IBS vs SIBO: What’s Actually Causing Your Bloating, Gas & Digestive Symptoms?
Key Takeaways
IBS and SIBO can look very similar on the surface, often causing symptoms like bloating, abdominal discomfort, and changes in bowel habits.
IBS is a symptom-based diagnosis, while SIBO refers to an overgrowth of bacteria in the small intestine that may contribute to those symptoms.
All SIBO is IBS, but not all IBS is SIBO
If you’ve been told you have IBS but still find yourself wondering why you’re dealing with bloating, gas, abdominal discomfort, constipation, diarrhoea, or food sensitivities, you’re not alone.
In clinic, I often meet people who have been given the IBS label, but very little explanation of what is actually driving their symptoms.
More recently, Small Intestinal Bacterial Overgrowth (SIBO) has gained attention as a potential underlying factor in many cases that would previously have been grouped under IBS.
While IBS and SIBO can present in very similar ways, they are not the same thing.
And understanding the difference can be an important step in making sense of your symptoms, rather than feeling like your gut is just “randomly” reacting to everything
What Is IBS?
IBS, or Irritable Bowel Syndrome, is considered a functional digestive disorder.
This means symptoms are present, but standard medical testing often doesn’t reveal any obvious structural disease or damage.
Common IBS symptoms include:
Bloating
Abdominal pain or discomfort
Constipation
Diarrhoea
Alternating bowel habits
Sensitivity to certain foods
IBS is extremely common, affecting millions of people worldwide.
However, it’s important to understand that IBS is not a single disease with one clear cause.
Instead, it’s best thought of as a description of symptoms rather than an explanation of why those symptoms are happening.
What Is SIBO?
SIBO stands for Small Intestinal Bacterial Overgrowth.
It occurs when bacteria that normally found within the large intestine begin to accumulate within the small intestine.
The small intestine is responsible for digesting food and absorbing nutrients. When excess bacteria are present in this region, they can begin fermenting food too early in the digestive process and in an environment that isn’t designed for fermentation.
This can lead to:
Bloating
Excess gas
Abdominal discomfort
Constipation
Diarrhoea
Food intolerances
Changes in bowel habits
SIBO has become a major focus in gut health because its symptoms significantly overlap with IBS.
IBS vs SIBO: What's the Difference?
All SIBO is IBS but not all IBS is SIBO.
read that again.
| IBS (Irritable Bowel Syndrome) | SIBO (Small Intestinal Bacterial Overgrowth) |
|---|---|
| A syndrome diagnosed based on symptoms. | A condition involving an overgrowth of bacteria in the small intestine. |
| Bloating, abdominal pain, constipation, diarrhoea, or mixed bowel habits. | Bloating, gas, abdominal discomfort, constipation, diarrhoea, and food intolerances. |
| No single known cause. Multiple factors may contribute. | Excess bacterial fermentation occurring in the small intestine. |
| Can vary greatly between individuals and triggers. | Often worsens after meals, particularly those containing fermentable carbohydrates. |
| Diagnosed using symptom-based criteria after excluding other conditions. | Commonly investigated using a hydrogen and methane breath test. |
| Describes the symptoms someone is experiencing. | May help explain one underlying cause of those symptoms. |
How Did SIBO Start in the First Place?
One of the most important questions in digestive health is not just whether SIBO is present, but why it began in the first place.
Bacteria don’t overgrow in the small intestine without a reason. Usually, there is an underlying disruption in normal digestive function that allows this environment to develop over time.
Some of the most common contributing factors include:
Impaired Gut Motility
Your digestive system relies on coordinated muscle movements (peristalsis) to keep food and bacteria moving in one direction.
When this process slows down, bacteria have more opportunity to linger and multiply in the small intestine. Stress, nervous system imbalance, and poor sleep can all influence motility.
Previous Gut Infections
Many people notice their digestive symptoms begin after an episode of food poisoning, gastroenteritis, or traveller’s diarrhoea.
Even after the infection has resolved, it can sometimes leave behind changes in gut function that affect motility and digestion.
Chronic Stress
Stress doesn’t just affect the mind, it directly impacts digestion.
When the nervous system is stuck in a heightened “fight or flight” state, digestion naturally slows down. Over time, this can contribute to changes in gut function and bacterial balance.
Digestive Insufficiency
Effective digestion relies on stomach acid, enzymes, and bile working together.
If food is not properly broken down, it can contribute to fermentation, bloating, and increased digestive workload further along the gut.
Structural or Anatomical Factors
In some cases, previous surgery, adhesions, or structural changes in the digestive tract may influence how efficiently food and bacteria move through the system. This may also be the case for those with Endometriosis.
Undereating or Restrictive Eating Patterns
Interestingly, not eating enough can sometimes contribute to digestive issues.
Adequate food intake helps stimulate gut motility and digestive secretions. Long-term under-eating may reduce this natural rhythm.
Low Fibre Intake & Dehydration
Fibre and hydration help support healthy bowel movements and regular gut transit.
When these are lacking, digestion can become slower and less efficient.
This is why I often take a top-down approach in clinic, looking beyond the label of SIBO itself and instead exploring the underlying systems that may have contributed to it developing.
The Naturopathic Approach to IBS and SIBO
IBS and SIBO are often discussed as if they are competing diagnoses, but in reality, digestive health is rarely that simple.
The most important question is to understand what is driving your symptoms in the first place.
That’s why my naturopathic assessment often includes a full review of:
Digestive symptoms and patterns
Diet and lifestyle
Stress and nervous system load
Medical history
Bowel habits and triggers
Where appropriate, further testing may be considered, such as:
SIBO breath testing
Comprehensive stool analysis
Blood testing
The goal is not just to label symptoms, but to understand what is actually driving them, so treatment can be targeted, personalised, and effective.
If you’re ready to get to the root cause, Bianca can help you identify the drivers behind your IBS or SIBO symptoms and guide you through a structured plan toward lasting digestive comfort.
Frequently Asked Questions About IBS and SIBO
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No. IBS is a symptom-based diagnosis, while SIBO refers to bacterial overgrowth in the small intestine.
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Yes. SIBO can produce very similar symptoms, including bloating, gas, abdominal discomfort, and altered bowel habits.
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No. Some people with IBS may have SIBO, but many do not. IBS can have multiple underlying drivers.
All SIBO is IBS, but not all IBS is SIBO.
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SIBO is commonly assessed using a breath test that measures gases produced by bacteria after consuming a test solution.
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Not necessarily. Bloating can have many causes, including stress, motility issues, food intolerances, digestive insufficiency, hormonal changes, and microbiome imbalance.
Exploring the causes is often the next step to getting control of your symptoms.
Bianca is a Clinical Naturopath who is passionate about giving women the answers they deserve. Through an individualised and investigative approach, she helps women understand the connections between digestion, hormones, skin, nervous system, lifestyle, and overall wellbeing.
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Every person's digestive symptoms are different. While articles like this can provide general education, understanding what's driving your symptoms often requires a comprehensive assessment of your health history, diet, lifestyle, stress levels, and digestive function.
