In terms of gluten-free eating, I have always learned that it’s an all-or-nothing approach. You must cut gluten completely (meaning 100%) out of your diet to ensure that your system is working properly.
Recently, however, I read an article about gluten-free legislative action being taken in the U.K. over gluten-free labeling. Under their legislation, foods can be labeled as “gluten-free” only if they contain less than 20 mg of gluten per kg of the product. This is common practice in most food manufacturing as a safe tolerable limit for indirect and unintentional food additives. When eating processed foods, it is common practice (under our own FDA guidelines) to accept that substances can accidentally get into foods during processing, production, packaging, and storage. As such, the FDA defines minimum permissible quantities of such unintended substances.