Photobiology of vitamins

This review explores contemporary ideas about the relationship between light exposure and vitamin biology. Nutritional biochemistry has long recognized the relationship between vitamins A and D and light exposure, but in recent years other vitamins have also been implicated in photoresponsive biological mechanisms that influence health, well-being, and even evolutionary processes. Interactions between light and vitamins can modify genotype-phenotype relationships across the life cycle, providing a basis for interesting new explanations relevant to wide aspects of human biology. This review examines both well-established and emerging ideas about vitamin photobiology in the context of the following: (1) light responsiveness of vitamin D (photosynthesized in skin), vitamin A (linked to vision), and vitamin B₃ (needed to repair genomic damage); (2) vulnerability of folate and vitamins B₁, B₂, B₁₂, and D to ultraviolet (UV) light (all potentially degraded); (3) protective/filtering actions of carotenoids and vitamins C and E, which act as antioxidants and/or natural sunscreens, against UV light; (4) role of folate, carotenoids, and vitamins A, B₃, C, D, and E in UV-related genomic regulation, maintenance, and repair; (5) role of folate and vitamins A, B₂, B₁₂, and D in a range of light-signaling and lighttransduction pathways; and (6) links between folate and vitamin D and the evolution of UV light-adaptive phenotypes.