The FDA refers to natural ingredients as "ingredients extracted directly from plants or animal products as opposed to being produced synthetically."
U. S. Food and Drug Administration, FDA Consumer
The USDA's definition, which only applies to meat & poultry, states the product "must not contain any artificial flavoring, color ingredients, chemical preservatives, or artificial or synthetic ingredients, and are only “minimally processed” (a process that does not fundamentally alter the raw product.)"
Definition: Produced by nature: present in or produced by nature, not artificial or synthetic
as defined by Encarta
All Natural Product Division
Products for consumption, whether internally or externally, by humans or animals are available for certification under our All Natural program. Please see our menu of specific programs at the left and if you have any questions please submit your information on our contact page.