"If you are old enough to remember the sci-fi movie from the 70s called Soylent Green, you might have started to connect the dots. In the movie, all humans were completely reliant on a nutritional juice called soylent green, but it just happened to be made out of discarded humans. Their skin and bones ground down into a sludge that was the only available source of food."
Actually, the soylent products (Soylent Green, Soylent Yellow, and Soylent Red, iirc) in the film were crackers or biscuits, not liquids. The "Soylent" liquid is a real-world meal replacement product that sought to capitalize on the name recognition of the film.