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17-07-2011 | Bone health | Article

Vitamin K effects on bone mineral density unclear

Abstract

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MedWire News: More high-quality research is needed to ascertain the effect of vitamin K on bone mineral density (BMD), say the authors of a meta-analysis.

The team aimed to address inconsistencies in results from previous research into the effects of vitamin K on BMD, but found that the variable quality of studies to date made the results of the meta-analysis unclear.

Chuanlai Hu and colleagues (Anhui Medical University, China) write: "Over the last several decades, vitamin K has been studied in relation to bone mineral regulation regarding its favorable effect on gamma-carboxy glutamate, a glutamate-containing protein produced by osteoblasts during bone formation."

More recently, randomized controlled trials (RCTs) have tried to determine exactly how vitamin K affects bone mass, but "have generated inconsistent results, possibly due to variations in sample size and study objective," Hu and co-authors write.

Noting this, the team performed a systematic literature review and meta-analysis of RCTs assessing the use of vitamin K treatment on BMD. The literature review identified 17 prospective RCTs, which included over 3300 patients.

Analysis of the pooled data showed that vitamin K supplementation improved BMD at the lumbar spine, but not the femoral neck, with an average difference in BMD between patients who did and did not receive a supplement of 21.6 mg/cm2 and 0.25 mg/cm2, respectively.

Further research revealed that the effects of vitamin K treatment on lumbar spine bone mass varied significantly according to ethnicity, gender, and the form of vitamin K given.

Importantly, the authors say that the quality of the studies included was "not optimal" and, after excluding poor quality studies, vitamin K was found to have no significant impact on BMD at the lumbar spine or femoral neck.

In addition, between-study heterogeneity and the bias toward publication of positive studies and non-publication of negative studies must be taken into account when considering the results of the meta-analysis, the investigators caution.

The team recommends further study focusing on the differences observed in the effects of vitamin K on BMD according to ethnicity, gender, and form of vitamin K used.

The results are published in the Journal of Bone and Mineral Metabolism.

MedWire (www.medwire-news.md) is an independent clinical news service provided by Springer Healthcare Limited. © Springer Healthcare Ltd; 2011

By Philip Ford

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