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What are FODMAPS and Why Should You Care?

Arrangement of low and high FODMAPs food.

FODMAPs is an acronym for fermentable short-chain carbohydrates, called oligosaccharides (fructans, galactans), disaccharides (lactose), monosaccharides (fructose), and polyols (sugar alcohols), which are naturally occurring compounds that can be found in some foods that are not absorbed completely by all people. If these substances are not absorbed properly in the small intestine, then they are carried on into the large intestine, where they become a source of food for the bacteria or candida that reside there. If too many of these foods are present, the microbes may be gluttons and overeat, which makes them proliferate; or if they are already present in high numbers, it enables them to thrive.

When the microbes digest/ferment the FODMAPS, their waste products produce a wide variety of disruptive gastrointestinal symptoms like nausea, gas, bloating, distension, abdominal pain, cramping, diarrhea and/or constipation, as well as fatigue, anxiety, depression, OCD, brain fog and more, that are commonly experienced by individuals with IBS, (irritable bowel syndrome), SIBO (small intestinal bowel overgrowth), or other functional gut disorders. These by-products may also increase or slow down transit times through the digestive tract. Some FODMAPs also have an osmotic effect; increasing fluid in the intestines, which leads to diarrhea.

Since people with SIBO have unusually high levels of bacteria in the small intestine that should not be there, then these bacteria will ferment the FODMAPS as well, which will encourage more proliferation of overgrowth and damage to the small intestine. Additionally, SIBO inhibits nutrient absorption and the enzymes needed to break down substances like lactose and fructose, thus it may be an underlying contributing factor to the intolerance of them in the first place.

When designing your Individualized Paleo Plan, foods that contain FODMAPs are another factor that some individuals need to take into consideration to achieve optimal results. Particularly, anyone who has SIBO, candida, or other gut problems, IBS, acid reflux, diarrhea, constipation, anxiety disorders, OCD, fatigue, or brain fog.

When individuals with IBS, SIBO, or other gut disorders reduce their intake of these foods, they can relieve many of their symptoms. Some research has found that 75% of people with functional gut disorders can achieve significant symptom relief by eating a low FODMAPs diet. Many other studies have demonstrated a high level of success in reducing symptoms of IBS by reducing or eliminating foods that are high in FODMAPs.

We have two primary types of bacteria in the gastrointestinal tract called bacteroidetes and firmicutes. Bacteriodetes will eat carbs, protein, and fat, but firmicutes eat mostly carbs and fiber. Research has found that people with IBS, (which is often a SIBO related condition) tend to have more firmicutes than bacteriodetes, which means there will be more of them around to ferment the FODMAPS.

Here’s a more detailed look at each of the individual substances in the FODMAPS diet list.


Lactose is the sugar that occurs naturally in cow’s, sheep’s, and goat’s milk. Intolerance for lactose is the result of decreased or completely absent production of the enzyme lactase that is needed to break down lactose. It is found most abundantly in soft cheese, milk, cottage cheese, yogurt, custard, and ice cream. (butter and cream have only trace amounts). The severity of intolerance will be influenced by how much lactase is or isn’t present. A hydrogen breath test can help you diagnose lactose intolerance.


Fructans are oligosaccharides made of fructose molecule chains with a glucose molecule at the end, which some are incapable of breaking down because the small intestine is lacking in the enzymes that are needed to do so, therefore they are not absorbed at all. Fructans are found in wheat, rye, barley, inulin, FOS, onions, artichokes, cabbage, Brussels sprouts, radish, snow peas, lettuce, broccoli, asparagus, butternut squash, beetroot, scallions/leeks, chicory, garlic, fennel, okra, shallots, watermelon, and pistachio.

For you garlic lovers, you may want to note, that garlic oil can be used with no problems, as it doesn’t contain fructans and the green tops of scallions can be used for the same reason.


