Vitamin D, a seco-steroid hormone, has undergone a paradigm shift from a mediator of bone metabolism to a systemic pleiotropic regulator. This comprehensive study synthesizes contemporary evidence on its immunomodulatory, cardiovascular, neuroprotective, and anti-proliferative roles, mediated via the ubiquitously expressed vitamin D receptor (VDR). Serum 25-hydroxyvitamin D [25(OH)D] is the established biomarker, with deficiency (<50 nmol/L) linked to increased morbidity across multiple organ systems. To contextualize this knowledge within a specific population, we conducted a cross-sectional survey (n=126) assessing awareness, knowledge, and practices related to vitamin D within a Syrian cohort in Damascus. Results revealed a significant dissociation between high awareness and suboptimal practices: while 97.6% recognized the health risks of deficiency and 73% associated it with depression, 42.9% reported insufficient sunlight exposure, dietary intake was predominantly irregular, and 55.6% had never undergone serum 25(OH)D testing. Notably, 72.2% reported symptoms consistent with deficiency (fatigue, myalgia, bone pain), yet objective clinical assessment remained lacking. This pronounced knowledge-practice gap underscores a critical public health challenge. Our findings advocate for a dual-strategy approach: enhancing clinical protocols through targeted screening and management of high-risk individuals, and implementing precise, culturally adapted public health interventions that translate theoretical awareness into actionable behaviors—such as safe sun exposure guidelines, dietary modifications, and judicious supplementation. Future research must prioritize rigorous, long-term randomized controlled trials to define causal relationships and optimal thresholds for non-skeletal benefits. Ensuring vitamin D sufficiency represents a fundamental, modifiable component of holistic preventive medicine strategies against a broad spectrum of communicable and non-communicable diseases.