Original: The reason that the set of vitamins skips directly from E to K is that the vitamins corresponding to letters F-J were either reclassified over time , discarded as false leads , or renamed because of their relationship to vitamin B , which became a complex of vitamins .
Simplified: Currently there are no vitamins F to J/O. These existed at some time . Today they are either reclassified ( no longer seen as vitamins ) .