Evidence-Based Dietary Management of Functional Gastrointestinal Symptoms

Abstract and Introduction

Abstract

Background and aim: Functional gastrointestinal symptoms are common and their management is often a difficult clinical problem. The link between food intake and symptom induction is recognized. This review aims to describe the evidence base for restricting rapidly fermentable, short-chain carbohydrates (FODMAPs) in controlling such symptoms.
Methods: The nature of FODMAPs, their mode of action in symptom induction, results of clinical trials and the implementation of the diet are described.
Results: FODMAPs are widespread in the diet and comprise a monosaccharide (fructose), a disaccharide (lactose), oligosaccharides (fructans and galactans), and polyols. Their ingestion increases delivery of readily fermentable substrate and water to the distal small intestine and proximal colon, which are likely to induce luminal distension and induction of functional gut symptoms. The restriction of their intake globally (as opposed to individually) reduces functional gut symptoms, an effect that is durable and can be reversed by their reintroduction into the diet (as shown by a randomized placebo-controlled trial). The diet has a high compliance rate. However it requires expert delivery by a dietitian trained in the diet. Breath hydrogen tests are useful to identify individuals who can completely absorb a load of fructose and lactose so that dietary restriction can be less stringent.
Conclusions: The low FODMAP diet provides an effective approach to the management of patients with functional gut symptoms. The evidence base is now sufficiently strong to recommend its widespread application.

Introduction

Functional gastrointestinal disorders (FGID) are very common and present as major challenges for clinicians, particularly as pharmaceutical therapies offer little more than mild palliation in the vast majority of patients. The symptoms can markedly interfere with quality of life and rank second in the causes of absence from work or school.^[1] While the predominant underlying cause of symptoms appears to reside in the enteric nervous system, manifesting as visceral hypersensitivity and/or motility disturbances, multiple other factors contribute to symptoms generation, including psychological factors and diet. Consequently, treatment has spanned multiple modalities and has involved a variety of health professionals, including medical practitioners, psychologists, hypnotherapists, dietitians and naturopaths, each bringing a different perspective. A major limitation has been the limited evidence base for many therapies, not helped by the considerable placebo response seen in these disorders. However, dietary therapy, specifically the low FODMAP diet (see below for explanation), has now emerged as a key player with a well-substantiated mechanism of action and evidence-based efficacy. This review will describe the theoretical basis for the diet, the evidence for efficacy and its implementation, and it will address unanswered questions.

Table 1. Food sources of FODMAPs (where FODMAPs are problematic based on standard serving size) and suitable alternatives
FODMAP	Excess fructose	Lactose	Oligosaccharides (fructans and/or galactans)	Polyols
Problem high FODMAP food source	Fruits: apples, pears, nashi pears, clingstone peaches, mango, sugar snap peas, watermelon, tinned fruit in natural juice Honey Sweeteners: fructose, high fructose corn syrup Large total fructose dose: concentrated fruit sources; large serves of fruit, dried fruit, fruit juice	Milk: cow, goat and sheep (regular & low-fat), Ice cream Yoghurt (regular & low-fat) Cheeses: soft & fresh (e.g. ricotta, cottage)	Vegetables: artichokes, asparagus, beetroot, Brussels sprout, broccoli, cabbage, fennel, garlic, leeks, okra, onions, peas, shallots. Cereals: wheat & rye when eaten in large amounts (e.g. bread, pasta, couscous, crackers, biscuits) Legumes: chickpeas, lentils, red kidney beans, baked beans Fruits: watermelon, custard apple, white peaches, rambutan, persimmon	Fruits: apples, apricots, cherries, longon, lychee, nashi pears, nectarine, pears, peaches, plums, prunes, watermelon Vegetables: avocado, cauliflower, mushrooms, snow peas Sweeteners: sorbitol(420), mannitol(421), xylitol(967), maltitol (965), isomalt (953) & others ending in '-ol'
Suitable alternative low-FODMAP food source	Fruit: banana, blueberry, carambola, durian, grapefruit, grape, honeydew melon, kiwifruit, lemon, lime, mandarin, orange, passionfruit, paw paw, raspberry, rockmelon, strawberry, tangelo. Honey substitutes: maple syrup, golden syrup Sweeteners: any except polyols	Milk: lactose-free, rice milk Cheese:'hard' cheeses including brie, camembert Yoghurt: lactose-free Ice cream substitutes: gelati, sorbet Butter	Vegetables: bamboo shoots, bok choy, carrot, celery, capsicum, choko, choy sum, corn, eggplant, green beans, lettuce, chives, parsnip, pumpkin, silverbeet, spring onion (green only), tomato Onion/garlic substitutes: garlic-infused oil Cereals: gluten-free & spelt bread/cereal products	Fruits: banana, blueberry, carambola, durian, grapefruit, grape, honeydew melon, kiwifruit, lemon, lime, mandarin, orange, passionfruit, paw paw, raspberry, rockmelon Sweeteners: sugar (sucrose), glucose, other artificial sweeteners not ending in 'ol'

Table 1. Food sources of FODMAPs (where FODMAPs are problematic based on standard serving size) and suitable alternatives

FODMAP

Excess fructose

Lactose

Oligosaccharides (fructans and/or galactans)

Polyols

Problem high FODMAP food source

Fruits: apples, pears, nashi pears, clingstone peaches, mango, sugar snap peas, watermelon, tinned fruit in natural juice
Honey
Sweeteners: fructose, high fructose corn syrup
Large total fructose dose: concentrated fruit sources; large serves of fruit, dried fruit, fruit juice

Milk: cow, goat and sheep (regular & low-fat), Ice cream
Yoghurt (regular & low-fat)
Cheeses: soft & fresh (e.g. ricotta, cottage)

Vegetables: artichokes, asparagus, beetroot, Brussels sprout, broccoli, cabbage, fennel, garlic, leeks, okra, onions, peas, shallots.
Cereals: wheat & rye when eaten in large amounts (e.g. bread, pasta, couscous, crackers, biscuits)
Legumes: chickpeas, lentils, red kidney beans, baked beans
Fruits: watermelon, custard apple, white peaches, rambutan, persimmon

Fruits: apples, apricots, cherries, longon, lychee, nashi pears, nectarine, pears, peaches, plums, prunes, watermelon
Vegetables: avocado, cauliflower, mushrooms, snow peas
Sweeteners: sorbitol(420), mannitol(421), xylitol(967), maltitol (965), isomalt (953) & others ending in '-ol'

Suitable alternative low-FODMAP food source

Fruit: banana, blueberry, carambola, durian, grapefruit, grape, honeydew melon, kiwifruit, lemon, lime, mandarin, orange, passionfruit, paw paw, raspberry, rockmelon, strawberry, tangelo.
Honey substitutes: maple syrup, golden syrup
Sweeteners: any except polyols

Milk: lactose-free, rice milk
Cheese:'hard' cheeses including brie, camembert
Yoghurt: lactose-free
Ice cream substitutes: gelati, sorbet
Butter

Vegetables: bamboo shoots, bok choy, carrot, celery, capsicum, choko, choy sum, corn, eggplant, green beans, lettuce, chives, parsnip, pumpkin, silverbeet, spring onion (green only), tomato
Onion/garlic substitutes: garlic-infused oil
Cereals: gluten-free & spelt bread/cereal products

Fruits: banana, blueberry, carambola, durian, grapefruit, grape, honeydew melon, kiwifruit, lemon, lime, mandarin, orange, passionfruit, paw paw, raspberry, rockmelon
Sweeteners: sugar (sucrose), glucose, other artificial sweeteners not ending in 'ol'

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