The low FODMAP diet has gained a lot of popularity in recent years, and it is now being promoted as one of the top treatments for IBS. FODMAP is an acronym for a certain class of carbohydrates called fermentable short-chain carbohydrates. These carbohydrates are not completely digested or absorbed in our intestinal tract, which means that bacteria in our gut can then break them down. This bacterial fermentation produces gas and other chemicals that cause uncomfortable symptoms like gas, bloating, abdominal discomfort, constipation, and/or diarrhea. These are all symptoms that are typically associated with IBS.

What foods are high in FODMAPS?

Many foods that are commonly thought of as healthy are high in FODMAPS. Some of the highest FOPMAP foods are fruits like apples, blackberries, and mango, beans and lentils, wheat and oats, dairy based milk and yogurt products, and many vegetables like asparagus, artichokes, onions, and garlic. A full list of high-FODMAP foods published online typically lists over 100 foods for patients to severely limit or avoid (example: In addition, most IBS patients have already identified many other foods that make them feel ill, which makes the addition of all these new restrictions incredibly difficult to adhere to.

Why I disagree with the using low FODMAP diet to “treat” IBS:

Experts agree that high FODMAP foods are not bad for everyone, and only people who are “sensitive” to FODMAPs should follow the diet. But this is where the questioning and discussion stops, instead of asking the more important question, “What is it about this patient and their health that makes them sensitive to FODMAPs in the first place?”. If we want to accomplish a deeper level of healing – one that includes getting patients back to tolerating a varied and healthy diet without negative symptoms — this is the ultimate question that must be asked and answered.

So, what underlying conditions cause people to become sensitive to FODMAPs? Here are the three top conditions I see and treat at my practice:


SIBO stands for small intestinal bacterial overgrowth. I often see this condition co-occurring with large intestinal dysbiosis as well. While the large intestine is supposed to house a large colony of beneficial bacteria (often known as the gut microflora), a healthy small intestine should have very few bacteria residing in it. But in patients with SIBO, there is an abnormal and unhealthy number of bacteria waiting to ferment food as soon as it leaves the stomach and enters into the small intestine.

While a person without SIBO might still experience very mild fermentation symptoms like gas and bloating when eating high-FODMAP foods, a person with SIBO will have excessive symptoms due to the sheer number of bacteria exacerbating the issue. While limiting FODMAP foods may decrease the severity and frequency of SIBO symptoms, the diet would have to be incredibly restrictive to have even a slight chance at starving the SIBO bugs death. In fact, the only way to actually do this is with something called the Elemental Diet (, which completely strips food down to its amino acid components and limits patients to only drinking these elemental shakes without any additional food for two weeks.

For the average patient, limiting FODMAP foods will make their symptoms more manageable, but as soon as they try to go back to eating normally their symptoms will return. To eradicate the SIBO, more aggressive antibiotic and/or herbal antimicrobials must be used to first kill off the bacteria. Once the SIBO has been effectively treated, patients are usually able to reintroduce FODMAP foods without experiencing negative symptoms. 

Pancreatic Enzyme Insufficiency:

Low digestive enzyme production is an extremely under-diagnosed condition in our society today. The pancreas is a major producer of digestive enzymes in the human body, with lesser amounts of enzymes being produced in the stomach, mouth, and gallbladder. Enzymes are proteins that break down food into smaller molecules that can later be absorbed from the intestinal tract.

The pancreas produces three major types of enzymes: amylase- which breaks down carbohydrates, protease and elastase- which break down protein, and lipase- which breaks down fats. When food exits the stomach, the pancreas releases these enzymes into the duodenum (the first part of the small intestine) to continue the process of food breakdown that began in mouth and stomach. There are known causes of pancreatic enzyme insufficiency including chronic pancreatitis, inflammatory bowel disease, celiac disease, and bariatric surgery. But outside of these more severe cases, many everyday patients also experience low digestive enzyme output. One reason for this may be due to chronic stress (enzyme production decreases in a high cortisol state), and I theorize lower more “everyday” levels of intestinal irritation (from things like food intolerances, toxins, etc.) also decrease enzyme output.

