All About FODMAPs: Who Should Avoid Them and How?

FODMAPs are a group of fermentable carbohydrates.

They are notorious for causing common digestive issues like bloating, gas, stomach pain, diarrhea and constipation in those who are sensitive to them.

This includes a surprising number of people, particularly those with irritable bowel syndrome (IBS).

Luckily, studies have shown that restricting foods high in FODMAPs can dramatically improve these symptoms.

This article explains what FODMAPs are and who should avoid them.

Young Blonde with a Questioning Expression Holding an Apple

What Exactly Are FODMAPs?

FODMAP stands for Fermentable Oligo-, Di-, Mono-saccharides and Polyols (1).

These terms are the scientific names given to groups of carbs that may cause digestive issues for some people.

FODMAPs typically consist of short chains of sugars linked together and they are not completely absorbed by your body.

These two key characteristics are why some people are sensitive to them (2).

Here are the main groups of FODMAPs:

  • Oligosaccharides: Carbs in this group include fructans (fructo-oligosaccarides and inulin) and galacto-oligosaccharides. Key dietary sources include wheat, rye, various fruits and vegetables, pulses and legumes.
  • Disaccharides: Lactose is the main FODMAP in this group. Key dietary sources include milk, yogurt and soft cheese.
  • Monosaccharides: Fructose is the main FODMAP in this group. Key dietary sources include various fruit, honey and agave nectar.
  • Polyols: Carbs in this group include sorbitol, mannitol and xylitol. Key dietary sources include various fruits and vegetables, as well as some sweeteners like those in sugar-free gum.

As you can see, FODMAPs are found in a wide range of everyday foods.

Sometimes they are naturally present in foods, while other times they’re added to enhance a food’s appearance, texture or flavor.

Bottom Line: FODMAP stands for Fermentable Oligo-, Di-, Mono-saccharides and Polyols. These carbs are poorly digested by humans.

How Do FODMAPs Cause Gut Symptoms?

FODMAPs can cause gut symptoms in two ways: by drawing fluid into the intestine and through bacterial fermentation.

1. Drawing Fluid Into the Intestine

Because FODMAPs are short chains of sugars, they are “osmotically active.” This means they pull water from your body tissue into your intestine (3, 4, 5, 6).

This can lead to symptoms like bloating and diarrhea in sensitive people (7, 8, 9, 10).

For example, when you eat the FODMAP fructose, it draws twice as much water into your intestine as glucose, which is not a FODMAP (4).

2. Bacterial Fermentation

When you eat carbs, they need to be broken down into single sugars by enzymes before they can be absorbed through your intestinal wall and used by your body.

However, humans cannot produce some of the enzymes needed to break down FODMAPs. This leads to undigested FODMAPs traveling through the small intestine and into the large intestine, or colon (3, 4).

Interestingly, your large intestine is home to trillions of bacteria (11).

These bacteria rapidly ferment FODMAPs, releasing gas and other chemicals that can cause digestive symptoms, such as bloating, stomach pain and altered bowel habits in sensitive people (7, 8, 9, 10).

For instance, studies have shown that when you eat the FODMAP inulin, it produces 70% more gas in the large intestine than glucose (4).

These two processes occur in most people when they eat FODMAPs. However, not everyone is sensitive.

The reason why some people get symptoms and others do not is thought to be related the sensitivity of the intestine, which is known as colonic hypersensitivity (6).

Colonic hypersensitivity is particularly common in people with IBS (12).

Bottom Line: FODMAPs draw water into the intestine and trigger bacterial fermentation in the large intestine. This occurs in most people, but only those with sensitive intestines have a reaction.

So Who Should Try a Low-FODMAP Diet?

Plate with Steak, Potatoes, Gravy and Bell Peppers

A low-FODMAP diet is achieved by simply avoiding foods high in these carbs.

A group of researchers first suggested the concept for the management of IBS in 2005 (1).

IBS is more common than you may realize. In fact, one in 10 adults has IBS (13).

Furthermore, there have been over 30 studies testing the low-FODMAP diet in people with IBS (9, 10, 14, 15, 16).

Results from 22 of these studies suggest that following this diet can improve the following (14):

  • Overall digestive symptoms
  • Abdominal pain
  • Bloating
  • Quality of life
  • Gas
  • Altered bowel habits (both diarrhea and constipation)

It’s worth noting that in nearly all of these studies, the diet was given by a dietitian.

What’s more, the vast majority of the research was conducted in adults. Therefore, there is limited evidence about children following low-FODMAP diets (17).

There is also some speculation that a low-FODMAP diet may benefit other conditions, such as diverticulitis and exercise-induced digestive issues. However, the evidence for its use beyond IBS is limited (18, 19).

Bottom Line: A low-FODMAP diet improves overall digestive symptoms in approximately 70% of adults with IBS. Yet, there is not enough evidence to recommend the diet for the management of other conditions.

Things to Know About a Low-FODMAP Diet

Here are a few things you should know about this diet.

It’s a Low-FODMAP Diet, Not a No-FODMAP Diet

Unlike food allergies, you do not need to completely eliminate FODMAPs from your diet. In fact, they are beneficial for gut health (20).

