One Piece Manga and Anime — Vol. 80 Chapter 798 (p. 9) and Episode 743, Law asks Sengoku about the "D." initial.

In foods and dietary supplements, vitamin D has two main forms, D 2 (ergocalciferol) and D 3 (cholecalciferol), that differ chemically only in their side-chain structures. Both forms are well absorbed in the small intestine. Absorption occurs by simple passive diffusion and by a mechanism that involves intestinal membrane carrier proteins [ 4]. The concurrent presence of fat in the gut enhances vitamin D absorption, but some vitamin D is absorbed even without dietary fat. Neither aging nor obesity alters vitamin D absorption from the gut [ 4].He and his crew are said to be the only people to have fully explored the Grand Line, meaning both Paradise and the New World.

From about late March/early April to the end of September, the majority of people should be able to make all the vitamin D they need from sunlight on their skin.

Appointments at Mayo Clinic

a b Constable, Peter (2004-04-19). "L2/04-132 Proposal to add additional phonetic characters to the UCS" (PDF). Archived (PDF) from the original on 2013-08-19.