Calcium and Gastrointestinal Disorders: Mechanistic Insights and Therapeutic Interventions.

Calcium plays a central role in gastrointestinal (GI) physiology through regulating smooth muscle contractility, acid secretion, epithelial barrier integrity, and immune signaling. The dysregulation of calcium homeostasis has been increasingly implicated in the pathogenesis of GI disorders, including colorectal cancer, inflammatory bowel disease, peptic ulcer, and pancreatitis. Specifically, aberrant calcium-sensing receptor (CaSR) signaling has emerged as a critical molecular mechanism in colorectal tumorigenesis; meanwhile, calcium-mediated pathways influence gastric acid production and intestinal motility. This review critically evaluated recent advances in calcium signaling within the GI tract, highlighting the crosstalk involved with the gut microbiota and the roles of downstream effectors, including transient receptor potential vanilloid type 6 and store-operated calcium entry. This review also examined the therapeutic implications of calcium supplementation across various GI conditions, including bioavailability challenges under different disease states and nutrient interactions involving vitamin D and phosphate. Our review further addresses the role of calcium in mucosal immunity, the clinical relevance of hypocalcemia in GI diseases, and the potential of microbiome-guided nutritional interventions. However, despite growing mechanistic insights, considerable gaps remain in understanding host-microbiota-calcium interactions, genotype-specific responses to calcium, and long-term clinical outcomes. Thus, future research should clarify the dose-response relationships, stratify patient populations by CaSR polymorphisms and microbiome profiles, and establish precision strategies for calcium-based interventions in digestive health.