The Potential Role of Vitamin D in BRCA1 Pathogenic Variant Carriers: A Narrative Review.

Vitamin D is a fat-soluble secosteroid essential for skeletal development and calcium homeostasis, but it also exerts pleiotropic effects on numerous biological processes via its active metabolites. Vitamin D metabolites act as steroid hormones that regulate cell-cycle progression, proliferation, differentiation, apoptosis, immune responses, and multiple intracellular signaling pathways. Moreover, they modulate the expression of genes involved in carcinogenesis. As circulating vitamin D levels are influenced by diet, fortified foods, and supplementation, they represent a potentially modifiable factor. Whether vitamin D status affects cancer risk or disease progression in carriers of pathogenic BRCA1 variants remains unclear and continues to be actively investigated. Clarifying this relationship could have significant clinical implications for risk stratification and prevention in this high-risk population. This narrative review summarizes current evidence from epidemiological, clinical, and molecular studies examining the role of vitamin D in BRCA1 pathogenic variant carriers. It also highlights key limitations in the existing literature and identifies critical directions for future research, emphasizing the need for well-designed prospective studies in representative cohorts.