Small Intestinal Bacterial Overgrowth (SIBO) is a condition that has gained traction in recent years, but its complexity, especially in women, remains underappreciated. While digestive complaints are common, SIBO presents a particular challenge due to its ability to mimic other disorders like IBS, food intolerances, hormonal imbalances, and even anxiety.
For many women, this can mean years of misdiagnosis, symptom chasing, and unnecessary interventions. This post will explore what makes SIBO different in women, how hormonal shifts play a role, and why a functional medicine lens is essential for identifying and addressing the root cause.
What is SIBO, Really?
SIBO occurs when bacteria that normally reside in the large intestine start colonizing the small intestine in excess. This region is not built for bacterial fermentation—so when these microbes begin breaking down carbohydrates prematurely, the result is bloating, gas, abdominal discomfort, and changes in bowel habits (diarrhea, constipation, or both).
Although estimates vary, studies suggest that up to 60-80% of patients diagnosed with IBS may actually have underlying SIBO. Yet many women are told they “just have IBS” and are left without adequate testing or treatment.
Why Women? The Hormone-Gut Connection
Women experience a unique hormonal landscape that shifts through various life phases: puberty, menstrual cycles, pregnancy, postpartum, perimenopause, and menopause. Each of these stages involves fluctuations in estrogen and progesterone—hormones that impact gastrointestinal motility.
Slower gut motility (as seen in low progesterone states or during luteal phase dominance) impairs the function of the migrating motor complex (MMC), the wave-like mechanism that sweeps bacteria out of the small intestine between meals. When MMC activity is suppressed, bacteria linger and multiply where they shouldn’t.
In fact, women with hormonal conditions such as PCOS, endometriosis, and hypothyroidism are found to have significantly higher rates of SIBO. A 2025 case–control study in the *International Journal of Gynecology & Obstetrics* found that 91.9% of women with endometriosis tested positive for SIBO or intestinal methanogen overgrowth (IMO).
The Symptom Puzzle: It’s Not All in Your Head
What makes SIBO even more elusive is the overlap of its symptoms with other chronic conditions:
– Bloating that worsens throughout the day
– Brain fog and fatigue unrelated to sleep quality
– Nutrient deficiencies, especially B12, iron, and magnesium
– Mood fluctuations, often mistaken for anxiety or PMS
– Food sensitivities that seem to multiply over time
When a woman presents with these complaints, she may be referred to a gastroenterologist, a therapist, an allergist, or even a gynecologist—but rarely does anyone connect the dots.
The result? Frustration and a growing list of foods to avoid, supplements to try, and diagnoses that don’t quite fit.
The Functional Medicine Lens: Looking at the Whole Woman
Functional medicine approaches SIBO not just as a gut issue, but as part of a broader systemic imbalance. Here’s what that looks like in practice:
1. Comprehensive Testing
– Lactulose or glucose breath testing for SIBO
– Stool testing for microbiome imbalances or pathogens
– Hormone panels to evaluate estrogen, progesterone, thyroid, and cortisol
– Nutrient testing for deficiencies like B12, iron, and vitamin D
A 2020 guideline from the American College of Gastroenterology emphasizes the importance of comprehensive workups to distinguish SIBO from other gut disorders.
2. Targeted Nutrition
– Temporary use of low-FODMAP or Specific Carbohydrate Diet (SCD)
– Reintroduction strategies to rebuild tolerance and microbial diversity
– Support for liver detox pathways to process estrogen efficiently
3. Herbal or Pharmaceutical Antimicrobials
– Rifaximin (a non-systemic antibiotic)
– Herbal blends (e.g., oregano oil, berberine, allicin)
These options are often paired with prokinetics to restore MMC function. A 2008 study published in *The American Journal of Gastroenterology* noted that recurrence is common, and long-term strategies are needed for success.
4. Hormone Balancing
– Cycle tracking and support for ovulatory function
– Stress management for cortisol regulation
– Botanical adaptogens or bioidentical hormone therapy (when indicated)
5. Nervous System Regulation
Because the gut-brain axis plays a critical role, stress management is not optional. Modalities like vagal nerve stimulation, breathwork, and trauma-informed therapy can support gut repair.
A Note on Recurrence and Root Causes
SIBO often comes back if the underlying cause is not addressed. That means if the initial trigger was hypothyroidism, unmanaged stress, surgical adhesions, or long-standing use of PPIs or antibiotics, those factors need to be part of the healing plan.
It’s not about killing bacteria once; it’s about restoring the terrain.
Final Thoughts: It’s Time to Be Believed
At Eterna, we understand how exhausting it can be to navigate symptoms that don’t fit neatly into one diagnosis. That’s why we take a deeper, more personalized approach—especially for women whose stories have been too often overlooked. Our care isn’t one-size-fits-all. It’s built on listening closely, investigating thoroughly, and supporting the whole person.
For too long, women’s gut complaints have been minimized or mislabeled as psychosomatic. But research and clinical experience now make it clear: there is a physiological, testable, and treatable explanation for these symptoms.
If you’re someone who has been told “everything looks normal” yet your body tells a different story, know that you’re not alone—and you’re not crazy.
With the right approach, it is possible to get to the root, heal the gut, and finally feel like yourself again.