Food Sensitivities vs Allergies: A Nutritional Perspective

Food Sensitivities vs Allergies: A Nutritional Perspective?

Understanding Food Allergies, Intolerances, and Sensitivities:

1. Introduction

Food allergies, intolerances, and sensitivities represent a range of adverse reactions to foods that vary greatly among individuals. These reactions can be immunological (true food allergies) or non-immunological (food intolerances and sensitivities). Understanding the nature of these reactions is crucial for dietary management, particularly in identifying and avoiding trigger foods.

2. Food Allergies

• Definition: True food allergies are abnormal immune responses to specific food components, typically proteins, that are generally harmless to the majority of the population. These reactions are mediated by the immune system and involve the production of specific antibodies, particularly Immunoglobulin E (IgE).
• Types of Food Allergies:
• Immediate Hypersensitivity Reactions (IgE-mediated):
• Mechanism: Involves the rapid onset of symptoms, usually within minutes to an hour after consuming the allergenic food. The immune system produces IgE antibodies specific to the allergen, leading to the release of histamine and other mediators from mast cells and basophils.
• Symptoms: Can include hives, swelling, respiratory distress, and gastrointestinal symptoms. In severe cases, anaphylaxis can occur, which is a life-threatening condition requiring immediate medical attention.
• Delayed Hypersensitivity Reactions (Non-IgE-mediated):

• Mechanism: Symptoms develop 24 hours or more after ingesting the allergen, involving sensitized T cells rather than IgE antibodies.
• Symptoms: These are less well-defined compared to immediate reactions and can include gastrointestinal disturbances and chronic skin conditions like eczema. Celiac disease is an example of a delayed hypersensitivity reaction involving an abnormal response to gluten in wheat and related grains.

3. Allergy-Like Intoxications

• Histamine Poisoning:
• Definition: Resembles true food allergies but is caused by the ingestion of foods containing high levels of histamine, a mediator of allergic reactions.
• Common Sources: Spoiled fish (e.g., tuna, mackerel) and aged cheeses like Swiss cheese.
• Mechanism: Unlike true allergies, histamine is ingested directly from food, overwhelming the body's protective mechanisms and leading to symptoms similar to an allergic reaction.
• Symptoms: Flushing, headaches, hives, and gastrointestinal upset.

4. Food Intolerances

• Definition: Abnormal reactions to foods that do not involve the immune system. These can be metabolic disorders, anaphylactoid reactions, or idiosyncratic reactions.
• Types of Food Intolerances:
• Metabolic Food Disorders:
• Lactose Intolerance: Caused by a deficiency in lactase, the enzyme required to digest lactose, leading to gastrointestinal symptoms like bloating, diarrhea, and gas.
• Favism: A metabolic disorder triggered by the consumption of fava beans, leading to hemolytic anemia in susceptible individuals, usually those with G6PD deficiency.
• Anaphylactoid Reactions:
• Mechanism: Involves the release of histamine from cellular stores within the body rather than from the food itself. Though rare, these reactions can mimic true food allergies.
• Idiosyncratic Reactions:
• Example: Sulfite-induced asthma, where the mechanism is unknown, but ingestion of sulfites in foods can trigger asthma attacks in susceptible individuals.

5. Secondary Food Sensitivities

• Definition: Adverse reactions to foods or food components that occur as a consequence of other underlying conditions.
• Examples:
• Lactose Intolerance Secondary to Gastrointestinal Disorders: Conditions like Crohn’s disease or ulcerative colitis can damage the gut lining, leading to secondary lactose intolerance.
• Drug-Induced Sensitivities: Certain medications, such as monoamine oxidase inhibitors (MAOIs), can increase sensitivity to specific food components like tyramine, potentially leading to hypertensive crises.

6. Nutritional Management of Food Allergies and Intolerances

• Identification and Avoidance: The cornerstone of managing food allergies and intolerances is the identification of offending foods through clinical evaluation, elimination diets, and food challenges.
• Dietary Substitutions:
• For Dairy Allergies and Lactose Intolerance: Use of lactose-free products or plant-based alternatives such as almond milk, soy milk, or rice milk.
• For Gluten Sensitivity and Celiac Disease: Avoidance of gluten-containing grains and substitution with gluten-free grains like rice, quinoa, and millet.
• Monitoring and Education: Patients should be educated on reading food labels, recognizing hidden sources of allergens, and managing cross-contamination risks. Regular follow-ups are necessary to adjust dietary plans as needed.

