When dementia has progressed to an advanced degree, the diet has no beneficial effect. Cortical myoclonus appears to be treatment-resistant on both gluten-free diet and immunosuppression. People with gluten-related disorders have to remove gluten from their diet strictly, so they need clear labeling rules. The term "gluten-free" is generally used to indicate a supposed harmless level of gluten rather than a complete absence. The exact level at which gluten is harmless is uncertain and controversial. A 2008 systematic review tentatively concluded that consumption of less than 10 mg of gluten per day is unlikely to cause intestinal damage in people with celiac disease, although it noted that few reliable studies had been done. Regulation of the label "gluten-free" varies. The "Codex Alimentarius" international standards for food labeling has a standard relating to the labeling of products as "gluten-free". It only applies to foods that would normally contain gluten. By law in Brazil, all food products must display labels clearly indicating whether or not they contain gluten. Labels for all food products sold in Canada must clearly identify the presence of gluten if it is present at a level greater than 20 parts per million. In the European Union, all prepackaged foods and non-prepacked foods from a restaurant, take-out food wrapped just before sale, or unpackaged food served in institutions must be identified if gluten-free. "Gluten-free" is defined as 20 parts per million of gluten or less and "very low gluten" is 100 parts per million of gluten or less; only foods with cereal ingredients processed to remove gluten can claim "very low gluten" on labels. All foods containing gluten as an ingredient must be labelled accordingly as gluten is defined as one of the 14 recognised EU allergens. In the United States, gluten is not listed on labels unless added as a standalone ingredient. Wheat or other allergens are listed after the ingredient line. The US Food and Drug Administration (FDA) has historically classified gluten as "generally recognized as safe" (GRAS). In August 2013, the FDA issued a final ruling, effective August 2014, that defined the term "gluten-free" for voluntary use in the labeling of foods as meaning that the amount of gluten contained in the food is below 20 parts per million.