Low-FODMAP Diet Provides Proven Results For Multiple Chronic Conditions

Low-FODMAP diet

The low-FODMAP diet is an elimination diet developed in the early 2000s.  The Monash University’s Department of Gastroenterology developed the FODMAP diet for patients with irritable bowel syndrome (IBS). Thanks to extensive research other groups began benefiting from the FODMAP diet including those with:

  • Irritable Bowel Disease (IBD) including Crohn’s Disease and Ulcerative Colitis
  • Hashimoto’s
  • Rheumatoid Arthritis
  • SIBO
  • GERD
  • Fibromyalgia
  • Endometriosis

FODMAP is the acronym for fermentable oligosaccharides, disaccharides, monosaccharides and polyols. It refers to a type of carbohydrate known as a short chain carbohydrate.

A Lesson On Carbohydrates

Carbohydrates are more than starches. They also include sugars and fibers that make up fruits, vegetables, milk products, legumes and grain. Carbohydrates are made up of sugar molecules strung together to form a chain. Short chain carbohydrates contain from 3 to 10 molecules of sugar. They move through the body quickly and draw fluid into the intestines.  In comparison, long chain carbohydrates, also known as complex carbohydrates, can contain hundreds or thousands of sugar molecules.  They take much longer to digest.

With the popularity of diets like the low-carb diet and ketogenic diet, carbohydrates have received a lot of negative publicity. But the body needs carbohydrates like fruits, vegetables, milk products, legumes and grain to function. Carbohydrates provide your body with fuel and nutrients. They help to regulate the bowels. And for women, carbohydrates are important for menstrual health.

FODMAP Food Groups

FODMAP foods can be categorized into 4 groups based on the presentation of their sugar molecules. This is important to know because you could be sensitive to foods in 1 or more groups. 

  • Monosaccharides consist of a single sugar molecule. Fructose is a type of monosaccharide. Fructose can be found in most fruit juices, grapes and apples. It’s also found in zucchini, peas and sweeteners like honey and agave syrup.
  • Disaccharides consist of 2 monosaccharides. Lactose is a disaccharide. Because foods can contain varying amounts of lactose, some foods containing lactose are still classified as low-FODMAP. Sucrose, or table sugar is another disaccharide made from glucose and fructose. 
  • Oligosaccharides consist of 3 to 10 monosaccharides. Fructans fall in this category and include wheat products such as bread and pasta. Because this category includes wheat products, similarities exist between the gluten free and low-FODMAP diets. Onions, garlic, cabbage, and  asparagus are also fructans. Galacto-oligosaccharides (GOS) feed the “good” gut bacteria and are found in beans, lentils, chickpeas and legumes. 
  • Polyols are also known as sugar alcohols. They are typically found in stone fruits like cherries, peaches and plums. They can also be found in avocados and blackberries. Some vegetables containing polyols include cauliflower, mushrooms and sweet potatoes. Polyols like mannitol and sorbitol provide sweetness and are low in calories

FODMAPS and Digestion

The human body doesn’t produce all of the enzymes needed to digest FODMAPS. For example, people who are lactose intolerant are deficient in the enzyme lactase.

Undigested FODMAPS pass into the large intestine from the small intestine. There they are greeted by the trillions of bacteria living in the gut. These bacteria put the “fermentable” in FODMAP. In other words the bacteria cause FODMAPS to rapidly ferment. In fact, gut bacteria use FODMAPS as a source of fuel.  As FODMAPS ferment, they release gas and other chemicals.  

