The prevalence of food allergies and intolerances has risen exponentially within the past decade. Emerging research indicates that alterations in the intestinal flora may play an important role in the development of these disorders. Read on to learn how a disrupted gut microbiome predisposes to food allergies and intolerances and how restoration of the microbiome may be beneficial in the treatment of these conditions.
What are food allergies and intolerances?
Food allergy is defined as an immune response to a food that occurs reproducibly on exposure and generates adverse health effects. (1) Food allergies may be IgE-, non-IgE-, or IgG-mediated. IgE-mediated food allergies occur when the immune system produces IgE antibodies to foods; the antibodies bind to mast cells and basophils, stimulating the release of proinflammatory cytokines that induce an acute, and sometimes life-threatening, allergic response. Non-IgE-mediated food allergies involve components of the immune system other than IgE and can take up to several days to manifest; the symptoms are usually isolated to the GI tract. (2) While still controversial, there is evidence to suggest that food allergies can also be IgG-mediated; this type of allergy causes a delayed hypersensitivity to foods. (3, 4)
Food allergies and intolerances are on the rise
Nowadays, allergy-friendly aisles have become commonplace in grocery stores, and many schools and restaurants offer dietary accommodations for individuals with food allergies and intolerances. However, food allergies and intolerances have not always been such a big concern. In fact, it is only within the past decade that the prevalence of these conditions has skyrocketed. (6) Between 1997 and 2011, IgE-mediated food allergies increased by 50 percent in American children. (7) In addition, research has found that more than 20 percent of the population of industrialized countries, including the United States, United Kingdom, Australia, and China, suffer from food allergies or intolerances. (8, 9, 10)
Despite the dramatic rise in food allergies and intolerances, few treatment options are available. Conventional medicine advises patients to strictly avoid their trigger foods and to have epinephrine on hand for accidental exposures. However, neither of these strategies addresses the underlying cause of food allergy and intolerance. Novel treatment approaches are desperately needed. An emerging body of research indicates that alterations in the normal human gut flora play a role in the development of food allergies and intolerances. Modulation of the gut microbiota may alleviate food allergies and intolerances and potentially restore tolerance to triggering foods. (11, 12)
Alterations in gut flora, food allergies, and food intolerance
Notable differences have been observed in the gut flora between food-allergic and nonallergic individuals, suggesting that alterations in the normal human gut flora play an important role in the pathogenesis of food allergies and intolerances. (27) The normal human microbiome is composed of a diverse array of bacteria, including Bacteroides, Enterobacteria, Bifidobacteria, and Lactobacilli. These commensal bacteria interact with the mucosal immune system of the gut to promote immune tolerance of foods. (28) Lifestyle factors that decrease numbers of beneficial gut microbes can impair immune tolerance, resulting in allergic sensitization or intolerance to foods.
Alterations in specific types of gut bacteria have been linked to the development of food allergies. Most of the studies examining this phenomenon have been conducted in infants and children. In children, decreased Lactobacilli and increased Staphylococcus aureus are associated with egg and milk allergies. (29) Children with decreased levels of L. rhamnosus, L. casei, L. paracasei, and Bifidobacterium adolescentis during their first two months of life were found to be at a higher risk of developing allergic sensitization to cow’s milk, egg white, and inhalant allergens. (30) Reduced Bacteroides, Proteobacteria, and Actinobacteria are also associated with food allergen sensitization in infants. (31)
In addition to increasing the risk of food allergies, a lack of microbiome diversity may predispose to non-immunologic food intolerances such as gluten, FODMAP, and histamine intolerance. Certain species of bacteria assist in the breakdown of gluten proteins, and a lack of these may predispose to gluten intolerance. (32) Bacterial overgrowth of the small intestine is a common cause of FODMAP intolerance. (33) Histamine intolerance may occur when there is an overgrowth of bacteria that produce histamine or that make enzymes that interfere with the metabolism of histamine. (34, 35)
Eat a whole-foods diet
A whole-foods, nutrient-dense diet may proffer additional protection against food allergies and intolerances. Consumption of omega-3 fatty acids; vitamins C, E, and A; beta-carotene; and zinc are associated with a decreased incidence of food allergies. (56) Conversely, a diet high in refined carbohydrates, artificial sweeteners, gluten, omega-6 fatty acids, and food additives may predispose to food allergies and intolerances. While the evidence is not conclusive, the consumption of genetically modified foods may also contribute to food allergies and intolerances, due to the potential allergenicity of the technologically altered proteins in these foods. (57)
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