Gut Health and Endometriosis
The science behind endo belly
Around 90% living with endometriosis have gut symptoms. Bloating is most common, followed by nausea, and other bowel disturbances (e.g. constipation, diarrhoea). A key hallmark of endometriosis is the classic “endo belly” - an extremely painful, swollen abdomen that resembles a pregnancy bump, and it’s associated with the intense inflammation that endometriosis lesions bring. Along with this, those with endometriosis are more likely to suffer from Irritable Bowel Syndrome (IBS), and mental health conditions like anxiety and depression, which are all intricately connected to the gut. Encouragingly, certain dietary changes may help alleviate endometriosis symptoms.
To better understand the relationship between the gut and endometriosis, we’re going to dive into a few research areas: the mechanisms behind “endo belly”, the role of small intestinal bacterial overgrowth (SIBO), differences in the gut microbiome, and the impact of dietary interventions.
Exploring these areas provides insight into both symptom development and potential management strategies.
What Causes “Endo Belly”?
Endo belly happens because of interconnected mechanisms:
1. Chronic inflammation
Endometriosis lesions release inflammatory chemicals, which can travel through the fluid in the pelvic cavity and irritate the intestines. This happens even if the lesions aren’t directly in the bowel (e.g. they may be on the ovaries or pelvic wall). This inflammation can also cause fluid retention, contributing to a bloated, distended abdomen.
2. Visceral Hypersensitivity
Studies show those with endometriosis can develop heightened intestinal sensitivity. Chronic inflammation sensitises nerve endings, lowering pain thresholds and can end up making even normal digestive activity painful.
3. Physical Gut Disruption
Bowel lesions, or adhesions (scar tissue) in or near the bowel, can alter the gut's natural position. They can pull on intestinal segments and impact mobility - ultimately preventing proper digestion and trapping gas.
SIBO and Endometriosis: Why Is It So Common?
SIBO is when large amounts of bacteria which should be in the large intestine (lower down in our gut), accumulate in the small intestine (much higher up in our gut). SIBO causes intense bloating, abdominal pain, gas, nausea, diarrhoea, and constipation. It can even contribute to nutrient deficiencies by influencing absorption.
SIBO is very common in those living with endometriosis. A 2025 study saw that 91.9% with endometriosis and digestive symptoms tested positive for Small Intestinal Bacterial Overgrowth (SIBO), Intestinal Methane Overgrowth (IMO), or both,
Why are there such high rates of SIBO in the endometriosis community?
Endometriosis can lead to SIBO, because lesions can cause adhesions (scar tissue) and inflammation, both slowing gut motility and creating the perfect environment for this bacterial overgrowth.
And unfortunately, SIBO can then worsen endometriosis symptoms:
• Endo belly: Slowed transit and gas producing bacteria contribute to bloating, distension and constipation
• More inflammation: Bacterial overgrowth releases toxins like lipopolysaccharide (LPS) which can then translocate across the gut epithelium into our circulation. LPS can bind to immune cells to trigger a massive release of pro-inflammatory chemicals, which promote survival and growth of endometrial lesions. Additionally, this chronic inflammation can begin to sensitise surrounding nerve endings, contributing to visceral hypersensitivity and painful digestion.
How does the gut microbiome differ in those with endometriosis? (1, 2)
In those with endometriosis, overall gut microbiome diversity is lower when compared to those without endometriosis. There appear to be fewer beneficial bacteria, like Bifidobacterium and higher levels of harmful bacteria like E. Coli. Also, a higher Firmicutes to Bacteroidetes ratio was observed, which can be a sign of gut dysbiosis.
Alterations in the gut microbiome can contribute to immune system disruption, inflammation, and altered estrogen metabolism, all relevant to endometriosis. Let’s dive deeper into the estrogen piece…
The Estrobolome
The estrobolome consists of the gut bacteria that regulate the circulating levels of estrogen in the body. They can influence whether estrogen is excreted from our body, or re-enters our bloodstream!
Gut dysbiosis can increase the bacteria that produce an enzyme called beta glucuronidase. This enzyme actually prevents estrogen from being expelled from your body, and instead allows it to be reabsorbed into the blood stream, so that it can reach endometriosis lesions. This matters, because endometriosis thrives off estrogen!
The Gut-Brain Axis
The bidirectional communication between the gut and the nervous system might also play a role in the development of the psychological aspect of endometriosis. Those with endometriosis are 2-3 times more likely to develop anxiety or depression, which is multifactorial to include the combinatorial effects of medical gaslighting, pain and also perhaps gut dysbiosis. Dysregulation in the gut can affect the production of key neurotransmitters in the brain including GABA and serotonin. Not only can this contribute to the development of mental health conditions, but it can also contribute to the alterations of hormone release from the brain, and the body’s stress management system (HPA axis).
Improving Symptoms Through Diet (3, 5, 6, 7, 8)
Diet influences two key areas that could help in endometriosis management: the gut microbiome and inflammation. It is being increasingly studied for its benefit in those with endometriosis.
