Analysis of data from over 850 people indicated that low vitamin K1 levels in people with high blood pressure and taking anti-hypertensive medications may increase the progression of arterial calcification.
“We unexpectedly showed that hypertensives (defined according to medication use) were significantly more likely to have extreme CAC [coronary artery calcium] progression if they had low serum vitamin K1 than were persons who were not taking antihypertension medication,” wrote the researchers in the American Journal of Clinical Nutrition.
Since one in five (20%) adults in the US are treated for hypertension, and about half of all US adults may have low vitamin K status, the researchers called for additional studies to further explore the observations from their study.
K forms
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% of the vitamin K in a typical Western diet; and menaquinones (vitamins K2), which make up about 10% of Western vitamin K consumption and can be synthesized in the gut by the 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.
Potential for Vitamin K2
Commenting on the study, Dan Murray from vitamin K supplier Xsto Solutions told NutraIngredients-USA that the study relies on an estimation of vitamin K intake from consumed food, and that this is further weakened when taking into account the extremely short half-life of K1 (1-2 hours).
“In general it’s difficult to get the serum concentration of vitamin K1 above 1- 2 nmole/l, due to the short half-life, even after intake of ‘RDI’ doses,” said Murray. “This doesn’t negate the total value of consuming vitamin K1 in food or supplements but it means more frequent dosing or larger doses or both are need to try and reach higher measurable values.
“The benefit of vitamin K2 menaquinone-7 with its extended half-life vs K1 becomes more obvious when we start digging into this type of research,” he said.
Murray added that, while this paper attempts to establish a correlation between Vit K and arterial calcification, this conflicts with prior data.
“The most significant finding in this study is the relation between the hypertension medication, Vit K1 intake and the progression of CAC. This is interesting and does warrant additional investigation, perhaps even with various forms and doses of Vit K supplementation rather than estimating food intake of Vitamin K1.
“In general, its challenging to conduct studies on the effects and correlations of Vit K1 due to its very short half-life. This presents a strong argument for Vitamin K2 MK7 supplementation (vs K1) where we can easily maintain longer serum levels of Vit K and better evaluate it benefits and associations to health conditions and medication interactions (both positive and negative).
“It’s exciting to see new and interesting research on a Vitamin K. We’ve been supplementing with K for decades but we are just starting to have a much better appreciation for the benefits of the ‘quinone’ family of Vitamin K.”
Study details
Led by Kyla Shea from Wake Forest School of Medicine, the researchers analyzed data from 296 people with extreme coronary artery calcium progression and compared this with data from 561 healthy controls. Blood samples were used to measure vitamin K1 levels.
Results showed that, in general, people extreme CAC progression were 34% more likely to have low vitamin K1 levels, compared with people without extreme CAC progression, but this result was not statistically significant, said the researchers.
A significant association between vitamin K1 levels and CAC in people taking anti-hypertension medication was observed.
“Low serum vitamin K1 was significantly associated with CAC progression in antihypertension medication users, which, to our knowledge, is a novel finding conditionally replicated by using an independent sample,” said the researchers. “Intervention trials are needed to determine whether improving serum vitamin K1 reduces CAC progression, especially in hypertensives.”
Source: American Journal of Clinical Nutrition
Published online ahead of print, doi: 10.3945/ajcn.112.056101
“Association between circulating vitamin K1 and coronary calcium progression in community-dwelling adults: the Multi-Ethnic Study of Atherosclerosis”
Authors: M.K. Shea, S.L. Booth, M.E. Miller, G.L. Burke, H. Chen, M. Cushman, R.P. Tracy, S.B. Kritchevsky