A SIBO diet is a way of eating designed to reduce symptoms of small intestinal bacterial overgrowth by cutting back on the carbohydrates that feed excess bacteria in the small intestine. There isn’t one single “SIBO diet.” Instead, the term covers several related approaches, including the low FODMAP diet, the Specific Carbohydrate Diet, and the elemental diet, all built around the same core idea: starve the overgrown bacteria of their preferred fuel.
How a SIBO Diet Works
In a healthy gut, most carbohydrate digestion and absorption happens in the small intestine before food reaches the colon. When bacteria have overgrown in the small intestine, they intercept certain carbohydrates and ferment them before your body can absorb them. That fermentation produces hydrogen, methane, and carbon dioxide gas, along with substances that pull extra water into the intestine. The result is the hallmark cluster of bloating, pain, diarrhea, and distention that makes SIBO miserable.
A SIBO diet works by removing the fermentable carbohydrates those bacteria thrive on. With less fuel available, the bacteria produce less gas and less osmotic activity, and symptoms decrease. This is not a cure for the overgrowth itself (antibiotics or other treatments address that), but it can dramatically reduce day-to-day symptoms during and after treatment.
The Low FODMAP Approach
The low FODMAP diet is the most widely studied dietary strategy for SIBO-related symptoms. FODMAPs are a group of short-chain carbohydrates: fermentable sugars, sugar alcohols, and certain fibers found in a broad range of everyday foods. The diet temporarily eliminates high-FODMAP foods, then reintroduces them in a structured way to identify personal triggers.
In a clinical study of IBS patients, many of whom also had SIBO, about 91% reported symptom improvement after following a low FODMAP diet. Bloating showed the greatest reduction of any individual symptom, and overall symptom burden scores dropped by roughly 60%. Notably, the benefit held regardless of whether patients had been diagnosed with IBS alone or with concurrent bacterial overgrowth.
A low FODMAP elimination phase typically lasts two to six weeks. During that time, you avoid high-FODMAP foods like garlic, onions, wheat-based products, most legumes, certain fruits (apples, pears, watermelon), and dairy products high in lactose. After symptoms stabilize, you reintroduce one FODMAP group at a time to figure out which categories actually bother you. The goal is to return to the broadest diet you can tolerate, not to stay restricted indefinitely.
The Specific Carbohydrate Diet
The Specific Carbohydrate Diet (SCD) takes a different angle. Rather than targeting specific fermentable sugars, it eliminates all complex and hard-to-digest carbohydrates, allowing only simple carbohydrates that are easy for your body to break down and absorb before bacteria can get to them. The logic is the same: if your small intestine absorbs the carbohydrate quickly, the overgrown bacteria don’t get a chance to ferment it.
On the SCD, you avoid all grains and grain products (bread, pasta, cereal, rice, oats, quinoa), starchy vegetables like potatoes and sweet potatoes, processed sugars including corn syrup and maple syrup, high-lactose dairy like milk and ice cream, and certain legumes like chickpeas and soybeans. What remains is a diet built around meat, fish, poultry, eggs, hard cheeses, nuts, non-starchy vegetables, and fruit. Homemade yogurt fermented long enough to consume most of its lactose is a staple of the traditional SCD protocol.
The Elemental Diet
The elemental diet is the most aggressive option and the only one with evidence for actually clearing the overgrowth rather than just managing symptoms. It replaces all food with a liquid formula containing predigested nutrients: amino acids, simple sugars, and fats that are absorbed high in the small intestine, leaving almost nothing for bacteria further down.
In one study, 80% of SIBO patients had a normal breath test after 14 days on an elemental diet. Among those who continued to day 21, the success rate rose to 85%. These are strong results, but the diet is difficult to follow. You consume nothing but the formula for two to three weeks, which most people find monotonous and socially isolating. It’s generally reserved for cases that haven’t responded to antibiotics or for patients who want to try a non-antibiotic approach to clearing the overgrowth.
