Microalgal Fucoxanthin in Environmental Medicine: Sustainable Bioproduction, Bioavailability Enhancement, and Translational Health Applications

Microalgal fucoxanthin is a marine xanthophyll relevant to environmental medicine because it links sustainable resource recovery with prevention-oriented research on environmentally driven metabolic disorders. Methods: This critical narrative review synthesizes recent peer-reviewed studies, related reviews, and regulatory documents on fucoxanthin chemistry, microalgal sources, cultivation, downstream processing, bioavailability enhancement, safety, and translational evidence. Findings: Diatoms and haptophytes, including Phaeodactylum tricornutum, Tisochrysis lutea, Isochrysis galbana, Nitzschia laevis, Cyclotella meneghiniana, and Conticribra weissflogii, are candidate production platforms, while Poterioochromonas malhamensis currently lacks the safety and regulatory evidence required for food use. Evidence for metabolic dysfunction-associated steatotic liver disease (MASLD), obesity, diabetes, inflammation, lipid metabolism, microbiota modulation, and chemoprevention remains predominantly preclinical or is derived from macroalgal or combined marine formulations. No randomized clinical trial evaluating a standardized microalgal fucoxanthin formulation with pharmacokinetic characterization was identified in the literature reviewed. Wastewater-derived biomass faces a strict regulatory barrier to oral human use and is currently best suited to environmental and agricultural applications unless contaminant clearance and product-specific safety are demonstrated. Conclusions: Bioavailability is constrained by instability, poor aqueous dispersibility, intestinal de-esterification to fucoxanthinol, and hepatic oxidation to amarouciaxanthin A, but encapsulation and lipid-matrix systems are promising. Translation requires authenticated strains, human-grade cultivation, validated processing, product-specific toxicology, regulatory dossiers, and controlled clinical studies.