Fucoidan as an anti-inflammatory and immunomodulatory agent in humans: a systematic review of clinical evidence and translational potential.

Purpose: fucoidan is a sulphated polysaccharide from brown seaweeds, commonly used as a dietary supplement due to its proposed anti-inflammatory, immunomodulatory, and potential tumour-related properties. However, despite substantial preclinical evidence, its clinical effects in humans remain unclear. This systematic review aims to evaluate and synthesise current clinical evidence on the effects of fucoidan on inflammatory, immune, metabolic, and tumour-related outcomes in humans. Methods: a systematic literature search was conducted in PubMed, Scopus, and Web of Science in accordance with the PRISMA guidelines. Human interventional studies evaluating fucoidan supplementation and reporting clinically relevant outcomes were included. Eligible populations comprised healthy adults, individuals with metabolic or inflammatory conditions, and patients with cancer. Outcomes included immune function, inflammatory biomarkers, metabolic parameters, tumour-related outcomes, quality of life, and safety. Risk of bias was assessed using the OHAT tool. Due to heterogeneity in study design and outcomes, meta-analysis was not performed. Results: five clinical studies met the inclusion criteria, including three randomised controlled trials and two open-label studies involving patients with cancer, with intervention durations of 2 to 24 weeks. Fucoidan was consistently well-tolerated, with no serious adverse events reported. Individual controlled trials reported reductions in selected pro-inflammatory cytokines, sex-specific changes in NK cell activity, and changes in gut microbiota composition in individuals with metabolic risk. However, these findings were not consistently replicated across studies. Studies involving patients with cancer reported short-term reductions in inflammatory markers and stable quality-of-life (QOL) measures; however, tumour-related outcomes were inconclusive. Conclusions: current evidence suggests that fucoidan may exert modest anti-inflammatory and immunomodulatory effects under selected clinical conditions; however, the available evidence remains limited, heterogeneous, and inconsistent. Although oral fucoidan was generally well tolerated, the small number of studies, limited replication of findings, heterogeneity in study populations and fucoidan characteristics, and methodological limitations preclude definitive conclusions regarding clinical efficacy. Well-designed, adequately powered randomised controlled trials using well-characterised fucoidan and clinically meaningful outcomes are required to establish the clinical efficacy of fucoidan in humans.