The acronym FODMAP (Table 1) stands for Fermentable, Oligosaccharides, Disaccharides, Monosaccharides and Polyols.

The term FODMAP refers to short-chain carbohydrates that are absorbed poorly by the small intestine and pass directly to the colon, where they are fermented by the intestinal microbiota, giving rise to of gases such as methane, butyrate or propionate. The osmotic load that they produce increases the volume of water in the colonic lumen, which in turn causes symptoms such as abdominal distension and pain.1

The foods that contain FODMAPs are numerous and ubiquitous in Western diets: dairy products, fruits, vegetables, legumes and beans, cereals, baked goods, sauces, candies, beverages, jams or frozen treats, among others. Table 2 presents the different FODMAP categories, examples of the main sources, the digestion and absorption process and their effects on the gastrointestinal (GI) tract.

On one hand, fructose is absorbed by the small intestine via the GLUT5 (high-affinity) or GLUT2 (low-affinity) transporter. Physiological fructose malabsorption occurs if the GLUT5 transporter is saturated, when the fructose intake exceeds 20 g in a single eating episode.2 Glucose aids the absorption of fructose via GLUT2, so foods containing fructose and glucose in a 1:1 ratio are better tolerated. However, when there is an excess of fructose relative to glucose (fructose excess = free fructose – free glucose), the former is not well absorbed, producing an increase in the water influx into the lumen. The fruits with fructose excess include pear, apple, mango and melon, and the vegetables, asparagus.2,3

When it comes to sorbitol and fructose, when consumed together, the former hinders the absorption of the latter, as they compete for GLUT5 uptake. The consequence of a fructose excess is the development of GI problems. Fruits with fructose excess combined with sorbitol exacerbate the GI symptoms (Table 2).

Lactose, once ingested, undergoes hydrolysation by lactase, (β-galactosidase).4,5 Following digestion (hydrolysis), the resulting glucose and galactose are absorbed through active transport. In humans, lactase activity peaks around age 2 years and decreases from age 3–4 years in a variable percentage of the population, depending on ethnicity (lactase activity is greater in the Mediterranean Basin compared to Asia, for example).5 Lactase deficiency tends to manifest from age 5–7 years, although in some populations the onset is delayed to adolescence, and entails the development of a constellation of symptoms such as flatulence, abdominal pain and distension and/or diarrhoea due to the arrival of lactose that has not been hydrolysed to the colon.

As regards fructooligosaccharides (FOS) and galactooligosaccharides (GOS), their malabsorption is due to humans not producing the enzymes required to hydrolyse them, so they are not absorbed.

On the other hand, polyols (see Table 2) are absorbed through passive diffusion along the length of the small intestine. The degree of absorption varies depending on the size of the molecule and of the intestinal pores, the time in the small bowel in relation to the absorption time window and the presence of GI disorders.4–6

The aim of this document is to establish a protocol for the use of the low-FODMAP diet in paediatric patients and to review the current evidence on the efficacy of this diet.

We conducted a narrative review of sources obtained through the PubMed and Web of Science databases, Google Scholar and websites of agencies and other official institutions.

In the search conducted in PubMed, we applied selection criteria such as “human” and “child”, limiting the search to sources published in the past 5 years in English or Spanish language. In this search, we used the key words “fodmap” and “low fodmap diet” and the operator AND to combine either with the additional key word “children”.

On the other hand, in the search conducted in Web of Science, we applied selection criteria such as “human” and “children”, limiting the search to sources published in the past 5 years in English or Spanish language. we used the key words “fodmap” and “the low fodmap diet” and the operator AND to combine either with the additional key word “children”.

The low-FODMAP diet is a therapeutic tool that can improve symptoms and nutrition in multiple GI disorders, such as irritable bowel syndrome (IBS),5,7 inflammatory bowel disease (IBD),8 small intestinal bacterial overgrowth (SIBO),9–11 non-coeliac gluten sensitivity (NCGS)8 or coeliac disease (CE).8 It has been found to be effective not only against IBS,7 but also in patients with fibromyalgia, sclerosis and endometriosis.12 Most studies in patients with IBS (and without CE) have been conducted in the adult population, demonstrating that dietary intake of gluten can cause symptoms. This suggests that individuals with IBS may either have NCGS or respond poorly to wheat fructans, which would explain why adherence to a low-FODMAP diet, which excludes them, can have beneficial effects.5