Galactans are chains of the sugar galactose combined with a fructose molecule, which is completely unabsorbed because the human body lacks the enzymes that are necessary to break them down. Thus, why beans produce gas in everyone. However, for some individuals (e.g. people with candida or SIBO) the distress is much broader and severe. Galactans are found in chickpeas (garbanzos), lentils, kidney beans, black-eyed peas, soy-based products, and broccoli.


Polyols are more commonly known as sugar alcohols. They consist of molecules that are too large to be broken down by the small intestine by anyone and produce a laxative effect by pulling water into the colon (osmotic diarrhea), and can be consumed by bacteria, but not candida. Polyols occur naturally in some fruits and vegetables and are often used as a sweetener in many foods as an alternative to sugar.

Not all polyols are created equal; the size of the molecule affects its ability to be absorbed and therefore determines its effect on the gastrointestinal tract. Erythritol is smaller in size (four-carbon) and, therefore, is absorbed better than those that contain six-carbon. Data also suggest that mannitol causes less distress than sorbitol and xylitol even less. Although polyols are called sugar alcohols, they are neither sugars nor alcohols.

Polyols can be found in apples, peaches, apricots, plums, prunes, blackberries, pears, watermelon, cherries, nectarines, snow peas, button mushrooms, avocado, persimmons, cauliflower, celery, sweet potato, green bell pepper, maltitol, sorbitol, mannitol, erythritol, isomalt,  xylitol, and the nutritional supplement inositol.


Fructose, known more commonly as fruit sugar, may not be completely absorbed (fructose malabsorption) if GLUT5 (a fructose transporter in your small intestine) is deficient. Some fruits contain a 1:1 ratio of glucose to fructose, which are often tolerated better by people who have issues with fructose, but the fruits that have a larger ratio of fructose in comparison to glucose are the ones that are most problematic.

However, even when accompanied by the 1:1 ratio with glucose, fructose can still be problematic in some people, so FODMAP-friendly fruit should also be limited, as all fruit contains fructose.

Fruit that is not ripe contains higher levels of fructose than fruit that is ripe, so your fruit should be consumed when ripe. It also contains higher amounts of resistant starch, which can have the same negative effect on the gut.

A hydrogen breath test can also be used to identify whether one has fructose malabsorption.

The following foods are not FODMAPs friendly due to their high fructose content: high fructose corn syrup, honey, agave, sweet corn, asparagus, artichokes, eggplant, agave, apples, pears, mangoes, peaches, grapes, cherries, watermelon, coconut, dried fruit, fruit juices, and some alcohol like wine (sherry and port are highest in fructose).

As you may have noticed, some fruits like apples, pears, and cherries contain both fructose and polyols, which means they often result in more severe symptoms than those that contain just high fructose. Additionally, fructans, lactose, polyols and galactans each have an additive effect when combined with fructose, meaning the severity of symptoms may increase.

(Ironically, table sugar which is sucrose bound to glucose, is not in this list, but obviously, this food should be avoided due to its devastating effect on blood sugar and the brain, and its role in many chronic health conditions like insulin resistance, type 2 diabetes, obesity, heart disease, cancer, compulsive overeating, depression, anxiety, addiction, hyperactivity, dementia, PCOS, and more.)

It’s important to note that fructose malabsorption is not the same as hereditary fructose intolerance. The latter is a relatively rare and serious disorder caused by a defective gene that results in a deficiency in an enzyme called aldolase B that is needed to break down fructose, and in this case, all fructose must be avoided.

Identifying Your FODMAPs Threshold

If you are following the Paleo diet, as I hope you are, then you know that some of these foods like wheat, rye, high fructose corn syrup, agave, and legumes are already eliminated. However, as you can see, there are many foods that are not on the low FODMAP diet list that are Paleo friendly, rich in nutrients, and health-enhancing, like many fruits and vegetables.

