Astaxanthin as an age-adapted dietary modulator of gut microbiota and metabolism: Towards precision nutrition strategies for healthy aging

The gut microbiome's composition and function undergo significant remodeling with age, contributing to declining health. While the marine carotenoid astaxanthin (AST) is known to beneficially modulate the gut microbiota, its effects have primarily been studied in young organisms. Whether AST exerts age-divergent effects on the gut ecosystem remains unexplored. We employed an in vitro colonic fermentation model inoculated with fecal samples from healthy young (23–25 years) and elderly (70–75 years) cohorts to investigate the age-specific impact of AST on microbial community structure, ecological networks, and metabolic output. Our findings reveal that AST orchestrates fundamentally distinct, age-adapted ecological strategies. In young microbiomes, AST enhanced microbial diversity and fostered a highly interconnected, cooperative network, concurrently increasing the acetate/propionate ratio and favoring the production of neuroactive metabolites like serotonin. In stark contrast, in elderly microbiomes, AST did not broadly increase diversity but instead induced a targeted restructuring: enriching beneficial taxa, depleting potential pathobionts, and promoting ecological niche specialization. Most notably, AST preferentially and profoundly amplified butyrate synthesis and redirected tryptophan metabolism towards neuroprotective and antioxidant intermediates, such as 3-Hydroxyanthranilic Acid and Niacin, specifically in the aged gut. This study demonstrates that astaxanthin acts as an age-responsive dietary modulator of the gut microbiome. Its ability to tailor its effects—promoting microbial integration in youth while driving functional specialization and restoring key health-related metabolites in old age—highlights its significant potential for developing precision nutrition strategies aimed at promoting healthy aging.