The evidence on the use of the low-FODMAP diet in the paediatric population is scarce.13 Notwithstanding, a significant improvement in symptoms related to gas production and abdominal pain and distention has been observed in paediatric patients on this diet.11,13 Constipation is the symptom that improves the least, which could be related to the low fibre intake in this dietary approach. In a study conducted by Baranguán Castro et al. in children aged 5–15 years (2019),14 most considered that the diet was easy to follow and there was a high proportion of adherence, associated with improved symptom control. Patients have also reported a decrease in abdominal pain associated with an improved quality of life.11,14

Final products of digestion that are not absorbed may produce gases, swelling, gastro-oesophageal reflux, heartburn, decreased appetite, abdominal distension /meteorism, borborygmus, colicky abdominal pain, epigastric pain and changes in bowel movements ranging from softer or more frequent stools to diarrhoea or even constipation.5 These symptoms have a deleterious impact on quality of life, so alleviating them is a priority.

For now, the efficacy of the diet in children with IBS has not been fully proven. However, there is evidence that suggests that implementation and adherence of the diet can improve its symptoms.5

In order to improve adherence to the low-FODMAP diet and its effectiveness, it is essential to perform a rigorous evaluation of abnormal dietary habits before and during the intervention. The reason is that there are complex psychosocial factors at play that are particularly significant in children and/or adolescents.8

The efficacy of the low-FODMAP diet is related to the baseline composition of the gut microbiota and its metabolic capacity. There are studies that suggest that the response ot the diet is better in children with IBS and a microbiota with a greater saccharolytic metabolic capacity. Therefore, this could be a predictive biomarker of the responsiveness to a low-FODMAP diet.8

Analyses of the gut microbiota after the implementation of the diet have revealed a decrease in microbial fermentation, evincing the efficacy in improving GI symptoms, especially abdominal pain, in children with IBS.5,11,15

The limitation of the duration of the elimination phase to 2 weeks in the paediatric population reduces the associated nutritional risks and facilitates adherence, which could contribute to the efficacy of the diet.13,14

As regards the total duration of the diet, previous studies suggest that issues with adherence emerge with a duration longer than 2 months, which reduces its efficacy.11,15 Determining the appropriate duration of this diet in children entails considering the minimum time required for efficacy, maximum time accepted for feasibility, and nutritional risks.8

Phases of treatment

The outcomes of the low-FODMAP diet improve when it is managed by a multidisciplinary team consisting, essentially, by a dietitian/nutritionist, GI doctor and mental health professional with specific training in this area. In many cases, symptoms improve within 2 weeks, so if there is no improvement after 3 or 4 weeks, the patient should not continue on the diet.

The diet is structured into 3 phases. In studies in paediatric patients,14 phase 1 lasts 2–3 weeks, phase 2–8 weeks and phase 3 has a variable duration. Fig. 1 summarises the phases of the diet, which has an approximate duration of 2–3 months in most patients.

Figure 1.

Chart of the low-FODMAP diet phases.

(0.07MB).

Source: adapted from Grez et al.5

First phase: elimination of FODMAP-containing foods

Foods with a high FODMAP content are eliminated for 2–3 weeks while monitoring changes in symptoms. If symptoms persist, both the proposed diet and the patient’s adherence to it need to be evaluated.

A duration of 2 weeks in the paediatric population may be as effective as 3 weeks in adults while decreasing the potential risks and facilitating adherence. In fact, some studies14 found that the majority of patients in the sample considered the diet easy to follow and a high adherence, which is associated with improved symptom control. At 2 weeks, patients exhibited an improvement in symptoms.13

Tables 3 and 4 present lists of the foods that are allowed and not allowed and the potential nutrient deficiencies associated with the low-FODMAP diet.6,7,17,18 We ought to highlight that the allowed foods differ between studies, which complicates the implementation of the diet.

Table 3.

Lists of foods that are not recommended (“not allowed”) and recommended (“allowed”) in the low-FODMAP diet.

