Low Dose Daily Intake of Vitamin K2 (Menaquinone7) Improves Osteocalcin γ-Carboxylation: A DoubleBlind, Randomized Controlled Trials
Vitamin K is essential for bone health due to its activation of the K-dependent protein osteocalcin. But researchers felt the effects of low-dose vitamin K intake in Japanese subjects remained unclear. To that end, they investigated the effective minimum daily menaquinone-7 (MK-7) dose for improving osteocalcin γ-carboxylation (i.e., activation).
The first study (Study 1) was a double-blind, randomized, controlled, dose-finding trial where 60 postmenopausal women aged 50-69 years were allocated to one of four dosage groups and consumed 0, 50, 100, or 200 μg menaquinone7 daily for 4 wk, respectively, with a controlled diet in accordance with recommended daily intakes for 2010 in Japan.
The second study (Study 2) was a double-blind, randomized, placebo-controlled trial based on the results of Study 1. In this study, 120 subjects aged 20-69 years were allocated to the placebo or MK-7 group and consumed 0 or 100 μg MK-7 daily for 12 weeks, respectively.
In both studies, circulating carboxylated osteocalcin (cOC) and undercarboxylated osteocalcin (ucOC) were measured. The cOC/ucOC ratio decreased significantly from baseline in the 0 μg MK-7 group, in which subjects consumed the recommended daily intake of vitamin K with vitamin K1 and menaquinone 4 (Study 1). Menaquinone-7 increased the cOC/ucOC ratio dose dependently, and significant effects were observed in both the 100 and 200 μg groups compared with the 0 μg group. ucOC concentrations decreased significantly, and the cOC/ucOC ratio increased significantly in the 100 μg MK-7 group compared with the placebo group (Study 2).
The researchers concluded that daily menaquinone-7 intake ≥100 μg was suggested to improve osteocalcin γ-carboxylation.
Inaba N, Sato T, Yamashita T. Low Dose Daily Intake of Vitamin K2 (Menaquinone7) Improves Osteocalcin γ-Carboxylation: A DoubleBlind, Randomized Controlled Trials. J Nutr Sci Vitaminol (Tokyo). 2015;61(6):47180. doi: 10.3177/jnsv.61.471