Modifying Paleo for FODMAP-Intolerance (a.k.a. Fructose Malabsorption)

August 7, 2012 in Categories: , , , by

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One of the many challenges that people face when adopting a paleo diet is dealing with the confounding factor of additional food sensitivities.  Sometimes these sensitivities are known (perhaps you had allergy testing done at some point or react so violently to certain foods that it was a no-brainer).  Sometimes these sensitivities are unknown and make it frustrating when we don’t experience the instant improvements to our health touted by so many paleo enthusiasts.  One such sensitivity is FODMAP-intolerance (also referred to as fructose malabsorption).  This isn’t a food sensitivity in the sense that there is any sort of immune reaction to these foods.  Instead, it is a case of a person who cannot properly digest the fructose (and longer sugar molecules containing fructose) in these foods.

The term FODMAP is an acronym, derived from “Fermentable, Oligo-, Di-, Mono-saccharides and Polyols”.  FODMAPs are short chain carbohydrates rich in fructose molecules which, even in healthy people are inefficiently absorbed in the small intestine.  I know you’ve heard the limerick “beans, beans, the magical fruit…”; the punchline refers to the large amount of FODMAP carbohydrates in beans (or any of other vegetable that has a reputation for being “gassy”) that are only partially absorbed in the small intestine.  When this excess fructose enters the large intestine, which is full of those wonderful beneficial bacteria we love so much, they feed the bacteria allowing for overgrowth of bacteria and excess production of gas.  The presence of FODMAPs in the large intestine can also decrease water absorption (one of the main jobs of the large intestine).  This causes a variety of digestive symptoms, most typically: bloating, gas, cramps, diarrhea, constipation, indigestion and sometimes excessive belching.  In individuals with FODMAP-intolerance, a far greater portion of these sugars enter the large intestine unabsorbed, causing exaggerated symptoms.  In fact, some researchers believe that Irritable Bowel Syndrome is purely a case of FODMAP-intolerance 1,2.

Carbohydrates, which are just chains of sugar molecules, are broken down into individual monosaccharides (a single sugar molecule) by digestive enzymes in the small intestine (actually, this sugar digestion process begins with the salivary amylase enzyme in the mouth when you chew, but it continues all the way through the small intestine).  Monosaccharides are then absorbed into the blood stream by first being transported through the cells that line the small intestine, the enterocytes.  Enterocytes have specialized transporters, or carriers, embedded into the membrane that faces the inside of the gut.  These carriers bind to specific sugar molecules and transport them into the cell (where the cell can either use those sugars for energy or transport those sugars to the other side of the cell where they can easily enter the blood stream).  FODMAP-intolerance may be due to lack of digestive enzymes required to break longer chains of carbohydrates down to their individual monosaccharides and/or due to an insufficient amount of these carbohydrate carriers, specifically the carrier called GLUT5, which is the specific carbohydrate carrier for fructose (why this is also called fructose malabsorption). 

FODMAP-intolerance means that large amounts of dietary fructose and longer carbohydrate chains that are rich in fructose are problematic.  These longer, fructose-rich carbohydrate chains are called fructans (inulin, which is a type of fiber, is also rich in fructose and problematic for those with FODMAP-intolerance).  Sugar alcohols, called polyols, (sorbitol is an example) are additionally problematic because these sugars have the ability to block GLUT5 carriers (and if you’re working with a deficiency, that’s really not helpful!).  Why do some people develop FODMAP-intolerance?  Researches don’t know yet.  It may be a reaction of the body to high fructose and fructan consumption with the Standard American Diet.  It may be a side effect of a very distressed and/or leaky gut.  There are also very likely to be genetic factors at play.  The good news is that, for many, as their gut and bodies heal, their ability to digest and absorb these sugars improves.

When it comes to modifying your diet to address a suspected FODMAP-intolerance, dose is the key.  The type of FODMAP may be important for some people.  Some people are more sensitive to the fructose and polyols (due to GLUT5 carrier deficiency) while some are more sensitive to fructans (due to digestive enzyme deficiency).  Some people are sensitive to both.  How much you can handle is very individual and is likely to change as your gut heals.  There are medical tests available to diagnose fructose malabsorption, however an elimination diet approach is more reliable.  Research has shown that the removal of FODMAPs from the diet is beneficial for sufferers of irritable bowel syndrome and other functional gut disorders 1.  

The following table was created by Aglaée the Paleo Dietitian, and is posted with her permission.  It breaks down common foods into three categories:  safe (very low to no FODMAP), be careful (low to moderate FODMAP), and avoid (high FODMAP).  It also contains which kind of FODMAP is richly present in each food in parentheses (helpful for those who are more sensitive to one versus the other). (Aglaée told me that this table is likely to be updated in the near future.  I will repost the edited version when it becomes available.  You can see the original table here:  

 As you can see from this table, many of the moderate to high FODMAP foods are foods that we typically increase consumption of when adopting a paleo diet.  How frustrating for those who experience an increase in gastrointestinal symptoms when they adopt a paleo diet compared to so many who find instant alleviation of symptoms!  If you suspect (or know you have) FODMAP-intolerance, I recommend eliminating all food sources of FODMAPs from your diet for a couple of weeks.  If you are sensitive, you should notice a fairly dramatic effect on your digestive symptoms.  You can try reintroducing some of the lower FODMAP fruits and veggies and see if your symptoms return.  In many cases, following a gut-healing protocol (as outlined in this post, this post or in the book Practical Paleo) will improve digestion of FODMAPs and they can be reintroduced carefully but successfully. 

