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FODMAPs and Paleo

Leeks are high in FODMAPs

FODMAPs are a frequently discussed group of foods that many people are confused about – learn what they are and whether you need to worry about them.

Introduction; FOD-what?

“FODMAPs:” it sounds like a bizarre military acronym, or maybe the name of some incredibly specialized and complicated exercise that only the most dedicated of Crossfitters ever attempt. But FODMAPs actually stands for a list of several types of carbohydrates that can be difficult for many people to digest properly. Some people transition to a Paleo diet and immediately start to feel wonderful, but if you’re dutifully eating according to Paleo guidelines and still struggling with gas, bloating, constipation, or diarrhea, FODMAPs might be the culprit.

FODMAP stands for Fermentable Oligosaccharides, Disaccharides, Monosaccharides, And Polyols. These are all types of carbohydrates found in many different types of fruits, vegetables and grains. The most common Paleo foods high in FODMAPs are:

Onions are a FODMAPThis isn’t a complete list (a full list of FODMAPs commonly eaten on Paleo is here), but it does give you an idea of what kinds of foods contain FODMAPs, especially the variety of fruits and vegetables that can be problematic. Other foods, like beans, wheat, and rye, also contain high levels of FODMAPs, but since these foods are also harmful in so many other ways, they aren’t a good idea for anyone to eat, FODMAPs-sensitive or not.

Because they’re so difficult to digest and absorb, FODMAPs are strongly correlated with symptoms of all kinds of functional gastrointestinal disorders (digestive problems that aren’t caused by a physical abnormality, like IBS). In one study, a FODMAPs-restricted diet showed a 75% success rate for treating patients with IBS – the FODMAPs didn’t cause IBS to develop, but removing them from the diet was very helpful in controlling symptoms. This makes FODMAPs prime suspects for inexplicable digestive symptoms on a strict Paleo diet: not only are they very common in the diet, but restricting them also has a high likelihood of doing some good.

FODMAPs, in Detail

Doing any kind of research into FODMAPs can be very confusing because the words in the abbreviation refer to very large groups of carbohydrates, and each of those groups has several subgroups. To make it all even more complicated, not all members of every group are actually problematic, only the fermentable ones (remember that Fermentable is the “F” in FODMAPs). For example, “monosaccharides” is just a chemical name for simple sugars, but only one type of monosaccharide is actually a FODMAP, because only one kind is fermentable. For reference, the list below details all the different types of carbohydrates that commonly pop up in the discussion about FODMAPs, and their relationships to each other.

Letter in FODMAPs abbreviation Sub-groups that are FODMAPs Commonly found in…
Oligosaccharides raffinose, fructans (fructo-oligosaccharides) galactans (galacto-oligosaccharides) onions, garlic, cabbage, broccoli, Brussels sprouts, asparagus, artichoke, eggplant
Disaccharides Only lactose, the sugar found in milk (other disaccharides are fine) milk and dairy products
Monosaccharides Only fructose (other monosaccharides are fine) apples, mango, fruit juice, watermelon, added fructose, dried fruit, honey, agave
Polyols sorbitol, mannitol, xylitol, maltitol apples, apricots, avocados, cherries, peaches, pears, watermelons, cauliflower, green peppers, mushrooms, sugar alcohols (any sweetener that end sin –ol)

Almost everyone is sensitive to oligosaccharides and polyols to some extent, but many people don’t show any reaction to the amount of them in a normal diet – the dose is just too low for them to notice. But other people (especially people with IBS or other functional digestive disorders) do react even to the amount of these carbohydrates in a bowl of coleslaw or a stick of sugar-free gum sweetened with sorbitol.

FODMAPs sensitive individuals also react to some carbohydrates that healthy people have no problems with: the disaccharides and monosaccharides (D and M in FODMAPs). This doesn’t mean that they’re sensitive to all disaccharides and monosaccharides: only two types of these sugars commonly cause problems. Lactose (the sugar found in milk) is the only disaccharide in this category, and fructose (the sugar found in fruit) is the only monosaccharide.

Healthy digestionFODMAPs and Digestion

One of the reasons all these different types of carbohydrates are so irritating is that they aren’t completely digested by the time they reach the large intestine. Chemically, anything you eat is broken down by one or more enzymes: these are chemicals that digest foods into energy that your cells can actually use. The main enzyme responsible for carbohydrate digestion is amylase, which is first produced in your mouth as you chew, and continues to work on the carbohydrates as they travel through the digestive system. As the carbohydrates travel from your mouth through your stomach and into the gut, amylase breaks them down into their individual sugars. Then, the cells lining your gut can absorb them and distribute them to other parts of your body for energy.

