Is It Really IBS? Why Vegans Need to Know About SIBO
If you’re eating a colourful, fibre-rich, plant-filled diet yet still dealing with bloating, reflux, or unpredictable trips to the bathroom, you may have been told you just have “IBS.” But for many vegans, the real issue isn’t IBS at all—it’s something called SIBO (Small Intestinal Bacterial Overgrowth).
This is one of the most important conversations in vegan gut health right now. Because while IBS is often used as a “diagnosis,” it doesn’t explain the root cause of digestive symptoms—and for plant-based eaters, that can lead to years of confusion and unnecessary suffering.
In this article, I’ll walk you through:
The difference between IBS and SIBO
Why vegans may be especially vulnerable to SIBO symptoms
The most common signs of SIBO in plant-based eaters
What happens when doctors mistake SIBO for IBS
How to begin addressing SIBO without abandoning a vegan lifestyle
Let’s start by looking at why “IBS” often doesn’t tell the full story.
Why IBS Doesn’t Explain Everything
IBS—short for Irritable Bowel Syndrome—is one of the most common gut labels given today. If you walk into a GP’s office complaining of bloating, cramping, constipation, or diarrhoea, chances are high you’ll leave with an IBS diagnosis.
But here’s the problem: IBS isn’t a disease with a clear cause. It’s what doctors call a “diagnosis of exclusion.” That means if your bloodwork looks normal, your colonoscopy doesn’t show anything alarming, and you don’t have signs of celiac disease or inflammatory bowel disease, you may be told: “You have IBS.”
For many vegans, this feels unsatisfying. You’re eating the foods we’re told should promote digestive health—beans, lentils, leafy greens, nuts, seeds, and whole grains. Yet instead of feeling nourished, your gut feels like a ticking time bomb.
This is where SIBO comes in.
What Is SIBO?
SIBO stands for Small Intestinal Bacterial Overgrowth. It happens when bacteria that normally belong in the large intestine migrate upward into the small intestine, where they don’t belong.
The small intestine is meant to absorb nutrients. It isn’t designed to house large populations of bacteria. When bacteria set up camp there, they ferment food too early in the digestive process. The result? Excess gas, bloating, cramping, reflux, nausea, and sometimes even systemic symptoms like brain fog and fatigue.
Research shows that SIBO is actually one of the most common underlying causes of IBS. In fact, for a significant percentage of people diagnosed with IBS, what’s really happening is bacterial overgrowth in the small intestine.
This means that many vegans walking around with a vague “IBS” label are actually dealing with undiagnosed SIBO.
Why Vegans May Be More Vulnerable to SIBO Symptoms
Plant-based diets are high in fibre and resistant starch—nutrients that are wonderful for the microbiome when bacteria stay in the large intestine, where they belong. But when bacteria are living in the small intestine, fibre becomes fuel for fermentation in the wrong place.
That’s why many vegans with SIBO feel frustrated and confused. Foods that are celebrated as pillars of health—chickpeas, lentils, kale, smoothies, quinoa—can trigger intense bloating or reflux.
To make matters more confusing, many plant-based eaters are told by well-meaning practitioners to simply “eat more fibre.” While that advice may work for some gut issues, it often makes SIBO worse.
The key takeaway here is simple: it’s not that your vegan diet is wrong. It’s that the bacteria are in the wrong place.
Common Symptoms of SIBO in Vegans
Not sure whether your “IBS” might really be SIBO? Here are the most common signs to look for:
Excessive bloating after meals – especially after beans, lentils, or cruciferous vegetables.
Gas, cramping, and abdominal discomfort that doesn’t match the amount of food eaten.
Reflux or nausea even when eating light meals.
Constipation, diarrhoea, or a mix of both.
Food intolerances – especially to high-FODMAP foods like garlic, onion, and apples.
Brain fog, fatigue, or low mood that worsens after eating.
Because these symptoms overlap with IBS, many people never realise that SIBO is the underlying cause.
IBS vs SIBO: What’s the Difference?
Here’s a simple way to think about it:
IBS = A collection of symptoms without a clear cause.
SIBO = One possible cause of those symptoms.
That’s why IBS can feel like a dead end. It doesn’t explain why your symptoms are happening. It simply names them.
SIBO, on the other hand, gives us a framework for understanding why a healthy vegan diet might feel like it’s backfiring.
Why Doctors Often Miss SIBO
Most conventional tests for gut health don’t look for bacterial overgrowth in the small intestine. Bloodwork, stool tests, and even colonoscopies may appear normal. That’s why so many people are told: “Everything looks fine. It’s just IBS.”
Hydrogen and methane breath tests are the most common way to identify SIBO, but they’re not always offered in standard care. As a result, vegans may spend years thinking their gut issues are a mystery—when in fact, there’s a clear physiological explanation.
What Happens if SIBO Is Left Untreated?
When bacteria keep fermenting food in the wrong place, the small intestine can become inflamed. This can lead to:
Poor nutrient absorption – even on a nutrient-dense vegan diet.
Chronic fatigue – because your body isn’t getting what it needs.
Ongoing food intolerances – which can make eating feel stressful.
Increased risk of relapse – because the longer bacteria remain, the harder it can be to restore balance.
Healing Without Giving Up Your Vegan Diet
One of the most common fears vegans express in clinic is: “Do I have to start eating meat to fix my gut?”
The answer is no. Addressing SIBO doesn’t require abandoning your ethics. It requires a structured approach to:
Reduce bacterial overgrowth in the small intestine.
Support the gut lining and motility.
Gradually reintroduce fibre in a way the body can handle.
When managed properly, a vegan diet can absolutely support recovery from SIBO.
Emotional Impact: It’s Not “All in Your Head”
Living with daily bloating, reflux, and unpredictable bowels isn’t just a physical burden. It can also take an emotional toll. Many vegans start doubting themselves, wondering if they’re somehow “doing it wrong.” Others feel isolated when friends or family suggest abandoning plant-based eating.
But here’s the truth: your gut issues aren’t proof that veganism is unhealthy. They’re a sign that your digestive system needs support.
Key Takeaways
IBS is a label for symptoms, not a cause.
SIBO is a common hidden cause of IBS-like symptoms.
Vegans may be especially vulnerable to SIBO symptoms due to the high fibre content of plant-based diets.
The problem isn’t your diet—it’s bacterial overgrowth in the wrong part of the gut.
With the right support, it’s possible to address SIBO while staying true to your plant-based lifestyle.
Final Word
If you’re vegan and struggling with bloating, reflux, or unpredictable digestion, don’t settle for the label of “IBS.” There may be more going on. Understanding the role of SIBO can give you the clarity you need to begin true healing—without abandoning your values or your plant-based way of life.
About the Author
Camilla Brinkworth BHSc Naturopathy, Grad Cert Human Nutrition, is a naturopath, nutritionist, and trauma-informed practitioner specialising in vegan and plant-based health. After navigating her own mental and physical health struggles, she now helps clients worldwide find real answers to complex gut issues like SIBO, IBS, and bloating—without abandoning their plant-based lifestyle. Through her integrative approach combining nutrition, naturopathy, and mind-body healing, Camilla empowers people to restore balance and thrive.