SIBO: Symptoms, Root Causes & Natural Treatment — A Naturopath's Guide
By Joana Amram, Registered Nutritional Therapist & Naturopath (ANP) · Lisbon, Portugal
You've been bloated for years. You've tried cutting gluten, cutting dairy, cutting almost everything. You've been told it's IBS. Maybe you've even been given a diagnosis of anxiety. And yet nothing has worked.
If that sounds like you, there's a good chance nobody has properly investigated SIBO.
SIBO — Small Intestinal Bacterial Overgrowth — is one of the most common and most misdiagnosed conditions in gut health. It is thought to be the underlying driver in up to 80% of IBS cases. And most people with it have never even heard the term.
What Is SIBO?
Your digestive system is not uniformly populated with bacteria. The large intestine — your colon — is home to trillions of bacteria, and that's completely normal and necessary. But the small intestine, where most of your nutrient absorption happens, is meant to be relatively sterile in comparison.
SIBO occurs when bacteria that should be living further down in your gut migrate upward into the small intestine and establish themselves there. The result is that your food gets fermented by bacteria before your body can absorb the nutrients in it.
That fermentation produces gas — primarily hydrogen, methane, or hydrogen sulphide depending on the type of bacteria involved. And that gas has nowhere to go quickly, which is why SIBO bloating is often dramatic and rapid.
SIBO Symptoms: What to Look For
SIBO symptoms overlap heavily with IBS, which is one of the main reasons it goes undetected. The most common symptoms include:
Digestive symptoms:
Significant bloating — often appearing within 30–90 minutes of eating and worsening through the day
Excess gas, often foul-smelling
Alternating constipation and diarrhoea, or predominantly one or the other
Abdominal pain or cramping, particularly after meals
Nausea, especially after eating
Acid reflux or burping
Systemic symptoms — less obvious but equally important:
Chronic fatigue and low energy that doesn't improve with sleep
Brain fog and difficulty concentrating
Anxiety or low mood (the gut produces around 90% of the body's serotonin)
Nutrient deficiencies — particularly B12, iron, and fat-soluble vitamins — because malabsorption is common
Skin issues including acne, eczema, and rosacea
Unexplained weight loss or difficulty maintaining weight
One pattern I see consistently in practice: SIBO bloating tends to accumulate through the day. Many people wake up with a relatively flat stomach and end the day looking visibly pregnant. If this is your experience, bacterial overgrowth should be high on the list of possibilities.
What Causes SIBO?
Understanding the root cause is not just academically interesting — it is essential to treating SIBO properly. Without addressing the underlying cause, relapse after treatment is extremely common.
1. A Disrupted Migrating Motor Complex (MMC)
The migrating motor complex is a wave of muscular contractions that sweeps through the small intestine between meals, clearing undigested food particles and bacteria downward toward the colon. Think of it as your gut's housekeeping cycle.
The MMC only activates during fasting periods. Constant snacking, eating very frequently, or having a delayed gastric emptying rate can prevent the MMC from functioning properly — allowing bacteria to build up in the small intestine rather than being swept along.
2. Low Stomach Acid
Stomach acid is your gut's first line of defence against bacterial overgrowth. When acid levels are adequate, bacteria that enter through food and drink are largely neutralised before they reach the small intestine.
When stomach acid is chronically low — which is common with age, stress, or long-term use of proton pump inhibitors — far more bacteria survive the stomach and establish themselves further up the gut.
3. Previous Gut Infections or Food Poisoning
This is one of the most important root causes, and one that many practitioners overlook. A significant episode of food poisoning — particularly with bacteria like Campylobacter, Salmonella, or Escherichia coli — can trigger an immune response that inadvertently damages the nerves controlling gut motility.
This condition, called post-infectious IBS, can leave the gut with a permanently impaired MMC, making bacterial overgrowth much more likely to develop and recur.
4. Structural Issues
Scar tissue from previous surgeries, adhesions, or anatomical variations can create pockets in the small intestine where bacteria pool and accumulate rather than being swept through.
5. Hypothyroidism and Other Hormonal Imbalances
The thyroid regulates metabolism throughout the body, including gut motility. An underactive thyroid slows the movement of food and bacteria through the digestive tract, creating conditions that favour bacterial overgrowth.
6. Chronic Stress
The gut-brain axis is bidirectional. Chronic stress suppresses digestive function, reduces stomach acid production, and slows gut motility — all of which increase the risk of bacterial overgrowth.
