Comparative standards are reference values from reputable and authoritative sources such as government agencies, independent scientific panels, standards organizations, and scientific and professional organizations.
For comparison of nutrient intake to established standards of the Dietary Reference Intakes (DRI) see: http://fnic.nal.usda.gov/dietary-guidance/dietary-reference-intakes/dri-tables
See also: TABLE #3, Recommended Intakes of PHE, TYR and Protein for PKU Treated with Dietary Therapy Recommended intakes of PHE, TYR and Protein for Individuals with PKU