Symptoms of FODMAP Intolerance

Since FODMAPS are not digested, symptoms tend to be gastrointestinal in nature. However that’s not always the case. Some people aren’t adversely affected by FODMAPS. People with the following conditions may experience gastrointestinal symptoms:

  • Small intestine bacterial overgrowth (SIBO) 
  • Irritable Bowel Syndrome (IBS)
  • Irritable Bowel Disease (IBD) 

Gastrointestinal symptoms usually occur within 4 hours and can include:

DiarrheaResulting from excess fluid drawn to the intestines by FODMAPS, particularly fructose, lactose and polyols. 
ConstipationFermenting FODMAPS can sit in the gut and slow down motility (the movement of food through the esophagus, stomach, small intestine and large intestine and out of the body)
Resulting from gas and other chemicals that are released as FODMAPS ferment in the gut.
Nausea VomitingCan occur if large quantities of FODMAPS are consumed and/or in the presence of IBD or IBS

Other symptoms have also been noted:

  • Anxiety
  • Depression
  • Fatigue
  • Lethargy
  • Poor concentration
  • Inflammation

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Connection between FODMAPS and SIBO

SIBO results when colonic bacteria, usually found in the large intestine, grow at an abnormal rate in the small intestine. SIBO has many causes including gut motility issues, abdominal surgery and long-standing diabetes. While FODMAPS may not be the cause of SIBO, they certainly don’t help. FODMAPS provide fuel for bacteria. SIBO is a bacterial overgrowth. So FODMAPS can worsen an already bad situation. 


The FODMAP diet is considered the gold standard for IBS patients. According to Harvard Health Publishing one study showed a 76% improvement in symptoms for IBS patients.  Although patients with constipation can benefit from the diet, it’s most effective in those with diarrhea.  

Patients with inactive IBD tend to have IBS-like symptoms. Studies show that these patients experience the same benefits as those patients with IBS from the FODMAP diet. However since IBD patients are already at risk for under-nutrition due to the nature of their disease, care should be taken when restricting foods.

Low-FODMAP Diet for Treatment of Fibromyalgia, Arthritis and Endometriosis 

According to the Arthritis Foundation, recent research has indicated that gut bacteria can impact autoimmunity. By balancing gut bacteria, inflammation in other areas of the body, including joints, could potentially be reduced.

Conditions like fibromyalgia, endometriosis and Hashimoto’s tend to run comorbid with gastrointestinal disorders like IBS. In one Scandanavian study, pain scores of fibromyalgia patients were noticeably lowered in patients who consumed a low-FODMAP diet.  And patients with both endometriosis and IBS saw a 72% improvement in symptoms while on a low-FODMAP diet, according to another study.

FODMAP Thresholds

A key component of the FODMAP diet is determining what your personal thresholds are. In other words, how much FODMAPS can you consume before experiencing symptoms. 

Average threshold levels were established by the Monash University’s Department of Gastroenterology for IBS patients. Initially foods were categorized as either high-FODMAP or low-FODMAP. In recent years, serving sizes were determined.  However thresholds can vary by person. 

What You Should Know About FODMAP Stacking 

FODMAPS aren’t problematic for everyone. But for those who are sensitive, “stacking” FODMAPS is an issue. Stacking occurs when you eat several FODMAP servings within the same group over a given period. So you may consume black beans without incident. But symptoms can occur when 

  • The FODMAP is consumed in larger portions
  • The FODMAP is combined with other FODMAP foods in the same group
  • FODMAPS in the same group are eaten in close proximity to one another.

That’s because each of us has a personal threshold for a given time period. And the more FODMAPS you consume during that time period, the closer you’ll get to that threshold. When you exceed that threshold, you may experience symptoms.

How Does the FODMAP Diet Work?

The FODMAP diet is a 3-phase elimination diet.

