They all deserve their own research, but I generally find frozen food to often be fresh and less chemical-filled than many "fresh" foods. Canned stuff can be good as I don't get behind the whole "BPA will kill you in any amount" team, but there are certainly canned foods that use iffy processes. And then processed foods should be avoided as very few are really good for you on both the nutrition and chemical side of things. I like to keep things to a "Can I do this at home?" theory to buying food. Canning and freezing are both easy to do at home, but processing a soy bean into a steak-flavored potato chip is a bit much.