The reason raw spinach gen. does not do the trick is because most do not eat enough in one sitting to have the desired effect. Most eat 1/4-1/2 a spinach bunch (and that is a lot of leaves) but when you cook a whole spinach bunch, it only gives you a small portion (about the size of your hand). Therefore, consuming it cooked, you are consuming more but it seems like less because of the diminutive size it takes on once it has been steamed...does this make sense?