Eating foods low in certain carbohydrates called FODMAPs may help ease some IBS-C symptoms. But it’s just one part of an overall IBS-C management plan.

If you live with irritable bowel syndrome with constipation (IBS-C), you may have come across information about FODMAPs.

Foods that are high in certain types of carbohydrates are known as high FODMAP foods. Some people with IBS-C find that high FODMAP foods worsen their symptoms.

There’s no single IBS-C treatment that will work for everyone. But there’s good evidence that a low FODMAP diet may help with many symptoms of IBS.

Managing IBS-C involves many things, such as:

  • eating enough fiber
  • drinking plenty of fluids
  • exercising
  • taking medications as prescribed

Here’s what we know about a low FODMAP diet and whether it may be helpful as a part of your management plan for IBS-C.

IBS is divided into subtypes based on how it affects bowel movements. If constipation is the predominant type of bowel movement, it’s called IBS-C.

Constipation can cause:

  • infrequent bowel movements
  • pain or difficulty passing stool
  • stools that are hard, dry, or lumpy
  • a feeling that you’re not able to fully empty your bowels

Other symptoms of IBS-C include:

  • abdominal pain
  • cramping
  • bloating
  • gas

While everyone gets constipated from time, IBS-C is diagnosed when symptoms continue for many months or years.

A diagnosis of IBS-C may be made if:

  • someone has had abdominal pain at least one day a week for the past 3 months
  • the pain is related to changes in stool consistency and frequency
  • more than 25% of bowel movements are small, dry, and hard to pass

It’s not clear what causes IBS-C to develop in the first place. There may be times when your symptoms are under control and other times when they flare.

FODMAPs is an acronym for fermentable oligosaccharides, disaccharides, monosaccharides, and polyols. These are types of carbohydrates that are harder to digest.

Foods high in FODMAPs can worsen symptoms in people with IBS. They’re not absorbed easily in the small intestine. Since they’re not fully broken down, they attract extra water as they travel through the small intestine.

When they arrive in the large intestine, the bacteria that live there work to break them down. This process creates excess gas. For someone with IBS, this can cause pain and bloating. It can also result in constipation, diarrhea, or both.

A low FODMAP diet is a temporary elimination diet. The goal is to find out more about which types of foods might be causing your symptoms. It can be restrictive and isn’t meant to be followed long-term. It’s typically recommended that people don’t follow the elimination diet for longer than 4 to 6 weeks.

You may want to work with a doctor or registered dietitian to safely develop and follow a low FODMAP diet.

There are three stages:

  1. Elimination diet: All high FODMAP foods are avoided until symptoms improve or up to four to six weeks.
  2. Reintroduction: Each group of high FODMAP foods is individually reintroduced and symptoms are monitored.
  3. Maintenance: Once symptom triggers are identified, you’ll follow a modified FODMAP diet for the long term based on your tolerance.

Here are some examples of high FODMAP foods and lower FODMAP alternatives:

High FODMAP foodsLow FODMAP foods
Grain productsanything containing wheat, rye, or barleyoats, quinoa, rice, wheat-free products
Dairycow’s milk, yogurt, ice cream, soy beverageslactose-free milk, milk alternatives such as almond milk or oat milk, hard cheeses
Fruitsapples, cherries, mango, peaches, plums, watermelonblueberries, cantaloupe, kiwi, grapes, raspberries, strawberries
Vegetablesasparagus, broccoli, Brussels sprouts, cauliflower, garlic, onioncarrots, bell pepper, green beans, spinach, tomato, zucchini
Meatssome processed meats with added ingredientsbeef, chicken, lamb, pork
Nuts, beans, legumescashews, chickpeas, lentils, most beanspeanuts, pumpkin seeds, sesame seeds, sunflower seeds
Sweetenershigh fructose corn syrup, honeyartificial sweeteners not ending in ‘-ol,’ maple syrup

There’s evidence that a low FODMAP diet can reduce the bloating, gas, and pain that are part of IBS-C. It won’t necessarily improve constipation, although some people do find it helps. A low FODMAP diet is more likely to improve symptoms in people with diarrhea as the primary bowel change (IBS-D).

Constipation can be a little more complicated to manage. A low FODMAP diet alone isn’t usually enough but may help with some of the symptoms of IBS-C.

Many people with IBS-C feel better with an increase in fiber intake, especially sources of soluble fiber. One of the challenges with a low FODMAP diet is that the restrictions can make it hard to get enough fiber. This can make constipation worse for some people.

Other things that can also be part of managing IBS-C include:

  • medications
  • physical activity
  • stress management strategies
  • pelvic floor physiotherapy
  • eating on a regular schedule
  • drinking more fluids

A low FODMAP diet can be complicated to follow. The very restrictive phase is short-term, but it can still be difficult. Usually, a low FODMAP diet is considered if other approaches haven’t worked for IBS-C. It’s recommended to work with a dietitian who has experience with a low FODMAP diet, if you have access to one. It can be overwhelming to navigate it on your own.

For some people, high FODMAP foods can make IBS-C worse. High FODMAP foods can cause bloating and pain in someone with IBS-C.

Everyone’s IBS-C triggers are unique. It may be helpful to keep a record of your symptoms to see if you notice any patterns.

Here are some things that can worsen symptoms of IBS-C:

  • changes in eating routine
  • not drinking enough fluids
  • a low fiber diet
  • being sedentary
  • ignoring the urge to have a bowel movement
  • some medications

Having a good balance of fiber and fluids is important. Make sure you have a plan to still meet your needs with a low FODMAP diet.

There are two types of fiber:

  • soluble fiber, found in oat bran, barley, nuts, seeds, beans, fruit, and some vegetables
  • insoluble fiber, found in whole-grain foods, wheat bran, and vegetables

Sources of soluble fiber may be most helpful for IBS-C. Soluble fiber helps keep stool soft and easier to pass.

Insoluble fiber helps add bulk to stool. Some sources of insoluble fiber are tougher to digest and can create more gas and bloating.

Most fiber sources have both soluble and insoluble fiber. As you increase your fiber intake, you will get both types.

Eating too much fiber or increasing your intake suddenly can trigger IBS symptoms, so it’s best to gradually add more fiber to your diet.

Adding low FODMAP sources of soluble fiber may help with IBS-C symptoms. Here are some examples of what to add:

  • ground flaxseed
  • oatmeal (make sure they are pure oats that have not come into contact with wheat)
  • psyllium fiber
  • sweet potato
  • almonds (keep serving size to 10 almonds due to FODMAP content)
  • carrots
  • brown rice
  • kiwi

There are many approaches to managing IBS-C. A low FODMAP diet is just one option. Research shows that a low FODMAP diet can help reduce the pain, gas, and bloating that is part of IBS-C. A low FODMAP diet seems to improve diarrhea more than it does constipation.

If you decide to try a low FODMAP diet, you’ll still need to consider your overall fiber and fluid intake. Other things that can help are a consistent meal routine and regular physical activity.

You may consider working with a dietitian who’s experienced with a low FODMAP diet so you’re not trying to figure it out on your own.