Anxiety might be in your gut, not in your head: SIBO and gut-brain axis

By Simone Jeffries, Naturopath, Herbalist, Perimenopause coach

You've been told it's IBS. You've tried the low FODMAP diet religiously. You feel anxious about eating out, constantly worried about when symptoms will strike next. The bloating hits like clockwork after meals, and you find yourself declining social invitations because you can't predict how your body will react.

Anxiety and gut symptoms might not be two separate battles you're fighting. What if there's actually a testable, treatable reason behind both that you haven't explored?

"Digestive upset doesn't have to control your life any more. There are many ways a naturopath can help you to heal your digestive system holistically and take back control of your eating and digestion. Symptom relief is important but an emphasis will be placed on discovering the underlying cause of the problem."– Simone Jeffries, Naturopath

The curious highway between your gut and your mind

Your digestive system and your brain are in constant conversation through what we call the gut-brain axis. This isn't just a poetic way of describing gut feelings – it's a very real network of nerves, hormones, and immune signals connecting your digestive system to your mind.

When something goes wrong in your gut, your brain gets the message loud and clear. This is why women with digestive conditions are twice as likely to experience anxiety compared to women without gut issues. It's not that you're being dramatic or that it's "all in your head" – your gut is literally sending stress signals to your brain.

I see this connection daily in my clinic. Women come to me feeling dismissed, frustrated, and often embarrassed that they can't seem to get their symptoms under control.

They've been managing their anxiety separately to their digestive issues, not realising these two challenges are often part of the same story.

The SIBO revelation that changes everything

Research shows that 60 to 70% of people diagnosed with IBS actually have a condition called SIBO – Small Intestine Bacterial Overgrowth.

SIBO occurs when bacteria that normally live happily in your large intestine migrate up into your small intestine, where they don't belong. These misplaced bacteria feast on your food before you can properly absorb the nutrients, creating gases that cause that familiar bloating, pain, and unpredictable bowel movements.

But here's where it gets really interesting for those of you dealing with anxiety: these bacteria don't just cause digestive chaos. They steal your nutrients, and interfere with your body's production of neurotransmitters like serotonin – the chemical that regulates your mood and anxiety levels.

Research confirms this connection is real. A Polish study found that SIBO patients had significantly higher levels of anxiety and stress compared to those without SIBO. Clinical evidence shows that 50-90% of people with IBS who seek medical care also experience anxiety disorders, panic disorder, or depression – and we now know that most IBS cases are actually undiagnosed SIBO.

Even more encouraging, studies show that when SIBO is properly treated, anxiety and depression symptoms often improve significantly alongside digestive healing.

The most telling sign of SIBO? Bloating that starts 30 minutes after eating. If this sounds familiar, you might be onto something significant.

The Vicious Cycle: how stress feeds SIBO (and SIBO feeds anxiety)

It gets really interesting – and frustrating for many women. Stress and anxiety can actually make SIBO worse, creating a vicious cycle that keeps you trapped. When you're stressed or anxious, your body's 'rest and digest' nervous system shuts down. This slows your digestive motility – the natural wave-like contractions that sweep waste and bacteria through your system. Slower motility gives bacteria more time to multiply in your small intestine, worsening SIBO symptoms such as constipation.

SIBO then triggers more anxiety through the gut-brain axis, which creates more stress, which slows digestion further, which feeds the bacterial overgrowth... and round and round you go.

This is why many women tell me they feel like they're 'going crazy' – their anxiety seems to make their gut worse, but their gut symptoms make their anxiety worse. You're not imagining this connection – it's a real biological cycle that needs to be addressed from both ends.

This is exactly why I begin treatment by supporting your stress levels with personalised herbal medicine while we're organising testing for SIBO and monitoring your digestive symptoms. Breaking the stress-SIBO cycle often requires calming your nervous system first, so your body is in the right state to heal when we address the bacterial overgrowth.

As an accredited SIBO naturopath trained by Dr Nirala Jacobi, I've seen countless women discover that their "IBS" diagnosis was actually SIBO all along. The relief they feel when they finally have an explanation – and more importantly, a pathway to healing – is profound.

I primarily work with women's gut health because hormones play such a significant role in digestive function. Your menstrual cycle, life stage – whether you're navigating puberty, perimenopause, or post-menopause – and hormonal fluctuations, all influence your gut microbiome, and digestive symptoms.