7. Conclusion

A clear understanding of the differences between food allergies, intolerances, and sensitivities is essential for effective dietary management. Individualized nutrition plans that account for specific sensitivities and provide safe and nutritious alternatives can significantly improve the quality of life for affected individuals.

Relationships between the various types of food sensitivities.

?

Mechanism of IgE-mediated allergic reaction

Symptoms of IgE-Mediated Food Allergies

Most Common (“The Big Eight”) Causes of IgE-Mediated Food Allergy Worldwide

Wheat?

Crustacea?

Eggs Fish?

Peanuts?

Milk

Tree nuts

Soybeans

Therapeutic Management

3.1 Approaches to Dietary Management

Two therapeutic strategies can be adopted based on symptom severity and the quality of triggering foods:

• Bottom-Up Approach: Involves the elimination of only the causative foods. This approach is generally suitable for mild cases.
• Top-Down Approach: Necessary for severe cases, particularly where failure to thrive or dehydration is evident. This approach may involve starting with an elemental diet and gradually reintroducing individual foods.

3.2 Use of Specialized Formulas

• Extensively Hydrolyzed Cow’s Milk Formula: Suitable for long-term management in infants with cow's milk allergy, both IgE- and non-IgE-mediated.
• Amino Acid-Based Formula (AAF): Required in only 10–20% of infants with non-IgE-mediated cow’s milk allergy. AAF can be essential when infants do not tolerate extensively hydrolyzed formulas.

3.3 Development of Tolerance

• Milk-Induced FPIES: Approximately 50% of infants develop tolerance by one year of age, and 90% by three years.
• Solid Food-Induced FPIES: Tolerance tends to take longer to develop compared to milk-induced FPIES.

3.4 Breastfeeding Considerations

• Breastfeeding-Related FPIES: When FPIES occurs during breastfeeding, it is essential to identify the trigger food. The mother must follow an elimination diet if a food trigger is identified.

4. Nutritional Concerns in Non-IgE-Mediated Food Protein-Induced Allergy

4.1 Common and Rare Triggers

• Common Triggers: The most frequently implicated foods in FPIES are cow's milk, soy, and rice.
• Rare Triggers: Other potential triggers include cereals, legumes (peanut, green pea, string bean), sweet potato, squash, carrot, egg white, chicken, turkey, fish, and banana.

4.2 Supplementation Needs

• Calcium and Vitamin D: Essential supplements when cow’s milk is the trigger food, as its elimination could lead to deficiencies, particularly in young children.

4.3 Nutritional Surveillance

• Monitoring: Given that conditions like FPIES and FPIAP often resolve by three years of age, strict nutritional surveillance is crucial only for a limited period.
• Avoiding Unnecessary Restrictions: During follow-up visits, healthcare providers must address any unnecessary dietary restrictions, particularly concerning milk and dairy products, to prevent compromising overall health and quality of life.

5. Pathophysiology of Immunologic Adverse Reactions to Food

5.1 Th2-Biased Immune Response

The central pathogenesis of non-IgE-mediated allergic diseases involves a T helper (Th) 2-biased, allergen-specific immune response. This response is characterized by:

• IgE Synthesis: Even though IgE-mediated mechanisms are not involved in non-IgE-mediated allergies, understanding this aspect is crucial in the broader context of allergic diseases.
• Eosinophilia and Organ Hyperresponsiveness: These are hallmark features of Th2-biased responses, contributing to the allergic phenotype.

5.2 Hygiene Hypothesis

The Hygiene Hypothesis provides a framework for understanding the increasing prevalence and severity of allergic and chronic inflammatory conditions over the past 40 years. It suggests that a modified environment leads to an imbalance in immune reactivity, particularly in genetically predisposed individuals.

5.3 Immune Response and Antigen Recognition

• Atopy and Immune Response: The predisposition to allergic diseases, collectively referred to as atopy, remains poorly understood. While it is hypothesized that allergen-specific T cells may have an intrinsic bias, the evidence remains inconclusive.
• Tolerance Mechanisms: Exposure to allergens in non-allergic individuals may result in tolerance or no response, suggesting the involvement of additional checkpoints in antigen recognition and immune response modulation.