FODMAP Intolerance

What FODMAPs are

FODMAP stands for Fermentable Oligosaccharides, Disaccharides, Monosaccharides And Polyols. They are short-chain carbohydrates that:

• are poorly absorbed in the small intestine
• pull water into the bowel (osmotic effect), which can cause diarrhea
• are fermented by gut bacteria in the large intestine, producing gas

Everyone ferments FODMAPs to some extent. People with IBS have a more sensitive gut (visceral hypersensitivity), so normal amounts of gas and stretching cause pain and bloating. FODMAP intolerance is therefore not an allergy and does not damage the gut.

FODMAP groups and common high-FODMAP foods

Examples of lower-FODMAP alternatives

• Grains: rice, oats, quinoa, sourdough spelt bread, gluten-free bread
• Vegetables: carrots, zucchini, spinach, bell peppers, cucumber, potatoes, the green tops of scallions
• Fruit: oranges, kiwi, strawberries, grapes, unripe bananas
• Dairy: lactose-free milk and yogurt, hard cheeses
• Protein: meat, fish, eggs, firm tofu
• Flavor: garlic-infused oil (fructans do not dissolve in oil), chives, herbs

Portion size matters: many foods are low-FODMAP in small servings and high-FODMAP in large ones. The Monash University FODMAP app lists tested servings.

Symptoms

• bloating and a swollen belly, often worse as the day goes on
• excess gas and flatulence
• cramping belly pain
• diarrhea, constipation or both
• urgency
• symptoms usually start within a few hours of eating and can last into the next day

Related conditions

• Irritable bowel syndrome: about half to three quarters of people with IBS improve on a low-FODMAP diet
• Lactose intolerance: a single-FODMAP problem from low lactase enzyme
• Fructose malabsorption
• Non-celiac gluten sensitivity: some people who feel better without wheat are actually reacting to fructans
• SIBO: bacterial overgrowth can increase fermentation
• Inflammatory bowel disease in remission with IBS-like symptoms

Diagnosis

There is no reliable test for FODMAP intolerance. Before changing your diet, a doctor should:

• test for celiac disease while you are still eating gluten, because going low-FODMAP reduces wheat and can make celiac testing inaccurate
• check for red flags and do blood tests, and stool tests such as calprotectin to rule out inflammatory bowel disease
• consider breath tests for lactose or fructose malabsorption in some cases

The diagnosis is then confirmed by improvement on a low-FODMAP diet and symptom return when foods are reintroduced.

The low-FODMAP diet: 3 steps

1. Restriction (2 to 6 weeks): replace high-FODMAP foods with low-FODMAP alternatives. If symptoms do not improve after 4 to 6 weeks, the diet is unlikely to help and should be stopped
2. Reintroduction (6 to 8 weeks): test one FODMAP group at a time, in increasing amounts over 3 days, while staying low-FODMAP otherwise. Record symptoms
3. Personalization (long term): eat as varied a diet as possible, limiting only the FODMAPs and amounts that trigger symptoms

Working with a registered dietitian improves results and helps avoid nutritional gaps.

Other ways to ease symptoms

• eat regular meals, eat slowly and do not skip meals
• soluble fiber such as psyllium for IBS, especially constipation
• regular exercise and stress management
• gut-directed hypnotherapy and cognitive behavioral therapy for IBS
• peppermint oil capsules for cramping
• lactase enzyme tablets with dairy if lactose is a trigger

Frequently asked questions

What is FODMAP intolerance?

It is a tendency to get bloating, gas, belly pain and changes in bowel habit after eating FODMAPs, a group of poorly absorbed carbohydrates. It is common in irritable bowel syndrome. It is not an allergy and does not damage the gut.

What foods are high in FODMAPs?

Common high-FODMAP foods include wheat, rye, onions, garlic, beans, lentils, milk, soft cheese, apples, pears, mango, watermelon, honey, stone fruits, mushrooms, cauliflower and sugar-free products with sorbitol or xylitol.

How long does it take for a low-FODMAP diet to work?

Most people who respond notice improvement within 2 to 4 weeks of the restriction phase. If symptoms do not improve after 4 to 6 weeks, the diet is probably not the answer, and you should review other options with your doctor.

Is FODMAP intolerance the same as gluten intolerance?

No. Wheat contains both gluten and fructans, a FODMAP. Many people who feel better avoiding wheat are reacting to fructans, not gluten. Celiac disease, a true immune reaction to gluten, must be ruled out with testing before changing your diet.

Do I have to avoid FODMAPs forever?

No. The low-FODMAP diet is a short-term test. After reintroduction, most people find they tolerate several FODMAP groups or moderate amounts, and only need to limit their specific triggers.