EP.390/ SIBO, Gut Dysbiosis, and Elevated Oestrogen Levels
Some of you may know I am working on a practitioner training on endometriosis and SIBO, and a key part of this training is helping practitioners understand why addressing SIBO is so important to managing endo.
Now, there are several reasons why SIBO and gut dysbiosis can influence endo growth, but today, I want to talk about just one of them, and that’s β-glucuronidase.
So, once your body has used up oestrogen, it needs to get rid of it, and to do this, it goes through a number of steps.(1)
The first of these steps happens in the liver, which we’ve talked about previously on this podcast, but it’s then carried from the liver, either to the kidneys for removal in urine, or in the bile and into the gut, where it should be removed through bowel movements.
Now, your liver has done a lovely job of wrapping up your waste oestrogen, ready for its delivery in the gut (in theory, this process can also go wrong, but that’s another podcast!).
But, there is an enzyme in our guts called β-glucuronidase, which can unwrap the oestrogen package, and make it available for use again, and allows for oestrogen to be recirculated into the blood stream.(1)
When at a normal amount, β-glucuronidase plays a key role in maintaining healthy levels of oestrogen and actually, research has shown that most of the oestrogen that is being sent to the gut, is recirculated, with only about 10% being excreted through bowel movements. So most of our waste oestrogen is excreted in urine, but the portion that is sent to the gut, is mainly reused.(1)
Now, this balance is crucial for proper oestrogen regulation, and when levels of beta-glucruonidase increase, this can cause too much oestrogen to be recirculated, and this can pave the way for oestrogen dependent conditions and diseases, including endometriosis.(1)
A 2026 systematic review found that across the research, microbiome dysbiosis in endometriosis was associated with higher levels of β-glucuronidase and circulating oestrogen levels.(2)
The review observed that common overgrowths included e.coli, which is the primary producer of β-glucuronidase, with research showing that 94-96% of e.coli strains produce the enzyme.(3)
One 2021 study the review highlighted, found that people with stage 3 and 4 endometriosis had higher levels of specific bacteria (some of which produce β-glucuronidase) and circulating oestrogen levels.(4)
Researchers believe that alterations in the gut microbiome and the resulting elevated beta-gluronidase and oestrogen levels are involved in the pathogenesis of endometriosis.(5)
In fact, a 2023 study identified microbiome dysbiosis in patients and mice with endometriosis, with a higher level of gram-negative bacteria, which are key contributors to β-glucuronidase activity (though some gram-positive also produce β-glucuronidase). They also found higher levels of β-glucuronidase were linked to an increased number and volume of endometriotic lesions in mice, and higher levels of β-glucuronidase in humans led to more proliferation and migration of endometrial cells and immune dysfunction.(6)
It’s worth noting that the elevated levels of β-glucuronidase were also found in the serum (blood) and endo lesions of endo patients, and researchers suggested that gut dysbiosis could be leading to abnormal β-glucuronidase activity.
It’s also important to note here that low or elevated oestrogen levels can also cause microbiome dysbiosis, perpetuating this cycle. (7)
Testing
The test for β-glucuronidase is relatively simple, but not pleasant! It’s a stool test, so you will need to collect part of your bowel movement, normally in a paper bowl that goes over the toilet.
The two tests I use are either the GI Map, which is a comprehensive stool test and this will tell us about your full microbiome and show us whether there’s any dysbiosis there, but it’ll also show us inflammation levels, and some other markers of things like intestinal permeability.
Now, the GI Map is a more expensive test, it’s about £395.
So, most of my clients can’t afford to do that test, so we just to do a stool test for beta-glucronidase only, and that test is £139, with the company I use, which is Nordic Labs.
I order these tests on for my clients and interpret them, but you may very well be able to find these tests direct to consumer, meaning you can order them yourself and then you’ll get a test report back to read over.
If you do want help ordering these and understanding what the results mean and how to treat and move forward, you could always book in for a single Endo Session with me, if the full one to one coaching doesn’t feel like a fit for you.
How to address
So, if your levels of β-glucuronidase do come back elevated, what do you need to do?
Research has shown that a low fibre diet is associated with higher levels of β-glucuronidase activity, whilst a high fibre diet is associated with lower levels.(8)
Additionally, previous research linked a high fat diet with higher circulating oestrogen levels, whilst a high fibre diet is associated with lower circulating oestrogen levels, including diets like the Mediterranean diet, which is high in fruits, vegetables and legumes (all high fibre foods).(9)
However, the data around a high fat diet and higher oestrogen levels is now being debated, with more recent research disproving this theory.(10)
So, how could dietary fibre influence β-glucuronidase levels? Because dietary fibre supports the diversity and health of the gut microbiome, and promotes the growth of beneficial bacteria, and inhibits the growth of certain harmful bacteria that can promote oestrogen reabsorption.(11)
In fact, research shows that dietary fibre can reduce the risk of oestrogen dependent cancers like breast cancer by changing the gut microbiome.(12)
As a result, scientists are recommending the manipulation of the gut microbiome with probiotics and dietary changes as a way to modulate β-glucuronidase levels and protect against oestrogen dependent diseases.(13)
Additionally, probiotics and prebiotics have been shown to reduce oestrogen-dependent cancer risk by modulating the gut microbiome and as a result, reducing β-glucuronidase activity. (14)
Flavanoids, which are found in plant foods, have also been shown inhibit β-glucuronidase activity. (15) It’s worth noting here, that the studied flavonoids are not typically found in every day foods but in herbal teas like mulberry bark and bitters.
