You’ve Googled your symptoms. You have abdominal bloating, pain, diarrhea, constipation—or maybe both—and you think, “I must have IBS.” You visit your doctor, and the conversation revolves around your bowel habits more than anything else.
But after further examination, there are additional red flags: fatigue, unexplained weight loss, high levels of fat in your stool, nutrient deficiencies, and difficulty concentrating.
What does this mean? It’s possible you don’t have IBS at all. Instead, you might have Small Intestinal Bacterial Overgrowth (SIBO)—a condition that often gets mistaken for IBS due to overlapping symptoms.
IBS vs. SIBO: How Are They Different?
While IBS and SIBO share many of the same symptoms, they affect different parts of your digestive system. IBS primarily impacts the large intestine, while SIBO occurs in the small intestine, where most nutrient absorption takes place.
Some research suggests that SIBO may even be a root cause of IBS, which explains why the two conditions are often confused. However, there are key differences:
✔ IBS tends to be more pain-predominant, meaning abdominal pain is often the most significant symptom.
✔ SIBO is more bloating-predominant, meaning excessive gas, bloating, and distension are often the standout issues.
✔ SIBO is associated with malabsorption, leading to nutrient deficiencies (such as low vitamin B12, iron, and fat-soluble vitamins like A, D, and E), whereas IBS doesn’t usually cause significant malnutrition.
✔ SIBO may cause changes in stool appearance, such as greasy or floating stools, due to poor fat absorption—a symptom that’s not common in IBS.
Because SIBO symptoms are non-specific, it’s easy to misdiagnose it as IBS or another digestive disorder. That’s why working with a knowledgeable dietitian is essential to getting the right diagnosis and treatment.
What Exactly Is SIBO?
SIBO occurs when bacteria that normally live in the large intestine start overgrowing in the small intestine. While bacteria play a crucial role in digestion, they’re meant to stay in their designated areas. When too many bacteria (especially the wrong kinds) set up shop in the small intestine, they interfere with digestion, nutrient absorption, and gut motility.
Your small intestine is about 20 feet long and is responsible for:
✔ Breaking down food with digestive enzymes
✔ Absorbing nutrients and water into the bloodstream
✔ Moving waste towards the colon
When bacteria overgrow in this part of the gut, they ferment carbohydrates too early, creating excessive gas, bloating, and discomfort. This fermentation process can also lead to diarrhea or constipation, depending on the type of gas produced.
Zahra Tromsness, RD
How SIBO Affects Digestion and Nutrient Absorption
Because SIBO interferes with digestion, it can lead to some surprising symptoms beyond typical digestive distress:
✔ Floating, pale, or greasy stools (steatorrhea): This happens when fats aren’t properly absorbed, leading to fatty stools that may be harder to flush. While this can occasionally happen after a high-fat meal, if it’s frequent, it could signal SIBO.
✔ Nutrient deficiencies: SIBO can block the absorption of essential nutrients, leading to low levels of vitamin B12, iron, and fat-soluble vitamins (A, D, E, and K). This can cause fatigue, hair loss, brittle nails, poor skin health, and even neurological issues like brain fog.
✔ Unexplained weight loss: When nutrients aren’t absorbed properly, it can lead to unintended weight loss.
✔ Brain fog and fatigue: Malabsorption and inflammation caused by SIBO may impact cognitive function, leaving you feeling mentally sluggish and tired.
If you experience any of these alongside IBS-like symptoms, it’s worth discussing SIBO with your doctor to ensure you’re treating the right condition.
How Is SIBO Diagnosed?
If SIBO is diagnosed, treatment is aimed at reducing bacterial overgrowth, restoring gut balance, and improving digestion.
SIBO Treatment: What You Need to Know
Treatment for SIBO usually includes a combination of:
✔ Antibiotics or herbal antimicrobials: These help reduce bacterial overgrowth. Rifaximin is a commonly prescribed antibiotic, but some people opt for herbal alternatives.
✔ Nutritional support: Because SIBO can lead to deficiencies, your dietitian may recommend supplements such as vitamin B12, iron, or fat-soluble vitamins to restore nutrient balance.
✔ Dietary changes: Many individuals find relief by following a low-carbohydrate, lactose-free, or low-FODMAP diet, which reduces fermentable sugars that feed bacteria. However, diet should be personalized to your specific needs—there’s no one-size-fits-all approach.
✔ Prokinetics: These medications or supplements help improve gut motility, reducing the likelihood of bacterial overgrowth returning.
Final Thoughts
SIBO and IBS have a lot in common, but they’re not the same condition. If you’re experiencing persistent bloating, unusual stool changes, or nutrient deficiencies, it’s worth exploring whether SIBO could be the real culprit behind your symptoms.
The good news?
With the right approach, SIBO can be managed effectively—and you don’t have to suffer in silence. If you suspect SIBO or IBS, work with a healthcare professional who can guide you toward the right diagnosis and treatment plan.
Could SIBO Be the Missing Piece in Your IBS Struggle?
If you’ve been battling ongoing digestive issues like bloating, discomfort, or unpredictable bowel movements, there may be more to the story than just IBS. Since SIBO and IBS share many symptoms, it’s crucial to get to the root cause so you can treat it effectively.
Many people spend years trying different diets and treatments for IBS without lasting relief—simply because they’re not addressing the real issue. Understanding whether SIBO is playing a role in your gut health can be a game-changer in finding a treatment plan that actually works.
Have questions about SIBO, IBS, or gut health? Let’s connect! Drop a comment or explore my other blog posts for expert insights.
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