Background: The high serum undercarboxylated osteocalcin (ucOC) value is a risk factor for proximal femoral fractures independent of the BMD. The vitamin K insufficiency is indicated of high ucOC value. Natto, which is one of the food to eat in breakfast well in Japan, is a major source of vitamin K. The purpose of present study is to determine whether the incidence of new osteoporotic fractures is associated with vitamin K insufficiency and with the ucOC value, a surrogate marker of vitamin K insufficiency in bone in postmenopausal Japanese women.
Methods: We conducted a survey in 289 postmenopausal women who were inpatients or outpatients. Age, vitamin K intake (frequency of natto intake per week), ucOC value, urinary cross-linked N-telopeptides of type I collagen (u-NTX), BMD (lumbar, femoral neck, total hip), the presence or absence of new osteoporotic fractures, and use of osteoporosis medications (antiresorptive drugs, other drugs, none) were surveyed.
Results: The mean age of the subjects was 74.6±9.6 years. As many as 207 (72%) of the 289 women reported low natto intake (once a week or less or none) and thus low intake of vitamin K. Low natto intake was associated with significantly higher ucOC values. The incidence of new osteoporotic fractures increased with decreasing natto intake. Further analysis revealed a higher incidence of new osteoporotic fractures in the high-ucOC subgroup. A multivariate logistic regression using the presence or absence of new osteoporotic fractures as an objective variable revealed that age, total hip BMD, and ucOC value were independently associated with the incidence of new osteoporotic fractures.
Conclusions: High ucOC values were demonstrated to be associated with insufficient intake of vitamin K and with the appearance of new osteoporotic fractures.
Disclosure: The authors declared no competing interests.