Foods to Avoid
Across the different SIBO diet frameworks, the high-risk foods share a common trait: they’re rich in fermentable sugars, fibers, or sugar alcohols. The University of Virginia’s gastroenterology nutrition program provides one of the most detailed lists of triggers to eliminate:
- Vegetables high in fermentable sugars or fiber: garlic, onions, leeks, shallots, asparagus, artichokes, broccoli, Brussels sprouts, cabbage, cauliflower, corn, peas, sweet potato, and beets
- Sweeteners: honey, agave, high fructose corn syrup, maple syrup, molasses, brown rice syrup, and regular granulated sugar in large amounts
- Sugar alcohols: sorbitol, mannitol, xylitol, maltitol, isomalt, and erythritol, commonly found in sugar-free gums, candies, and protein bars
- High-fiber grains: bran, barley, brown rice, wild rice, oatmeal, quinoa, and any cereal with two or more grams of fiber per serving
- Sweets and processed foods: cakes, cookies, ice cream, sherbet, chocolate, jams, jellies, trail mix, and frozen desserts
- Fiber supplements: products containing psyllium, inulin, or similar fermentable fibers
Foods That Are Generally Safe
Foods without carbohydrates or fiber don’t usually cause problems because bacteria have nothing to ferment. This gives you a solid foundation to build meals around:
- Proteins: beef, pork, lamb, chicken, turkey, duck, fish, shellfish, and eggs
- Plant proteins: tofu, tempeh, unsweetened peanut butter, unsweetened almond butter, and small amounts of nuts and seeds (about a tablespoon per serving)
- Fats: butter, oils, and vinegar-based salad dressings without added sugars
- Low-fermentation vegetables (up to half a cup per meal): green beans, carrots, spinach, kale, tomato, and butternut squash
- Starchy vegetables in small portions: white potato (up to half a cup)
- Hard cheeses: cheddar, Parmesan, Swiss, and similar aged varieties that are naturally low in lactose
Portion size matters even with “safe” foods. Keeping vegetable servings to half a cup at a meal helps prevent overloading the small intestine with fermentable material, even from lower-risk options.
Lactose and False Intolerances
Many people with SIBO believe they’re lactose intolerant because dairy triggers bloating, gas, and diarrhea. What’s often happening is that excess bacteria in the small intestine are fermenting lactose before it can be absorbed normally. Lactose breath tests in these patients can even come back positive for intolerance when the real issue is bacterial overgrowth, not a true enzyme deficiency. Once the overgrowth is treated, some people find they can tolerate dairy again. This is worth keeping in mind during the reintroduction phase.
Nutritional Risks of Long-Term Restriction
SIBO itself causes nutrient deficiencies because the overgrown bacteria interfere with normal absorption. The bacteria can break down bile acids in the upper small intestine, reducing fat absorption and leading to deficiencies in fat-soluble vitamins: A, D, and E. Vitamin B12 deficiency is also common because bacteria consume it before you can absorb it. Iron stores tend to run low as well, particularly in people who produce both hydrogen and methane on breath testing.
Layering a restrictive diet on top of these existing deficiencies can make things worse. People with SIBO already tend to eat less fiber and less dairy at baseline because they’ve learned those foods trigger symptoms. Cutting even more foods for weeks or months can lead to inadequate calorie intake, low protein levels, and worsening of the very deficiencies SIBO already causes. If you’re following a SIBO diet for more than a few weeks, tracking your intake and working with a dietitian familiar with SIBO can help you avoid nutritional gaps, especially for vitamin D, iron, and B12.
Choosing the Right Approach
The low FODMAP diet is the easiest starting point for most people. It has the most clinical evidence, allows a wide variety of foods, and includes a built-in reintroduction process that helps you identify your specific triggers rather than staying on a blanket restriction. The Specific Carbohydrate Diet is a reasonable alternative if you don’t respond well to the FODMAP approach, or if you prefer a framework that doesn’t require sorting foods into FODMAP categories. The elemental diet is typically a last resort or a deliberate treatment choice, not a long-term eating plan.
All three approaches are meant to be temporary. The elimination phase reduces symptoms and, in some cases, helps clear the overgrowth. But the long-term goal is always to reintroduce as many foods as possible while keeping symptoms under control. A SIBO diet that you stay on indefinitely, cutting more and more foods over time, is a sign that something else needs to be addressed, whether that’s incomplete treatment of the overgrowth, an underlying motility problem, or both.