Food hypersensitivity, affecting approximately 15%-20% of the global population, encompasses a wide array of non-immune adverse reactions to food with varying causes. These hypersensitivities are believed to be triggered by metabolic factors (such as enzyme deficiencies like lactose malabsorption), pharmacological factors (sensitivity to natural or artificial food chemicals), or undefined/idiopathic mechanisms. Symptoms can manifest immediately or be delayed. Common gastrointestinal symptoms include diarrhoea, bloating, vomiting, nausea, abdominal cramping, and pain. Extraintestinal symptoms can affect the nervous system (headache, migraine, fatigue), skin (urticaria, rash, eczema, swelling, mouth ulcers), and respiratory system (nasal congestion, mucous, asthma). Currently, there are no definitive biological markers to diagnose food hypersensitivity.
This article delves into the Royal Prince Alfred Hospital (RPAH) Elimination Diet Protocol, a dietary approach used in Australia since the 1980s, also known as "The Elimination Diet" or "FAILSAFE" diet, to manage food hypersensitivity.
Understanding Food Hypersensitivity
Food hypersensitivity is prevalent in conditions like irritable bowel syndrome (IBS), chronic urticaria, and aspirin-exacerbated respiratory disease (AERD). Reactions can occur in response to various foods and components, including lactose, fructose, wheat, fermentable carbohydrates (FODMAPs), caffeine, and naturally occurring (salicylates, glutamates, vaso-active amines) or added food chemicals (monosodium glutamate (MSG), propionates).
Salicylate hypersensitivity may involve pseudo-allergic reactions, where salicylate ingestion inhibits the cyclo-oxygenase (COX) enzyme, reducing anti-inflammatory prostaglandins and increasing pro-inflammatory mediators. Histamine hypersensitivity is thought to arise from an imbalance between histamine intake and the body's ability to break it down. MSG hypersensitivity has been linked to its potential neurotoxic and neuroexcitatory effects.
The RPAH Elimination Diet: An Overview
Food hypersensitivity cannot be cured, but symptoms can be managed through dietary elimination and subsequent reintroduction of suspected trigger foods. The RPAH Elimination Diet is a low-chemical diet that involves a Restrictive Phase followed by a Rechallenge Phase.
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Restrictive Phase
The Restrictive Phase involves short-term restriction (at least 2 weeks) of specific food chemical components and dietary additives. The dietitian determines the level of restriction (simple, moderate, or strict) based on symptom patterns and patient preference, potentially including restrictions on wheat, dairy, and soy.
Rechallenge Phase
The Rechallenge Phase begins after symptom improvement or resolution. It involves systematically reintroducing food chemical components in graduated amounts to assess tolerance and develop an individualized diet.
Aims and Concerns
The low-chemical diet is a lengthy intervention with limited supporting data. Concerns exist about prolonged, unnecessary dietary restriction and nutritional inadequacy, especially without expert monitoring. A retrospective clinical file audit was conducted to:
- Evaluate whether the low-chemical diet improves gastrointestinal or extraintestinal symptoms and identify which symptoms are alleviated.
- Evaluate whether challenges with specific food chemical components induce symptoms to determine individual food triggers.
Study Protocol and Methods
A retrospective chart review was conducted on patients referred to an Australian dietetic clinic between January 2011 and December 2022. Patients eligible for inclusion had documented use of the low-chemical diet, including the Restrictive and/or Rechallenge Phases. The allergist recommended that all patients follow a low-chemical diet and the allergy clinic's practice manager guided implementation of the Restrictive Phase. Referrals were then made to the dietetic clinic for help with the Rechallenge Phase of the diet.
Electronic medical records were screened for eligibility, de-identified, and relevant data extracted, including patient demographics, appointment details, and clinical notes. Outcome measures included Restrictive Phase implementation and duration, adherence, symptom improvement, and specific symptoms improved. Rechallenge Phase outcomes included implementation, duration, number of challenges, symptom provocation, and identification of specific food triggers.
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Quantitative data were presented as mean or median and range for continuous data and counts and proportions for categorical data. Data analyses were calculated using Microsoft Excel and heatmaps were generated using GraphPad Prism.
Study Results
Out of 53 patient files accessed from 2011 to 2022, 50 were audited, and 3 were excluded because they did not involve the use of a low-chemical diet. The majority of patients were female (80%) and ranged in age from 7 to 85 years (median 49 years). The most common presenting complaint at initial assessment was IBS, reported by 20% of patients. The most common gastrointestinal symptoms at baseline were diarrhoea (44%), constipation (32%), bloating (30%), and abdominal pain (26%). Extraintestinal symptoms of nasal congestion (28%), fatigue/lethargy (22%), and itch (20%) were also commonly reported at baseline. Baseline symptom duration were documented in 54% of patient files and ranged from 6 months to “most of their life” that is, > 50 years. Patients attended a median of 5 (range 3-15) food chemical‐specific dietitian appointments.
Restrictive Phase Outcomes
All patients completed the Restrictive Phase, lasting from 2 to 78 weeks (median 6.5 weeks). Most patients (66%) adhered to the Restrictive Phase 'all of the time', while 26% adhered 'most of the time'. 88% of patients reported improvement in at least one symptom. 44% reported a significant improvement in their 'overall' symptoms. The individual symptoms that were most significantly improved included sinus/nasal pain/inflammation (8% of the total sample). Constipation (20% of the total sample) was most often reported to be 'not at all' improved following the Restrictive Phase.
