Study emphasises importance of differentiating between vitamin K1 and K2
Researchers from the Norwegian Institute of Public Health, University of Bergen, University of Oslo and Oral Health Centre of Expertise, in Norway, have evaluated the association between intake of both K1 and K2 and subsequent CHD events among community-living middle-aged adults in Norway.
According to the authors of the study, published in the British Medical Journal, the role of vitamin K in the regulation of vascular calcification is established, and it has been shown that patients with both medial and intimal calcification have a higher cardiovascular risk when compared with similar patients without calcification. Therefore, they say an inverse association between vitamin K intake and coronary heart disease (CHD) could be expected.
However, they point out that results from previous observational studies on the association between intake of vitamin K and CHD are inconsistent with some showing a benefit from K1 and others showing a benefit from K2.
The team of researchers followed participants (2,987 Norwegian men and women aged 46-49 years) in the community-based Hordaland Health Study from 1997 to 2009. Baseline diet was assessed by a past-year food frequency questionnaire. During a median follow-up time of 11 years, they documented 112 incident CHD cases.
In the adjusted analyses, the researchers saw no association between intake of vitamin K1 and CHD, while there was a lower risk of CHD associated with higher intake of energy-adjusted vitamin K2. Further adjustment for potential dietary confounders did not materially change the association for K1, while the association for K2 was slightly attenuated.
The team says their results should help to clarify the importance of a K2-specific recommended daily intake (RDI). However, given the limited number of epidemiological studies, and the fact that dietary vitamin K sources and content differ between countries, the researchers noted that further research is warranted.
Commenting on the study, Dr. Hogne Vik, chief medical officer for NattoPharma, a global giant in vitamin K2 research and development, says this study builds on the body of evidence linking vitamin K status to health concerns such as peripheral arterial disease, coronary calcification, dementia, vascular stiffness in chronic kidney disease patients and more.
He says: “The common link is calcification and the need for adequate vitamin K2 intakes to inhibit this in our circulatory system and tissues. Due to its very molecular structure, vitamin K2 can move beyond the liver to support other systems of the body, such as the bones and vasculature, where K1 cannot.
"There remains a great deal of confusion that K1 supports both bone and heart health, and this paper helps to identify the difference between the two in that K1 is not linked to cardiovascular health, whereas K2 is linked to both.
“These results mirror what we have seen in epidemiological studies, where populations who consume a lot of dietary Vitamin K2 have healthier hearts and more flexible arteries.
“Recognition of vitamin K2’s benefits as strong and significant elucidated inhibitor of vascular and soft tissue calcification is one of the core reasons a separate RDI should be established.”
Source: BMJ Open
Haugsgjerd TR, Egeland GM, Nygård OK, et al.
"Association of dietary vitamin K and risk of coronary heart disease in middle-age adults: the Hordaland Health Study Cohort."