It is involved with the production of proteins in bone, including osteocalcin, which is needed to prevent the weakening of bones. In addition, low blood levels of vitamin K have been linked with low bone density. A report from the Nurses’ Health Study suggests that women who get at least 110 mcg of it a day are 30% less likely to break a hip than women who get less than that.
Among the nurses, eating a serving of lettuce or other green, leafy vegetable a day cut the risk of hip fracture in half when compared with eating one serving a week. Data from the Framingham Heart Study also showed an association between its high intake and reduced risk of hip fracture in men and women and increased bone mineral density in women.
However, the results of clinical trials and meta-analyses have been conflicting whether its supplements reduce bone fractures.
This may be due to a variety of other factors that affect bone health, including a lack of calcium, vitamin D, and weight-bearing exercise, all of which might mask a benefit of vitamin K supplementation.