The problem with FODMAPs is that, unlike other carbs, they aren’t completely digested in the small intestine, and pass through to the large intestine intact, instead of being absorbed in the gut and used for energy. Depending on the specific type of carbohydrate, this can be for one of two reasons.

Whatever the reason, FODMAPs carbohydrates all cause problems because they stay in your gut when they should be digested, passed through the intestinal wall, and absorbed into your bloodstream.

In the large intestine, the gut flora couldn’t be happier about getting these carbohydrates – carbs are their favorite food. Unfortunately, bacteria chow down on their carbohydrate feast by fermenting the sugar molecules (this is why the F in FODMAPs stands for Fermentable). Think of a loaf of bread rising: it changes from a flat, dense lump of flour and water to a light, fluffy mound with plenty of air inside because it’s being fermented by the yeast. Now imagine that happening in your gut, and you’ll understand why FODMAPs can cause so many intestinal symptoms!

Another reason why FODMAPs carbohydrates can cause digestive symptoms is that they draw water into the intestine (technically, this is known as osmosis). Osmosis can cause both bloating and diarrhea, because it causes the intestinal wall to swell. This exacerbates the problems already caused by the bacterial overgrowth.

FODMAPs, Gut Flora, and SIBO

Since FODMAPs have so much to do with the gut flora, and since they cause overgrowth problems very similar to SIBO (Small Intestinal Bacterial Overgrowth, also known as SBBO, for Small Bowel Bacterial Overgrowth), it’s worth taking the time to distinguish between these two problems – they’re similar, but they aren’t the same. For a FODMAPs-sensitive person, these carbohydrates affect not only the bacteria in the small intestine (where they aren’t supposed to be at all) but also in the large intestine (where they are supposed to be, just not in such large numbers). Thus, it’s perfectly possible to react to FODMAPs without having SIBO.

Even though these are two different conditions, though, they are actually related. FODMAPs foods have to pass through the small intestine, so if a person has pre-existing SIBO, eating FODMAPs can aggravate the problem by feeding the bacteria there. On the other hand, reducing FODMAPs in the diet can also help treat SIBO, and reducing bacterial overgrowth in other ways can help improve FODMAPs tolerance.

FODMAPs and Fructose Malabsorption

On the list of FODMAPs, the one most familiar to most Paleo dieters is probably fructose (the monosaccharide “M”). “Fructose malabsorption,” or the inability to properly digest fructose, is a familiar term to anyone who’s spent much time researching Paleo, but many people don’t recognize that since fructose is a FODMAP, fructose malabsorption is really one kind of FODMAP sensitivity.

Not recognizing the relationship between fructose and other FODMAPs can make fructose malabsorption unnecessarily hard to treat because the effects of FODMAPs in the body are cumulative. In other words, eating a second kind of FODMAPs can make your reaction to the first one worse. For example, someone sensitive to fructose who also eats a lot of onions (a major source of oligosaccharides) will have a worse reaction to fructose because of the onions. If you know you have trouble absorbing fructose, but don’t feel entirely better even when you strictly avoid all high-fructose foods, other FODMAPs may be the key to your symptoms.

Testing for FODMAPs Intolerance

If that uncomfortable feeling of having a beach ball trapped in your stomach (often accompanied by cramps, diarrhea, constipation, or other gut symptoms) sounds like you, and a Paleo diet alone isn’t helping, restricting FODMAPs is a logical next step to try. This doesn’t have to mean cutting out all FODMAPs completely forever, but a strict elimination period can be a very useful diagnostic tool to work out exactly what you do and don’t tolerate well, and in what quantities.

This is where it gets painful: a FODMAPs elimination diet can be very difficult to follow because it cuts out so many vegetables, which are one of the main sources of Paleo variety. Trying to plan even one meal, much less a week of food, without any onions or garlic is a tall order. But since the symptoms of FODMAPs intolerance are cumulative, it’s most helpful to eliminate everything for a trial period, so you can be sure you’ve covered all your bases. If the low FODMAP diet is helpful, try re-introducing foods from each category a little at a time (see the next section), to see if there are any categories you don’t react to.

