Low FODMAP basics: what FODMAPs are and how the diet works
You may have heard the low FODMAP diet mentioned as a way to calm IBS symptoms. It is not a general healthy eating plan, and it is not meant to be followed forever. Here is what FODMAPs are, who the diet is for, how its three steps work, and why keeping a diary matters so much.
Updated November 3, 2026 · 7 min read · By the Log For Your Log team · 5 sources
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General information, not medical advice. This page can help you notice patterns and talk with a clinician. It cannot tell you what is causing a symptom.
What are FODMAPs?
Monash University, whose researchers came up with the concept of FODMAPs, describes them as a collection of short-chain carbohydrates, or sugars, that are not absorbed properly in the gut. They are found naturally in many foods and food additives.
Monash explains what happens next. FODMAPs move slowly through the small intestine, drawing in water. When they reach the large intestine, gut bacteria ferment them and produce gas. This happens in everyone, and Monash says most people eat high FODMAP foods every day without any problem.
The difference in irritable bowel syndrome (IBS) is how the gut responds. Monash says people with IBS can have problems with how fast contents move through the intestines, a highly sensitive gut wall, or both. The extra water and gas stretch the intestinal wall, which can lead to pain, excess wind, bloating, distension and changes in bowel habit.
What the letters stand for
FODMAP is an acronym. Monash gives these examples of where each group is found:
- Fermentable. The process by which gut bacteria break down undigested carbohydrate and produce gas.
- Oligosaccharides. Fructans and GOS, found in foods such as wheat, rye, onions, garlic and legumes or pulses.
- Disaccharides. Lactose, found in dairy products like milk, soft cheeses and yogurt.
- Monosaccharides. Fructose, found in honey, apples and high fructose corn syrup.
- And Polyols. Sorbitol and mannitol, found in some fruits and vegetables and used as artificial sweeteners.
Who the diet is for
This is the most important part. Monash says a FODMAP diet is intended for people with IBS that has been confirmed by a medical doctor, and that if a doctor has not assessed your gut symptoms, you should not be following it. It points out that several conditions have symptoms similar to IBS, including coeliac disease, inflammatory bowel disease and endometriosis, and that a doctor may need to run tests to rule these out.
NIDDK describes the low FODMAP diet as one of the changes a doctor may suggest for IBS, alongside other options such as adjusting fiber. The NHS also starts with simpler steps for people with IBS, such as eating regular meals, not eating too quickly and keeping a diary of food and symptoms.
So if you have ongoing tummy pain, bloating or changes in your poo and nobody has looked into them yet, the first step is a doctor's appointment, not a new diet.
How the three steps work
Monash describes the diet as three steps. The low FODMAP part is only the first one.
- Step 1: swap. Replace high FODMAP foods with low FODMAP alternatives for 2 to 6 weeks. Monash gives the example of switching wheat toast with honey for sourdough spelt toast with jam. If your symptoms have not improved by then, your IBS may not be sensitive to FODMAPs, and other approaches may be worth discussing.
- Step 2: test. While staying low FODMAP, you complete a series of challenges. Each one involves eating a food rich in just one FODMAP group daily for 3 days and monitoring your symptoms. Monash uses milk as an example, as it is high in lactose but contains no other FODMAPs.
- Step 3: personalize. Foods and FODMAPs you tolerated well go back into your diet, and the ones that caused trouble are limited only as much as needed for relief. Monash suggests repeating challenges over time, as your tolerance may change.
It is not meant to be permanent
Cleveland Clinic says that even if you feel great during the restrictive phase, it is not meant to be permanent, and that many people find only one or two FODMAP groups bother them. Many high FODMAP foods are nutritious vegetables, fruits and whole grains, and the goal is to widen your options as much as possible. Monash adds that the diet is not intended as a weight loss plan.
Examples of high and low FODMAP foods
Monash says it is impossible to guess the FODMAP content of a food, which is why it measures foods in a laboratory. It gives these examples of high FODMAP foods and lower FODMAP alternatives. Portion size matters too, so treat this as a sample, not a full list.
| Food group | Higher FODMAP examples | Lower FODMAP alternatives |
|---|---|---|
| Vegetables | Cauliflower, garlic, mushrooms, onion | Carrot, cucumber, lettuce, potato, zucchini |
| Fruits | Apples, mango, peaches, pears, watermelon | Cantaloupe, green kiwi fruit, orange, pineapple |
| Dairy and alternatives | Cow's milk, ice cream, yogurt | Lactose-free milk, hard cheeses, almond milk |
| Protein | Most legumes and pulses, some processed meats | Eggs, firm tofu, plain cooked meat, poultry and seafood |
| Breads and cereals | Wheat, rye and barley based breads and cereals | Oats, corn flakes, sourdough spelt bread |
| Sweeteners | Honey, high fructose corn syrup | Maple syrup, table sugar |
Why a dietitian matters
Monash says a FODMAP diet should be followed under the guidance of a dietitian with specialist skills in IBS and FODMAPs, and that its own trained dietitians are listed in a directory on its website and app. Cleveland Clinic adds that there is a lot to keep track of, including different portion sizes for different foods, and that a guide makes it easier to follow.
