If you have SIBO, the core dietary strategy is simple: reduce the fermentable carbohydrates that feed the excess bacteria in your small intestine. The bacteria responsible for SIBO thrive on specific sugars and fibers, particularly fructose, lactose, and short-chain carbohydrates known as FODMAPs. When these bacteria ferment those carbohydrates, they produce hydrogen and methane gas, leading to bloating, pain, and altered bowel habits. Cutting off their food supply is one of the most effective ways to manage symptoms.
Why Certain Foods Make SIBO Worse
In a healthy gut, most carbohydrates are absorbed in the upper portion of the small intestine before bacteria can get to them. With SIBO, bacteria have colonized areas where they don’t belong, and they intercept those carbohydrates before your body can absorb them. The result is fermentation: gas, distension, and irritation of the intestinal lining. Foods that are harder to digest or that contain complex sugars give these bacteria exactly what they need to grow and multiply.
This is why dietary approaches for SIBO all share one principle: make your food easy to digest and absorb high up in the digestive tract, leaving less fuel for the bacteria further down.
Foods to Limit or Avoid
The biggest triggers tend to be high-FODMAP foods, which contain the types of carbohydrates that bacteria ferment most readily. These include:
- Fruits: apples, pears, cherries, watermelon, and dried fruits
- Vegetables: onions, garlic, cauliflower, mushrooms, and asparagus
- Dairy: milk, ice cream, soft cheeses, and yogurt with added sugars
- Legumes: beans, lentils, and chickpeas
- Grains: wheat and rye products, including most bread and pasta
- Nuts: pistachios and cashews in particular
- Sweeteners: honey, agave, and sugar alcohols like xylitol, sorbitol, and mannitol
You don’t necessarily need to eliminate every item on this list permanently. The goal during the active treatment phase is to dramatically reduce the overall load of fermentable material reaching your small intestine. Many people find they can tolerate some of these foods in small amounts once their bacterial levels are under control.
Foods That Are Generally Well Tolerated
Proteins and fats don’t feed bacteria the way carbohydrates do, so they form the backbone of most SIBO-friendly diets. Meat, poultry, fish, and eggs are all safe choices. Cooking oils, butter, and olive oil are fine. For carbohydrates, focus on starches that your body absorbs quickly and efficiently: white rice, potatoes, and sweet potatoes are staples recommended by gastroenterologist Mark Pimentel at Cedars-Sinai, whose low fermentation diet was designed specifically for SIBO patients.
Low-FODMAP vegetables like zucchini, bell peppers, carrots, spinach, cucumbers, and tomatoes are typically well tolerated. For fruit, stick to lower-sugar options in moderate portions: blueberries, strawberries, grapes, and oranges. Hard cheeses like cheddar and Parmesan contain very little lactose and are usually fine. Lactose-free milk and dairy products are also good substitutes.
One counterintuitive point: fiber is not your friend during active SIBO. While fiber is generally healthy for the gut, it’s highly fermentable, and reducing it temporarily is a key part of starving the overgrowth.
The Two Main Dietary Approaches
Low FODMAP Diet
The most widely used dietary approach for SIBO is the low FODMAP diet, originally developed for irritable bowel syndrome. In clinical studies, about 91% of patients with IBS and SIBO reported symptom improvement on this diet. Bloating improved in roughly 80% of patients, abdominal pain in 67%, and diarrhea in 45%. These improvements occurred regardless of the initial diagnosis, suggesting the diet works by reducing fermentation rather than targeting any single condition.
The diet is meant to be followed in phases. During the restriction phase, which typically lasts two to six weeks, you remove all high-FODMAP foods. Then comes the reintroduction phase, where you test individual food groups one at a time over three-day challenges. If symptoms stay under control during the three days, that food is considered tolerated and can go back into your regular diet. If symptoms return on any day, you stop the challenge and mark that food as a trigger. This process lets you build a personalized long-term diet rather than staying on a blanket restriction indefinitely.
Low Fermentation Diet
The Cedars-Sinai low fermentation diet is simpler and slightly less restrictive than a full low FODMAP approach. It focuses on reducing fiber, fructose, and lactose while allowing easily digested starches like rice and potatoes. It’s less granular about FODMAP subcategories, which makes it easier to follow but potentially less precise for identifying individual triggers. Many clinicians recommend starting here and moving to a stricter low FODMAP approach only if symptoms don’t improve enough.
The Elemental Diet Option
For severe cases or when other approaches haven’t worked, the elemental diet is a more aggressive option. This is a liquid-only formula where all nutrients are pre-broken-down into their simplest forms: amino acids, simple sugars, and fats. Because everything is absorbed in the very first section of the small intestine, virtually nothing reaches the bacteria further along.
In a study of 93 patients, a two-week elemental diet normalized breath test results in 80% of participants. Those who continued for a third week saw an additional 5% normalize, bringing the total to 85%. It’s effective, but it’s also difficult. You consume nothing but the formula and water for 14 to 21 days. Most people use this as a last resort or as a jumpstart before transitioning to a food-based approach.
Meal Spacing and the Cleaning Wave
What you eat matters, but when you eat plays an important role too. Your small intestine has a built-in housekeeping mechanism called the migrating motor complex (MMC), a wave of muscular contractions that sweeps bacteria and debris from the small intestine into the colon. The catch: this cleaning wave only activates during fasting. Every time you eat, it resets.
The MMC needs roughly five to six hours between meals to complete a full cycle. This means constant snacking or grazing throughout the day prevents your gut from ever clearing itself. For SIBO management, aim for three meals spaced five to six hours apart with only water between them. This single habit change can make a meaningful difference, especially if you’re someone who tends to eat small amounts throughout the day.
Probiotics During SIBO Treatment
Probiotics for SIBO might sound contradictory since the problem is too many bacteria. But certain strains appear to help, particularly when combined with antibiotic treatment. The yeast-based probiotic Saccharomyces boulardii is the most studied option for SIBO. Because it’s a yeast rather than a bacterium, antibiotics don’t kill it, so you can take both simultaneously. In one study, combining it with antibiotic treatment reduced SIBO in 55% of patients compared to 25% with the antibiotic alone.
Probiotic blends containing Lactobacillus and Bifidobacterium strains have also shown benefit in reducing symptoms and bacterial counts in specific patient groups. That said, probiotics are generally studied as a complement to treatment, not a standalone dietary fix. They work best as one piece of a broader approach that includes dietary changes and, in most cases, antimicrobial treatment.
Building a Sustainable Long-term Diet
The restrictive phase of any SIBO diet is temporary. Staying on a very limited diet for months can lead to nutritional gaps and an overly narrow gut microbiome, which can create its own problems. The goal is to be strict during the treatment window, then systematically expand your diet based on your individual tolerance.
During reintroduction, test one new food category every three days. Keep portions small on day one, increase on day two, and eat a normal serving on day three. Track your symptoms each day. If you tolerate a food across all three days, it’s safe to include regularly. If symptoms flare on any day, pull it back out and try again in a few weeks, as tolerance often improves over time as your gut heals.
Most people with SIBO end up with a personalized diet that avoids their specific triggers while being far less restrictive than the initial treatment phase. Common long-term adjustments include keeping meal spacing habits, staying moderate with high-FODMAP fruits and vegetables, choosing rice-based grains over wheat, and limiting sugar alcohols in processed foods and gum.