The SIBO Diet: What to Eat, What to Avoid and for How Long

In short: there is no single proven “SIBO diet”. Diet alone does not usually clear the overgrowth, but a short-term low-fermentation (low-FODMAPFODMAPs Fermentable oligo-, di- and monosaccharides and polyols: short-chain carbohydrates that are poorly absorbed and quickly fermented by gut microbes.) diet can ease bloating, gas and pain while you are treated¹². The restrictive phase is meant to last about 4 to 6 weeks, followed by a gradual reintroduction of foods¹. The one diet shown to clear SIBO on breath tests is the elemental diet, a liquid formula used for two to three weeks³⁴.

Can diet cure SIBO?

For most people, no. The aim of a SIBO diet is to reduce the food available to the overgrown bacteria, which lowers fermentation, gas and symptoms¹. It does not remove the bacteria or fix the reason they overgrew, which is why diet is normally combined with antibiotics or herbal antimicrobials. In a 2024 randomized trial, for example, both groups of patients followed a low-FODMAP diet alongside their antibiotic treatment⁵.

The research behind specific SIBO diets is thin. A 2022 review concluded that the benefit of the low-FODMAP diet, which was developed for irritable bowel syndrome, is “largely hypothetical” in SIBO and that a diet designed specifically for SIBO still needs to be tested². Popular multi-phase protocols, such as the “bi-phasic” SIBO diet, have not been evaluated in published clinical trials.

Why fermentable carbohydrates cause symptoms

FODMAPs are short-chain carbohydrates that are poorly absorbed and quickly fermented: fermentable oligosaccharides (fructans and galactans), disaccharides (lactose), monosaccharides (fructose) and polyols (sugar alcohols)¹. Normally most of them are absorbed or reach the colon. When bacteria have overgrown in the small intestine, they ferment these sugars before the body can absorb them, producing gas and drawing water into the bowel¹.

This is also why people with SIBO often seem lactose or fructose intolerant. Bacteria in the small intestine ferment lactose before it is fully digested, which can even make a lactose breath test look positive when the real problem is the overgrowth¹. Read more in our guide to dairy and SIBO.

Foods to limit during the restrictive phase

The table below lists the main high-FODMAP foods to limit during the first phase¹. Small amounts may still be tolerated, because symptoms depend on the total amount eaten over a meal or a day¹.

A simpler alternative used in practice is “low-fermentation eating”: cutting out the most common triggers such as dairy, high-fructose foods, beans, cauliflower, Brussels sprouts and sugar alcohols, rather than following the full FODMAP list¹.

Foods that are usually easier to tolerate

The review recommends building meals around low-fermentation fruits and vegetables, such as citrus fruits, berries, leafy greens, root vegetables and zucchini, so the diet stays balanced while the high-FODMAP foods are reduced¹. Our low-FODMAP diet guide covers the diet’s phases and trade-offs in more detail.

How long to follow it: the three phases

Low-fermentation diets are designed to be temporary and have three phases¹:

1. Restriction: high-FODMAP foods are limited for about 4 to 6 weeks.
2. Reintroduction: each FODMAP group is added back one at a time to find out which ones, and how much, cause symptoms.
3. Personalization: a long-term diet that avoids only your own trigger foods.

When people search for “SIBO diet phase 1”, this restriction phase is usually what they mean. Moving on to reintroduction matters. FODMAPs act as food for beneficial gut bacteria such as Bifidobacterium and Akkermansia muciniphila, and staying on a strict diet for too long may make the microbial imbalance worse and risks nutritional gaps¹². For that reason, the review recommends working with a dietitian who knows the condition¹.

If you have methane-dominant SIBO

People with methane-dominant overgrowth, called intestinal methanogen overgrowth (IMO), are more likely to be constipated. Because many high-fiber foods are also high in FODMAPs, it is important to keep fiber intake up by choosing low-fermentation fruits and vegetables, so the diet does not make constipation worse¹.

Meal spacing and the migrating motor complex

Between meals, the small intestine is swept clean by the migrating motor complex, a wave of contractions that only runs when you are not eating. Low-fermentation eating therefore also includes spacing meals at least 5 hours apart and avoiding eating overnight, while continuous grazing throughout the day may worsen bloating¹.

The elemental diet: the only diet shown to clear SIBO

An elemental dietElemental diet A liquid diet of pre-digested nutrients (amino acids, simple sugars and easily absorbed fats). They are absorbed in the upper small intestine, which starves bacteria further down. replaces all food with a liquid formula of pre-digested nutrients that are absorbed high up in the small intestine, leaving almost nothing for the bacteria further down¹. In a 2004 study of 93 patients, 80% had a normal breath test after 14 days on the diet, rising to 85% after 21 days, and those whose test normalized reported much greater symptom improvement³. A newer, better-tasting formula tested in 2025 was completed by all 30 participants; 73% normalized their breath test and 83% reported adequate symptom relief⁴.

The elemental diet is demanding and needs medical supervision. In the original study, some patients could not tolerate the formula¹. See our full guide to the elemental diet.

Eating after treatment

Dietary changes to keep SIBO from returning have not been rigorously studied¹. Based on evidence from irritable bowel syndrome, a low-fermentation diet with meal spacing may help, and fiber, prebiotic foods, polyphenol-rich foods and extra virgin olive oil may support gut motility and a healthy microbiome, although these still need to be tested in people with SIBO¹. A typical Western diet, high in refined sugar, processed food and animal fat and low in plants, is linked to an unhealthy gut microbiome¹. Our guide to eating after SIBO treatment covers reintroduction in more detail.

Because SIBO itself can cause malabsorption, weight loss and malnutrition, nutritional support is part of treatment, and any restrictive diet should be planned so it does not add to those risks⁶.