How Is SIBO Diagnosed?
The most accessible way to test for SIBO is a breath test, which measures the levels of hydrogen and methane gas in your breath after drinking a sugar solution. If bacteria in the small intestine ferment the sugar, the gas produced travels through the bloodstream to the lungs and is measurable in your breath.
Breath tests are not perfect — they have both false positive and false negative rates — but they are currently the most practical first-line investigation available outside of direct endoscopic sampling.
In practice, I also conduct a detailed case history looking at symptom patterns, history of gut infections, medication history, and dietary patterns. The clinical picture is often highly suggestive even before testing.
Natural Treatment for SIBO
Treatment for SIBO needs to accomplish two things: reducing the bacterial overgrowth, and addressing the underlying cause so it does not return.
Herbal Antimicrobials
Several herbal preparations have strong evidence for reducing bacterial overgrowth in the small intestine. The most well-researched include:
Oregano oil — contains carvacrol and thymol, which have broad-spectrum antimicrobial activity
Berberine — derived from plants including barberry and goldenseal, highly effective particularly against methane-producing bacteria
Allicin (from garlic) — particularly useful for hydrogen sulphide SIBO
Neem leaf — supportive for overall gut microbiome balance
Herbal protocols are used for typically 4–8 weeks depending on severity, and should be tailored to the type of SIBO based on testing.
Dietary Adjustments
A low-fermentation diet — often called a low-FODMAP diet or a specific carbohydrate diet — reduces the amount of fermentable substrate available to the overgrown bacteria, helping to reduce symptoms during treatment.
This is a temporary measure, not a long-term solution. The goal is to heal the small intestine and restore normal motility so that a broad, varied diet becomes tolerable again. I see many patients who have been on severely restricted diets for years because the underlying overgrowth was never properly treated.
Restoring Motility
Addressing the MMC is central to preventing relapse. This means:
Eating 3 distinct meals per day with proper fasting gaps of 4–5 hours between them
Avoiding snacking entirely during the treatment phase
Using prokinetic herbs or supplements where appropriate — ginger, 5-HTP, and low-dose naltrexone are among the options used in practice
Addressing the Root Cause
This is non-negotiable. If SIBO is driven by low stomach acid, that must be addressed. If it follows food poisoning, the post-infectious nerve damage needs to be supported. If stress is a driver, the nervous system needs attention.
SIBO that is treated without addressing its root cause has a high relapse rate — some studies suggest over 40% within a year.
What Doesn't Work (and Why)
Generic probiotics: In active SIBO, adding more bacteria — even beneficial ones — to an already overgrown small intestine can worsen symptoms significantly. Lactobacillus-based probiotics in particular can exacerbate hydrogen SIBO. Probiotics should be used carefully, if at all, and only after the overgrowth has been addressed.
Antibiotics alone: While rifaximin (a non-absorbed antibiotic) is used in conventional SIBO treatment, antibiotics do not address the underlying motility or acid issues. Relapse without these being corrected is common.
Indefinite elimination diets: Cutting out food groups manages symptoms without treating the problem. The goal is always to expand the diet, not narrow it permanently.
How Long Does SIBO Take to Resolve?
This depends entirely on the root cause, the severity of overgrowth, and how consistently the protocol is followed. Most people notice significant improvement in symptoms within 4–6 weeks of a targeted protocol. Full resolution, including rebuilding the gut lining and reintroducing a varied diet, typically takes 3–9 months.
The length of time you have had symptoms does not necessarily predict how long treatment takes — I have seen people with 10 years of symptoms turn around in 3 months when the root cause is correctly identified and addressed.
When to Seek Help
If you have been experiencing chronic bloating, alternating bowel habits, post-meal fatigue, or gut symptoms that have not improved despite dietary changes, it is worth having SIBO properly investigated.
A good practitioner will not simply give you a protocol and send you away. They will investigate your root cause, personalise your treatment, and support you through the reintroduction phase.
Joana Amram is a registered Nutritional Therapist and Naturopath accredited by the ANP (Association of Naturopathic Practitioners) and trained at the College of Naturopathic Medicine in London. She specialises in gut health, IBS, SIBO, microbiome balance, and digestive disorders. Consultations available online worldwide and in-person in Lisbon, Portugal, in English, Portuguese, Spanish, and French.
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Disclaimer: This article is for educational purposes only and does not constitute medical advice. Please consult a qualified healthcare practitioner for personalised recommendations.