This pilot, genotype-stratified clinical trial aims to evaluate the safety and preliminary efficacy of vitamin K2 (menaquinone-7, MK-7) supplementation in patients with low bone mineral density (osteopenia or osteoporosis) who carry a specific "unfavorable" variant in the vitamin D receptor (VDR) gene (e.g., BsmI or ApaI polymorphisms). The trial will compare improvements in bone health and related biomarkers between two cohorts: (1) homozygous carriers of the VDR variant and (2) non-variant carriers (wild-type). Investigators hypothesize that MK-7 supplementation will lead to greater improvements in bone mineral density (BMD) and bone turnover markers in the homozygous variant group due to their potentially reduced baseline response to vitamin D signaling.

Vitamin D receptor (VDR) polymorphisms have been associated with varying responses to vitamin D and calcium supplementation, ultimately influencing bone health. Menaquinone-7 (vitamin K2) is crucial for carboxylation of osteocalcin, facilitating calcium deposition in bone. This study investigates whether individuals with an "unfavorable" VDR gene variant - who might have lower basal responsiveness to vitamin D - experience enhanced benefit from MK-7 supplementation in conjunction with a standard vitamin D3 regimen. By focusing on this genotype-stratified approach, the study aims to generate preliminary data supporting the role of personalized supplementation strategies in skeletal health.

Inclusion Criteria:

• Adults aged 40-75 years with a confirmed DXA-based diagnosis of osteopenia or osteoporosis (T-score ≤ -1.0).
• Stable dietary habits and willingness to maintain current exercise regimen throughout the study.
• Willingness to undergo genotyping for the VDR variant. For the VDR Variant Cohort: confirmed homozygous "unfavorable" variant (e.g., BsmI or ApaI).
• For the Non-Variant Cohort: confirmed absence of the "unfavorable" allele (wild-type).

Exclusion Criteria:

• Current or recent (last 3 months) use of high-dose bisphosphonates, anabolic agents (e.g., teriparatide), or selective estrogen receptor modulators (SERMs). Known allergy or hypersensitivity to vitamin K or vitamin D supplements.
• Severe renal or hepatic dysfunction, uncontrolled hyperthyroidism, or other significant comorbidities that could confound bone metabolism assessments.
• Pregnancy or breastfeeding.
• Inability or unwillingness to provide informed consent or to comply with study procedures.