The Definitive Guide to FODMAPs

You could be having a fairly routine conversation about health and nutrition where everything discussed is familiar. You hear things like “carbs” and “medium chain triglycerides” and “fructose” and “macros” and “gluten” and “PUFAs,” thinking nothing of it. Like I said, routine. Then someone mentions FODMAPs. Huh? What the heck is that? Quite possibly one of the strangest, seemingly contrived acronyms in existence, FODMAPs represents a collection of foods to which a surprisingly large number of people are highly sensitive. To them, paying attention to the FODMAPs in their diets is very real and very serious if they hope to avoid debilitating, embarrassing, and painful digestive issues.

What is a FODMAP?

FODMAPs are carbohydrates and fibers that gut bacteria can ferment in the gut and cause excessive gas, intestinal discomfort, diarrhea, and/or constipation. In other words, FODMAPs are a potential source of digestive distress in susceptible people.

What does FODMAP stand for?

FODMAP is an acronym. F is for Fermentable carbohydrates that gut bacteria ferment. O is for Oligosaccharides, chains of carbohydrates. D is for disaccharides, pairs of sugar molecules. M is for monosaccharides, single sugar molecules. P is for Polyols, or sugar alcohols.

F is for Fermentable – Fermentable carbohydrates are carbohydrates that are fermented by bacteria instead of broken down by our digestive enzymes. In most people, some fermentable carbohydrates are healthy sources of food for the (helpful) bacteria that ferment them; these can include the prebiotics I’ve championed in the past and can actually improve digestive and overall health. In people with FODMAPs intolerance, certain carbohydrates can become too fermentable, resulting in gas, bloating, pain, and poor digestion, as well as proliferation of unwanted pathogenic bacteria.

O is for Oligosaccharides – Oligosaccharides are short-chain carbohydrates, including fructans (fructooligosaccharides, or FOS, and inulin) and galactans (raffinose and stachyose). Fructans are chains of fructose with a glucose molecule at the end; galactans are chains of galactose with a fructose molecule.

D is for Disaccharides – These are pairs of sugar molecules, with the most problematic being the milk sugar lactose (a galactose molecule with a glucose molecule).

M is for Monosaccharides – This describes a single sugar molecule. Free fructose is the monosaccharide to watch out for with FODMAPs intolerance.

A is for And – Every list needs a good conjunction.

P is for Polyols – Polyols include sugar alcohols like xylitol, sorbitol, or maltitol. For an idea as to their effects, type one of them into Google and note the autofill choice (hint: it’s usually “diarrhea” or “constipation” or “gas”). Since large amounts of polyols rarely occur in nature, lots of people have trouble with them.

Most people probably don’t need to worry about these categories. Most people enjoy pristine, effortless trips to the toilet that happen like clockwork and finish in under a minute. Heck, as I understand it, most people don’t even use toilet paper these days; they are that efficient and clean. Yes, it’s true: digestion worldwide has never been better!

The reality, of course, is that digestive difficulties are widespread, particularly in the industrialized world. If it’s not constipation, it’s diarrhea. Or bloating. Or gas. Or hemorrhoids. Or IBS (irritable bowel syndrome). Or all of the above. These complaints are sadly very common (even more common than those stats would suggest, since many people are too embarrassed to admit they have an issue). For many of these people, FODMAPs may be exacerbating their symptoms.

Why are FODMAPs an Issue for Some People?

Normal carbohydrate digestion takes place in the small intestine, where polysaccharides are broken up into glucose, fructose, and galactose and transporters like GLUT2 and GLUT5 absorb them for the body to use as nutrients. Sometimes those sugar molecules make it past the small intestine into the large intestine where colonic bacteria – the gut flora we (sorta) know and love – gobbles it up via fermentation, potentially causing gas and painful bloating. The presence of too many sugars in the colon can also cause an influx of fluid, which could lead to diarrhea. Constipation is another common symptom, though it’s not clear exactly how FODMAPs cause it. And some polysaccharides, like the oligosaccharides, make it through to the colonic bacteria as a rule because they resist digestion in everyone (in healthy people, these have a useful prebiotic effect).

You might be thinking, “Cool, so I can just avoid those weird sounding sugars and be fine, right?” Probably not. FODMAPs are very prevalent in the food supply. Even if you avoid free fructose, don’t drink milk, and ditch processed food containing sugar alcohols, you’ll still run into them in many fruits and vegetables.

