system
Given the following post, respond as if you're commenting on Reddit:
human
ELI5 why it goes vitamin A to E, then jumps to K. What happened to F to J?
gpt
Most of them were renamed upon being grouped into the B Vitamin group; for example vitamin G was the old name for riboflavin, which later became known as vitamin B2.

Vitamin F was different: It was the old name for essential fatty acids, which were considered vitamins at the time of their discovery but have since been reclassified as fats.