Astaxanthin and Male Reproductive Health: Mechanisms, Experimental Evidence, and Clinical Perspectives.

Oxidative stress is a primary driver of male infertility, underscoring the critical importance of effective antioxidant defense systems in maintaining reproductive function. Astaxanthin, a xanthophyll carotenoid with potent free radical-scavenging capacity and membrane-stabilizing properties, has garnered interest as a therapeutic agent for male reproductive health. Experimental evidence indicates that astaxanthin modulates cellular redox homeostasis, preserves mitochondrial integrity, and attenuates lipid peroxidation in spermatozoa and testicular cells. Through these mechanisms, it potentially maintains sperm structural integrity and functional competence under oxidative stress. Preclinical studies demonstrate that astaxanthin supplementation enhances sperm quality, supports mitochondrial bioenergetics, and protects against testicular oxidative injury. However, clinical evidence in men remains limited and heterogeneous, with variations in study populations, treatment durations, dosages, and outcome measures. Although some clinical investigations report improvements in semen parameters and markers of oxidative stress, others lack consistent findings. Consequently, these clinical data must be interpreted with caution. This narrative review synthesizes knowledge on the biological mechanisms through which astaxanthin influences male reproductive physiology, including oxidative regulation and stress response modulation. It evaluates existing data, identifies significant knowledge gaps, and highlights research priorities. To clarify the therapeutic utility of astaxanthin in male infertility, well-designed, large-scale randomized controlled trials featuring standardized formulations and robust clinical outcomes are required.