Will old entries change if the database is updated?

No. A saved entry keeps a snapshot of the food values, source and amount used when you saved it. Updating the shared database does not silently recalculate your past meals.

New entries can use the newer food version. If you want an old meal to use different values, edit that entry deliberately and check the resulting total. The same principle applies to saved recipes: changing a recipe for future use is different from changing a portion already recorded in your history.