Understanding these connections allows me to create treatment plans that work with your body's natural rhythms rather than against them.

Simone Jeffries is trained and certified by Dr Nirala Jacobi "The SIBO Doctor"

Why your low FODMAP diet isn't working long-term

If you've been following a low FODMAP diet, you've probably experienced some initial relief. You might have even felt quite good for a few weeks or months. But then something frustrating happens: symptoms start creeping back, or you find that every time you try to reintroduce foods, you react poorly.

This happens because the low FODMAP approach manages symptoms rather than addressing the underlying cause. While it can provide temporary relief by reducing the food sources that bacteria ferment, it doesn't actually deal with the bacterial overgrowth itself.

Even more concerning, following a restrictive diet long-term can harm your gut microbiome diversity. Your beneficial bacteria need a wide variety of fibres and nutrients to thrive. When you limit these foods for months or years, you're inadvertently creating an environment where your gut becomes less resilient and more reactive over time.

I often work with women who've been on restrictive diets for years, feeling more limited and anxious about food than when they started. They worry about social events, feel guilty about "cheating" on their diet, and notice their symptoms becoming more unpredictable despite their careful food choices.

What Comprehensive Gut Mapping Reveals about the gut-brain axis

I don't target SIBO in isolation. I also like to test for imbalances and symptoms that are centred in your large bowel, to make sure we have an explanation for all your symptoms.

I always order comprehensive gut mapping using the GI Map stool test alongside the SIBO test. This sophisticated analysis reveals what's actually happening in your large bowel.

The beauty of having both tests is that we get a complete picture.

The SIBO breath test tells us if you have bacterial overgrowth and what type, while the GI Map shows us the broader ecosystem of your gut – what else might be contributing to your symptoms and exactly which beneficial bacteria need support.

Recently, I worked with Sarah, a busy 43 year old mum who'd been told she had IBS three years earlier. She'd been following a low FODMAP diet religiously and managing her anxiety separately with counselling and medication. Despite all her efforts, she still experienced burping and bloating after most meals and found her anxiety and constipation was actually getting worse.

Her GI Map revealed she had an overgrowth of Candida, and markers indicating leaky gut. No wonder the low FODMAP diet wasn't working – she was dealing with multiple issues that needed specific, targeted treatment. Experiencing the early stages of perimenopause was also contributing to her anxiety due to dropping progesterone levels.

I started Sarah on a herbal formula to balance her hormones and support her nervous system while we confirmed with testing that she had SIBO.

The GI Map also showed us exactly which beneficial bacteria were missing from her microbiome, giving us a clear roadmap for healing. Within eight weeks of targeted treatment, Sarah's bloating was gone, her anxiety had significantly improved, and she was eating a much wider variety of foods than she had in years.

Sarah still sees me for ongoing assistance with perimenopause, and is working on a gut healing protocol.

The magic of individualised herbal medicine

What makes the difference in my practice is creating individualised herbal formulas based on exactly what your gut microbiome results reveal. Rather than taking a one-size-fits-all approach, I craft specific herbal medicines that target the particular bacteria, fungi, or imbalances shown in your results.

As a herbalist with over ten years of experience, I've seen how powerful the right combination of plants can be when they're matched precisely to what's happening in your gut. Every formula I create is unique to the woman I'm working with, addressing not just the bacterial overgrowth, but also supporting your nervous system, improving your digestive capacity, and rebuilding your gut barrier.

This targeted approach is why my clients often see improvements within weeks rather than months.

We're not guessing or trying generic treatments – we're working with precise information about your gut to create a healing plan that makes sense for your body.

SIBO testing: your roadmap to answers

SIBO testing is a simple, non-invasive breath test to measure the gases produced by bacteria in your small intestine, confirming whether SIBO is contributing to your symptoms.

Many women tell me they wish they'd discovered these tests years earlier. After months or even years of trying different diets and supplements based on guesswork, finally having concrete information about what's happening in their gut feels like coming home.

Beyond symptom management: addressing the underlying cause

I take a holistic approach because I understand that your digestive symptoms don't exist in isolation. Your gut health affects your mood, energy levels, immune function, and overall wellbeing. When we heal your gut properly, many women are surprised to find their anxiety improves dramatically as well.

