Soy: a type of food typical in Asian cusine.
Lent: associated with fasting, especially to christians.
You know I just realized that old movie might have been some marketing scheme against soy products, typically from asia, to build an unconcious negative bias when encountering the word 'soy'.
I mean, why pick a word like soylent at all? (Note haven't watched the movie, Heston's acting is unbearably horrible.)