Citation

Food allergy is defined as an adverse reaction to otherwise harmless dietary proteins. Food allergy is a health problem affecting young children and adults worldwide and has increased in prevalence during the past few decades. The cause of the increase in food allergy prevalence is largely unknown, but suggested to be a result of changes in both environmental and lifestyle parameters, including our eating habits. The gastrointestinal tract is constantly exposed to a wide range of dietary components, potential antigens, bacteria and fungi. Dietary components may affect the intestinal barrier functions, which might impact food allergy sensitisation. Saponins are natural substances widely distributed in plant species, and known for their membrane perturbing effects, and may therefore potentially influence intestinal barrier functions. Saponins are found in high amounts in quinoa (Chenopodium quinoa) seeds. The seeds of quinoa originally served as a main dietary component in the Andean region of South America but have within the last decade gained a profound popularity in North America and in Europe, probably due to its high nutritional value and natural gluten-free composition. The aim of this project was to (1) extract and quantify the aglycones (the non-glycosylated moiety of saponins) found in quinoa, and (2) investigate the health related effects of quinoa in relation to intestinal permeability and the impact of quinoa on allergic sensitisation. A literature review was conducted to obtain an overview of digestion, intestinal barrier functions and dietary protein uptake in the gastrointestinal tract in relation to food allergy (Manuscript I). The aglycone content in several quinoa samples was determined by solid phase extraction and high resolution HPLC-MS analysis (Manuscript II). The influence of quinoa on intestinal permeability was studied in Caco-2 cells, by assessing intestinal transport through the cells, and in Brown Norway rats by detecting intestinal protein uptake, cell junction gene expression, and immune regulations (Manuscript III). The inherent allergenicity of quinoa proteins and potential cross-reactivity was evaluated in Brown Norway rats by assessing antibody response and reactivity, protein stability and sequence homology to known allergens (Manuscript IV). The intestinal effects of quinoa and the consequential impact on sensitisation to quinoa and co-administered cow’s milk whey was investigated in Brown Norway rats by assessing antibody response, intestinal protein uptake and cell junction gene expression (Manuscript V). The content of the four main aglycones found in quinoa ranged between 151 and 704 mg/kg within the 23 different quinoa samples, with phytolaccagenic acid quantified as the dominant aglycone. The aglycone content was not influenced by the seed colour or the geographical origin of the seeds (Manuscript II). Quinoa had no effect on the intestinal transport in epithelial Caco-2 cells, whereas an increased intestinal permeability was observed in rats daily administered quinoa for seven days. An increased protein uptake was particularly observed in rats administered quinoa in the presence of the mucosal adjuvant cholera toxin (CT). Administration of quinoa did not reveal immune regulatory effects, but the results suggested specific inflammatory properties (Manuscript III). In the light of the v effects of quinoa on intestinal permeability, rats co-administered cow’s milk whey with quinoa did not lead to an increased sensitisation to cow’s milk whey. In contrast, administration of quinoa in the presence of CT reduced the sensitising capacity of whey proteins (Manuscript V). On the other hand, quinoa proteins were found to possess a high sensitising and eliciting capacity in Brown Norway rats, both when administered by the intraperitoneal route (Manuscript IV) and by the oral route without the use of an adjuvant (Manuscript V). Quinoa revealed potential cross-reactivity with known allergens, in particular with peanut and tree nuts (Manuscript IV). Collectively, these studies reveal a diverse amount of the non-glycosylated moiety of saponins in quinoa seeds, thus administration of quinoa has the potential to increase the intestinal permeability, though without increasing the sensitising capacity of co-administered cow’s milk whey. Moreover, the presented results reveal a high allergenic and cross-reactive potential of quinoa, highlighting the importance of allergy assessment of ‘new’ grains.