Sodium caseinate is derived from casein, a protein found in milk from mammals (most commonly, cows). It is often used in protein powder, coffee creamer including the non-dairy kind, cheese, cheese flavoring, whipped topping, and more. It is used as an emulsifier and frother and is deemed safe for consumption except for those with a milk-protein allergy. If you are lactose-free, you can still consume sodium caseinate, but if you are vegan you'll want to skip this ingredient.