Going back to our FODMAP discussion, how does pancreatic enzyme insufficiency relate? If we are not making enough of our own digestive enzymes, then the food we eat will pass through the intestinal tract without being broken down into small enough pieces to cross the intestinal barrier and be properly absorbed. So instead, the large food particles remain in the intestine and continue their journey all the way to the other side. Normal “healthy” bacteria in the colon then have free ability to breakdown (aka ferment) these larger food particles that otherwise would not be present.

Just like in our SIBO discussion, limiting high FODMAP foods will likely decrease symptoms somewhat for these patients. But dietary changes alone do nothing to treat the real underlying issue, nor do they treat the nutrient deficiencies that often occur in patients with low enzyme output and subsequent malabsorption.

Multiple Food Sensitivities/Leaky Gut Syndrome:

The last category of people who may see symptom improvement with the low FODMAP diet are patients with multiple food sensitivities and/or leaky gut syndrome (also known as increased intestinal permeability). These two conditions often go hand in hand, as one condition typically plays into the perpetuation of the other.

In simple terms, leaky gut syndrome occurs when the lining of the small intestine becomes inflamed to the point of damage. If this mucosal lining is destroyed, then large, incompletely-digested food particles can pass directly into the bloodstream — a place they definitely do not belong. When your immune system comes across these “invader” particles in the blood, it does what it is supposed to do and mounts a reaction against them. This eventually creates abnormal antibody responses to all foods eaten regularly, as these foods are passing into the bloodstream instead of being contained safely within a healthy GI tract.

What happens for many people is that one or two significant but undiagnosed food intolerances trigger an inflammatory reaction in the gut each time those foods are consumed. This chronic inflammation continues to build and build as the unknowing person continues to eat these foods. Eventually, the inflammation reaches a point where it begins to break down the intestinal lining. At this point, the patient has developed leaky gut syndrome and suddenly their food reactions skyrocket! Now it seems like everything they eat causes intestinal symptoms and it becomes impossible to tell by symptoms alone what the underlying intolerances that started it all even were.

Why do some of these leaky gut syndrome/multiple food sensitivities patients experience symptom improvement on the FODMAP diet? The likely reason for this is that high FODMAP foods like gluten, diary, and many nuts are common intolerances for many people. Even though the reasoning behind removing these foods is wrong (assuming they cause fermentation and not an inflammatory reaction), if you remove a major food intolerance for a patient they will likely experience symptom improvement. The problem with this is that we haven’t objectively identified that the patient has a food intolerance, so they will likely go back to eating that in the future and all improvement will be lost. Also, while we might have accidentally removed some intolerances with FODMAP diet, the patient is also avoiding 100 other foods that they are likely not intolerant to at all!

In my practice, I use the lab US Biotek to perform easy and accurate food intolerance testing on patients. By testing patients for their own specific intolerances, we learn exactly what a patient can eat and what must be removed to heal the gut. This approach typically allows patients to eat a much less restrictive diet while achieving superior treatment results.

In conclusion, there are potential benefits to following a low FODMAP diet for certain patients for a restricted period of time. The two main ways I use the FODMAP diet in my practice are as follows: 1) Diagnostically- If a patient tells me that they had significant symptom improvement using the FODMAP diet, I can conclude that the patient likely has either SIBO, intestinal dysbiosis, pancreatic enzyme insufficiency, or multiple food sensitivities (or a combination more than one of these disorders).  I can then do additional testing and treatment for these conditions. 2)Therapeutically- I often have patients who are aggravated by FODMAP foods continue to limit them while we treat the underlying cause. This makes life much less uncomfortable for patients and it will accelerate the healing process. But the FODMAP diet on its own is not curative and I do not feel patients should remain on this diet indefinitely even if it relieves symptoms. If we want deeper healing, we must always find and treat the root cause.

Dr. Katie Nuckolls is a naturopathic physician and owner of Thrive GI: Natural Digestive Medicine in Vancouver, Washington. She currently sees patients that live in Washington, Oregon, and Arizona using telemedicine. For more information, visit our contact page or schedule a free 15-minute consultation online.  

%d bloggers like this: