Polyphenols regulate bone health through the gut-bone axis: molecular and applications in animal nutrition

This review summarizes the regulatory roles of polyphenolic compounds in animal skeletal health through the gut-bone axis and explores their benefits for animal nutrition. First, this review focuses on their key roles in maintaining skeletal homeostasis through gut microbiota, intestinal barrier integrity, immune regulation, microbial metabolites, and endocrine signaling. Then, from a biological mechanism perspective, we summarize how polyphenolic compounds regulate animal bone metabolism by reshaping gut microbiota composition, promoting short-chain fatty acid production, enhancing intestinal barrier function, reducing oxidative stress and systemic inflammation, and modulating osteogenic and osteoclastic signaling pathways. Furthermore, this review comprehensively discusses representative subclasses of polyphenolic compounds (including flavonoids, phenolic acids, lignans, stilbenes, and other bioactive compounds) and elucidates their mechanisms in animal skeletal protection and nutritional regulation. In conclusion, this review provides a theoretical foundation for understanding the polyphenol-mediated gut-bone axis regulatory mechanisms and offers new insights into nutritional strategies for promoting bone health in animals.