The goal is always to get you back to eating a wide variety of foods without fear, feeling confident in your body's ability to digest well, and experiencing the calm, settled feeling that comes with a healthy, balanced gut.

Your next steps toward gut-brain healing

If you're reading this and thinking "this sounds like me," you're not alone. Many women have been exactly where you are right now – frustrated with being told their symptoms are "just IBS," tired of restrictive diets that don't provide lasting relief, and wondering if there's something else going on.

The encouraging news is that SIBO and other digestive issues are very treatable when we know exactly what we're dealing with. Comprehensive testing takes the guesswork out of your healing journey and gives us the specific information needed to create your individualised treatment plan.

I'd love to help you discover what's really happening in your gut and support you on your journey back to confident, comfortable digestion.

Your symptoms are telling you something important – let's listen to what your body is trying to say.

Simone :)

Ready to get some answers? You deserve to feel well, and I'm here to help you get there.

Begin your health journey

Simone Jeffries is a naturopath specialising in women's hormonal, digestive and vaginal health based on Sydney's Northern Beaches.

Simone holds a Bachelor of Health Science (Naturopathy) and is an accredited SIBO naturopath with Dr Nirala Jacobi.

This blog is intended as information only, and is not to diagnose or provide specific treatment advice. If you are struggling with anxiety and/or digestive symptoms, please seek medical advice.

Frequently Asked Questions

Q: How do I know if my symptoms are SIBO or just regular IBS?

A: We can test for SIBO using a breath test. I suspect SIBO in anyone who bloats approximately 30 minutes after eating and regularly experiences any of the following: burping, belching, gas, constipation or diarrhoea. If you fit this picture, then I would recommend SIBO testing.

Q: Why hasn't my gastroenterologist mentioned SIBO testing?

A: SIBO testing isn't routinely offered in conventional gastroenterology, partly because the treatment approach differs from standard IBS management.

Q: Is the low FODMAP diet helpful?

A: The low FODMAP diet can be helpful short-term for symptom management, but it's not designed to be a long-term solution. Extended restriction can reduce beneficial bacterial diversity in your gut microbiome. It's best used as a temporary tool while investigating and treating the underlying cause of your symptoms.

Q: How long does SIBO treatment take?

A: Treatment typically takes 6-8 weeks for the initial phase, followed by a healing and rebuilding phase. Many women notice symptom improvements within the first few weeks. The key is not just treating the bacterial overgrowth, but also addressing why it developed and rebuilding healthy gut function.

Q: Will I have to avoid foods forever?

A: No! The goal is always to restore your digestive system's ability to handle a wide variety of foods. While some temporary dietary modifications may be needed during treatment, most women can return to eating normally once we've addressed the underlying gut dysfunction.

References

1. Pimentel M, Saad RJ, Long MD, Rao SSC. ACG Clinical Guideline: Small Intestinal Bacterial Overgrowth. Am J Gastroenterol. 2020;115(2):165-178.

2. Mari A, Abu Baker F, Mahamid M, et al. The Evolving Role of Gut Microbiota in the Management of Irritable Bowel Syndrome: An Overview of the Current Knowledge. J Clin Med. 2020;9(3):685.

3. Cryan JF, O'Riordan KJ, Cowan CS, et al. The Microbiota-Gut-Brain Axis. Physiol Rev. 2019;99(4):1877-2013.

4. Tarar ZI, Zafar W, Ain QU, et al. Burden of anxiety and depression among hospitalized patients with irritable bowel syndrome: a nationwide analysis. Ir J Med Sci. 2024;193(2):851-858.

5. Jacobi N. The SIBO Therapy Centre. Dr Nirala Jacobi's Biphasic Diet and Treatment Protocols. Available at: www.thesibodoctor.com

6. Kossewska J, Bierlit K, Trajkovski V. Personality, Anxiety, and Stress in Patients with Small Intestine Bacterial Overgrowth Syndrome. Int J Environ Res Public Health. 2022;20(1):93.

7. Iovino P, Bucci C, Tremolaterra F, et al. Bloating and functional gastro-intestinal disorders: where are we and where are we going? World J Gastroenterol. 2014;20(39):14407-14419.