In [link|http://en.wikipedia.org/wiki/Make_Room%21_Make_Room%21|Make Room! Make Room!], the Harry Harrison short story that was made into the movie, soylent green was just soybeans and lentals.
I recall reading in a Harry Harrison collection of shorts that on the opening night a movie theatre had put a sign on their slushie machine along the lines of "Soylent Green/Yellow Slushies". Apparently the manager didn't know the movie had changed it. :-)