Analysis of the current vitamin A terminology and dietary regulations from vitamin A1 to vitamin A5.

Dietary recommendations on vitamin intake for human food fortification concerning vitamin A in various countries, larger economic zones and international organizations are mainly based on the Food and Agriculture Organization of the United Nations (FAO)/World Health Organization (WHO) "Codex Alimentarius standards". The general vitamin A terminology is based on regulations of the International Union of Pure and Applied Chemistry (IUPAC) that are used to describe the involved derivatives. These regulations and terminology were set up in the middle of the last century. Starting with the decade of the 80ies in the 20th century a large improvement of molecular biological methodologies, background physiological mechanisms as well as analytical techniques contributed to a large diversification of this simply claimed vitamin A terminology. Unfortunately, the following terminology and governmental regulations for food fortification are imprecise and non-harmonized. In this article we tried to unravel this terminology for updating terminology, nutritional suggestions and governmental regulations for vitamin A, which are currently based on various uncertainties. According to the current regulations, the newly found vitamin A₅/X can be included in the current vitamin A terminology as "vitamin A₅" or alternatively or even in parallel as a new vitamin A-independent terminology as "vitamin X". Based on the detailed knowledge of research from the early beginning of general vitamin A pathway identification towards detailed research of the last decades the commonly used and simplified term vitamin A with relevance for governmental recommendations on vitamin intake and food fortification advice was now more correctly sub-categorized to further vitamin A₁, and A₅ sub-categories with vitamin A₁-alcohol as retinol, vitamin A₂-alcohol as 3,4-didehydroretinol and vitamin A₅-alcohol as 9-cis-13,14-dihydroretinol as their mainly relevant vitamin forms present in the human organism. Here we suggest and advise how the vitamin A terminology and further governmental regulations should be organized depending on a successful unraveling of the organization of the current vitamin A terminology.