Vitamin K supplementation did not protect against age-related BMD decreases

Postmenopausal women with osteopenia taking daily vitamin K1 supplementation still experienced age-related decreases in bone mineral density, but experienced fewer fracture and cancer incidences compared with women taking placebo, according to recent findings.

Researchers at the University of Toronto and the University Health Network in Toronto conducted a two-year, randomized, placebo-controlled, double-blind study to determine the efficacy of daily vitamin K1 supplementation on bone loss, bone turnover and fractures among postmenopausal women with osteopenia.

The study included 440 women with mean serum 25-hydroxyvitamin D levels of 77 nmol/L at baseline. Participants were randomly assigned to 5 mg vitamin K1 or placebo daily. Primary outcomes were changes in BMD at the lumbar spine and total hip at two years, according to the researchers.

At the lumbar spine, BMD decreased by –1.28% for the vitamin K group and –1.22% for placebo (P=.84). At the hip, BMD decreased by –0.69% for the vitamin K group and –0.88% for placebo (P=.51).

During the two- to four-year trial period, the researchers reported no significant differences between the two groups in BMD changes at any other sites.

Serum vitamin K1 levels increased 10-fold in the supplement group, and the percentage of undercarboxylated osteocalcin and total osteocalcin levels decreased.

Though their study was not powered to examine fractures or cancers, the researchers reported that, compared with placebo, women in the supplement group had fewer clinical fractures (20 vs. nine; P=.04) and fewer cancers (12 vs. three; P=.02).

“More studies are needed to further examine the effect of vitamin K on fractures and cancers,” the researchers wrote.

PLoS Med. 2008;5:1461-1471.