The Low-FODMAP Diet: What It Is and Who It Helps

What FODMAPs are

FODMAP stands for fermentable oligosaccharides, disaccharides, monosaccharides and polyols. These are carbohydrates that are hard to digest. [1][2] When carbohydrates that the small intestine does not fully digest reach the large intestine, bacteria break them down and create gas, which can cause bloating and discomfort in some people. [3]

The low-FODMAP diet is a structured way to reduce those carbohydrates for a short period and then work out which ones bother you. It is not a general "healthy eating" plan, and it is not meant to be followed forever.

Who it has been studied in

The strongest evidence is in irritable bowel syndrome (IBS). NIDDK says doctors may recommend trying it for a few weeks to see if it helps IBS symptoms. [1] The 2021 American College of Gastroenterology IBS guideline recommends a limited trial of a low-FODMAP diet to improve global IBS symptoms. [2] This page focuses on IBS because that is where the guideline support is. See irritable bowel syndrome.

The three stages

1. Restriction. Reduce high-FODMAP foods for a few weeks. [1]
2. Reintroduction. If symptoms improve, foods containing FODMAPs are slowly added back. [1]
3. Personalisation (long-term plan). You may be able to eat some foods with FODMAPs without symptoms. [1] Reviews describe the diet as having these three stages: restriction, reintroduction and personalisation. [4]

NIDDK gives examples of foods that contain FODMAPs: some fruits (apples, pears, mango, cherries, watermelon), vegetables such as onions, garlic, cabbage, cauliflower and mushrooms, beans and lentils, milk, soft cheese and yogurt, wheat and rye products, honey and high-fructose corn syrup, and sweeteners ending in "-ol" such as sorbitol, mannitol and xylitol. [1] Lists from other organizations may differ, so work from a dietitian's list. See also bloating and gas.

What the research shows

Evidence labels: established recommendation = a guideline or health agency recommends it; promising but limited = some positive human studies that are small or uncertain; mixed = results differ; insufficient evidence = not enough reliable human research.

Why professional support matters

The diet is complex, and clinical effectiveness is achieved with dietitian-led education. Alternatives such as apps, webinars and leaflets remove the personalized approach and may raise nutritional-adequacy concerns. [4] NIDDK also says your doctor may recommend talking with a dietitian. [1] If you eliminate foods without guidance you risk missing nutrients; for example, avoiding all dairy can lower calcium and vitamin D intake. [8]

Do not start a low-FODMAP or gluten-free diet before ruling out conditions with similar symptoms. Celiac disease should be tested for before a gluten-free diet because it can affect test results. [9] Doctors may also check for inflammatory bowel disease when symptoms suggest it. [10] See celiac disease. If you have or have had an eating disorder, or restricting food worries you, see eating disorders and disordered eating and speak with a clinician first.

Related approaches

• Add fiber slowly and prefer soluble fiber for IBS. [1] See fiber, fluids and meal patterns.
• A Mediterranean-style low-FODMAP diet showed promising longer-term results in individual trials, but evidence is still developing. [6]
• Probiotics: see probiotics and prebiotics for gut health for strain-specific evidence.
• Beans and lentils are on NIDDK's list of foods that contain FODMAPs. [1] See legumes for what they offer nutritionally before cutting them back.

When to get help

See a clinician before restricting foods if you have unexplained weight loss, blood in stool, black stools, anemia, severe or constant pain, or vomiting, since these suggest a cause other than IBS. [10] See digestive symptoms: red flags. In the US, call 911 in an emergency. Check supplements with how interactions work.