The Fundamentals of FODMAPS with Digestive Nutrition Clinic

The Fundamentals of FODMAPS with Digestive Nutrition Clinic

What Are FODMAPs? 

By the Digestive Nutrition Clinic

FODMAPs is the acronym used for a group of small chain carbohydrates (sugars and fibers), which are found naturally in foods.

F - Fermentable

O - Oligosaccharides

D - Disaccharides

M - Monosaccharides

A - And

P - Polyols

Breaking Down FODMAPs

Fermentable means that molecules are easily broken down by gut bacteria producing gases as a byproduct.

Oligosaccharides consist of fructooligosaccharides (FOS or fructans) and galactooligosaccharides (GOS or galactans). Fructans are chains of fructose with a glucose unit attached at the end, while galactans are galactose chains with a fructose molecule attached at the end.

Disaccharides consist of two joined sugar units. Of all the disaccharides, Lactose, a molecule made up of the two digestible sugars glucose and galactose, is the main culprit of digestive troubles.

Monosaccharides are single sugar units that require no digestion. These are glucose, fructose and galactose. In the case of FODMAPs, fructose poses a problem only when present in excess of glucose, meaning in larger quantities than glucose when ingested. This happens because fructose absorption into the gut happens efficiently and effectively only when glucose exists in equal or bigger proportions.

Polyols are sugar alcohols, which is a sugar molecule with an alcohol group attached to it. These are isomalt, maltitol, mannitol, polydextrose, sorbitol and xylitol.

Why Are FODMAPs Problematic?

FODMAPs enter the body when food is ingested but are not absorbed into the bloodstream and instead build up in the small intestine. Upon consumption, fructans and galactans are undigested as humans lack the enzymes to break them down. Furthermore, lactose builds up in the intestine because many IBS or other GI sufferers do not have enough enzymes to break it down. Additionally, fructose is a molecule that is readily absorbed in the intestine; however, it needs to be accompanied by glucose. If fructose is ingested in excess of glucose, this results in malabsorption and it builds up in the intestine. Lastly, polyols are only partially and very slowly absorbed by the body, therefore accumulating in the small intestine in large quantities.

What Happens When FODMAPs Are Not Absorbed?

FODMAPs are small and soluble and therefore osmotically active, which means they draw water into the small intestine. This excess water and the malabsorbed FODMAPs enter the colon, are broken down by bacteria in the colon and release methane and hydrogen gas. This combination causes swelling and distension in the intestines, which leads to bloating, pain, diarrhea and/or constipation. Fructose, polyols and, in some cases, lactose increase luminal water in the small intestine, while fructans, some galactans and polyols increase colonic gas.

In addition, patients with functional gastrointestinal disorders (FGIDs), particularly IBS, often suffer from visceral hypersensitivity, a heightened sensitivity to pain in the inner organs, which in this case is the gastrointestinal tract. Therefore, the bloating, pain and altered bowel movements due to the accumulation of ill-absorbed FODMAPs is exaggerated and results in a feeling of greater pain and discomfort. Keep in mind that high FODMAPs do not induce such exaggerated symptoms in people without IBS. A little bit of bloating is perfectly normal.

A Few Foods High in FODMAPs

High in Fructans: Wheat, Barley, Rye, Nectarines, Watermelon, Garlic, Onion, Cashews, Pistachios, Chamomile Tea and Fennel Tea.

High in GOS: Pulses, Legumes, Cashews and Pistachios.

High in Lactose: Whole, Reduced Fat or Skimmed (Cow, Goat or Sheep’s) Milk, Evaporated Milk, Sweetened Condensed Milk, Ice Cream, Cow’s or Goat’s Yoghurt, Cream Cheese, Cottage Cheese and Fresh Cream.

With Excess Fructose: Apples, Cherries, Figs, Mangoes, Pears, Dried Fruit, Asparagus, Artichokes, Agave Syrup, Honey, High-Fructose Corn Syrup and Fruit Juices.

High in Polyols: Apples, Pears, Apricots, Peaches, Plums, Prunes, Blackberries, Watermelon, Cauliflower, and Items with Artificial Sweeteners such as Chewing Gum, Mints and Desserts.

Introducing the Low FODMAP Diet

Research in this field has shown that foods high in FODMAPs result in bloating, gas, diarrhea, constipation and pain for many people with functional gastrointestinal disorders (FGIDs), especially IBS.