Therefore, you don’t want to remove some of these foods unnecessarily. If you don’t have IBS,  SIBO, GERD or acid reflux, heartburn (which can be SIBO related), or any other bowel or gut disorder, then there is no reason to be concerned about these substances; you apparently aren’t having an issue with them. However, if you have already been following a Paleo diet and continue to have gut disorders or unexplained gastrointestinal or psychological symptoms, then you should explore whether FODMAPs may be one of the underlying contributors.

A low FODMAPs diet may also be beneficial for anyone with candida overgrowth as long as it is combined with basic candida diet principles, as many of these foods also feed candida, and because candida often occurs in conjunction with the overgrowth of pathogenic bacteria.

However, it is vital to understand that intolerance to FODMAPs is highly individual and the severity of intolerance can vary greatly from person to person as everyone has a different threshold. One person may have a lot of trouble with them, another person may have a little intolerance, and another may not notice much of an impact.

Furthermore, your threshold may not be the same across the board. You may have a different threshold for each of the individual types of FODMAPs. For example, you may have a severe intolerance to polyols, a mild intolerance to fructose, fructans, and galactans, but no problem with lactose or vice versa, in many different combinations. So just because you have an intolerance to one, does not mean you have to eliminate them all.

The presence or severity of intolerance may also be dependent upon how much is consumed and whether more than one FODMAP is present. You may be able to eat a half of an apple, a half cup of broccoli, or a small number of polyols with no symptoms, but a larger serving produces severe discomfort. So the food does not always have to be eliminated completely, it may only need to be reduced. Or, you may only have symptoms when you combine an apple with broccoli or cabbage with onion and garlic. For example, in my own life I can consume a product that contains erythritol or xylitol with no symptoms if the serving is small, but if I eat too much then I get cramping and diarrhea. Some data suggests that onions, wheat, apples, and pears tend to be most problematic for the majority of people.

Additionally, if you have consumed a meal that contains lactose, fructose, fructans, polyols, and galactans you may experience some significant distress, as this would take you over your threshold, but a meal that contains lactose or fructan only may not.

Intolerance may also be affected by whether the food is raw or cooked. You may have more symptoms when the food is raw than when it is cooked.

Additionally, your threshold may fluctuate from time to time depending on other factors like your stress level, the health of your gut, exposure to toxins, how many bacteria or fungi are present, and inflammation; so your level of intolerance may change at some point in your life if there are changes in these areas.

Stress can significantly impair your digestion because the digestive system is essentially shut down when we are under high stress so that resources can be directed elsewhere. It inhibits GLUT2, the transporter in the small intestine needed for transporting glucose, and kills friendly bacteria in the gut, which allows pathogenic organisms to overpopulate that would then feed on FODMAPs.

So just because you have candida, SIBO, IBS, or other gut disorders does not mean you should automatically assume that you have to eliminate all foods in this group. Use the FODMAPs list of foods as a guideline, but then like all other aspects of your diet, it should be fine-tuned and customized for your unique body chemistry depending on your threshold and severity of response for each one.

FODMAPs are not the cause of IBS or other functional gut disorders, they exacerbate a condition that already exists. The real problem lies in an imbalance of or the types of organisms that are present in the gut, or the lack of enzymes that are needed to break down the particular substances.

Some research has demonstrated that even healthy people will experience a lot of flatulence if they eat a high FODMAPS diet, but people with IBS also experienced fatigue and numerous other GI symptoms, suggesting that the level of pathogenic organisms that are present is what determines how intolerant you are of FODMAPs. Even the good guys can become pathogenic if they are present in too many numbers.

Furthermore, some degree of fermentable carbohydrates is beneficial, because your healthy gut bacteria use them as a food source as well and produce short-chain fatty acids in the fermentation process, which will improve your gut and overall health (when in moderation), so you don’t want to eliminate all of them. But, if you have too much of a particular type of bacteria or fungi that feeds on FODMAPs, then too much fermentation takes place and results in the symptoms of FODMAPs intolerance and encourages the microbes to multiply in numbers. On the flip side, if you eat a diet that is high in FODMAPs, this provides the organisms with a large food source, which can be the inciting incident of overgrowth.

