conservative threshold for gluten exposure for sensitive individuals would lie between 20 and 100 ppm.
Table III-1. Estimated Daily Gluten Consumption from Combinations of Different Amounts of Food Containing Different Levels of Gluten
Gluten Content in Food (ppma)
Daily Amount of Gluten-Free Food Consumed (g)
Daily Amount of Gluten Consumed (mg)-----------------
Source: Collin et al., 2004.
a ppm=mg/kg Note: Gluten content in food multiplied by food consumed equals gluten consumed. Six slices of bread is equivalent to approximately 100 g baking mix.
In an alternate approach, Collin et al. (2004) analyzed gluten levels in a number of different types of wheat starch (n=24) and naturally gluten-free (n=59) flours consumed by 76 individuals with celiac disease who had been on gluten-free diets for 1 to 10 years. These individuals had no reported evidence of mucosal deterioration or significant provocation of signs or symptoms while on this diet. The range of gluten found in these products was 0 to 200 ppm. Collin et al. (2004) then estimated that the total daily flour consumption for these individuals to be 10-300 gm (median 80 gm). Based on this estimate and the gluten content of the flour, a chart depicting estimated daily gluten exposures was devised (Collin et al., 2004). Collin et al. (2004) used this chart and data from low dose gluten challenge studies to suggest the use of a threshold of 100 ppm gluten. The main limitations of this study include lack of a prospective study design (for actual dose-response information) and the lack of information detailing diagnostic assessment (i.e., minimal mucosal involvement) for characterizing mucosal relapse in these individuals.
H. Measuring Gluten in Food Currently, commercial immunology-based ELISA test kits for the detection of gluten in foods are manufactured by Immunotech (Czech Republic), Ingenasa (Spain), Morinaga (Japan), Diffchamb (Sweden), Neogen Corporation (U.S.), R-Biopharm (Germany), and Tepnel BioSystems (U.K.). All of these detect prolamins, the proteins found in soluble aqueous-alcohol extracts from cereals. None is designed to detect all proteins associated with celiac disease. Five of the assays have separately undergone multi-laboratory validation studies (Skerritt and Hill, 1991; Akiyama et al., 2004; Gabrovská et al., 2004; Immer et al., 2003). Each of these studies employed different target levels and matrices. The Tepnel kit was validated by AOAC at >160 ppm gluten (Skerritt and Hill, 1991). All the ELISA kits rely on the preparation of an aqueous-alcohol extracts as analytical samples, and four of the manufacturers include the use of reducing–denaturing conditions
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