What's the youngest you would let a child help in the kitchen?

I don't mean help as in cutting things I mean like putting potatoes in a pot, putting toppings on pizza and putting ingredients in cakes or pasta sauces. my 2 1/2 year old loves to help do these things and while he's always very closely supervised we've had some negative comments about it from family members that he is way too young to be in the kitchen. opinions?