For follow-up discussion and general commentary on the topic. Comments are sorted chronologically.
Yes I feel I is very important to ask for blessings on the food our Father has given us. It reminds us, that He is the one who provided the food, and when we ask for his blessing, I think we are expressing our sincerest thanks for the food he has provided.
You don't have to do anything, however loving God means you will want to thank Him for his provision.