The Endo-Gut Overlap
Endometriosis is a condition in which tissue similar to the uterine lining grows outside the uterus, causing chronic pain, inflammation, and often infertility. It affects an estimated 10% of women of reproductive age. What many patients and clinicians do not fully appreciate is that gastrointestinal symptoms are present in up to 90% of endometriosis cases — and they are frequently the dominant complaint.
Bloating (so common it has been termed "endo belly"), constipation, diarrhoea, nausea, painful bowel movements, and cyclical abdominal pain are hallmark features. These symptoms lead to a staggering rate of misdiagnosis: studies suggest that up to 40% of endometriosis patients receive an initial diagnosis of IBS, delaying appropriate endo treatment by an average of 7-10 years.
Why Endometriosis Causes Gut Symptoms
Direct Bowel Involvement
Endometriotic lesions can implant directly on the bowel surface. Rectovaginal and bowel endometriosis affects the rectum, sigmoid colon, and occasionally the small intestine. These implants cause localised inflammation, scarring, and adhesions that physically alter bowel function, producing pain during bowel movements, alternating constipation and diarrhoea, and rectal bleeding during menstruation.
Systemic Inflammation
Even without direct bowel involvement, endometriosis is a systemic inflammatory condition. Elevated peritoneal and systemic levels of pro-inflammatory cytokines (TNF-alpha, IL-1, IL-6) alter gut motility, increase visceral sensitivity, and compromise intestinal barrier function. This explains why women with peritoneal endometriosis (not touching the bowel) still experience significant GI symptoms.
Oestrogen, the Estrobolome, and Endometriosis
Endometriosis is an oestrogen-dependent condition — the ectopic tissue grows in response to oestrogen. The gut microbiome plays a crucial role in oestrogen regulation through the estrobolome. Dysbiotic gut bacteria can increase beta-glucuronidase activity, reactivating oestrogen that was being excreted, effectively recycling it back into the bloodstream. This elevates circulating oestrogen levels, potentially fuelling endometriotic growth.
Microbiome Findings in Endometriosis
Emerging research has identified consistent microbiome differences in women with endometriosis:
- Reduced overall diversity — lower alpha diversity in both gut and vaginal microbiomes compared to controls
- Altered Firmicutes-to-Bacteroidetes ratio — a pattern associated with increased inflammation and oestrogen dysregulation
- Increased gram-negative bacteria — which produce LPS that may contribute to the inflammatory milieu sustaining endometriotic lesions
- Reduced Lactobacillus dominance in the vaginal microbiome — associated with increased susceptibility to ascending infections and pelvic inflammation
Gut-Focused Strategies for Endometriosis
Anti-Inflammatory Diet
An anti-inflammatory dietary pattern has shown benefit in endometriosis studies. Key principles include high omega-3 intake from fatty fish, elimination of trans fats and reduction of omega-6-dominant seed oils, abundant colourful vegetables and fruits (polyphenol-rich), and limited red meat (a source of arachidonic acid that promotes inflammatory prostaglandin production).
Support Healthy Oestrogen Metabolism
Cruciferous vegetables (broccoli, kale, brussels sprouts, cauliflower) contain DIM and I3C, which support Phase I and Phase II oestrogen metabolism. Calcium-D-glucarate (found in citrus fruits, apples, and cruciferous vegetables) inhibits beta-glucuronidase, reducing oestrogen recirculation. Ground flaxseeds (2 tablespoons daily) contain lignans that modulate oestrogen receptor activity.
Rebuild Microbial Diversity
Increasing dietary fibre diversity to 30+ plant foods per week supports SCFA production and healthy estrobolome function. Fermented foods introduce beneficial bacteria that compete with beta-glucuronidase-producing species. A targeted probiotic containing Lactobacillus strains may support both gut and vaginal microbiome health.
Address "Endo Belly"
The severe bloating characteristic of endometriosis may have overlapping causes: inflammatory fluid, visceral hypersensitivity, SIBO (more common in endo patients), and hormonal fluctuations. Addressing each component — anti-inflammatory diet, low-FODMAP trial if SIBO is suspected, stress management, and gut barrier support — can significantly reduce this distressing symptom.
GutIQ's assessment can help distinguish whether your GI symptoms are driven by endometriosis-related inflammation, concurrent gut conditions like SIBO, or a combination of both. This distinction matters because the treatment approach differs for each.