Proteins in wheat, barley and rye cause an autoimmune response in people with Coeliac Disease.
A. K. Akobeng & A. G. Thomas Department of Paediatric Gastroenterology, Booth Hall Children’s Hospital, Central Manchester and Manchester Children’s University Hospitals, Manchester, UK published a study of how much gluten a person with Coeliac Disease can tolerate. The report concluded “The amount of tolerable gluten varies among people with coeliac disease. Although there is no evidence to suggest a single definitive threshold, a daily gluten intake of less than 10 mg is unlikely to cause significant histological abnormalities.”
In 1982, the Codex Alimentarius Committee on Nutrition and Food for Special Dietary Uses (CCNFSDU) established labeling standards in its Standard for Gluten-Free Foods. These references provide some additional context in the labeling of foods in the US: Proposed Rule: Gluten-Free Labeling of Foods January 23, 2007 Questions and Answers on the Gluten-Free Labeling Proposed Rule January 23, 2007.
Dozens of international standards for the determination of gluten in wheat and wheat flour are available. The International Standards Organization, ISO Technical Committee 34 is responsible for standardization in the field of human and animal foodstuffs. ISO/TC 34 Food Products Subcommittee SC4 is concerned with Cereals and Pulses.