Dietary Polysaccharides in Skin Health: Structure–Function Relationships and Implications for Nutritional Dermatology

Skin health depends on the coordinated maintenance of barrier integrity, immune homeostasis, redox balance, microbial ecology, and systemic metabolic status. Among dietary constituents, polysaccharides have attracted increasing attention because they represent a structurally heterogeneous class of complex carbohydrates whose biological behavior is shaped by molecular weight, monosaccharide composition, glycosidic linkage patterns, branching, higher-order conformation, and physicochemical properties. However, many current skin-related studies remain primarily phenomenon-driven, with insufficient attention to how specific structural features influence biological function and dermatologic relevance. From a structure-function perspective, key structural features of dietary polysaccharides may influence several skin-relevant biological processes, including microbiota-associated signaling, immune regulation, barrier homeostasis, oxidative balance, and extracellular matrix protection. The relevance of these structure-linked functions differs across dermatologic contexts: it appears most direct in photoaging, more conditional in atopic dermatitis, and relatively indirect in psoriasis, whereas wound-repair-related settings are less closely aligned with strict dietary relevance. Current evidence therefore supports structure-function associations more strongly than direct associations between specific structural features and dermatologic outcomes. Dietary polysaccharides are not functionally interchangeable in skin-related contexts, and their skin-related effects depend on structural background, disease setting, and mode of application. Where non-dietary evidence is discussed, it serves primarily as mechanistic or translational contextualization rather than as a basis for nutritional recommendation. Clarifying these relationships may support future mechanistic research and facilitate more rational nutritional applications of dietary polysaccharides in skin health.