The Mediterranean diet: Interestingly, one study found that women with greater adherence to the mediterranean diet had 94% lower odds of having endometriosis. This diet contains high levels of omega-3 polyunsaturated fatty acids, which have been shown to decrease bacteria that produce inflammatory chemicals through LPS. It’s also rich in micronutrients which can help reduce inflammatory factor production and oxidative stress in the body, which are tightly linked to endometriosis. However, this study observed correlations. More research is needed to test causation.
Low FODMAP diet: This is designed to be a temporary diet, that should only ever be undertaken under supervision with a dietitian. A low FODMAP diet restricts fermentable oligo-, di- and mono-saccharides and polyols - things like onions, garlic, wheat, certain fruits, and legumes - before gradually reintroducing them to identify triggers. It is often the case that a selection of these types of foods can exacerbate gut symptoms in endometriosis because they draw water into the intestine and are rapidly fermented by gut bacteria, producing gas that drives bloating and pain. However, which foods may trigger a person is very individual.
A recent study confirmed that 60% of those with endometriosis responded to the low FODMAP diet and had significantly decreased abdominal pain, bloating, and increased quality of life compared to a control diet.
Gluten-free diet: Early evidence suggests that for a proportion of those with endometriosis, a gluten-free diet could help ease symptoms. In one study, 75% of participants reported a significant reduction in painful symptoms after 12 months of eating gluten-free. This may be because removing gluten helps reduce inflammation and reduce immune system activation for some.
Despite these findings, the impact of diet and endometriosis remains largely understudied and we look forward to more studies coming out to provide a clearer picture!
The Takeaway
Gut health and endometriosis is an area of increasing interest, especially when it comes to symptom management, and processes central to disease progression. However, it is crucial to keep in mind that endometriosis is a complex condition that is very different from person to person. Though the gut microbiome has important relevance, it is only be one piece of the puzzle when it comes to endometriosis
References:
1. Yuanyue L, Dimei O, Ling L, Dongyan R, Xiaomei W. Association between endometriosis and gut microbiota: systematic review and meta-analysis. Front Microbiol. 2025;16:1552134.
2. Halfon P, Estrade JP, Penaranda G, Choucroun N, Bouaziz J, Nicolas-Boluda A, Retornaz F, Gurriet B, Plauzolles A. High prevalence of small intestinal bacterial overgrowth and intestinal methanogen overgrowth in endometriosis patients: A case-control study. Int J Gynaecol Obstet. 2025 Jul;170(1):284-291. doi: 10.1002/ijgo.70005. Epub 2025 Feb 17. PMID: 39959963.
3. Guo C and Zhang C (2024) Role of the gut microbiota in the pathogenesis of endometriosis: a review. Front. Microbiol. 15:1363455. doi: 10.3389/fmicb.2024.1363455
4. Li, W., Feng, H., & Ye, Q. (2025). Relationship between endometriosis and mental health. A systematic review and meta-analysis. Archives of medical science : AMS, 21(5), 1985–1996. https://doi.org/10.5114/aoms/208502
5. Khodaverdi S, Mohammadbeigi R, Khaledi M, Mesdaghinia L, Sharifzadeh F, Nasiripour S, Gorginzadeh M. Beneficial Effects of Oral Lactobacillus on Pain Severity in Women Suffering from Endometriosis: A Pilot Placebo-Controlled Randomized Clinical Trial. Int J Fertil Steril. 2019 Oct;13(3):178-183. doi: 10.22074/ijfs.2019.5584. Epub 2019 Jul 14. PMID: 31310070; PMCID: PMC6642422.
6. Noormohammadi, M., Hashemi Javaheri, F. S., Ghasemisedaghat, S., Ghoreishy, S. M., Eslamian, G., Nouri, M., Kazemi, S. N., Nematifard, E., Rashidkhani, B., & Taheripanah, R. (2025). Mediterranean diet adherence and healthy diet indicator might decrease odds of endometriosis. Scientific reports, 15(1), 36750. https://doi.org/10.1038/s41598-025-20621-6
7. Varney, J. E., So, D., Gibson, P. R., Rhys-Jones, D., Lee, Y. S. J., Fisher, J., Moore, J. S., Ratner, R., Morrison, M., Burgell, R. E., & Muir, J. G. (2025). Clinical Trial: Effect of a 28-Day Low FODMAP Diet on Gastrointestinal Symptoms Associated With Endometriosis (EndoFOD)-A Randomised, Controlled Crossover Feeding Study. Alimentary pharmacology & therapeutics, 61(12), 1889–1903. https://doi.org/10.1111/apt.70161
8. Marziali M, Venza M, Lazzaro S, Lazzaro A, Micossi C, Stolfi VM. Gluten-free diet: a new strategy for management of painful endometriosis related symptoms? Minerva Chir. 2012.