I know some smaller brands estimate using the USDA Food Composition Database (https://ndb.nal.usda.gov/ https://ndb.nal.usda.gov/), which in turn gets its data

I know some smaller brands estimate using the USDA Food Composition Database (https://ndb.nal.usda.gov/ https://ndb.nal.usda.gov/), which in turn gets its data under the National Food and Nutrient Analysis Program (http://www.ars.usda.gov/News/docs.htm?docid=9446 http://www.ars.usda.gov/News/docs.htm?docid=9446). This is what I could find about their data: "Data have been compiled from published and unpublished sources. Published data sources include the scientific literature. Unpublished data include those obtained from the food industry, other government agencies, and research conducted under contracts initiated by USDA’s Agricultural Research Service (ARS)." (http://www.ars.usda.gov/sp2UserFiles/Place/80400525/Data/SR/SR28/sr28_doc.pdf http://www.ars.usda.gov/sp2UserFiles/Place/80400525/Data/SR/... <- page 2)