It is very important to note that the symptoms of FODMAP-intolerance are virtually identical to the symptoms of Small Intestinal Bacterial Overgrowth (SIBO).  The reason for this is that these two conditions are highly related.  The difference is simply a matter of location, larger versus small intestine.  Without testing it can be difficult to discern which of these paleo diet modifications to try first (for more information on SIBO, read this post and this post).  Even more confusing, FODMAP-intolerance may or may not be linked to Small Intestinal Bacterial Overgrowth.  In some cases, the unabsorbed sugars caused by FODMAP-intolerance will lead to an environment in the small intestine where bacteria will grow, thus causing SIBO.  So, you may have SIBO without FODMAP-intolerance, you may have FODMAP-intolerance without SIBO, or you may also have both.  If you have digestive symptoms and are unsure which condition is the problem, then, I’m sorry to say that you’ll need to either have some tests done or follow the diet restrictions for both.  After a period of a couple of weeks, you can try adding in either the starchy vegetables eliminated in the modification for SIBO or some of the FODMAP fruits and veggies (choose whichever food you miss the most).  It should be clear fairly quickly which foods are problematic.  Also note that both of these conditions are likely to resolve completely with continued elimination of these foods (although in some cases this will take 6-12 months or even longer), so you may find that you can add everything back in and your symptoms don’t return (fingers crossed!)

1 Gibson PR and Shepherd SJ. Evidence-based dietary management of functional gastrointestinal symptoms: The FODMAP approach. J Gastroenterol Hepatol. 2010. 25(2):252-8.

2 Born P Carbohydrate malabsorption in patients with non-specific abdominal complaints World Journal of Gastroenterology, 2007, 13(43): 5687-5691


I keep hearing that cutting out fodmaps should not be a permanent solution because it starves the good and bad bacteria in the gut. The idea is that they ought be excluded for a certain amount of time and then slowly reintroduced. This has not been my experience, but I am interested to know if paleomom has an opinion on the issue?

I’m trying to combine aip and fodmaps, but the question I have is how to eat nutrient dense meals if most veggies and fruits are off the list? I thought, maybe I should just do fodmaps, but I cringe thinking about eating potatoes and other things I know aren’t very good for health.

Potatoes are good for health. There is plenty of evidence for this. Just Google posts by Paul Jaminet, Chris Kresser, Mark Sisson, and Dallas and Melissa Hartwig for starters. It opens up one’s diet a lot to include potatoes, including sweet potatoes. They also provide resistant starch which is very good for one’s gut.

Hi Sarah,

Going to start reading Paleo Approach tonight, just got it. Thanks so much for sharing your knowledge! I have had digestive issues for years relying on local Doctors advice…..bad idea; “here take this med”. I went Paleo some time ago and could reduce my PPI’s by half. Now I found a great physician in Philadelphia who treated me for SIBO with Xifaxan for two weeks and put me on a low FODMAP diet. I am doing so much better! I was diagnosed with Barrett’s Esophagus years ago and had her do a Upper Endoscopy, she did biopsies and saw irritation but no proof of Barretts. So, I have the go ahead to slowly reduce the PPI’s even more . I am excited! I was going to propose to one of you…….oh that’s right, we are all married, lol. Seriously, thanks for what you do.

Hi! Question: If i get an allergy test , I can stop doing the FODMAP diet? And just stick with the ones I got the allergy?

FODMAP intolerance is different than an allergy because with an allergy it is a reaction to the protein, whereas with a FODMAP intolerance it is a carbohydrate that you’re reacting to. FODMAP intolerances won’t show up on a traditional allergy test, unless you are also reacting to a protein in one of the high FODMAP foods. The only way to really determine whether FODMAP intolerance is an issue is to do an elimination diet, unfortunately. -Kiersten

Limiting FODMAPs is not a permanent solution for SIBO. I have been working with a funtional medicine doctor for lyme, mold and gut issues. I have borderline SIBO, but enough to cause me some symptoms. You have to get to the root cause of the SIBO possibly take antimicrobials and deal with motility issues. A SIBO and low FODMAP diet might reduce symptoms but everything I am learning about it says that is not all that you have to do. If you have not figured out the root cause then it will just come back when you re-introduce foods. There is just a lot more to it than that and being on such a restrictive diet for so long is just not a good solution. For me lyme and mold exposure has made me susceptible to SIBO.

So true Rachel, I have been battling IBS since I was 25 and now 52! I find the hardest part in living in a rural area without very many doctors to pick from and none of them have any answers for you but “Oh you have IBS” “I can’t do anything but give you a drug” The drugs don’t find the cause they usually make you feel worse with side effects. I stopped going to the doctors, I got more out of Sara’s explanation about FODMAPs than even the print out a specialist Gastrologist gave me. I have done so many elimination diets! The symptoms always come back in my case. So so frustrating.

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