Vitamin K2 supplementation does not influence bone loss in early menopausal women: a randomised double-blind placebo-controlled trial

Abstract

Vitamin K2 may preserve bone strength and reduce fracture risk. In this randomised double-blind placebo-controlled trial among healthy postmenopausal Norwegian women, 1 year supplementation of vitamin K2 in the form of Natto capsules had no effect on bone loss rates. Japanese studies indicate that vitamin K2 (menaquinone-7 (MK-7)) intake may preserve bone strength, but this has not been documented in Europeans. The aim of this study was to assess the effect of MK-7 on bone mineral density (BMD) changes in postmenopausal Norwegian women. Three hundred thirty-four healthy women between 50 and 60 years, 1-5 years after menopause, were recruited to a randomised double-blind placebo-controlled trial. The participants were randomly assigned into two groups, one receiving 360 microg MK-7 in the form of Natto capsules and the other the same amount of identical-looking placebo capsules containing olive oil. BMD was measured at total hip, femoral neck, lumbar spine and total body at baseline and 12 months together with serum levels of bone-specific alkaline phosphatase, Crosslaps, total osteocalcin (N-mid OC), carboxylated (cOC) and under-carboxylated osteocalcin (ucOC). After 12 months, there were no statistical differences in bone loss rates between the groups at the total hip or any other measurement site. Serum levels of cOC increased and ucOC decreased in the treatment versus the placebo group (p < 0.001). MK-7 taken as Natto over 1 year reduced serum levels of ucOC but did not influence bone loss rates in early menopausal women.