Effects of Phytochemicals on Atherosclerosis: Based on the Gut–Liver Axis

Background: Atherosclerosis (AS) is the primary pathological basis for cardiovascular and cerebrovascular events, with its development closely linked to dyslipidemia and chronic inflammation. The gut–liver axis, serving as a core bridge connecting gut microbiota, hepatic metabolism, and systemic inflammation, has gained increasing prominence in AS pathogenesis. Phytochemicals exhibit multifaceted biological activities, yet their mechanisms for preventing and treating AS via the gut–liver axis remain to be systematically summarized. This review aims to summarize the potential mechanisms of phytochemicals interventions in AS from an intestinal–hepatic axis perspective. Methods: A systematic literature search was conducted using PubMed, Web of Science, and Embase, focusing on previously published articles, reviews, and meta-analyses. Keywords included “phytochemicals”, “flavonoids”, “atherosclerosis”, “AS”, “gut–liver axis”, “gut axis”, “intestinal axis”, “gut microbiota” and “TMAO”. This narrative review synthesizes current research evidence on the interactions among phytochemicals, the gut–liver axis, and atherosclerosis, summarizing their action pathways and molecular mechanisms. Results: Phytochemicals (such as polyphenols, carotenoids, saponins, etc.) have low bioavailability but can be metabolized and transformed by gut microbiota. Through multiple mechanisms—including modulating gut microbiota composition, enhancing intestinal barrier function, regulating bile acid metabolism, and exerting anti-inflammatory and antioxidant effects—they positively influence gut–liver axis function. This alleviates lipid metabolism disorders, suppresses systemic inflammation, and thereby combats the onset and progression of atherosclerosis at multiple stages. Conclusions: Phytochemicals can intervene in the progression of atherosclerosis through the gut–liver axis. Future studies should further investigate dose–response relationships and conduct clinical validation to determine optimal usage strategies.