Introduction
An elimination diet is a commonly utilized dietary approach in which a particular food or group of foods is removed from the diet. Elimination diets can be employed to identify and treat food intolerances, food allergies, and other disorders, such as urticarial disease, eosinophilic esophagitis, irritable bowel syndrome, or migraine headaches.[1][2][3][4]
The specific protocol that guides each elimination diet is dictated by the presenting symptoms or established disease process. The elimination process can either be directed by food allergen testing or instituted empirically.[5][6] Highly regimented elimination diets exist, including the gluten-free diet and the low-FODMAP (Fermentable Oligo-, Di-, Monosaccharides, and Polyols) diet. For severe food-related reactions, such as anaphylaxis, other diagnostic avenues, including skin prick tests, serum-specific IgE measurements, or component-resolved diagnostics, can be employed before an elimination diet with oral food challenges is pursued.[7]
Elimination diets have proven efficacy in symptom control and patient satisfaction in various disease processes and are backed by various randomized control trials and observational studies.[8][9][10] This activity reviews commonly utilized elimination diets, the disease processes they may help identify and treat, the limitations of such diets, and the optimal approach to improving patient outcomes through their implementation.
Function
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Function
Elimination diets have proven diagnostic and therapeutic for patients with food allergies or intolerances.[11] Elimination diets also benefit individuals with functional gastrointestinal (GI) disorders, such as irritable bowel syndrome (IBS), which are often triggered by particular foods.[12]
Several approaches to food elimination are utilized in clinical practice; the six-food elimination diet (6-FED) is the most frequently employed approach. The 6-FED comprises 3 distinct steps.
- Step 1: The empiric elimination of the 6 most frequently implicated food allergens: milk, eggs, soy, wheat, nuts, including tree nuts and peanuts, and fish, including shellfish.
- Step 2: Maintain elimination of these food groups for 4 to 6 weeks while monitoring for symptom resolution.
- Step 3: Slowly reintroduce each food group into the diet to identify the culprit that exacerbates symptoms. Once the offending agent is identified, eliminate it from the diet.[6]
One-food, 2-food, and 4-food elimination diets have also been employed similarly to the 6-FED. A 1-food elimination diet removing animal milk has proved comparable to the 6-FED in achieving histological remission in patients with eosinophilic esophagitis.[13] Another approach is eliminating specific food products, such as the low-FODMAP diet for IBS or the gluten-free diet for celiac disease. General elimination diets eliminate and subsequently identify particular foodstuffs associated with symptoms to facilitate arriving at a specific diagnosis. Once a formal diagnosis is made, strictly avoiding the offending food until symptom control is maintained becomes the primary focus.
Issues of Concern
Elimination diets are detail-oriented; multiple barriers to optimal compliance exist. Medical literacy, socioeconomic status, unvarying food choices, and anxiety regarding diets all contribute to incomplete adherence.[14]
Restricted diets can cause nutritional deficiencies. This has been demonstrated in children adhering to elimination diets and in adults with inflammatory bowel disease who choose to exclude major food groups under the preconceived notion that certain foods exacerbate their disease state.[15][16] Patients who follow a strict gluten-free diet are reported to consume less iron, fiber, and carbohydrates than their previous gluten-containing diet.[17] Individuals on a low-FODMAP diet have demonstrated lower calcium intake than controls consuming a standard diet, possibly secondary to the reduced intake of carbohydrates, specifically the disaccharide lactose, a component of calcium-rich dairy products.[18] The low-FODMAP diet has also been shown to alter the gut microbiome, reducing the concentration of bifidobacteria, possibly secondary to the reduced intake of complex carbohydrates and fiber. The long-term impact of this alteration is yet to be determined.[19] Nutritional education is of utmost importance when implementing an elimination diet, as inadequate intake of vitamins and minerals, depending on the specific foods eliminated, can ensue.[20]
Clinical Significance
Food allergies are common and are estimated to affect 3% to 4% of adults and up to 6% of children in the United States. Statistics vary by region and ethnicity; certain populations have a much higher incidence of food allergies.[21][22] Employing an elimination diet with oral food challenges in patients with allergies and intolerances can be a cost-effective and noninvasive method of identifying trigger foods.
Celiac disease is a condition for which the complete elimination of dietary gluten is the mainstay of treatment. The serological prevalence of this disease is estimated at 1.4%, and the biopsy-proven prevalence is 0.7% globally.[23] Remission of this enteropathy is maintained with sustained elimination of gluten-containing food products from the diet. Cross-contamination with gluten-containing food products must also be avoided, as all gluten must be eliminated to allow intestinal healing.[24]
The prevalence of eosinophilic esophagitis is increasing and is estimated at 0.5 to 1 per 1000 people. In North America, eosinophilic esophagitis is present in 2% to 7% of patients who undergo esophagogastroduodenoscopy (EGD) for any indication and in 12% to 23% of patients who undergo EGD to evaluate dysphagia.[25] A stepwise or 6-FED elimination diet is an excellent diagnostic and therapeutic tool for removing inciting allergens, improving symptoms, and facilitating overall disease management.
Patients with IBS frequently benefit from an elimination diet. Symptoms of IBS are common, but the actual disease prevalence varies by country and the formal diagnostic criteria utilized. An 11.2% pooled prevalence was reported across 80 different study cohorts totaling 260,960 patients, though the individual prevalence for each country ranged from 1.1% to 45%.[26] IBS is a commonly encountered clinical disorder, but it is a diagnosis of exclusion; a comprehensive evaluation must be pursued to rule out more severe organic conditions, such as inflammatory bowel disease or celiac disease. Once more severe pathologies have been eliminated through laboratory evaluation or endoscopy, a specific elimination diet, such as the low-FODMAP diet, can be prescribed.[27] Patients following a low-FODMAP diet to manage IBS are advised to eliminate gluten-containing grains, including wheat, barley, and rye; specific fruits, such as cherries, peaches, and apricots; and certain cruciferous vegetables.[28]
Enhancing Healthcare Team Outcomes
Achieving desirable results with an elimination diet is best accomplished with an interprofessional approach. Patients with food allergies or gastrointestinal complaints frequently present to the primary care practitioner, who should obtain a comprehensive medical history and perform a thorough physical examination. The medical history must include a detailed account of the present illness, past medical and surgical history, family history, current medications, and social determinants of health. Guideline-directed medical care should be implemented according to the needs of each patient. Pathologies mimicking the presenting symptoms should be ruled out before assuming a food allergy or intolerance. An elimination diet can be a powerful diagnostic and treatment tool but cannot replace a comprehensive, guideline-directed evaluation. Clinicians must understand the limitations and appropriateness of elimination diets and how to avoid pitfalls that can lead to failure.
Once an elimination diet is prescribed, ensuring the patient understands the specific instructions and goals of the regimen is essential. Registered dieticians can improve patient education by assessing understanding and offering comprehensive dietary instructions. Dieticians can instruct patients on how to read food labels, which specific foods to avoid, and how to avert nutritional deficiencies. The clinical nursing and support staff are also integral to the success of an elimination diet by gathering valuable information about patient compliance, at what elimination or reintroduction stage or step the patient is currently in, and changes in symptomatology. Social workers are essential in cases where barriers to compliance with prescribed elimination diets must be addressed, including socioeconomic status, restricted access to necessary food resources and information, and harmful perceived attitudes toward elimination diets.[14] Elimination diets can be complicated for patients, who may struggle to follow the recommendations. An interprofessional team approach to each patient can optimize treatment, improve outcomes, and provide long-term symptom relief.
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