American Journal of Clinical Nutrition. 1984. PMID 6424430. DOI 10.1093/ajcn/39.5.756.

    Randomized trial · In 21 subjects through control, plain milk, control, lactobacillus-containing milk and control periods of 4 weeks each, the activities of beta-glucuronidase, nitroreductase and azoreductase fell 2- to 4-fold only during lactobacillus feeding, in all subjects (P from 0.02 to 0.001), returning to baseline within 4 weeks of stopping.

  32. 32.

    Ling WH, Korpela R, Mykkänen H, Salminen S, Hänninen O. Lactobacillus strain GG supplementation decreases colonic hydrolytic and reductive enzyme activities in healthy female adults. Journal of Nutrition. 1994. PMID 8283290. DOI 10.1093/jn/124.1.18.

    Randomized trial · In 64 women aged 20 to 41 randomized to a yogurt containing a live strain, that yogurt with or without a rye fiber product significantly decreased fecal beta-glucuronidase, nitroreductase and glycocholic acid hydrolase over 4 weeks, with activities returning to baseline during follow-up and added fiber making no difference.

  33. 33.

    De Preter V, Raemen H, Cloetens L, Houben E, Rutgeerts P, Verbeke K. Effect of dietary intervention with different pre- and probiotics on intestinal bacterial enzyme activities. European Journal of Clinical Nutrition. 2008. PMID 17327863. DOI 10.1038/sj.ejcn.1602706.

    Randomized trial · In a randomized crossover study of 53 healthy volunteers across five treatment groups over 4 weeks, two prebiotics significantly decreased fecal beta-glucuronidase activity and two probiotic organisms showed a tendency to decrease it, while a yeast had no influence and a synbiotic combination was no better than either component alone.

  34. 34.

    Marteau P, Pochart P, Flourié B, Pellier P, Santos L, Desjeux JF, Rambaud JC. Effect of chronic ingestion of a fermented dairy product containing Lactobacillus acidophilus and Bifidobacterium bifidum on metabolic activities of the colonic flora in humans. American Journal of Clinical Nutrition. 1990. PMID 2119557. DOI 10.1093/ajcn/52.4.685.

    Randomized trial · In nine healthy volunteers studied before, during and after 3 weeks of a fermented dairy product, fecal beta-glucuronidase and azoreductase activities did not change, beta-glucosidase increased and nitroreductase decreased.

  35. 35.

    Dwivedi C, Heck WJ, Downie AA, Larroya S, Webb TE. Effect of calcium glucarate on beta-glucuronidase activity and glucarate content of certain vegetables and fruits. Biochemical Medicine and Metabolic Biology. 1990. PMID 2346674. DOI 10.1016/0885-4505(90)90012-p.

    Laboratory method study · In rats, a single dose of calcium glucarate inhibited beta-glucuronidase in serum and liver, lung and intestinal microsomes by 57, 44, 37 and 39 percent; a 4 percent dietary supplement inhibited the activity of bacterial flora from the small intestine by 70 percent and from the colon by 54 percent; glucaric acid in foods ranged from 1.12 to 1.73 mg per 100 g in broccoli and potatoes to 4.53 mg per 100 g in oranges.

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