The low FODMAP diet is a proven plan that works to minimize IBS-related bloating and related symptoms. It was developed about 10 years ago by Monash University in Melbourne, Australia, where foods were analyzed and identified based on their FODMAP content. The diet, which is evidence-based, scientifically-backed and should be overseen by a trained registered dietitian, involves a strict following of the low FODMAP diet, usually for a period of 2 to 6 weeks in order to improve symptoms and identify whether the diet works on the patient. This is followed by a 6-to-10-week re-introduction phase in which FODMAP foods are re-introduced into the diet in a sequential and patient-by-patient basis depending on each patient’s response. Then comes the personalization and maintenance of the diet, which considers the variation in the quantities and types of foods containing FODMAPs that each patient can eat.

It is important to move away from the restriction phase in order to include a variety of foods in our diet, increase one’s chances of adherence to the plan, and decrease the effects on the patient’s microbiome. Evidence has shown that the restriction diet has an impact on gut microbiota, even though its long-term impact on health has not yet been determined. Long-term FODMAP elimination is very restrictive and unnecessary. Hence, the individual’s diet during the personalization phase should be both healthy and varied and be as near as possible to what would be considered a ‘normal’ diet.

Some Low FODMAP Foods Courtesy of Monash University

Vegetables: Arugula, Celeriac, Eggplant, Green Beans, Bok Choy, Bell Pepper, Carrot, Cucumber, Kale, Lettuce, Potato, Spinach and Tomato.

Fruit: Cantaloupe, Clementine, Dragon Fruit, Grapes, Kiwi, Mandarin, Passionfruit, Orange, Pineapple and Strawberries.

Dairy and Alternatives to Dairy: Almond Milk, Macadamia Milk, Unsweetened Quinoa Milk, Lactose-Free Milk, Soy Milk Made from Soy Protein, Camembert Cheese, Feta Cheese, Hard Cheeses and Lactose-Free Yoghurt.

Protein Sources: Eggs, Firm Tofu, Chicken, Beef, Lamb, Pork, Turkey, Seafood and Tempeh.

Breads and Cereals: Gluten-Free Corn Flakes, Oats, Quinoa Flakes, Quinoa/Rice/Corn Pasta, Sourdough Spelt Bread, and Wheat/Rye/Barley-Free Breads.

Nuts and Seeds: Chia Seeds, Chestnuts, Flax Seeds, Macadamias, Peanuts, Pecans, Pumpkin Seeds, Sesame Seeds, Tigernuts and Walnuts.

How Effective is the Low FODMAP Diet?

There is plenty of data supporting the low FODMAP diet’s positive impact on IBS. A recent review by K. Whelan et al. (2018) states that, to date, there are at least 10 randomized controlled or randomized comparative trials of the low FODMAP diet. The majority of these studies show that the low FODMAP diet has had a positive end result on 50 to 80% of the IBS patients involved.

Furthermore, studies show that a low FODMAP diet can improve gut symptoms, quality of life and abdominal pain in people with IBS. As measured by the IBS Quality of Life Instrument, William Chey’s group has shown a twofold increase in the quality of life of patients on the low FODMAP diet compared to those following standard dietary recommendations for IBS. More specifically, patients following this diet saw more significant improvements in their overall quality of life, levels of anxiety and ability to be active compared to those with the standard dietary recommendations for IBS.

Success data for the low FODMAP diet have mainly been gathered from studies for IBS-D or IBS-mixed patients. There is much less information on the diet’s efficacy on patients suffering from IBS-C. However, the fact that studies show that the FODMAP diet can help up to ¾ of people with IBS is very encouraging. Interestingly enough, a recent national survey of over 1500 gastroenterologists in the US showed that over half of the healthcare providers recommend diet therapy to more than 75% of their IBS patients, with the low FODMAP diet being the one most commonly recommended.

Other possibilities for potential application of the low FODMAP diet have been identified. However, more research and follow-up studies are required in order to make full recommendations. For instance, studies show that the low FODMAP diet helps reduce functional gastrointestinal symptoms of quiescent (inactive) IBD, which are IBS-like. Furthermore, preliminary research suggests that a breastfeeding mother’s low FODMAP diet could be correlated with a decrease in colic symptoms in the infant. Additionally, the low FODMAP diet could have a use in managing symptoms of SIBO, albeit there is not enough evidence to apply it as a primary type of treatment.


Do not self-diagnose. Bloating and other IBS symptoms may resemble symptoms of more serious conditions such as cancer (colon, ovarian or uterine), kidney failure, congestive heart failure or liver disease, which produces fluid that drains and collects in the abdomen. It can also signal damage of the GI tract or pancreatic insufficiency. Always seek the help and guidance of a healthcare professional.


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