  1. The first phase is the elimination phase, and is the most restrictive. In this phase you avoid all foods that are high in FODMAPS for a short period, usually two to six weeks.  This is enough time to significantly reduce symptoms in many people. For people with SIBO, “bad” gut bacteria can be significantly reduced in this phase. You can still consume foods that are low in FODMAPS. However serving sizes matter.
  1. The reintroduction phase is when you gradually begin adding the FODMAP food groups (mentioned earlier) back in your diet. A dietician can advise you on which groups and which foods to begin with. The goal is to determine what your tolerance level is. This phase is executed systematically. You’ll start out with a small serving and gradually increase the serving size over a 3-day period. During that time you will assess your symptoms. If no symptoms occur after day 1 you’ll increase your intake on day 2, and again on day 3 if symptom-free.
    1. During the personalization phase you avoid the foods you reacted to during phase 2. It isn’t necessary to avoid other FODMAPS. In fact doing so could be detrimental to your health. Foods identified as FODMAPS are prebiotics. They feed the “good” gut bacteria and help contribute to a healthy microbiome with diverse bacteria. 

Common Shortfalls With the FODMAP Diet

For all the benefits of the FODMAP diet, there are some drawbacks. Many people never make it to phase 3. They eliminate all, most or many of the foods in phase 1 but never carry out the reintroduction phase. However the elimination phase was never intended to be long-term. 

The goal of the FODMAP diet is to eliminate foods that you can’t tolerate and determine the threshold for foods you can.  Eliminating entire food groups or even several foods from one or more groups can have negative consequences. First, nutritional deficiencies can occur. Second, the vast array or limited selection of foods we consume affect the diversity of gut bacteria. All bacteria aren’t harmful as far as our gut is concerned. “Good” gut  bacteria impacts everything from digestion, the immune system, your weight and even brain health! The greater the diversity of gut bacteria, the better our health.

My Personal Experience With FODMAPS and Autoimmune Disease

Years ago I began identifying which foods caused my autoimmune disease, pemphigus vulgaris, to flare up. Gluten and dairy were at the top of the list. I decided to avoid foods containing these ingredients. I didn’t have any knowledge of the FODMAP diet at that time. Not only did I notice a decrease in my flare ups but my extreme bloating and distended stomach vanished. Having endometriosis, those symptoms had been with me for decades. 

Although my autoimmune disease flare ups decreased in frequency, I still got the occasional random flare. I couldn’t see any correlation.  I reacted to most fruit and some vegetables. Sometimes I reacted to honey, but not always. To the trained eye of a dietician, the connection was obvious. The foods were high in FODMAPS. Or if they weren’t high in FODMAPS, they were high when eaten in large portions or combined with other FODMAPS.  

Whenever I ate foods high in FODMAPS that I was sensitive to, I had a delayed reaction. So if the offending food was eaten during dinner, I’d wake up in the middle of the night with a flare up. 

Interestingly, I can tolerate some foods that are high in FODMAPS. Which is why I can’t stress enough the need for individualized nutritional counseling. Since I already knew exactly which foods I was sensitive to, I was able to bypass the first 2 phases of the FODMAP diet. However, one thing I learned from writing this article is that FODMAP intolerance can change over time. So periodically re-challenging yourself is worth considering.

I’ve lived with all 3 forms of irritable bowel syndrome at different points in my life:

  • IBS-C – irritable bowel syndrome with constipation
  • IBS-D – irritable bowel syndrome with diarrhea
  • IBS-A – irritable bowel syndrome with alternating constipation and diarrhea

I definitely noticed a correlation between certain high-FODMAP foods and IBS-D and IBS-A. 

As for IBS-C I can’t say that I noticed any connection. In fact, I find some high-FODMAP foods that I’m able to tolerate to be helpful in combating constipation. However, I must eat them in moderation or I will have an autoimmune flare up. 


The low-FODMAP diet can be helpful for people with IBS, IBD, SIBO, fibromyalgia, endometriosis and rheumatoid arthritis. However, I think there is still a lot to be discovered. What we do know is FODMAPS affect gut bacteria. “Bad” gut bacteria has been linked with inflammation. Inflammation can exacerbate autoimmune disease flare ups. So if you still find your autoimmune disease flaring up, the low-FODMAP diet is worth considering. Enlist the help of a nutritionist who can guide you through the process.