I remember somebody telling me, many years ago, that when it comes to people, psychology, conditioning and training, the following applies.

If you feed people and with each meal, you put a little piece of Dirt mixed in with it ( unnoticeable amount of course )......they'll eat it and won't notice the difference.  If you do that for long enough and very gradually, increase the amount of Dirt you put into the food; in the end, they just eat Dirt and love it.........I know, you know, what I'm saying.