Gut & digestive education
SIBO Diet: Foods to Limit, Foods to Emphasize
Small intestinal bacterial overgrowth happens when bacteria colonize the small bowel and ferment carbohydrates before they are absorbed. The result is bloating, gas, distension, variable bowel movements and sometimes new food sensitivities. This page explains which foods feed that fermentation, which foods calm it, and how breath testing turns a general list into your own plan.
Why food matters in SIBO
In a healthy gut, most bacteria live in the large intestine and carbohydrates are absorbed in the small intestine. In SIBO, those bacteria have moved upstream. When they meet starches, sugars and fibers, they ferment them into hydrogen, methane or hydrogen sulfide gas. That gas stretches the small bowel, slows or speeds motility, and damages the brush-border enzymes that finish digestion.
The right food changes reduce the fermentation load while we address the motility, digestion and microbiome drivers. This is why a SIBO-focused eating plan often calms symptoms faster than antimicrobials alone, and why the wrong foods can flare symptoms even after treatment.
Foods most often worth limiting
| Food | Why it comes up |
|---|---|
| Gluten and wheat | Wheat increases zonulin and intestinal permeability, and is a common IgG reactor in SIBO clients. It also feeds fermentation through its fructan content. |
| Dairy | Casein and lactose are frequent immune and fermentation triggers. Brush-border damage from SIBO reduces lactase production, making dairy harder to digest. |
| High-FODMAP vegetables | Onions, garlic, cauliflower, mushrooms and asparagus contain fermentable carbohydrates that bacteria in the small intestine convert to gas quickly. |
| Legumes | Beans, lentils and chickpeas are high in galacto-oligosaccharides, a FODMAP group that feeds bacterial overgrowth and produces bloating. |
This is a starting list, not a life sentence. A breath test, IgG food panel and stool analysis show which of these categories actually matter for you right now.
Foods to emphasize
- Well-cooked low-FODMAP vegetables, easier to digest than raw while the gut heals
- Wild caught fish, for anti-inflammatory omega-3s and gentle protein
- Bone broth, for glycine and collagen that support the gut lining
- White rice and oats, for low-fermentation starches that are easy on the small bowel
How testing turns a general list into your plan
A lactulose or glucose breath test tells us whether your overgrowth is hydrogen, methane or hydrogen sulfide dominant. That pattern changes the antimicrobial approach and the foods we emphasize first. A comprehensive stool analysis shows large-intestine microbiome balance, inflammation and digestive capacity. IgG food testing shows which proteins your immune system is currently reacting to, so we are not guessing.
From those results we build a written nutrition, supplement and retest plan specific to you. We recheck the breath test around four weeks after antimicrobial therapy and the IgG panel at 90 days. This is educational and assessment focused care to support your body, not a diagnosis or a treatment for SIBO, and it works alongside the care of your prescribing provider.
Common questions
What is SIBO?
SIBO, or small intestinal bacterial overgrowth, occurs when bacteria that normally live in the large intestine colonize the small intestine. They ferment carbohydrates before they are absorbed, producing hydrogen or methane gas and damaging the absorptive surface.
Is SIBO the same as IBS?
No, but they often overlap. Up to 60 to 80 percent of people with IBS test positive for SIBO on a breath test. SIBO is one of the underlying drivers that can create the symptom picture called IBS.
Do I have to avoid carbohydrates forever?
No. The goal is to lower the fermentation load while we address motility, digestion and the microbiome. Over time, most people can expand their diet again as the small intestine becomes a less hospitable place for overgrowth.
Why do my food sensitivities keep growing?
Bacterial overgrowth damages the brush border, the part of the small intestine that finishes digestion. When proteins cross that barrier half-digested, the immune system can tag them as threats. That is why the safe food list keeps shrinking until the gut lining is supported.
How is SIBO diagnosed?
A lactulose or glucose breath test measures hydrogen, methane and sometimes hydrogen sulfide after a sugar solution. We also use a comprehensive stool analysis, B12, iron and an IgG food panel to understand the full picture.
Will probiotics help or make SIBO worse?
Strain and timing matter. Some probiotics support the migrating motor complex and microbiome balance, while others can add to the bacterial load during active overgrowth. We choose probiotics based on your breath and stool results, not guesswork.