I never pray before meals unless other Christians are present, and then only because it seems to be important to them. I have never understood the custom. I am thankful for a lot of things, and I see no particular reason to single out food. Moreover, it seems to be a superstition for a lot of people (not picking on anyone here), like they think if they don't pray they will die of food poisoning or something. I pray at other times.

"The good Christian should beware the mathematician" ~Augustine, De Genesi ad Litteram, II, xvii.37