A recent trial from Norwegian researchers published in Osteoporosis International reported no benefits to bone health after 12 months of supplementation with 360 micrograms of vitamin K2 (menaquinone-7, MK-7).
However, Professor Cees Vermeer at the VitaK research center in Maastricht, a global leader in vitamin K research, said that the new study did not fulfil criteria in order to fully examine if vitamin K2 could affect bone health, specifically noting that each arm of the study should contain at least 50 people, and that the study should last for at least two years.
The new study did contain sufficient numbers per intervention arm, but only lasted for 12 months, which is not enough, added Dr Leon Schurgers, VP of R&D at vitamin K2 supplier NattoPharma.
“All vitamin K intervention trials lasting less than 2 years have unfortunately contributed to confusion regarding the effect of vitamin K supplements. The study of Emaus et al is no exception,” said Dr Schurgers.
A number of previous studies appear to support the benefits of vitamin K for boosting bone health and reducing the risk of osteoporosis. A significant body of evidence also exists supporting a role for the vitamin in enhancing cardiovascular health. Emerging evidence also supports a potential role for reducing the risk of prostate cancer, and boosting joint health.
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 scientists, led by Nina Emaus from the University of Tromso, recruited 344 healthy postmenopausal Norwegian women and randomly assigned them to receive a daily placebo capsule (olive oil) or vitamin K2 (360 micrograms, MK-7) for one year.
At the end of the study the researchers observed an improvement in levels of osteocalcin, a vitamin K-dependent protein that is essential for the body to utilise calcium in bone tissue, compared with placebo. Without adequate vitamin K, the osteocalcin remains inactive, and thus not effective. Levels of the inactive form of osteocalcin also decreased, said the researchers. However, no difference in bone loss was observed between the groups.
Commenting on the research, vitamin K2 supplier NattoPharma said the research may create “unnecessary uncertainty among consumers”.
“It is a fact that changes in biochemical markers appear faster than changes in bone mass,” said the company. “NattoPharma therefore believes that if the study had stretched over longer time, one would most likely have seen a positive result also in bone mass.”
The unKnown vitamin
The vitamin is less well known than vitamins A to E. Vitamin K has long been linked to blood health because about half of the 16 known proteins that depend on the vitamin are necessary for blood coagulation.
There are two main forms of vitamin K: phylloquinone (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.
K2 makes up about 10 per cent of consumption and can also be obtained from the dietary sources like animal meat, and fermented food products like cheese, and natto. Multivitamins contain either small amounts or no vitamin K at all.
Source: Osteoporosis International
Published online ahead of print, doi: 10.1007/s00198-009-1126-4
“Vitamin K2 supplementation does not influence bone loss in early menopausal women: a randomised double-blind placebo-controlled trial”
Authors: N. Emaus, C. G. Gjesdal, B. Almas, M. Christensen, A. S. Grimsgaard, G. K. R. Berntsen, L. Salomonsen and V. Fonnebo