system
Given the following post, respond as if you're commenting on Reddit:
human
[Snowpiercer] Do the people at the back not suffer from vitamin D deficiency?

There's no windows at the back and I'm sure they haven't seen the sun in 18 years, which isn't enough time to evolve into not needing it.
gpt
Yes they do.  Among many other nutritional deficiencies.  And among the challenges faced by the people in the back of the train, nutritional deficiencies are just one entry, fairly low down the list.