Research Progress in Sunlight Therapy for Chronic Kidney Disease

Chronic kidney disease (CKD) is a globally prevalent progressive disease characterized by complex interorgan signaling dysregulation. Fibroblast growth factor 23 (FGF23) and active vitamin D3 (VD3 and 1,25(OH) 2 D 3 ) play critical roles in calcium–phosphate homeostasis. FGF23 reduces intestinal phosphate absorption by inhibiting 1,25(OH) 2 D 3 synthesis, whereas 1,25(OH) 2 D 3 negatively regulates FGF23 expression. In patients with CKD, this balance is disrupted, leading to elevated FGF23 levels, reduced 1,25(OH) 2 D 3 levels, and exacerbated kidney dysfunction and complications. Since the primary source of VD3 is cutaneous synthesis via ultraviolet B radiation, sunlight exposure can markedly increase VD3 production, subsequently increasing 1,25(OH) 2 D 3 levels. This suggests that sunlight therapy may serve as a potential intervention for modulating FGF23 and improving calcium–phosphate metabolism in patients with CKD. This review systematically summarizes the regulatory mechanisms of sunlight on VD3 synthesis, the role of FGF23 in CKD progression, and the potential applications of sunlight therapy in CKD management. Additionally, we discuss the applicability of sunlight therapy across different individuals, its limitations, and potential optimization strategies, providing insights for future research.