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food may be used as an indicator that gluten proteins are present. The USDA National Nutrient Database for Standard Reference, Release 17 (USDA, 2004), the major source of composition data for foods in the U.S., includes hundreds of food items that contain wheat, rye, barley, triticale or oats as an ingredient. Wheat, in particular, is used to manufacture a wide range of food ingredients and finished foods. Rye, barley, triticale, and oats are used to make substantially fewer food products.

Koehler and FDA (2005) estimated the average amount of total grain and individual types of grain available for consumption per person in the U.S., and the total exposure to gluten-forming proteins that would result from this grain consumption. The estimated mean daily consumption rate was approximately 250 grams of grain per capita. Wheat provided 180 of the 187 grams per person per day of grains that are of concern for individuals with celiac disease.

There is no consensus as to whether oats present a hazard for all individuals with celiac disease. Several studies, including one that lasted 5 years, have reported that most celiac study participants tolerated moderate amounts (e.g., 50-70 grams daily) of oats (Janatuinen et al., 1995; Janatuinen et al., 2000; Janatuinen et al., 2002; Lundin et al., 2003; Arentz-Hansen et al., 2004). The oats used by Lundin et al. (2003) and Arentz- Hansen et al. (2004) were tested to ensure that they did not contain any gluten proteins from wheat, rye, or barley.

F. Gluten Contamination of Grains In the U.S., most commercially available oat products are believed to contain some gluten proteins from wheat, rye, or barley due to cross-contact with these grains during growth, harvest, transport, storage, or processing (Kasarda, 1999; Kasarda, 2001; AGA, 2001; Thompson, 2003). In a recent study, Thompson (2004) analyzed four lots of three brands of rolled or steel-cut oats commercially available in the U.S. for prolamins from wheat, barley, or rye. For one brand, all samples contained 338 to 1807 ppm gluten (expressed as the mean of duplicate determinations). For each of the other two brands, the level of gluten detected in all but one lot ranged from 12-725 ppm in one brand and 120-131 ppm in the other brand (expressed as the mean of duplicate determinations). Thus, only one lot of these two brands was negative for gluten. Thompson (2004) concluded that none of these three brands could be considered a reliable source of oats free of potentially harmful gluten proteins.

Grains that do not contain gluten can become contaminated with grains that contain gluten at any step in the farm-to-table continuum, particularly if shared equipment is not thoroughly cleaned between uses. It is difficult, if not impossible, to prevent all cross- contact situations, considering the tons of grain handled by farm equipment, bulk storage, and transport containers on a daily basis. In fact, the Official United States Standards for Grains (USDA, 1999) assume that most grains that have an established U.S. standard will contain a small percentage of other grains.

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