Alimentos	Not allowed	Allowed
Vegetables and roots	Garlic, onion, artichoke, asparagus, leek, celery, green pepper, okra, aubergine, common tomato, baby spinach, heart of lettuce, endive, chicory leaves, common cabbage, beets (root), button mushrooms (champiñón), other mushrooms (except oyster mushroom), spring onions (green part), peanut squash, sweet potato (in large amounts), Brussels sprouts, broccoli, bok choy, cauliflower, bean sprouts (in large quantities), sweet corn (in large quantities), fennel	Pumpkin, courgette (65 g), carrot, cherry tomato, turnip, unpeeled cucumber and pickled gherkins, red pepper, chard, spinach, borage, collards, thistle, arugula, kale, chicory, lettuce in general (preferably choose the tender leafy type and avoid the “white” core), endives, chives, radish, alfalfa, corn (in small amounts), ginger, bambooPotato, sweet potato (in small amounts), cassava (in small amounts), yams (in small amounts)
Fruits	Mango, cherries, nectarine, peach, plum, avocado, pear, apricot, persimmon, lychee, melon, watermelon, apple, grapefruit, raisins, prunes, canned fruit in juice, natural fruit juice (of not allowed fruits), fruit concentrates	Banana (unripe), orange, tangerine, kiwi, star fruit, lemon/lime, papaya, pineapple, raspberry, strawberries, passion fruit, loquat, cantaloupe melon, grapes (5−6), custard apple, quince, dragon fruit, guava, coconuta, blueberriesa, pomegranatea. Lemon juice (lemonade)
Cereals and derivates	Wheat, whole wheat, semolina, couscous, barley, rye, (bread, flour and pasta based on these cereals). Oatsb, spelt flourb, brown rice, millet, amaranth, muesli, breakfast cereals	Rice, corn, quinoa, buckwheat, breakfast cereals, bread and pasta based on these cereals. Gluten-free products, buckwheat flour, cornstarch
Legumes/beans	White, pinto and black beans; fava beans, frijoles, lentils, chickpeas, peas, soybeans (and derived products)	Bean sprouts
Nuts and seeds	Pistachios, hazelnuts, chestnuts, cashews, dates	Peanuts and peanut butter, walnuts (small amounts), almonds (small amounts), pine nuts (1 tablespoon), pumpkin and sunflower seeds, chia
Milk and dairy products	Fresh milk (cow's, goat's and sheep's) and derivate dairy products, powdered milk, condensed milk, yoghurt, kefir, curd, butter and margarine, semi-cured and fresh cheeses, cream cheese, cream, ice cream, custards and cream fillings, desserts based on milk or cream	Lactose-free milk, lactose-free yogurt, lactose-free cheese, aged cheese (small amounts)
Meat and meat products	Cold cuts, processed meat products (check labelling), processed hamburgers (of any kind), sausages (of all kinds), cured meats	This food group does not naturally contain FODMAPs; however, it is important to read the labels
Fish, shellfish, mollusks, other seafood and derivates	Fish substitutes (check additives)	This food group does not naturally contain FODMAPs; however, it is important to read the labels
Other beverages	Commercial fruit juices, alcoholic beverages, soft drinks, chamomile, infusions containing FODMAP-rich fruits	Plant-based drinks made of almond, rice, hazelnut, quinoa, macadamia, oats and coconut (all in small amounts), horchata, canned coconut milk (in small amounts), coconut-based nondairy yogurt, tea (based on tolerance), coffee (based on tolerance), chocolate powder (mixed with water), kombucha (180 mL)
Other	Garlic and onion powder, and all the spices that contain them. Keep in mind that many processed foods contain onions (herb salt, powdered vegetables, dried vegetables, broths, meat sauces, soups, marinades, and other sauces), even if it is not stated on the label. Pastries (milk chocolate, white chocolate, biscuits and sugary cereals, whole-grain biscuits, ice cream, cakes) and candies.Fibre supplements: inulin, FOS	All spices except garlic and onion powder, popcorn, dark chocolate, pure cocoa powder
Artificial sweetenersc	Isomaltose E953.Any ending in -ol: lactitol E966, maltitol E965, mannitol E421, sorbitol E420i, sorbitol syrup (E-420ii), xylitol E967, erythritol E968.Corn or fructose syrup, agave, honey	Acesulfame K E950, aspartame E951, cyclamate E952, steviol glycosides E960, neohesperidin DC E959, neotame E961, saccharine E954, aspartame-acesulfame salt E962, thaumatin E957, sucralose E955.Moderate consumption: white sugar (sucrose), brown sugar, dextrose (glucose), maple syrup

a

Moderate consumption.

b

Tolerance of these cereals varies between individuals; personal tolerance must be assessed.

c

Check the labelling. Avoid light or "sugar-free" products and commercial sauces such as ketchup, barbecue sauce.

Source: adapted from Broekaert et al.,6 Huysentruyt et al.16 and IBS Research.17

Table 4.

Possible nutrient deficits associated with the low-FODMAP diet.

