The protein bars in Snowpiercer use Insects as their primary ingredient, much to Curtis ' Horror.
Known as Entomophagy, the practice is actually not uncommon, as insects are used in diets around the globe.
There are plenty of Dystopian Entomophagic possibilities's being actively discussed right now, as some prominent researchers believe humanity's acceptance of an insect based diet is a key milestone to global sustainability.
During the course of the journey forward, they run into someone called Paul , who was taken away a while ago to start the conveyor something manually (that should have been a big clue for why the children were taken), and we get a peek into the grinders making the protein bar. Cockroaches.
Known People who ate it
Minister Mason Pike