Now, FODMAPs aren’t an issue for many people. They’re either digested normally or their gut bacteria are sufficiently diverse and healthy that they can benefit from the prebiotic input. But for those who can’t digest them properly, they should be aware of high- and low-FODMAP foods.

What are High-FODMAP Foods?

The highest FODMAP foods include fibrous fruits and vegetables, fruits and other foods that have concentrated levels of fructose and sugar, processed foods full of sugar alcohols, concentrated sources of sugar like plain sugar, honey, juice, and soda, and grains full of insoluble fiber.

Okay, just so you know what you’re dealing with, here’s a big list of all the foods that are high in FODMAPs including which FODMAP they contain.

FODMAP vegetables:

• Asparagus (fructose, fructans)
• Artichoke (fructose)
• Beets (fructans)
• Broccoli (fructans)
• Brussels sprouts (fructans)
• Butternut squash (fructans)
• Cabbage (fructans)
• Celery (polyols)
• Cauliflower (polyols)
• Eggplant
• Fennel (fructans)
• Garlic (fructans)
• Jerusalem artichoke/fartichoke (fructan)
• Jicama (fructan)
• Leek (fructans)
• Mushroom (polyol)
• Okra (fructans)
• Onion (fructans)
• Shallots (fructans)
• Sweet corn (fructose)
• Radicchio (fructans)
• Sweet potato (polyol)

FODMAP Fruits

• Apples (fructose, polyol)
• Apricots (polyol)
• Avocados (polyol)
• Blackberries (polyol)
• Cherries (fructose, polyol)
• Plums (polyol)
• Pluots (polyol)
• Lychees (polyol)
• Nectarines (polyol)
• Peaches (polyol)
• Pears (fructose, polyol)
• Persimmons (polyol)
• Mango (fructose)
• Watermelon (polyol, fructose)
• Dried fruit (fructose)
• Juice (fructose)

Other FODMAP Foods

• Honey (fructose)
• Agave nectar (fructose)
• White sugar (fructose)
• Maltitol, sorbitol, mannitol, xylitol
• Dairy that contains lactose, like milk, cream, butter, and soft cheeses
• Wheat, barley, rye, spelt, emmer, einkorn, oats
• Lentils and beans
• Almonds, cashews, pistachios

What are Low-FODMAP Foods?

Low-FODMAP foods include meat of all kinds, poultry, seafood, fish, shellfish, eggs, and hard low-lactose cheeses. Low-fiber vegetables, fruits, and nuts also tend to be lower in FODMAPs than more fibrous fruits, vegetables, and nuts; fermentation also reduces FODMAP content.

If you suspect you have digestive issues and want to try a low-FODMAP diet, here’s an exhaustive list of what you can eat.

Animal Foods

• Meat of all kinds: beef, lamb, pork, goat, game meats. They’re all completely free of FODMAPs.
• Poultry: name a bird and it’s FODMAP-free.
• Seafood, fish, and shellfish are also FODMAP-free.
• Eggs contain no FODMAPs.
• Hard cheeses, sour yogurts and kefirs are very low in FODMAPs.

Vegetables

• Zucchini
• Squash
• Potatoes
• Spinach
• Kale
• Lettuces of all kinds
• Arugula
• Green beans
• Collard greens
• Mustard
• Pumpkin
• Seaweed
• Turnips
• Rutabagas
• Cucumbers
• Chilis
• Fermented or pickled vegetables are low in FODMAPs, often even when the fresh versions are high. So pickled beets or sauerkraut will be lower in FODMAPs than fresh beets and fresh cabbage.

Fruits

• Melons (except for watermelon)
• Bananas (except if green)
• Strawberries
• Blueberries
• Oranges
• Grapes
• Pineapple
• Kiwi
• Raspberries

Grains

• Rice
• Buckwheat (technically a pseudocereal but close enough to count)
• Amaranth
• Quinoa
• Teff
• Any fermented grain (sourdough) will be lower in FODMAPs than the same unfermented grain. Sourdough bread is much lower in FODMAPs than unfermented bread, for example.

Nuts

• Mac nuts
• Walnuts
• Brazil nuts
• Chestnuts
• Peanuts (yeah, yeah, I know it’s a legume)

Let me reiterate before I go on, because I don’t want to scare everyone away from berries and broccoli: not everyone has problems with FODMAPs. Most people probably don’t. If you’re eating all that stuff without issue, continue doing so and consider this post merely an academic curiosity. They are largely healthy foods that provide prebiotic substrate for your healthy gut bacteria to thrive on.

