Menaquinone-7 Retention in Whole-Soybean Natto Fermentation Powder: A Formulation Framework for Vitamin-K-Dependent Bone Metabolism

Menaquinone-7 (MK-7) is a long-chain vitamin K2 form produced during natto fermentation and directly participates in vitamin-K-dependent γ-carboxylation of osteocalcin. We characterized MK-7 retention in a whole-soybean natto powder produced by controlled solid-state fermentation, low-temperature post-ripening, low-temperature drying and temperature-limited pulverization. Three optimized process conditions contained 26.8-48.5 μg MK-7/g together with 1.52-2.62% γ-PGA and 1,160-1,680 FU/g nattokinase. Human studies span a useful sequence of endpoints. Natto feeding increased circulating MK-7 and carboxylated osteocalcin [1], and a one-year natto exposure study in premenopausal women changed bone-formation markers [2]. Longitudinal Japanese data linked habitual natto intake with more favorable BMD change at selected sites [3]. In early postmenopausal women, 360 μg/day MK-7 improved osteocalcin carboxylation without changing one-year bone-loss rates [4]. A three-year trial of 180 μg/day reported less decline at selected skeletal sites [5]. In osteopenic women receiving calcium and vitamin D, 375 μg/day produced a marked osteocalcin response and a one-year tibial microarchitecture signal [6], but the three-year analysis did not show significant between-group BMD or microarchitecture differences [7]. The NVTIA® matrix therefore offers a measured MK-7 exposure that can be linked first to osteocalcin carboxylation and then, where appropriate, to longer-term skeletal endpoints.