Relationships between undercarboxylated osteocalcin and vitamin K intakes, bone turnover, and bone mineral density in healthy women.

Low vitamin K intakes and high levels of undercarboxylated osteocalcin (ucOC) are risk factors for hip fractures. However, the relationship between ucOC and vitamin K intakes, bone mineral density (BMD) and bone biochemical markers is not clarified. We enrolled 221 healthy women, and examined BMD, urinary type-I collagen cross-linked-N-telopeptide (uNTX), and nutrient intakes. BMD was measured at the lumbar spine and femoral neck. Vitamin K intakes were significantly and negatively correlated with ucOC after adjustment for age, height, and body weight (r=-0.305, p<0.0001). ucOC was negatively associated with lumbar BMD (r=-0.147, p<0.05), but not femoral neck BMD (r=-0.099, p=0.095) after adjustment for age, height, and body weight. In multiple regression analysis, even after adjustment for age, height, body weight, and vitamin K intake, a significant and positive correlation remained between ucOC and urinary NTX (r=0.493, p<0.0001). Moreover, in postmenopausal women, ucOC levels were positively correlated with urinary NTX, but not BMD. Dietary vitamin K intakes influence serum levels of ucOC in healthy women. Furthermore, ucOC may be linked to bone biochemical markers.