Beyond 100 years of vitamin E and related molecules - Milestones and open challenges

Over the past century, research on vitamin E has evolved from its initial identification as a fertility factor to the recognition of α-tocopherol (α-TOH) as an essential micronutrient with antioxidant and gene regulatory functions. Despite extensive investigation, controversies persist regarding its precise biological role, clinical efficacy, and classification as a vitamin. This review summarizes scientific milestones in vitamin E (tocochromanol) research. It highlights recent advances in understanding the absorption, metabolism, and molecular mechanisms of vitamin E. The review also outlines unresolved questions and methodological challenges. The focus is on α-TOH and its metabolites, which exhibit biological activities beyond classical antioxidant effects, such as the regulation of inflammation, lipid metabolism, and immune responses. Evidence from genetic, biochemical, and clinical studies supports the essentiality of α-TOH in humans, as demonstrated by ataxia with vitamin E deficiency (AVED). Other tocochromanols and their metabolites exhibit promising biological activities that suggest potential therapeutic applications. However, their physiological relevance must be confirmed. Advances in metabolomic profiling and molecular modeling now allow for a more comprehensive characterization of vitamin E metabolism and function. Understanding the molecular pathways and biological roles of vitamin E and its derivatives is crucial for refining its definition, establishing evidence-based dietary recommendations, and evaluating its potential in disease prevention and therapy.