I agree with the warnings about soy beans. I once thought they were healthy and overdid on them - trashed my thyroid so now I'm on meds for lifetime. Bummer! However, if you want to stretch your hamburger meat further, use chick peas (garbanzo beans - hubby calls them Gonzos). They are easy to grow and cook, have a more neutral flavor so they take the added flavors you include to make great meals. Even straight Gonzo burgers turn out great - and don't forget the tahini - yummm.