Therefore, it’s recommended that you include them in your diet — up to your own personal tolerance.

A Low-FODMAP Diet Is Not Gluten-Free

This diet is typically lower in gluten by default.

This is because wheat, which is a main source of gluten, is excluded because it’s high in fructans.

However, a low-FODMAP diet is not a gluten-free diet. Foods such as sourdough spelt bread, which contains gluten, are allowed.

A Low-FODMAP Diet Is Not Dairy-Free

The FODMAP lactose is typically found in dairy products. Nonetheless, many dairy products contain low levels of lactose, making them low-FODMAP.

Some examples of low-FODMAP dairy foods include hard and aged cheeses, crème fraîche and sour cream.

The Low-FODMAP Diet Is Not a Long-Term Diet

It is not desirable or recommended to follow this diet for longer than eight weeks.

In fact, the low-FODMAP diet process involves three steps to reintroduce FODMAPs to your diet up to your personal tolerance.

Information on FODMAPs Is Not Readily Available

Unlike other nutrient data for vitamins and minerals, information on which foods contain FODMAPs is not readily available to the public.

Nonetheless, there are many low-FODMAP food lists available online. Yet you should be aware that these are secondary sources of data and are incomplete.

That being said, comprehensive food lists that have been validated in studies can be purchased from both King’s College London (if you are a registered dietitian) and Monash University.

Bottom Line: The low-FODMAP diet may contain some FODMAPs, as well as gluten and dairy. The diet should not be strictly followed long term and you should consider the accuracy of your resources.

Is a Low-FODMAP Diet Nutritionally Balanced?

Bowl of Berries, Muesli and Milk

You can still meet your nutritional requirements on a low-FODMAP diet.

However, like any restrictive diet, you have an increased risk of nutritional deficiencies.

In particular, you should be aware of your fiber and calcium intake while on a low-FODMAP diet (21, 22).

Fiber

Many foods that are high in fiber are also high in FODMAPs. Therefore, people often reduce their fiber intake on a low-FODMAP diet (21).

This can be avoided by replacing high-FODMAP, high-fiber foods like fruits and vegetables with low-FODMAP varieties that still provide plenty of dietary fiber.

Low-FODMAP sources of fiber include oranges, raspberries, strawberries, green beans, spinach, carrots, oats, brown rice, quinoa, gluten-free brown bread and flaxseeds.

Calcium

Dairy foods are a good source of calcium.

However, many dairy foods are restricted on a low-FODMAP diet. This is why your calcium intake may decrease when following this diet (22).

Low-FODMAP sources of calcium include hard and aged cheese, lactose-free milk and yogurt, canned fish with edible bones and calcium-fortified nuts, oats and rice milks.

A comprehensive list of low-FODMAP foods can be found using the following app or booklet.

Bottom Line: A low-FODMAP diet can be nutritionally balanced. However, there is a risk of some nutritional deficiencies, including fiber and calcium.

Does Everyone on a Low-FODMAP Diet Need to Avoid Lactose?

Plastic Jug of Milk

Lactose is the Di-saccharide in FODMAPs.

It is commonly referred to as “milk sugar” because it’s found in dairy foods such as milk, soft cheese and yogurt.

Lactose intolerance occurs when your body makes insufficient amounts of lactase, which is an enzyme that digests lactose.

This leads to digestive issues with lactose, which is osmotically active, meaning it draws water in and becomes fermented by your gut bacteria.

Furthermore, the prevalence of lactose intolerance in people with IBS is variable, with reports ranging from 20–80%. For this reason, lactose is restricted on a low-FODMAP diet (23, 24, 25).

If you already know you are not lactose intolerant, you do not need to restrict lactose on a low-FODMAP diet.

Bottom Line: Not everyone needs to restrict lactose on a low-FODMAP diet. If you are not lactose intolerant, you can include lactose in your diet.

When You Should Seek Medical Advice

Digestive symptoms occur with many conditions.

Some conditions are harmless, such as bloating. Yet others are more sinister, such as celiac disease, inflammatory bowel disease and colon cancer.

For this reason, it is important to rule diseases out before starting a low-FODMAP diet. Signs of serious diseases include (26):

  • Unexplained weight loss
  • Anemia (iron deficiency)
  • Rectal bleeding
  • Family history of celiac disease, bowel cancer or ovarian cancer
  • People over 60 experiencing changes in bowel habits lasting more than six weeks

Bottom Line: Digestive issues can mask underlying diseases. It is important to rule out disease by seeing your doctor before starting a low-FODMAP diet.

Take Home Message

FODMAPs are considered healthy for most people. However, a surprising number of people are sensitive to them, particularly those with IBS.

In fact, if you have IBS, there is about a 70% chance your digestive symptoms will improve on a low-FODMAP diet (9, 10, 16, 21, 22).

This diet may also benefit other conditions, but the research is limited.

The low-FODMAP diet has been tested and is considered safe for adults. However, be sure to choose foods high in fiber and calcium, consult reputable resources and rule out underlying disease.

Scientists are currently working on ways to predict who will respond to the diet. In the meantime, the best way to find out if it works for you is to test it out yourself.