Rechallenge Phase Outcomes
All patients were educated by a dietitian for the Rechallenge Phase, which ranged from 5 to 191 weeks (median 39.5 weeks). Patients completed 3 to 20 challenges (median 10.5), with 0 to 7 challenges planned but incomplete (median 2). 96% of patients reported symptom provocation following at least one food challenge.
Regarding gastrointestinal symptom provocation during the challenges, diarrhoea and bloating were most commonly reported following challenges with salicylates (each 16%), amine (cheese) (each 8%), and dairy (6% and 10% respectively), while wheat also provoked bloating in 6% of patients. Gas was most reported following challenges with salicylates (12%), amine (banana) (8%), metabisulphites (6%), and propionate (6%).
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Regarding extraintestinal symptom provocation during the challenges, symptoms of itch were most commonly reported following challenge with salicylates (14%), amine (chocolate) (8%), and fish (8%); headache was also reported following challenge with salicylates (12%) and fish (10%), as well as glutamate (6%), dairy (6%), and metabisulphites (6%). Fatigue/lethargy and difficulty sleeping were both most reported following salicylate challenge (9% and 7% respectively). Cough was most reported following challenge with salicylates (8%), amines (cheese) (8%), and egg (8%). Post-nasal drip was most common following salicylate (6%), amine (chocolate) (6%), and dairy (6%) challenges, while nasal congestion was also provoked by amine (chocolate) (6%), as well as antioxidants (6%).
The low-chemical diet provided a clear indication of specific dietary triggers for 64% of patients, with salicylates being the most common trigger of both gastro- and extraintestinal symptoms. For 8% of patients, the Rechallenge Phase did not provide a clear indication of specific triggers. For the remaining 28% of patients, it was unclear whether symptoms were related to food chemical components or other dietary triggers (i.e., FODMAPs), non-diet factors such as psychological stress, COVID-19 pandemic, environmental factors (e.g., season, weather, hay fever, fumes, air-conditioning), concurrent illness (e.g., common cold, shingles, Kawasaki disease, fibromyalgia, gastroenteritis.
Natural Food Chemicals and Intolerance
Food chemicals are naturally found in many everyday foods, with significant variation in their makeup. The most common natural chemicals are salicylates, amines, and glutamate.
- Salicylates: Found in plants, fruits, vegetables, nuts, tea, coffee, honey, herbs, spices, flavorings, and most alcohols. Levels decrease as food ripens and are highest in the skin.
- Amines: Products of protein breakdown or fermentation, found in meats, cheese, fish products, fruits, vegetables, and many alcoholic beverages. Levels increase with ripening.
- Glutamate: An amino acid present in most foods as a building block for proteins. It enhances flavors and is found in cheese, tomato, mushrooms, meat and yeast extracts, soy sauce, and stock cubes.
Natural food chemical sensitivity or intolerance occurs when these chemicals cause symptoms by irritating nerve endings. Symptoms are dose-dependent, and small amounts may not cause immediate reactions. Since these chemicals are in many foods, they can accumulate over time.
Management and the Elimination Diet
Management depends on individual thresholds. Those with low thresholds are advised to avoid large doses and follow a low-chemical diet. An elimination diet is crucial for diagnosing food intolerances, as there are no reliable skin or blood tests. It helps identify which foods can be safely consumed and which trigger symptoms.
The RPAH Allergy Unit has developed a specific elimination diet for investigating and managing suspected food intolerances. It's followed for at least 2 weeks, but symptoms may take 6-8 weeks to settle. The diet involves restricting high food chemical foods to determine if symptoms decrease. The reintroduction of food chemicals is done systematically to ensure clear and accurate results.
Considerations and Alternatives
A low-chemical elimination diet is often recommended for those who haven't found significant improvement with a low FODMAP diet, which targets fermentable carbohydrates in IBS management. While a low FODMAP diet can improve gut symptoms in up to 75% of people with IBS, an elimination diet focuses on chemicals found in foods.
It is very important to remember that an elimination diet should only be completed under the supervision on an APD and only for a short amount of time. This is due to the fact that people following a restrictive diet, such as an elimination diet, are more at risk of nutrient deficiencies.
The FAILSAFE Diet
The FAILSAFE diet is also called the RPAH diet and tests for food chemical intolerances. Food chemicals can be naturally occurring or added during processing and are different from FODMAPs or gluten. Some people may also have histamine intolerance, meaning they may not have enough of the enzyme diamine oxidase, which breaks down histamine. Certain preservatives can produce sulphur dioxide and hydrogen sulphide, potentially causing hypersensitive reactions.
Who Should Try the FAILSAFE Diet and Does It Work?
If you have tried a low FODMAP diet properly and are still experiencing symptoms then you should consider the FAILSAFE diet. After consulting with your dietitian or referring to the RPAH Elimination Diet Handbook, based on your symptoms you can decide to follow the strict, moderate or simple version of the diet.
If you eliminated dairy and wheat in the first step, you will rechallenge these first. Next, move on to salicylates and amines, because they are present in the most amount of foods. If your reactions are severe, you can do challenges with a doctor or dietitian using capsules containing concentrated amounts of each food chemical. You will need to minimise the amount of the reactive food chemical in your diet.
Practical Tips for Managing Food Intolerance
- Keep a detailed food diary: Record everything you eat, along with any symptoms and their severity.
- Be patient: Finding the right approach can take time and experimentation.
- Seek professional help: A dietitian trained in food intolerance can provide valuable guidance and monitor your nutritional status.
- Establish a baseline: Ensure you have a good baseline level of symptom control before reintroducing foods.