Everything you need to know about the low FODMAP dietary pattern

Q: What is a FODMAP?  (ignoring the diet part)

A: The word FODMAP is just a quicker way of saying fermentable oligosaccharides, disaccharides, monosaccharides and polyols. 

  • F = fermentable 
  • O = oligosaccharides
  • D = disaccharides
  • M =monosaccharides
  • and
  • P = polyols

FODMAPs can be added into foods or products and they are also naturally present in many fruits, vegetables and grains! 

 FODMAPs can be added into probiotics as FOS, or into “sugar free” products as polyol, which are basically any artificial sweetener ending in -ol 

 Sometimes people think they are sensitive to a probiotic because of the strains in the product, but in fact it can be the FOS in the product that is causing the reaction 

 Some FODMAPs are fibers and some are carbohydrates 

Q: What is the low FODMAP diet?

A: The low FODMAP diet is an elimination diet. Where the person participating in the diet removes foods and products containing FODMAPs for 4-6 weeks.

THE GOAL: to figure out which FODMAP is causing gut issues like gas, bloating, pain and cramping! 

 The 4-6 weeks removal phase allows time for the gut to stop reacting to foods and to work with a health care provider to heal digestion. 

 As per most elimination diets, after that 4-6 the foods should slowly be added back in one at a time to determine which FODMAPs the body is incapable of digesting and where more work needs to be done on “healing the gut”.

Removing foods alone without working on healing the gut during the removal phase is not going to provide deep healing that lasts long term!

Instead you will figure out which foods bother you and your diet will be restricted forever. 

Q: What happens if I am not instructed to add back in foods?

A: This happens far too often…. Someone feels super great after removing FODMAPs because they have removed the irritants to the gut. Then they get told, awesome that’s great, keep going then!

And the reintroduction of the food phase never happens.  So these people end with a whole bunch of restrictions and no way forward, and that is the problem. 

Remember the low FODMAP diet is a TOOL to be used to CALM to gut over the 4-6 weeks, so it is actually clear which FODMAPs are triggering to the gut, instead of every food you eat being a trigger to the gut and finding no clarity on which is causing the gas, the bloat, the pain.

If someone tells you to be on the low FOD MAP diet forever, with no other guidance, they may not be the right person to be guiding you in healing.


Q: What happens if I dont “heal the gut” during the removal phase of the LOW FODMAP diet

A: It is very difficult to get gut issues to a stable “baseline”, meaning they dont go from a 3/10 to a 8/10 between days.

Instead of a stable baseline of 3/10 every day.

The “healing” means many different things to each patient. It can mean treating SIBO for some, others it may involve stomach acid support, anxiety treatment, pelvic floor health etc.

Q: What is the consequence of not having a stable/reliable baseline?

A: The consequence is never being able to tell which foods the gut is reacting to! What happens is many people cannot get off the fully restricted low FODMAP diet because when they test foods they react to almost everything.

Q: What is the benefit for trying a low FODMAP diet as a constipated person with gas, bloating and pain?

A: Reduced gas , Reduced bloating , Reduced pain 

It does not provide 100% symptom relief typically because the problem is not the food itself, the problem is the digestive capacity of the gut to break down the food.

It is essentially a band aid solution.

Q: when is a low FODMAP diet inappropriate?

There is a high prevalence of IBS in the population of people with eating disorders. Due to the fact that the low FODMAP diet is in fact restricting foods and can promote more disordered eating I would not suggest it for those in recovery or with an active eating disorder. Especially because the FODMAPs are not the root cause of the problem 


Q: Can you further explain what healing the gut means?

Healing the gut is really a fancy way of saying putting energy and a treatment plan towards getting the digestive tract and all the signals that it is sending to the rest of the body working at 100% capacity without being disrupted. The gut can do its job at 100% capacity. 

Getting to this end goal can show up in A LOT of different ways, which is why treatment needs to be individualized and not based on tips and tricks from the internet. 

Typically in those with FODMAP related symptoms it means that over time the gut has lost the capacity to release the enzymes it needs to break down whichever FODMAP is triggering. This can be a focus when “healing the gut”…

how do we get this enzyme production back up to 100%? Is it even possible to get this enzyme production to 100%

Because the FODMAP itself may be triggering symptoms, but is NOT the root cause problem, removing the FODMAP does not heal the gut.

What it can do is give the gut space to respond to treatment so it can in fact heal instead of being bombarded with treatment and triggers at the same time over and over. 


Q: Is there a harm in doing the low FOD MAP diet for long periods of time?

This is a big focus in the research right now.

