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Health News Archive 342 - Bone Health
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Vitamin K Supplementation Increases BMD and Reduces Hip Fracture 80%

In the June 2006 edition of the Archives of Internal Medicine, researchers pooled 13 randomized placebo-controlled trials on vitamin K supplementation for bone health.  In the seven trials included in this meta analysis which included information on bone fracture rates, it was found that vitamin K supplementation up to 45 mg daily reduced fracture rate between 60% and 81%. The researchers indicated that the benefit behind vitamin K's influence was from modification of a protein called osteocalcin which is required to bind calcium to the bone matrix.

There are two main forms of vitamin K: phylloquinone, also known as phytonadione, (vitamin K1) which is found in green leafy vegetables such as lettuce, broccoli and spinach, and makes up about 90 per cent of the vitamin K in a typical Western diet; and menaquinones (vitamins K2), which make up about 10 per cent of Western vitamin K consumption and can be synthesized in the gut by microflora.

In the seven trials, six used 45-milligram daily doses, and one used 15-milligram daily doses. Five studies used elderly women as the study population, while two used male and females.

The researchers, led by David Torgerson from the University of York, England, calculated that the vitamin K supplements were associated with a consistent reduction in all fracture types. Supplementation of vitamin K (MK-4) resulted in reductions in hip fractures of 77 per cent, vertebral fracture of 60 per cent, and all non-vertebral fractures of 81 per cent. The fracture rates were also reduced at all fracture sites, say the researchers, with hip fracture rates reduced by six per cent, vertebral fracture of 13 per cent, and all non-vertebral fractures of nine per cent.

“In this systematic review and meta-analysis, we have shown that supplementation with [vitamin K] phytonadione and menaquinone, particularly MK-4, is associated with increased bone mineral density (BMD) and reduced fracture incidence,” wrote lead author Sarah Cockayne. “The reduction in fracture incidence is particularly striking, with an approximate 80 per cent reduction in hip fractures,” she said.

No serious adverse effects were recorded in any of the studies, although some minor gastrointestinal problems were occasionally noted.

The mechanism behind the benefits is proposed to be due to vitamin K's influence on the secondary modification of osteocalcin, a protein needed to bind calcium to the bone matrix.

“From a clinical perspective, the results of this review suggest that patients at risk for fracture should be encouraged to consume a diet rich in vitamin K, which is chiefly obtained from green leafy vegetable and certain vegetable oil,” concluded the researchers.

One major limitation with this study is that the researchers did not look into the effects of other types of menaquinone, most notably MK-7 (vitamin K2), which is found in products such as the fermented soy product natto, and is more absorbable by the body. Many studies, mostly from Japan, have reported that increased MK-7 intake can also have significant benefits on bone health.

Osteoporosis is estimated to affect about 75,000,000 people in Europe, the USA and Japan. According to the International Osteoporosis Foundation, the total direct cost of osteoporotic fractures is $17,500,000,000 in the US (2002 figure).

Source: Sarah Cockayne; Joy Adamson; Susan Lanham-New; Martin J. Shearer; Simon Gilbody; David J. Torgerson. Vitamin K and the Prevention of Fractures: Systematic Review and Meta-analysis of Randomized Controlled Trials. Arch Intern Med. 2006 Jun;166:1256-1261.

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