Blackmores Institute

The prospective cohort study followed more than 2900 participants in the community-based Hordaland Health Study for a median of 11 years to evaluate associations between intake of vitamin K and incident coronary heart disease (CHD) using a past-year food frequency questionnaire and found that 112 incident CHD cases were recorded.Vitamin K1 and K2 were categorised into quartiles (Qn) with the majority of sources of K1 derived from vegetables, fruits and berries, milk and milk products and K2 sources being cheese and other dairy products, meat and eggs.“In the adjusted analyses, there was no association between intake of vitamin K1 and CHD (HRQ4vsQ1 = 0.92 (95% CI 0.54 to 1.57), p for trend 0.64), while there was a lower risk of CHD associated with higher intake of energy-adjusted vitamin K2 (HRQ4vsQ1 = 0.52 (0.29 to 0.94), p for trend 0.03). Further adjustment for potential dietary confounders did not materially change the association for K1, while the association for K2 was slightly attenuated (HRQ4vsQ1 = 0.58 (0.28 to 1.19)),” the authors reported.As a fat-soluble vitamin, vitamin K1 (K1; phylloquinone) is obtained from green leafy vegetables and vegetable oils as the main dietary sources, and vitamin K2 (K2; menaquinones) from dairy products, meat and egg yolk as the main dietary sources in Europe and both are absorbed from the small ileum and jejunum. “Vitamin K functions as a cofactor for the enzyme gamma-glutamyl carboxylase which protein-bound glutamate residues into gammacarboxyglutamate (Gla). Gla-containing proteins are involved in, for example, the coagulation of blood, inhibition of arterial calcification (Matrix Gla Protein) and vascular smooth muscle cell apoptosis and movement that is considered protective against vascular injury,” the authors explained.Although the mechanism of action is not established, the study suggested that the observed association for K2 may be due to the fact that in addition to being cleared by the liver, it is also transported to extrahepatic tissues. “One hypothesis is that intake of vitamin K has to be of a certain magnitude in order to have an effect on CHD. The different results on K1 and K2 may also be due to biological differences between K1 and K2 or to lower ability of the food frequency questionnaire to estimate K1. Due to different bioavailability, the contribution of K2 to vitamin K status is at least equal to that of K1 even though dietary K1 contributes to the majority of the total vitamin K intake. Alternatively, our findings may reflect that K2 may be a marker of another nutrient or food constituent that has heart-healthy properties. “Our findings contribute to the sparse literature relating dietary vitamin K to future CHD risk. Current dietary guidelines are based on insufficient knowledge with regard to vitamin K metabolism and the different characteristics of K1 and K2. Therefore, our results indicate a need for more studies on the association between K2 and CHD. In addition, more knowledge about the absorption, transport and bioactivity of K2 is warranted.” “In this Norwegian community-based study population, we observed that intake of K2 was associated with lower risk of CHD, while there was no association between intake of K1 and CHD. These results are considered generalisable to other middle-aged Western populations in which dairy products are the primary source of K2,” the authors concluded.Source:
 BMJ Open. 2020. DOI: <a href="http://dx.doi.org/10.1136/bmjopen-2019-035953">10.1136/bmjopen-2019-035953</a>

A higher intake of vitamin K2 has been associated with a lower risk of coronary heart disease a new study in BMJ Open has reported.

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