There’s no point putting yourself to all the trouble of a special restrictive diet if it doesn’t help, so make sure to plan thoroughly beforehand so your efforts will be worth it. Don’t let your efforts get sabotaged by accidentally eating something you’re trying to eliminate! Print out the full list of whatever foods you’re trying to avoid, tape it to the fridge, and leave a copy with your shopping list (even if you’re shopping for more than one person, you want to make sure you have enough safe foods for you to eat). If you aren’t the primary grocery shopper and cook for your household, make sure to talk about FODMAPs with whoever that person is.

During the initial elimination period, stick to a low-FODMAPs diet and take whatever steps necessary to restore the health of your gut flora (remember that FODMAPs foods cause gas and bloating by overfeeding the gut flora, so if you react poorly to FODMAPs, chances are you have a gut flora overgrowth to treat). It’s helpful to keep a journal of how you feel every day, so you have an accurate record to examine at the end of your experiment.

Upset StomachAfter 5-6 weeks of strictly avoiding FODMAPs, try re-introducing these foods into your diet a little bit at a time. A good strategy would be to re-introduce FODMAPs one by one, monitoring symptoms at every step. Fortunately, many people who initially suffer from FODMAPs intolerance can start to reintroduce these foods, at least in small quantities, once their guts have healed and their digestion has improved.

Living with FODMAPs Intolerance

After you’re finished with the elimination diet and re-introduction period, you’ll have a pretty good idea of which FODMAPs you tolerate and which ones you don’t. Finding out that you’re intolerant to FODMAPs (either to all of them or to one specific category) is a blessing and a curse. It’s wonderful to finally be in control of IBS symptoms, but it can also be discouraging to think of limiting your diet so much for the long term, especially if you’re new to Paleo and struggling just to cut out grains and seed oils.

After the initial elimination period is done, you might find that with a healthy gut, you can handle these carbohydrates much more easily. Remember that almost everyone who doesn’t notice any FODMAPs sensitivity is actually sensitive to oligosaccharides and polyols; they just never eat enough of them to notice symptoms. It’s also possible for people with FODMAPs sensitivity to find an amount of these carbohydrates that they can tolerate without a problem. Then they can plan their meals accordingly to maximize the variety and interest of their diet by including smaller amounts of FODMAPs foods alongside other safe foods.

It’s also important to note that even a low-FODMAPs diet isn’t as restricted as it seems at first. For example, fructose is technically a FODMAP, but most people don’t have trouble with it unless they either eat a very large amount, or they eat more fructose than glucose at the same meal. Remember that fructose causes intestinal symptoms because it’s hard to absorb, but most people can handle small doses, and eating glucose alongside a serving of fructose can make it easier to absorb. Thus, it’s perfectly possible to enjoy fructose-containing foods even if you’re sensitive to FODMAPs, as long as those foods also contain at least as much glucose as they do fructose.

Also, not all dairy products contain enough lactose for most people to notice. Butter, for example, has almost none, so even on a lactose-free diet it’s usually fine to cook with butter. If you’re very sensitive, you could also try making clarified butter, or ghee. Yogurt or kefir that you make yourself and ferment for 24 hours or longer is also usually fine.

Cooking and soaking also helps break down the FODMAPs carbohydrates before they get to your mouth at all – this is why so many people in traditional cultures soak and ferment their grains and legumes. If you’re sensitive to more than one category of FODMAPs, it’s also usually easier to eat them only separately: the effects build on themselves, so chewing gum sweetened with sugar alcohols (polyols) and then enjoying a huge bowl of yogurt (lactose) with honey (fructose) is likely to be much more difficult to digest than having these three things spread out over the course of the day.

FODMAPs-free cooking gets much easier with time, as you learn to adapt your favorite recipes or discover new ones that don’t set off your digestive symptoms. For FODMAPs-free meals, try some simple recipes like steak stuffed with herbs and prosciutto, or a whole grilled fish with beet salad or a simple plate of greens like spinach or arugula (both low in FODMAPs) drizzled with olive oil and balsamic vinegar. You might even find that you enjoy the challenge of cooking without FODMAPs and learning to use new flavors and vegetables.


Not everyone is FODMAPs intolerant. If your digestive system is working just fine and you don’t notice any symptoms from eating these foods, there’s nothing healthy about restricting them and no reason to artificially limit your diet – enjoy your tomato sauce, avocados, and cauliflower without guilt. But if you’re stuck wondering why your guts are still rebelling against you even on a strict Paleo diet, a test diet for FODMAPs intolerance is certainly worth trying. At worst, it’s one more potential reason to cross off your list, and at best, you’ll find out how to manage your symptoms without needing to rely on drugs or more invasive solutions.