Sex-Specific Effects of Menaquinone-7 (MK-7) Supplementation on Body Composition and Adiposity Markers

Background/Objectives: The benefits of vitamin K are well established in skeletal and cardiovascular health through activation of vitamin K-dependent proteins, including osteocalcin and matrix Gla protein. Emerging evidence also links vitamin K to pathways that influence body composition, including insulin sensitivity, adiponectin regulation, lipid oxidation, and inflammation. Vitamin K deficiency is linked to adverse health outcomes. We therefore evaluated whether menaquinone-7 (MK-7) supplementation alters body composition in adults with low vitamin K status. Methods: A total of 243 participants (166 women and 77 men) with low vitamin K status received 180 mcg of menaquinone-7 (MK-7), a form of Vitamin K, daily for one year. Changes in body mass index (BMI), body weight, fat mass, lean mass, and visceral adipose tissue (VAT) were assessed. Results: At baseline, higher dp-ucMGP, indicating lower vitamin K status, was positively associated with BMI (r = 0.223; p < 0.01), fat mass index (r = 0.200; p < 0.01), and VAT (r = 0.286; p < 0.001). After one year of supplementation, the total cohort showed a small but significant BMI reduction (−0.66%; p = 0.041). Responders (≥183 pmol/L dp-ucMGP drop) showed improvements in fat mass (−1.93%, p = 0.039), waist-to-hip ratio (−1.43%, p = 0.012), BMI (−1.37% ± 3.21, p = 0.004), and weight (−1.25%, p = 0.008), while non-responders exhibited an increase in VAT (+7.28%, p = 0.002). Women, especially premenopausal ones, experienced greater reductions in BMI, fat mass, and weight. dp-ucMGP levels significantly decreased in 90.9% of women (p < 0.001), whereas in men, although 77.8% showed a decrease, the change was not statistically significant. Among high responders (≥183 pmol/L dp-ucMGP reduction), both sexes demonstrated improvement, albeit significant body composition changes were seen only in women. Conclusions: Lower vitamin K status was associated with higher BMI, fat mass, and visceral adipose tissue. After one year of MK-7 supplementation, a modest reduction in BMI was observed, with more pronounced improvements in body composition among women. While these sex related differences may suggest that men require higher doses to achieve comparable responses, the current evidence remains preliminary. Further studies with larger cohorts are needed to clarify these findings.