NIDDK also says your doctor may recommend talking with a dietitian, and the NHS says a GP may refer you to a dietitian or specialist if you need to avoid lots of different foods to control your symptoms.
How a diary helps
Every step of the diet depends on noticing how you feel. Monash says that after each 3 day challenge you should record how well you tolerated the FODMAP, and that a diary can capture the challenge foods, the type and severity of your symptoms, your bowel habit and your stress levels.
A challenge week might look something like this:
- Day 1, lunch. Challenge food: a glass of milk, as agreed with your dietitian. Symptoms: none. Bowel movement: Bristol type 4.
- Day 2, lunch. Same challenge food. Symptoms: mild bloating in the afternoon. Bowel movement: Bristol type 5.
- Day 3, lunch. Same challenge food. Symptoms: cramps and wind. Bowel movement: Bristol type 6. Stress: busy day at work.
- Days 4 to 6. Back to Step 1 foods only. Symptoms settle. Note for your dietitian: lactose seems poorly tolerated at this amount.
Write it down the same day
Memory is unreliable, especially across a 3 day challenge. Our IBS symptom diary guide covers what to record, and the Bristol stool chart explains the poop types.
Does it work?
For many people, yes. Monash says its research showed IBS symptoms improve in 3 out of 4 people who follow a low FODMAP diet, with benefits usually seen within 2 to 6 weeks. It lists reduced pain and discomfort, less bloating and distension, improved bowel habit and better quality of life.
It does not help everyone. Monash says 1 in 4 people with IBS do not see their symptoms improve, and that other approaches may be needed instead, such as stress reduction, gut directed hypnotherapy, fiber or medicines. Talk to your doctor about which to try.
When to see a doctor
See a doctor before starting if your symptoms have never been checked. If you already have IBS, the NHS says to see a GP if diet changes and pharmacy medicines are not helping, or if you need to avoid lots of different foods to control your symptoms. Our when to see a doctor guide lists warning signs, such as blood in your poo or losing weight without trying, that should always be checked.
Common questions
What are FODMAPs?
They are short-chain carbohydrates that are not absorbed properly in the gut, according to Monash University. Gut bacteria ferment them, producing gas, and they draw water into the intestines, which can trigger symptoms in people with IBS.
What are FODMAPs and who should avoid them?
Monash says most people eat high FODMAP foods every day without problems. The low FODMAP diet is intended for people with IBS confirmed by a doctor, ideally with guidance from a dietitian. It is not recommended as a general diet.
Is the low FODMAP diet for IBS?
Yes. Monash developed it to help manage IBS symptoms, and NIDDK lists it among the diet changes a doctor may suggest for IBS. Monash says it improves symptoms in about 3 out of 4 people with IBS.
What does a low FODMAP diet plan look like?
Monash describes three steps: swap high FODMAP foods for lower FODMAP ones for 2 to 6 weeks, test one FODMAP group at a time over 3 days each, then build a personal diet that limits only the foods that trigger your symptoms.
What foods are on a low FODMAP food list?
Monash gives examples such as carrot, cucumber, potato, oranges, pineapple, eggs, firm tofu, plain cooked meats, oats and lactose-free milk. Portion size matters, which is why Monash measures foods in a lab and suggests working with a dietitian.
When to talk to a doctor
Contact a doctor promptly if you notice any of these. Get urgent help if you also feel faint, dizzy or very unwell.
- Blood in your stool, or black, tarry stool
- Pale, clay colored or white stool
- Losing weight without trying
- Severe or ongoing tummy pain
- A change in your usual pattern that lasts more than a few weeks
- Diarrhea with signs of dehydration, such as dizziness or very little urine
Sources
- About FODMAPs and IBS, Monash University
- Starting the low FODMAP diet, Monash University
- Eating, diet and nutrition for irritable bowel syndrome, NIDDK (NIH)
- Diet, lifestyle and medicines for IBS, NHS
- Low FODMAP diet, Cleveland Clinic
How this page was made. Written by the Log For Your Log team with AI drafting help, then checked line by line against the sources below. Read how we write Learn.