We know that the gut microbes need to be fed just like any living thing. FODMAPs are a source of food for some of these microbes. The question out there is 

If you don’t give the microbes their food for a while, will they die off? Is this detrimental to the microbiome? 

they die off, when you add back FODMAPs and there is nothing to eat them then will people feel worse on         FODMAPs than they did before they restricted them? 


The trend shown in the research is that a low FODMAP diet reduced the Bifidobacterium species in the microbiome.

Interestingly enough, one research article testing if giving a Bifidobacterium probiotic during a low FODMAP diet changed anything. The results showed this 

  • When testing the research participants poop, the people on the low FODMAP diet + a probiotic had higher Bifidobacterium levels than the people who were just on a low FODMAP diet BUT showed no different symptom improvement in gas, bloating and pain 


Can we really confirm that the decrease in some microbiome species from a low FODMAP diet make people feel WORSE from the diet? 


My conclusion is NO, and NO and NO again. 


What we know is this: Eating low FODMAP style does cause changes in the microbiome BUT it is unknown if there are actually any consequences to those changes. 


REMINDER: I am talking short term, not being on a FODMAP diet for 5 years.

Q: Why do some people feel worse when reintroducing FODMAPs

I have seen it and it has been reported that when people start reintroducing foods they feel like their reaction is WORSE than it originally was. 

Here is my completely unconfirmed hypothesis. 

A lot of these patients feel so much relief from the FODMAP removal for weeks on end. 

Whey they add back in a trigger food, the reaction seems dramatic because they are now comparing the reaction from

Non triggered gut → triggered gut. Think of it like going from 0% to 100% quickly. That’s a 100% change

INSTEAD of what they were doing before which is comparing 

Triggered gut → even more triggered gut. Think of it like going from 75% to 100% quickly. That’s a 25% change 

Going from feeling the usual 25% worse to 100% worse when eating trigger foods is DRAMATIC… and it is easy to confuse that with the reaction being worse than usual. 

Q: What nutrient deficiencies do you see on a low FODMAP diet due to the restrictions?

In general less calories tend to be eaten when someone switches from their regular dietary pattern to a low FODMAP style of eating. 


The switch from regular dietary pattern to low FODMAP results in 

  • Less total calories eaten
  • Less carbohydrates eaten 
  • A lot less added sugars eaten 
  • Less calcium eaten
  • Less salt (sodium) eaten 
  • Less B vitamins eaten 


Majority of these are actually associated with eating less calories and not because the low FODMAP diet actually causes a deficiency in these nutrients. Eating less calories is NOT necessary on a low FODMAP diet. 

This research was done on people who worked with a dietician to implement the low FODMAP diet. I think this is important to note because those making these changes on their own without a specialist will have more drastic nutrient deficiencies than the ones mentioned above. 


One of the biggest deficiencies I see that bothers me the most in regards to a constipated population of people is POTASSIUM. Those carrying out an undirected low FODMAP diet often are not eating enough potassium which the gut literally needs to move, but also we all need to stay hydrated and recover from exercise and stressors. 


The concern of these deficiencies worsens in athletes. There has been some talk and review articles introducing the idea of low FODMAP diets in athletes to reduce their gastrointestinal symptoms. Pain in the gut and other gut issues are very common in athletes. The concern is that the demand on their body requires many of the nutrients that tend to be depleted with the low FODMAP diet. 

Q: What happens if a food reintroduction is a “fail”?

A fail would mean eating one of the foods that was suspected to cause gut issues and finding out it does in fact trigger gut issues. Resulting in worsening of those symptoms such as gas, bloating and pain. 

That means that the food group would be removed from the diet until all other FODMAPs have been trialed. 


When I know a patient has a fail I now have a specific target to work on. 


For example, if lactose is a fail, can I find them a hack to allow them to digest lactose when they do have it so ice cream with dessert can be an enjoyable experience not a fearful one. Or if they fail fructans, how can a ramp up the digestive systems production of that enzyme, so that when we decide to re test that “fail” food we can get a smaller reaction or maybe no reaction at all. 


If we cant improve the reaction then we can play around with which dose is triggering. 


For example, if ½ cup of chickpeas causes a reaction, does ¼ cup of chickpeas do the same? If not then that patient now knows their limits.



Q: Would you prescribe a low FODMAP diet to those with diverticulitis?

A low FODMAP diet is not my first dietary intervention for diverticulitis. It is getting more traction for diverticulitis because fibrous material and undigested foods can get trapped in the diviticula and cause flairs and potentially even the need for surgery. 

In fact, the majority of the research shows fiber from whole grains and fruits can be protective for diverticulitis and not harmful. 



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