A recently published review in Nutrients has spotlighted vitamin A5, a newly defined micronutrient emerging more than 80 years after the last vitamin was characterised, with potential significance for diet-related health outcomes and nutraceutical innovation.
Traditionally, vitamin A has been understood as a family of compounds derived from dietary carotenoids and retinoids that support essential physiological functions.
However, research shows that 9-cis-13,14-dihydroretinoic acid (9CDHRA) — an endogenous ligand for the retinoid X receptor (RXR) — cannot be efficiently derived from classical vitamin A precursors.
Instead, dietary precursors such as 9-cis-β,β-carotene and 9-cis-13,14-dihydroretinol appear to be direct nutritional sources that feed into this RXR signalling pathway, prompting the categorisation of these compounds under a new vitamin class: vitamin A5.
The review highlights key criteria used to define vitamins and discusses how A5 fits into these definitions, offering a comprehensive assessment of its biological relevance.
Importantly, it concludes that vitamin A5 not only represents a bona fide micronutrient but may also help explain why diets low in vegetables, especially leafy greens (typical of Western dietary patterns), are associated with increased incidences of neurological diseases and poor mental health outcomes.
From a nutraceutical perspective, this emerging concept presents new opportunities for product development and dietary recommendations.
Estimates suggest that in Western populations, average intake of provitamin A5 may be below suggested nutritional guidance, with a substantial proportion of individuals consuming less than recommended levels.
This shortfall signals potential demand for targeted supplementation or fortified products to address this gap.
Industry players are already responding: for example, a new dietary supplement containing vitamin A5 has recently entered the European market, marking one of the first commercial products formulated around this novel vitamin concept.
As research continues to clarify the physiological roles and dietary requirements of vitamin A5, formulators and supplement developers may find a strategic niche in addressing this underserved micronutrient.