Does The Low FODMAP Diet Treat IBS-C?

Does The Low FODMAP Diet Treat IBS-C?

Irritable Bowel Syndrome (IBS) is a chronic condition that affects the digestive system. IBS affects both men and women, and it is the most common gastrointestinal disorder in the world. Much has been written about low FODMAP diets for IBS with diarrhea. In this post, we’ll take a closer look at what low FODMAP diets can do to help people who have IBS with constipation.



What is IBS-C and what are the symptoms? 

There are three major subtypes of IBS: IBS with predominant diarrhea (IBS-D), IBS with predominant constipation (IBS-C), and IBS with mixed bowel habits (IBS-M). This article is about IBS with constipation. People with IBS-C have lumpy or hard stools (poop) most of the time; they can still have diarrhea once it a while too. If you have IBS with constipation, you might also have abdominal pain, excess gas, and bloating. Bloating is an uncomfortable feeling of abdominal fullness. 

IBS is considered a disorder of gut-brain interaction. The symptoms are impacted by a combination of factors including stress, hormones, genetics, and diet. 


Stomach Pain

What is the Low FODMAP Diet and how does it work? 

A low-FODMAP diet is one of the most effective ways to reduce IBS-C symptom and improve your quality of life. The low FODMAP diet was developed by Monash University. It was designed to ease IBS symptoms while finding out whether FODMAPs are causing your digestive issues. 

FODMAPs are certain sugars and fibers in food that are rapidly fermented by the bacteria we have in our guts, a process that can produce a lot of gas over a short period of time. While this might not bother people with more resilient intestines, people with IBS experience bloating and abdominal pain as a result. Another interesting fact is that some people have gut microbes that produce a particular type of gas (methane). Methane gas production seems to go along with slower intestinal transit time and constipation. 

When you follow a low FODMAP diet, you cut back on your intake of rapidly fermentable carbohydrates. This reduces the favorite food supply of the gut microbes, slows down fermentation and reduces the rate of gas production. Fermentation is a normal part of the how the human body works.  Some of the substances produced during fermentation, such as short-chain fatty acids, are good for us. So we just want to slow down fermentation, not stop it. A low FODMAP diet replaces rapidly fermentable carbohydrates with others that are likely to be well tolerated because they are fermented more slowly. 


How to follow a Low FODMAP Diet 

The Low FODMAP Diet is the first part of a three-step process called a FODMAP Elimination Diet protocol. After 2-6 weeks of low-FODMAP eating, you’ll slowly reintroduce FODMAPs back into your diet one at a time, waiting a few days between them and keeping a log to track your symptoms (The Reintroduction Phase). Over time, you’ll notice a pattern in your symptoms, and you will learn which FODMAPs you need to limit or avoid (The Personalization Phase). 

Learning how to follow low-FODMAP diets can be challenging at first. It would be great to have a list of foods you can and can’t eat on the diet. But it’s a little more complicated than that. Many foods can be high, medium or low in FODMAPs depending on the serving size. There are only a few foods that should be eliminated completely during the low-FODMAP phase of the protocol. The best way to learn the details of what to eat and what to avoid is to consult the Monash University Low FODMAP app. (Download App)

The benefits of following a Low FODMAP Diet for IBS-C  

A 2022 study used ModifyHealth meals to help 403 patients with IBS follow a low FODMAP diet for 4 weeks. 73 of those patients had IBS-C. After 4 weeks, 67% of the patients with IBS-C felt significantly better! Although this is a little lower than the 77% of patients with IBS-D who got significant relief of their symptoms, if you are one of the 67% you will be glad you tried a low FODMAP diet! 

The IBS-C group had an 85% improvement in abdominal pain, 55% improvement in bloating, and 53% improvement in bowel satisfaction. In other words, after 4 weeks, their symptoms were less than half of what they were before they started the low FODMAP diet, with the most improvement in abdominal pain.  


Feeling Better

Potential side effects of following a Low FODMAP Diet for IBS-C 

Low FODMAP diets for IBS-C do not have side effects the way prescription or over-the-counter drug treatments for constipation do. But changing your diet does have a few potential risks that should be considered. For example, if you have had an eating disorder you should probably not try a FODMAP elimination diet. Another concern some people have is whether they’ll get enough nutrition on a low-FODMAP diet. Fortunately, there are good low-FODMAP sources of all nutrients. But, if you already have a limited diet because you are a vegan or for other reasons, it will take a lot of planning to get enough nutrients if you add a low FODMAP diet to your regimen. 

Fiber is one nutrient that is of special interest to people with IBS-C. You may have been advised in the past to eat a high fiber diet. While that is worth a try, as you have probably learned from experience, a high fiber diet can actually make IBS-C worse in many cases. High FODMAP fibers like those in large portions of wheat, nuts, beans, and certain vegetables can make you miserable. On a low-FODMAP diet, you’ll pay as much attention to the type of fiber as the amount. You’ll be encouraged to eat a variety of low-FODMAP fiber sources. And if you need it, you can use a low-FODMAP supplement like psyllium or acacia fiber to help you stay regular. 


Can the low FODMAP diet treat IBS-C? Since food is not the underlying cause of the condition, changing your diet will not cure it or fix it permanently, but the low FODMAP diet dies can help many people with IBS-C get relief from their IBS symptoms, and healthcare providers consider it a first-line management strategy for IBS. 

If you are interested in trying the Low FODMAP diet but don't know where to start then click the link to check out our Low FODMAP meal plans.

Author: Patsy Catsos, MS, RDN, LD

 Patsy Catsos


Dean G, Chey SW, Chey WD. The Low-FODMAP Diet Improves Abdominal and Overall Symptoms in Patients with All Subtypes of Irritable Bowel Syndrome. Abstract presented at American College of Gastroenterology 2022 Annual Scientific Meeting, Charlotte, NC.