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28-03-2011 | Bone health | Article

Vitamin K intake linked to bone quality

Abstract

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MedWire News: Dietary vitamin K intake is directly associated with calcaneus quantitative ultrasound (QUS) measurements, and may therefore have a role in bone density and structure, a study among elderly Spanish people has shown.

In addition, increasing vitamin K intake may protect against future bone loss, report Mònica Bulló (Universitat Rovira I Virgili, Reus, Spain) and colleagues in the journal Bone.

The researchers used QUS at the calcaneus to measure speed of sound (SOS) and broadband ultrasound attenuation (BUA), and estimate bone mineral density (BMD) in 362 men and women, aged 67 years on average, who had good nutritional status and followed a traditional healthy Mediterranean diet rich in vitamin K.

Each of the participants also completed a validated semi-quantitative 137-item food frequency questionnaire, which was used to estimate vitamin K intake.

Bulló and team report that, after adjustment for total energy intake, the median vitamin K intake was 319.4 µg per day in men and 311.4 µg per day in women, which they say is "higher than is recommended" for this age group. The majority (85%) of vitamin K came from vegetable consumption.

The researchers found that higher vitamin K intake was significantly associated with higher BMD and better QUS values. More specifically, each 100 µg increase in vitamin K intake was associated with a significant 0.007 g/cm2 increase in BMD, a 1.13 m/s increase in SOS, and a 0.96 dB/MHz increase in BUA, after adjustment for potential confounders including age, gender, and body mass index.

Furthermore, participants who increased their vitamin K intake during a 2-year follow-up period showed a significantly lower mean BMD loss (-0.009 vs -0.023 g/cm2), lower loss of bone porosity (SOS -7.27 vs -10.77 m/s) and increased elasticity (BUA 2.62 vs 0.16 dB/MHz), than those whose intake decreased during this time.

A low incidence of osteoporotic fractures (n=12) during the follow-up period meant that the team was unable to assess whether these were linked to vitamin K intake.

In spite of this, Bulló et al conclude that "high dietary vitamin K intake was associated with superior bone properties."

"Moreover, an increase in dietary vitamin K was significantly related to lower losses of BMD and smaller increases in the porosity and elasticity attributed to aging, which helps to explain the previously described protective effect of vitamin K intake against osteoporotic fractures," they add.

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

By Laura Dean

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