The way to determine whether you have an intolerance to any of these foods is to remove the foods you think may be problematic for 30 to 45 days and see if you have improvements. Keep a food journal to help you remember. Then bring back one food at a time, one week at a time, and monitor your response. Be sure to bring back only one food at a time and wait for a week before trying another food or you will not know which food is producing the symptoms.

Sometimes you can bring FODMAPs back to your diet after a short period of removing them and other foods that are disruptive to the GI tract simply because it kills off some of the microbes that were dominant, so there is a rebalancing of gut flora and less inflammation that occurs, so tolerance improves. Alternatively, you may be able to bring some back, but not others. Since many of the vegetables offer a variety of health benefits, one wants to try and bring back as many of these that you can comfortably consume. Don’t just eliminate them and keep it that way. Continually challenge yourself periodically to see if anything has changed.

It’s also important to note that FODMAPs are only one of many issues that can contribute to IBS, SIBO, GERD,  and other gut disorders or gastrointestinal symptoms. Other factors that should be considered besides stress include foods that contain phytates, saponins, and lectins, as well as depletion of neurotransmitters like serotonin and GABA, heavy metal toxicity, histamine intolerance, candida overgrowth, intestinal parasites, chemical sensitivities, and other unfriendly bacteria.


Kate Scarlata, RD, LDN The FODMAPs Approach – Minimize Consumption of Fermentable Carbs to Manage Functional Gut Disorder Symptoms. Today’s Dietitian, Vol. 12 No. 8 P. 30 August 2010 Issue

Shepherd EJ, Helliwell PA, Mace OJ, Morgan EL, Patel N, Kellett GL. Stress and glucocorticoid inhibit apical GLUT2-trafficking and intestinal glucose absorption in rat small intestine. J Physiol. 2004 Oct 1;560(Pt 1):281-90. Epub 2004 Aug 5.

Staudacher HM, Whelan K, Irving PM, Lomer MC. Comparison of symptom response following advice for a diet low in fermentable carbohydrates (FODMAPs) versus standard dietary advice in patients with irritable bowel syndrome. J Hum Nutr Diet. 2011 Oct;24(5):487-95. doi: 10.1111/j.1365-277X.2011.01162.x. Epub 2011 May 25.

Ong DK, Mitchell SB, Barrett JS, Shepherd SJ, Irving PM, Biesiekierski JR, Smith S, Gibson PR, Muir JG.  Manipulation of dietary short-chain carbohydrates alters the pattern of gas production and genesis of symptoms in irritable bowel syndrome. J Gastroenterol Hepatol. 2010 Aug;25(8):1366-73. doi: 10.1111/j.1440-1746.2010.06370.x.

Ostgaard H, Hausken T, Gundersen D, El-Salhy M. Diet and effects of diet management on quality of life and symptoms in patients with irritable bowel syndrome. Mol Med Rep. 2012 Jun;5(6):1382-90. doi: 10.3892/mmr.2012.843. Epub 2012 Mar 22.

2 thoughts on “What are FODMAPS and Why Should You Care?”

  1. I feel great without FODMAPS but I’m dying to introduce onions and garlic for their antimicrobial properties. Do you think a negative reaction to these foods is worth the benefits?

    Great website. Food is medicine.

    1. Admin - Cynthia Perkins

      Hi Yessi,

      Well it would depend on how severely they impact you in comparison to how much benefit you would get. If one’s threshold is low, then probably not. If the threshold is higher, then maybe so. As mentioned above, the food doesn’t always have to be eliminated, it may only need to be moderated. So in some cases, it may be possible for some consumption. And one may not have a problem with all FODMAPS, so it would vary from person to person. Thanks, glad you enjoy the site.

      Best Cynthia

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