Walnut oil from raw material to physiological function: an integrated process-chain perspective on quality, oxidative stability, authentication and health effects.

Walnut oil from Juglans regia L. and Juglans sigillata Dode is an edible oil characterized by high proportions of linoleic and α-linolenic acids and variable concentrations of tocopherols, phytosterols, squalene and phenolics. Its delivered composition and oxidative state vary with raw material, processing and storage history. This review integrates evidence on cultivar, origin, ripening, post-harvest handling, pretreatment, extraction, storage, authentication and health-related outcomes. Conventional and emerging extraction strategies are compared in terms of recovery, constituent retention, oxidative status and available sustainability information. Oxidative degradation is considered a potential confounder because oils administered at the same nominal dose may differ in intact polyunsaturated fatty acids (PUFAs), endogenous antioxidants and preformed oxidation products. Reported bioactivities are grouped into inflammatory, antioxidant, lipid-regulatory, microbiota-associated and cholinergic domains. The review distinguishes whole oil from oil-derived fractions and preclinical findings from human evidence. Direct human studies chiefly address short-term, outcome-specific surrogate endpoints. The proposed process-chain reporting and research framework links material quality to biological exposure and identifies priorities for reproducible studies and clinical validation.