Increased intakes of vitamin K2, but not vitamin K1, may decrease the risk of coronary heart disease in postmenopausal women, says a new study.
For every 10 microgram increase in the amount of vitamin K2 consumed, researchers from the Netherlands report a 9 per cent reduction in the risk of developing coronary heart disease (CHD).
The effects were mostly confined to the higher forms of vitamin K2, namely menaquinones 7 to 9, according to results published online ahead of print in the Nutrition, Metabolism and Cardiovascular Diseases.
“Our findings may have important practical implications on CVD prevention, it is important to mention that in order to increase the intake of vitamin K2, increasing the portion vitamin K2 rich foods in daily life might not be a good idea,” wrote lead author Gerrie-Cor Gast from the Julius Center for Health Sciences and Primary Care at the University Medical Center Utrecht.
“Vitamin K2 might be, for instance more relevant in the form of a supplement or in low-fat dairy.”
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; while K2 makes up about 10 per cent of Western vitamin K consumption.
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.
Ms Gast and her co-workers evaluated data from the Prospect-EPIC cohort, consisting of 16,057 post-menopausal women, aged between 49 and 70. None of the women had cardiovascular disease at the start of the study.
Dietary intakes were assessed using food frequency questions (FFQs), and participants were followed for over eight years. At the end of the study, the researchers observed an association between a higher consumption of natural vitamin K2, particularly menaquinone-7, -8, and -9 and a significantly reduced prevalence of CHD.
Consumption of vitamin K1 had no effect on vascular health, said the researchers.
The reason behind the different effects of K1 and K2 may be due to the different distribution of each in the body, said the researchers. K1 is primarily taken-up by the liver and then cleared from circulation, while K2 is the major form of vitamin K transported also to extra-hepatic tissues, such as vessel wall and bones-tissue.
“Of the subtypes of vitamin K2, it appeared that particularly MK-7, MK-8 and MK-9 affected the risk of CHD,” said the researchers. “A stronger effect of the longer subtypes could be due to a slower hepatic clearance of these subtypes, making them longer available for carboxylation reactions.”
The potential of supplementation
Commenting on the research, Dr Leon Schurgers from the University of Maastricht said: “This study confirms our findings in the Rotterdam study, showing that increased vitamin K2 intake strongly reduces the risk of coronary heart disease.”
Dr Schurgers, who was not involved with the new study, added: “Also this study showed that the reduction in CHD was tied to the longer-chain menaquinones 7, 8, and 9 - the menaquinones found most abundantly in fermented cheese. As the Western diet is likely deficient in K, supplementation or enrichment of long chain menaquinones is an obvious choice.”
Source: Nutrition, Metabolism and Cardiovascular Diseases
Published online ahead of print 28 January 2009, doi: 10.1016/j.numecd.2008.10.004
“A high menaquinone reduces the incidence of coronary heart disease in women”
Authors: G.C.M. Gast, N.M. de Roos, I. Sluijs, M.L. Bots, J.W.J. Beulens, J.M. Geleijnse, J.C. Witteman, D.E. Grobbee, P.H.M. Peeters, Y.T. van der Schouw