Vitamin K intake and hip fractures in women: a prospective study

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Abstract
Background: Vitamin K mediates the γ-carboxylation of glutamyl residues on several bone proteins, notably osteocalcin. High serum concentrations of undercarboxylated osteocalcin and low serum concentrations of vitamin K are associated with lower bone mineral density and increased risk of hip fracture. However, data are limited on the effects of dietary vitamin K. Objective: We investigated the hypothesis that high intakes of vitamin K are associated with a lower risk of hip fracture in women. Design: We conducted a prospective analysis within the Nurses' Health Study cohort. Diet was assessed in 72327 women aged 38–63 y with a food-frequency questionnaire in 1984 (baseline). During the subsequent 10 y of follow-up, 270 hip fractures resulting from low or moderate trauma were reported. Results: Women in quintiles 2–5 of vitamin K intake had a significantly lower age-adjusted relative risk (RR: 0.70; 95% CI: 0.53, 0.93) of hip fracture than women in the lowest quintile (Conclusions: Low intakes of vitamin K may increase the risk of hip fracture in women. The data support the suggestion for a reassessment of the vitamin K requirements that are based on bone health and blood coagulation.