Wasn't sure where to put this sorry if it's the wrong area!

Do you make your kids ask you before they get some food/drinks from the fridge? My kids have just started helpong themselves, and in the past few days, I have found them eating food which I haven't given them. Just now DS1 helped himself to some crackers int he cupboard while I was emptying the dishwasher!
I don't know if I should discourage it or not! I always had to ask for food when I was little. I still do when at mums or dads houses. Actually at anyones house I will ask, even if they say help yourself.
I think it's a good idea for them to ask as I can then regulate what they eat and when. So they don't eat not so great food (we don't really have junk in the house) when it's near lunch time or what ever, and I can just make sure they're getting a good variety and healthy options, plus talking to them about the foods they should eat. I don't think they would make good choices all the time! I do let them choose food to eat, but will tell them why or why not it's good/bad to eat.

So am I being a food nazi by not letting them get their own food, sometimes without me knowing they're eating? They are only 2 1/2 and almost 4, they really don't have any idea about what is actually healthy or not!