For example, consider a category of "bread", it is approved by different Government agencies and are the ingredients specifically included on all products? Do any of these agencies maintain a list of approved products and related data for public use?
The USDA maintains a National Nutrient Database with
nutrient information on over 8,000 foods using this new and improved search feature. You can now search by food item, group, or list to find the nutrient information for your food items.
The Nutrient Data Laboratory gives food composition and allows you to browse foods by nutrient.
FDA 'approval' of food products is somewhat less straight forward- see What does FDA regulate? section on food.