Microalgae are emerging as a valuable source of bioactive compounds with significant potential to modulate gut microbiota and improve human health. This review explores the roles of microalgal-derived polysaccharides, peptides, polyunsaturated fatty acids, polyphenols, pigments, and micronutrients in shaping intestinal microbial composition and function. These compounds promote beneficial bacteria, inhibit pathogens, enhance immune responses, and regulate key metabolic pathways through the production of short-chain fatty acids and other microbial metabolites. Moreover, microalgae exhibit antioxidant, anti-inflammatory, and antitumor properties that may support the prevention of chronic diseases. However, challenges such as bioavailability, safety, individual microbiota variability, and industrial scalability must be addressed. Despite these limitations, microalgae hold promise as sustainable, multifunctional ingredients for developing functional foods and therapeutic interventions. Future research could focus on clinical validation, optimized extraction methods, and personalized nutrition approaches to fully harness the health benefits of microalgae-derived bioactive compounds in modulating the gut microbiota.