Is the Low-FODMAP Diet an Irritable Bowel Syndrome Diet?

Low-FODMAP diets beat the pants off conventional dietary advice for people with IBS.¹ One study found that while healthy subjects had increased flatulence on a high-FODMAP diet, subjects with IBS had increased flatulence in addition to lethargy and gut pain.² This could indicate that both groups were feeding FODMAPs to their gut bugs (which produce the flatulence through fermentation), but only the IBS patients had enough pathogenic gut flora to produce adverse symptoms. Farts are funny. Bloating and severe pain are not.

Who else might benefit from limiting FODMAPs?

Anyone with small intestinal bacterial overgrowth (SIBO).

Normally, the small intestine has relatively low numbers of gut flora residents. In SIBO, it’s got tons that aren’t supposed to be there. They interfere with nutrient absorption, digestion, and just generally muck everything up. SIBO has been shown to correlate quite strongly with lactase deficiency.³ Without enough lactase, you won’t be able to digest lactose (one of the premier FODMAPs) and your colonic bacteria will have to do the job. Another, earlier study found that patients with SIBO also show malabsorption of fructose and sorbitol in addition to lactose; all three are FODMAPs.⁴

Anyone suffering from chronic stress.

Stress is a well-known disruptor of digestive function as anyone who’s gotten queasy, lost their appetite, or had explosive diarrhea before the big interview could tell you. There’s evidence that stress might be causing FODMAP-intolerance, too. First, stress inhibits the action of GLUT2, a transporter responsible for the small intestinal absorption of glucose, fructose, and galactose in the gut.⁵ If you’re unable to adequately absorb the sugar molecules in the small intestine, they end up making it to your large intestine for fermentation by colonic bacteria. Second, stress has an immediate impact on the composition and function of your gut flora, rendering your populations less diverse and allowing certain pathogenic species to overpopulate—species that feed on FODMAPs.

Anyone who thinks they’re gluten-sensitive.

Since gluten-containing grains also tend to be high in FODMAPs, many people who think they have gluten-sensitivity or celiac disease actually are just sensitive to the FODMAPs in the wheat, rye, or barley. Ask your doctor about testing for celiac, SIBO, and other digestive disorders.

Anyone with otherwise unexplained digestive problems.

Maybe you haven’t had a diagnosis. Maybe you just don’t feel right after eating almost anything. Maybe you’re chronically constipated (or the opposite). Trying a low-FODMAP diet can help you narrow your focus and start to identify some culprits.

How to Try a FODMAP Elimination Diet

If you decide you might be a good candidate for a low-FODMAP diet, try a FODMAP elimination diet trial. Go through the list of FODMAP foods from this article and eliminate the ones high in FODMAPs and limit your diet to the ones low in FODMAPs. If your symptoms improve, add FODMAP foods back into your diet one by one every three or four days to track which ones cause your symptoms. Consider keeping a diet journal to log your food and track your reactions to individual FODMAPs. Some people might really react poorly to fructose while having no issues with lactose. Point being: different FODMAPs affect different people differently. You can tolerate some and not others. And if you can tolerate them, they’re worth consuming.

Dosage matters, too. A gram of inulin might be fine, while five grams could cause distress. A half cup of blackberries might be fine while a full cup gives you bloating. Individual tolerance must be determined by, well, seeing what and how much you tolerate.

If you’re interested in healing your gut, whether from SIBO or IBS or anything else that might be predisposing you to FODMAP intolerance, well-established protocol like GAPS (Gut and Psychology Syndrome) diet or SCD (specific carbohydrate diet) may help and are worth looking into. 

Another good low-FODMAP diet to try is the carnivore diet. By virtue of eliminating all plant foods, it eliminates the vast majority of FODMAP foods. Read here for a good take on carnivore.

If you have no digestive issues, I would caution against trying a low-FODMAP diet “just because.” You’ll be missing out on some very nutritious, important foods, probably unnecessarily, while adding a bunch of unnecessary stress to your eating. FODMAP-related digestive issues are very noticeable. You’ll know it if you have it.

Well, that about sums it up. I hope this Definitive Guide to FODMAPs was helpful for you.

Now that we’re done, what about you? Do you have any sensitivities to FODMAPs? Has looking at that list of FODMAP foods made lightbulbs go off? Let me know below!

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