	Nutrients and compounds	Nutritional deficiency
F	Fermentable
O	Oligosaccharides: fructans, FOS (oligofructose) and GOS (raffinose, stachyose)	Reduced consumption of vegetables leads to a decreased intake of:
		• Fibre and natural antioxidants, such as flavonoids, carotenoids, and vitamin C, or phenolic acid (eg, wheat) and anthocyanins • Carbohydrates (eg, wheat products) • Iron (eg, due to reduced consumption of legumes)
D	Disaccharides (lactose)	Excluding dairy may result in vitamin D and calcium deficiency
M	Monosaccharides (fructose-free or with glucose excess)	Excluding fruits can lead to a reduction in natural antioxidants, such as flavonoids or vitamin C
A	And
P	Polyols (sorbitol, xylitol, maltitol)	Excluding vegetables and fruits can result in a reduction in natural antioxidants, such as flavonoids, carotenoids, and vitamin C, or phenolic acid and anthocyanins

Second phase: reintroduction of FODMAP-containing foods

Before starting the second phase, the team considers whether the previous phase has succeeded in alleviating the symptoms; if it has, FODMAP-rich foods are reintroduced in a planned schedule to determine which cause symptoms and which do not. The order in which the different FODMAP groups are reintroduced in children is the same as in adults and is presented in Table 5.

Table 5.

Order of FODMAP reintroduction.

Week	FODMAPa	Recommended food choicesb	Day 1c	Day 2c	Day 3c	Rest (low-FODMAP diet)
1	Lactose	MilkYoghurt (without sweetener or other FODMAP)	1/2 glass1 single-serve container	1 glass1.5 single-serve containers	1 glass and a half2 single-serve containers	4 consecutive days
2	Fructose	MangoHoney	½ mango1 Tbsp	Intermediate amount1,5 Tbsp	1 mango2 Tbsp	4 consecutive days
3	Polyols: sorbitol	BlackberriesAvocado	3 berries½ avocado	6 berriesIntermediate amount	10 berries1 avocado	4 consecutive days
4	Polyols: mannitol	CauliflowerButton mushrooms	½ cup½ cup	Intermediate amountIntermediate amount	1 cup1 cup	4 consecutive days
5	Fructose + sorbitol	ApplePear	½apple½ pear	Intermediate amountIntermediate amount	1 apple1 pear	4 consecutive days
6	FOS (wheat)	Whole wheat breadWhole wheat pasta (cooked)	1 slice½ cup	1.5 slices1 cup	2 slices1 ½ cup	4 consecutive days
7	FOS (onion/garlic)	Onion (raw)Garlic (raw)	½ cup½ clove	Intermediate amountIntermediate amount	½ onion1 clove	4 consecutive days
8	Galactans	Chickpeas (cooked)Almonds	½ cup5 almonds	Intermediate amountIntermediate amount	1 cup10 almonds	4 consecutive days

a

Appendix A-III details the total FODMAP content of fruits and vegetables.

b

Choose one of the two options.

c

If symptoms worsen during the challenge, do not increase the dose and wait 3–7 days to introduce a new food.

Source: adapted from Grez et al.5 to fit the dietary patterns of the Spanish population.

Each week, the indicated FODMAP is introduced for 3 days. For each FODMAP, the patient is given two choices of foods containing it and must pick only one of them, gradually increasing the amount consumed.14 During those days, a food and symptoms diary must be kept, recording the food item and the amount consumed per the prescription, in addition to any symptoms developed during or after its intake. This allows patients and/or the parents/guardians to identify specific FODMAP triggers and the dose at which they cause symptoms.8

After the 3 reintroduction days, the reintroduced foods are maintained in the diet at the tolerated dose for the remaining 4 days of the week while continuing with the previously prescribed low-FODMAP diet.

In patients that develop symptoms at any point in those 3 days, the dose should not be increased further or consumption of that food should be discontinued. After 4–7 days, once the symptoms resolve, another FODMAP can be introduced. Another possible approach is to continue reintroduction of the same food item the next day at half the dose or switching it to a different food containing the same FODMAP. If symptoms develop again after reducing the dose, it is likely that the patient will not be able to tolerate any foods in that FODMAP group well, so the patient should be advised to avoid them whenever possible.8,14Fig. 2 presents an algorithm for this process.

Figure 2.

Algorithm for the FODPAM reintroduction phase.

(0.28MB).

