The global ageing population is increasingly affected by age-related diseases, which are challenging healthcare systems. Current treatments often extend lifespan without improving healthspan. The geroscience hypothesis suggests that targeting the ageing process could prevent or delay multiple diseases, enhancing healthspan. Fucoidan, a sulfated polysaccharide from brown macroalgae, is a safe dietary supplement with Sirtuin-6 (SIRT6) activating properties, which are linked to longevity. Clinical studies have shown that it reduces inflammatory markers associated with biological aging and frailty and influences DNA methylation in vitro and in vivo; however, its effects on human DNA methylation remain unknown.