Finally, a supplement called calcium-d-glucurate is a typical go-to for inhibiting β-glucuronidase activity, so it can prevent oestrogen recirculation, but you do need to work on your gut microbiome in the long-term to get the levels of β-glucuronidase down. But in the meantime, calcium-d-glucurate can be very helpful.(16)
Because e.coli is the primary producer of β-glucuronidase in the intestine (17), supporting your gut with e.coli inhibitors such as PHGG, can be really helpful.(18) In fact, PHGG has also been shown to lower β-glucuronidase activity.(19)
However, if you do have SIBO, addressing this is important as the one of the main bacteria that cause hydrogen SIBO is e.coli, so if you have hydrogen SIBO, that is likely going to be elevating your β-glucuronidase levels. (20)
Now, if you’re worried about fibre and endo belly reactions, you can still increase your fibre intake but you may need to do so mindfully and very slowly. For example, if you’re on the low FODMAP diet for endo or SIBO, you can still reach your RDA of fibre, which is 30g, you just have to be intentional with how you do it, and I’ve linked to some further reading on this in the show notes.(21)
Also, if you’re wondering why you would use the low FODMAP diet for endo or SIBO, I have linked to my podcasts and the research on the low FODMAP diet.(22)
Okay, that’s it for today! I hope this has been an informative and helpful episode, and I hope it in part, helps you understand why I am so big on resolving what’s behind the endo belly, not just the symptoms!
References:
1) https://pmc.ncbi.nlm.nih.gov/articles/PMC10416750/
2) https://pmc.ncbi.nlm.nih.gov/articles/PMC12942269/
3) https://pmc.ncbi.nlm.nih.gov/articles/PMC12942269/, https://www.thieme-connect.com/products/ejournals/abstract/10.1055/a-1402-6431, https://pmc.ncbi.nlm.nih.gov/articles/PMC3768652/
4) https://pubmed.ncbi.nlm.nih.gov/33839907/
5) https://academic.oup.com/humupd/article/28/1/92/6412766, https://journals.plos.org/plosone/article?id=10.1371/journal.pone.0261362, https://www.mdpi.com/1422-0067/24/22/16301, https://www.mdpi.com/1467-3045/47/7/502, https://www.frontiersin.org/journals/microbiology/articles/10.3389/fmicb.2024.1363455/full, https://www.mdpi.com/2077-0383/12/22/7176
6) https://www.fertstert.org/article/S0015-0282(23)00241-8/fulltext
7) https://www.mdpi.com/2077-0383/12/22/7176, https://academic.oup.com/humupd/article/28/1/92/6412766, https://www.maturitas.org/article/S0378-5122(17)30650-3/fulltext, https://e-jmm.org/pdf/10.6118/jmm.24024
8) https://www.researchgate.net/publication/222032497_Dietary_fiber_and_activity_of_intestinal_tissue_ss-glucuronidase_in_rats, https://www.clinicalnutritionopenscience.com/article/S2667-2685(25)00039-7/pdf, https://pmc.ncbi.nlm.nih.gov/articles/PMC2858007/
9) https://pmc.ncbi.nlm.nih.gov/articles/PMC6474371/, https://pubmed.ncbi.nlm.nih.gov/17474873/, https://www.clinicalnutritionopenscience.com/article/S2667-2685(25)00039-7/pdf, https://www.sciencedirect.com/science/article/abs/pii/S0271531715003152
10) https://www.sciencedirect.com/science/article/pii/S0022316622105158, https://www.cancernetwork.com/view/high-fat-diet-not-associated-increased-estrogen-postmenopausal-women
11) https://www.clinicalnutritionopenscience.com/article/S2667-2685(25)00039-7/pdf
12) https://pmc.ncbi.nlm.nih.gov/articles/PMC10416750/, https://pubmed.ncbi.nlm.nih.gov/32249416/
13) https://pmc.ncbi.nlm.nih.gov/articles/PMC10416750/
14) https://pmc.ncbi.nlm.nih.gov/articles/PMC10416750/
15) https://pmc.ncbi.nlm.nih.gov/articles/PMC10416750/, https://pubmed.ncbi.nlm.nih.gov/33733438/, https://www.sciencedirect.com/science/article/pii/S0141813019392773
16) https://pubmed.ncbi.nlm.nih.gov/12197785/, https://pubmed.ncbi.nlm.nih.gov/2346674/
17) https://pubmed.ncbi.nlm.nih.gov/33733438/
18) https://www.sciencedirect.com/science/article/abs/pii/S0308814623016242, https://www.theendobellycoach.com/podcast/phgg-endo-belly-sibo-ibs
19) https://www.tandfonline.com/doi/pdf/10.1271/bbb.58.1364
21) https://www.monashfodmap.com/blog/getting-enough-fibre/
23) https://www.theendobellycoach.com/podcast/low-fodmap-diet-endometriosis, https://www.theendobellycoach.com/podcast/low-fodmap-diet-endometriosis-sibo
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