Thus, once the level of tolerance to different FODMAPs is established, their contents in the diet are adjusted to create a plan with the minimum possible restrictions to reduce the potential adverse effects on the gut microbiota, colonocyte metabolism and the patient’s long-term nutritional status.18 Anthropometric measurement during the follow-up is recommended, as patients tend to lose weight during this phase of treatment.4,5

Appendix A-II (Supplementary material) shows low-FODMAP plates to facilitate adherence during the reintroduction phase

We recommend starting with foods with the lowest FODMAP content. Appendix A-III (Supplementary material) details the amounts of FODMAP in some fruits and vegetables1 in increasing order. Using this information, patients can choose fruits that only have an excess of fructose, sorbitol, mannitol, fructose + sorbitol, etc. This is particularly helpful for the reintroduction of fructose, polyols and fructose + sorbitol.3

Table 6 presents a list of typical Spanish dishes that can be used to reintroduce foods after the elimination phase.12 However, the current evidence on the use of the low-FODMAP diet in Spain is scarce and hardly any local studies have estimated the feasibility and effectiveness of this strategy in reducing symptoms and improving health-related symptom reduction and quality of life in patients in Hispanic countries (Spain and Spanish-speaking countries in Latin America).12

Table 6.

Examples of typical Spanish dishes that can be reintroduced after the elimination phase of the low-FODMAP diet.

Food	Dish
Wheat	Toasted wheat bread with serrano ham and tomato
Asparagus	Grilled vegetables (asparagus, courgette, aubergine, fresh tomato) with cubed serrano ham
Onion	Spanish omelette with potato and onion
Lentils	Lentils stewed with potato and carrot

Source: adapted from Garicano et al.12

Third phase: personalization

This phase concerns the use of a long-term dietary plan individualised according to the needs, tolerance, culture and preferences of the patient that is more varied and less restrictive and excludes only those FODMAPs that cause symptoms.

If there is no improvement in symptoms, other possible causes need to be considered.8 It is important that the patient remains in follow-up during this phase, although keeping a food and symptoms diary is no longer necessary.

Since the low-FODMAP diet is quite restrictive, one of the associated risks is compromised nutrition; there is also evidence that patients may lose weight.5 Due to the decreased consumption of dairy, calcium levels and bone health should be monitored. However, calcium levels can be maintained through the consumption of lactose-free dairy products10 and/or consumption of other foods (such as sesame).18

The evidence regarding fibre intake is contradictory, as some studies show that it decreases due to the restriction of cereals, legumes and beans, while others have found no changes in fibre intake. As is the case of other restrictive diets, patients may end up having low or deficient levels of some micronutrients, such as vitamins (vitamin D or B vitamins) and natural antioxidants (flavonoids and carotenoids).18

There is no question that the role played by a specialist, the dietitian/nutritionist, is crucial for the successful management of the patient, as it promotes the implementation of and adherence to a more balanced diet.4 The dietary plan must be personalised based on the individual tolerance of each patient aiming at achieving balanced nutrition. While treatment is ongoing, it is important to assess and promote adherence.5 Long-term adherence may be harder to achieve and can cause difficulties in the social life of the patient. Thus, it is important to provide guidance through nutritional and dietary education, with an emphasis on lifestyle and dietary habits and the identified needs of the patient, helping the patient learn and develop skills that will allow them to improve their own quality of life. Keeping daily records of dietary intake and symptoms can help identify foods that worsen clinical manifestations.7 Appendix A-IV (Supplementary material) provides dietary advice and recommendations for eating outside the home.

The narrative review allowed drawing the following conclusions:

• none-

  The low-FODMAP diet is restrictive and must be supervised by a multidisciplinary team of experts in child nutrition.

• none-

  If there is no clinical response within 3 weeks, the diet should not continue.

• none-

  The tolerance to each food may vary between individuals and based on the clinical picture. In consequence, dietary recommendations must be personalised in terms of the type, amount and cooking/preparation of the foods.

• none-

  The diet is structured into 3 phases; phase 1 lasts 2–3 weeks; phase 2 lasts 8 weeks and, lastly, phase 3 (the personalization phase) is of variable duration. The total duration of the diet is usually of 2–3 months.

• none-

  Although several studies have shown that the low-FODMAP diet can improve symptoms in certain GI disorders, there is little evidence in the paediatric population. Therefore, high-quality studies need to be conducted before a consensus can be reached on the use of this diet in paediatric clinical practice.

• none-

  Further studies with controls need to be conducted to assess the prolonged use (several months or longer) of the low-FODMAP diet and its impact on GI symptoms and physiology and gut microbiota composition and function. Such studies are essential to guarantee the long-term efficacy and safety of this dietary intervention.

This research project did not receive specific financial support from funding agencies in the public, private or not-for-profit sectors.

The authors have no conflicts of interest to declare.