According to findings published in the journal Transplantation, a 180 microgram dose of vitamin K2 (menaquinone-7) was found to improve bone mineral density at the lumbar spine region in people following heart or lung transplants.
“The results suggest that dietary supplement with menaquinone-7 could have a favorable effect on bone mass, for bone mineral density more in the heart than the lung recipients, whereas for bone mineral content only in the lung recipients,” wrote the researchers, led by Liv Forli from Oslo University Hospital.
On the other hand, the researchers noted increases in levels of a hormone called parathyroid hormone (PTH) which is a marker of vitamin D status. This indicated a greater need for vitamin D in these patients, added the researchers.
“The results are suggestive, and further studies are needed before vitamin K2 treatment can be generally recommended in clinical practice,” wrote Forli and co-workers.
Bone health and transplants
Osteoporosis is characterized by low bone mass, which leads to an increase risk of fractures, especially the hips, spine and wrists. An estimated 75 million people suffer from osteoporosis in Europe, the USA and Japan.
Women are four times more likely to develop osteoporosis than men.
The Norwegian researchers note that osteoporosis is a problem after transplantation, and results of the new study indicate that vitamin K2 may have a beneficial role.
Over 3,500 organ transplants occurred in the UK between 1 April 2008 and 31 March 2009, according to Britain’s NHS Blood and Transplant. In the US about 4,400 people receive heart transplants and about 3,500 people received lung transplants, according to the Scientific Registry of Transplant Recipients.
The study, funded by NattoPharma, included 35 lung and 59 heart recipients. The participants were randomly assigned to receive either vitamin K2 supplements or placebo for one year. At the end of the study, BMD in the lumbar spine increased by 0.028 g/cm and bone mineral content increased by 1.33 g/cm.
The researchers also note that many people in both groups had insufficient vitamin D levels, particularly in the K2 group “indicating a higher need for vitamin D”, they added.
“One year of vitamin K2 supplement suggests a favourable effect on lumbar spine BMD with different response in lung and heart recipients,” wrote the researchers. “Vitamin D status should receive more attention,” they concluded.
There are two main forms of vitamin K: phylloquinone, also known as phytonadione, (vitamin K1) and menaquinones (vitamins K2). K1 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; while K2, which makes up about 10 per cent of Western vitamin K consumption and can be synthesised in the gut by microflora.
Menaquinones (MK-n: with the n determined by the number of prenyl side chains) can also be found in the diet; MK-4 can be found in animal meat, MK-7, MK-8, and MK-9 are found in fermented food products like cheese, and natto is a rich source of MK-7.
MK-4 is distinct from other MKs because it is not a major constituent of the spectrum of MKs produced by gut microflora, but can be derived from K1 in vivo.
A synthetic form of vitamin K, known as K3, does exist but is not recommended for human consumption.
Volume 89, Number 4, Pages 458-464
"Dietary Vitamin K2 Supplement Improves Bone Status After Lung and Heart Transplantation"
Authors: L. Forli, J. Bollerslev, S. Simonsen, G.A. Isaksen, K.E. Kvamsdal, K. Godang, G. Gadeholt, A.H. Pripp, O. Bjortuft