Nutraceuticals, functional foods, and bioactive compounds for healthy skin aging: Effects on hydration, elasticity, wrinkles, pigmentation, and photoprotection

<jats:p>Background: Skin aging reflects intrinsic aging and extrinsic stressors, particularly ultraviolet radiation, oxidative stress, inflammation, glycation, and the progressive deterioration of collagen, elastin, hydration, and barrier function. Oral functional foods and food-derived bioactive compounds are increasingly being studied as supportive approaches to maintaining skin health. Objective: This narrative review evaluates selected functional food categories in relation to hydration, elasticity, wrinkles, pigmentation, transepidermal water loss, and photoprotection. Methodology: PubMed and Functional Food Center journal sources, including Functional Foods in Health and Disease, were searched for literature published from database or journal inception through July 2026. No lower publication-date restriction was applied, although recent evidence was prioritized. Search terms, used individually and in combination, included "functional foods," "skin aging," "collagen peptides," "carotenoids," "polyphenols," "vitamin C," "photoprotection," and "gut-skin axis," together with ingredient- and outcome-specific terms. Reviews, systematic reviews, meta-analyses, randomized controlled trials, and mechanistic studies of orally consumed foods or food-derived components were prioritized; topical-only interventions, non-food drugs, and unrelated dermatologic conditions were excluded. Results: Oral collagen peptides have the most direct human evidence, with short-term trials reporting modest improvements in elasticity, hydration, wrinkle measures, or dermal structure, although findings remain formulation-specific. Additional product-specific signals arise from oral hyaluronan, milk- and rice-derived ceramide extracts, astaxanthin, selected probiotics, soy isoflavones, dietary lipids, whole foods, olive-leaf extract, and fermented papaya. Tomato-derived carotenoids and cocoa or green-tea polyphenols may improve resistance to ultraviolet-induced erythema and selected skin properties, but null or mixed findings occur across formulations. Direct clinical evidence for pigmentation remains limited, and heterogeneity in dose, matrix, population, outcome measurement, and industry involvement restricts broad claims.  Conclusion: Functional foods may complement sun protection and healthy lifestyle practices through effects on collagen metabolism, oxidative stress, inflammation, photoprotection, hydration, and barrier function. Larger independent trials using standardized formulations, quantitative endpoints, diverse populations, and longer follow-up are needed before product-wide or long-term claims can be justified. Novelty of the Study: This review separates whole foods, standardized extracts, isolated bioactives, and combination products and applies the Functional Food Center four-phase, 17-step framework to skin-aging evidence. It identifies which research and development steps are supported and where evidence remains insufficient regarding dose-time, food-vehicle, long-term safety, regulatory, epidemiological, and post-market evidence. Keywords: functional foods, skin aging, collagen peptides, carotenoids, polyphenols, vitamin C, photoprotection, gut-skin axis</jats:p>