What's the difference between an ESHA code, user code and government code?

Gov. code

In the ESHA database, the Gov. Code refers to the identification number assigned to a national database item, like NDBs assigned by the USDA to USDA SR foods or food codes assigned by Health Canada to Canadian Nutrient File foods.

ESHA Code

The ESHA Code is the ESHA identification number unique to each food in the ESHA database.

Government database foods included in the ESHA database are assigned both Gov. Codes and ESHA Codes.  Branded items from suppliers may only have ESHA Codes and no Gov. Codes. Foods without ESHA Codes indicate new ingredients and foods that you have entered in your software.

User Code

When adding a record to your database, you may choose to assign it a User Code, but this is not necessary. You can also assign a User Code to ESHA database items, but this data might be overwritten when your program is updated.  The User Code format would be a code of your determination and for your purposes.