Adverse Food Reactions: Physiological and Ecological Perspectives

Abstract

While food is essential for survival, it can also cause a variety of harmful effects, ranging from intolerance to specific nutrients to celiac disease and food allergies. In addition to nutrients, foods contain myriads of substances that can have either beneficial or detrimental effects on the animals consuming them. Consequently, all animals evolved defense mechanisms that protect them from harmful food components. These "antitoxin" defenses have some parallels with antimicrobial defenses and operate at a cost to the animal's fitness. These costs outweigh benefits when defense responses are exaggerated or mistargeted, resulting in adverse reactions to foods. Additionally, pathological effects of foods can stem from insufficient defenses, due to unabated toxicity of harmful food components. We discuss the structure of antitoxin defenses and how their failures can lead to a variety of adverse food reactions.

Keywords: adverse food reactions; food quality control; food science; gastrointestinal physiology; mucosal immunology.

Figure 1

Diagram of processes involved in food quality control. Food contains nutrients and other components, which can be beneficial, neutral, or toxic to the animal. Sensing of a subset of these food components (directly, by proxy, or by detection of the physiological effects of the food component) enables evaluation of food quality, which is also influenced by the animal’s physiological state and memory of previous food encounters. Evaluation determines the animal’s response to the food, which can involve processes that promote nutrient assimilation (digestion, absorption, etc.) or defensive processes that protect the organism from harmful food components (diarrhea, detoxification, etc.).

Figure 2

Summary of antitoxin defenses. Antitoxin defenses include multiple interacting components that function to optimize nutrient absorption while protecting from noxious food components through avoidance of, elimination of, or adaptation to the presence of the noxious component. Defenses operate preingestion, postingestion, or postabsorption of food. Defensive mechanisms (top) and involved systems (bottom) are shown. Abbreviations: AMP, antimicrobial peptide; CTA, conditioned taste aversion.

Figure 3

Framework for food-triggered diseases. Manifestations of food-triggered diseases classified by the appropriateness of the defense relative to the toxicity of the food component. Diseases in area A are due to mistargeted defenses against a benign component in food. Those in area B are due to defenses that are exaggerated relative to the toxicity of a food component. Diseases in area C are cases in which defenses are appropriate but generate costs that are perceived as disease. Diseases in area D are ones in which the primary failure is a defensive insufficiency. Each could occur on a range of severity, with the diagnoses becoming more difficult to discern at the milder end of the spectrum. This diagram aims to classify diseases by their primary cause, but it is also important to note that the initial cause might not be obvious in a chronic disease in which downstream defenses or other sequelae have developed.