Vitamin K levels may be too low in early menopause

NEW YORK (Reuters Health) - As estrogen levels drop in early menopause, vitamin K function - which is essential to maintain normal clotting -- in bone is impaired before any actual bone loss occurs, new research shows.

"Our study suggests that the generally accepted level of vitamin K in healthy women is inadequate to maintain bone health just at the onset of menopause," lead author Dr. Jane L. Lukacs, from the University of Michigan at Ann Arbor, said in a statement.

The findings, which appear in the current issue of Menopause, indicate that the percentage of osteocalcin is a marker for the bone condition of health women in early postmenopause.

Binding of osteocalcin to calcium is necessary for normal bone formation. However, only a modified form of the protein will bind to calcium, and this modification is dependent on adequate vitamin K levels. Thus, without enough vitamin K, bone formation can be impaired.

The current study involved a comparison of various hormone and vitamin K-related biomarkers in 19 cycling young women (20 to 30 years), 19 cycling older women (40 to 52 years) and in 21 women in early postmenopause (40 to 52 years).

The estradiol and vitamin levels in the cycling older women were similar to that of their younger peers, but they did have lower osteocalcin and bone mineral density at the total hip.

Bone mineral was similar at all sites in the two older groups of women, but osteocalcin was elevated in the early postmenopausal group, indicating increased bone turnover. Circulating vitamin K levels were highest in early postmenopausal subjects, yet they also had the highest percentage of unmodified osteocalcin.

The findings show that there is an association between early menopause and unusable osteocalcin, suggesting that the levels of vitamin K common in healthy women -- and presumed to be adequate to maintain normal clotting mechanisms -- are inadequate to maintain postmenopausal bone health," the researchers conclude.

SOURCE: Menopause, September/October, 2006.