Functional Gastrointestinal Disorders

Common pathophysiology: brain-gut axis

• Bloating
• Dyschiosis
• Inflammation
• Enteric Nervous System (ENS) dysfunction: visceral hypersensitivity

Irritable Bowel Syndrome

The most common chronic gastrointestinal disorder is irritable bowel syndrome (IBS) affecting 10- 15% of the community. It is a major cause for absenteeism and presenteeism and is associated with increased healthcare utilisation. Despite its importance, management of IBS has been unsatisfactory, beyond the use of placebo (an essential part of our management). The good news is that the therapeutic landscape for IBS is changing and new strategies, mostly involving active participation of the patients, are efficacious in the majority of patients.

Dietary approaches are being demanded by patients as they know that food induces symptoms. The low FODMAP (fermentable, oligosaccharide, disaccharide, monosaccharide, and polyol) diet is the first approach with the full hand of 1) proven pathogenic mechanisms; 2) high quality evidence for efficacy (3 out of 4 patients) from multiple countries with positive similar real-world experience; 3) dietitians with expertise in the delivering the diet; 4) excellent implementation tools (e.g., the Monash University Low FODMAP Diet digital app; and 5) incorporation of the diet into guidelines. Other diets commonly applied include the gluten-free diet (has efficacy, but it is not the gluten that causes the problem) and the low chemical diet (nutritionally and psychosocially challenging, and underpinned by ideas rather than deep science). The use of functional foods and fibre supplements is a poor substitute for better food choice, and carries little in the way of evidence for efficacy.¹

What can I eat on the low-FODMAP diet?

Certain fruits, vegetables, grains and proteins are higher and lower in FODMAPs. Some are OK to eat in limited amounts but will bother you in larger amounts. For example, most legumes and processed meats are high in FODMAPs, but plain-cooked meats, tofu and eggs are low-FODMAP protein sources. Apples, watermelon and stone fruits are high in FODMAPs, but grapes, strawberries and pineapples are OK. A ripe banana is high in fructose, but you can have up to a third cut up in your cereal, or you can have a whole one if it’s not quite ripe. Your dietician can help provide you with these kinds of specific guidelines for your diet.

Low FODMAP Diet, Cleveland Clinic

Psychotherapeutic approaches such as cognitive behaviour therapy (CBT), gut-directed hypnotherapy (GDH) and mindfulness behavioural therapy MBT) have good evidence for efficacy in 50-75% of patients with IBS (anxiety, depression, somatisation). A recent randomised comparative study of GDH with the low FODMAP diet showed similar efficacy for the gut symptoms; but GDH offered longer term benefits on psychological health. The limitations of such therapy are largely related to the skill-base available, but such approaches have the performance to be front-line, not rescue therapies. (Autonomic output e.g. CRF).¹

Manipulating the microbiota has become a popular concept, but desirability and evidence fall behind the dogma. Low FODMAP diet reduces the substrate availability for microbes to ferment, a major, but not the only mechanism by which this diet works. Antibiotics (specifically rifaximin) do have proven efficacy in some with non-constipation-predominant IBS, but is an unattractive option for public health and the environment. Probiotics have offered promise that has yet to be converted into high quality evidence for benefit, and their appeal is mostly based upon unproven concepts and safety. Prebiotics are devoid of good evidence for benefit (and may increase symptoms). Faecal microbiota transfer/transplantation has few efficacy data in IBS and has potential long term issues that have yet to be addressed. There are now available many tests associated with microbiota that purport to help individualise therapy. These include faecal analyses of microbiota and soluble factors, breath hydrogen testing for specific carbohydrate malabsorption and small intestinal bacterial overgrowth, and several other unvalidated tests. None of these are of current value in personalising therapeutic approaches. They should be avoided in general.¹

Paradigms of management of patients with IBS have changed with now a team approach involving the GP, dietitian, psychologist, nurse, gastroenterologist and, most importantly, the patient.

Food intolerance

Histamine toxicity – anaphylactoid reaction:

• Cheese
• Wines
• Fish – e.g. tuna, mackerel: especially bacterial contamination in fish not refrigerated properly

Food additives – sensitivity:

• Flavour enhancers: MSG  flushing, warmth, light-headed, headache or facial pressure, chest pain, feelings of def
• Colours: yellow dye #5  hives (rare)
• Preservatives: sulfites (previously used as spray-on preservative for fresh fruit and vegetables and during wine fermentation)  bronchospasm

Consumption of a large amount of these can produce symptoms that mimic the entire range of allergic symptoms.

Food poisoning – bacteria ± toxins from contaminated eggs, salad, milk, meat:

• Bacteria can produce symptoms that mimic food allergy

Differential diagnosis – other systemic reactions:

• Heart attack
• Panic attack
• Choking / seizure

True allergic reactions to foods occur in ~ 1-2% of Australians. True allergic reactions are characterised by:

• Hives
• Atopic dermatitis
• Asthma: especially infants / children
• Gastrointestinal symptoms:
  • Nausea, vomiting, diarrhoea
  • Red rash around mouth (or peri-oral dermatitis)
  • Itching / swelling mouth / throat
  • Stomach bloating / gas

Who to inform?

For patients with true allergy, family members, health care workers, employers or school personnel may all need to be informed about the health related risks from their exposure to allergen.

Generally, inhaled allergens such as dust mites, tree, grass, or weed pollens will produce respiratory symptoms and ingested (food) allergens will produce skin and/or Git symptoms or anaphylaxis; but both these types of allergens (ingested and inhaled) can produce the spectrum of allergy symptoms.

Common Inhaled Allergens:

• Products from dust mites
• Proteins from furry pets
  • Skin secretions (dander)
  • Saliva
  • Urine
• Moulds in home/air outside
• Tree, grass, and weed pollen
• Cockroach droppings

Testing:

• Skin-prick testing
• Intradermal
• Blood (RAST)

Total IgE antibodies may be raised in people with allergies. High blood eosinophil counts are seen in people with asthma, allergic rhinitis, and eczema, as well as other less common allergic conditions. Radioallergosorbent test (RAST) is a way of testing blood to help confirm an allergy by looking for antibodies to specific substances. An extended RAST Food Panel, for instance, will test for antibodies to the following food allergens: Almond; Avocado; Banana; Cashew; Codfish; Egg white; Hazelnut; Kiwifruit; Macadamia nut; Mango; Milk (cow); Peanut; Rice; Sesame seed; Shrimp (prawn); Soybean; Walnut; and Wheat.³

References

1. Peter Gibson Irritable Bowel Syndrome – Management with Diet, Psychotherapy and Microbiome The General Practice Education Day, Sydney 2017.
2. Marilia Carabottia, Annunziata Sciroccoa, Maria Antonietta Masellib, and Carola Severia. “The gut-brain axis: interactions between enteric microbiota, central and enteric nervous systems.” Annals of Gastroenterology (2015); 28: 203-9.
3. Allergy testing. Sullivan Nicolaides Pathology. https://www.snp.com.au/patients/patient-resources/patient-education/allergy-testing/.
4. Dulashi Withanage Dona and Cenk Suphioglu, “Egg Allergy: Diagnosis and Immunotherapy.” Int. J. Mol. Sci. 2020, 21(14), 5010; https://doi.org/10.3390/ijms21145010.