Most of us are familiar with the blood clotting aspect of this vitamin earning its reputation as the “band-aid” vitamin, however when we look at the different types K1 (phylloquinone), K2 (menaquinone) and K3 (menadione) we need a little more investigation to understand the wide scope of benefits this vitamin bestows. Before we take them one at a time its important to note that K1 and K2 are fat soluble and can be absorbed in the intestinal tract in the presence of certain intestinal flora. K3 is a synthesized vitamin originally produced for those that lack the bile necessary for the absorption of fat soluble vitamins.
We now understand enough about K1 and K2 to think about them separately, each having their own vital role in our health. And, this may be wisdom, as they have different dietary sources.
The main function of Vitamin K is to activate the calcium-binding properties of proteins. K1 is mostly involved in blood clotting, while K2 helps regulate where calcium ends up in the body. That’s right K2 (in concert with D) makes sure that it’s not the soft arterial walls that receive the calcium building patch but rather where its needed on the bones and teeth, et cetera. I see it as a sort of “which way do I go” vitamin. This could be the reason we are discovering K2’s importance in heart disease prevention. (The relationship between vitamin K and peripheral arterial disease. https://www.ncbi.nlm.nih.gov/pubmed/27494446) Prostate health is another interesting focus for K2. Studies are showing the bodies reliance on K2 but not K1 for battling advanced prostate cancer. (Dietary intake of vitamin K and risk of prostate cancer in the Heidelberg cohort of the European Prospective Investigation into Cancer and Nutrition (EPIC-Heidelberg). https://www.ncbi.nlm.nih.gov/pubmed/18400723) We’re just getting started on our understanding of K2’s potential health benefits for bone, cardiovascular, skin, brain and prostate.
Of course, all this is to say, “Get your vitamins!” Vitamin K1 is mostly found in plant foods like leafy green vegetables. It makes up about 75–90% of all vitamin K consumed by humans. However, as always, digestion and uptake are the end all and be all for nutrition. One study shows that less than 10% of the K1 makes it to usefulness in the body. (Effect of food composition on vitamin K absorption in human volunteers. https://www.ncbi.nlm.nih.gov/pubmed/8813897) That makes it even more essential to source the high end, rich sources of K like kale. Very convenient that kale starts with K don’t you think? Also remember that phyllo in phylloquinone means leafy.
We know less about the up-take of K2 but it is theorized that because these are fat soluble vitamins that K2 which is found in fatty foods like hard cheeses, butter and egg yolks from grass fed animals may have a better chance of absorption. Somewhere in my mind’s nutrition archive that translates to . . . “Yes, a nice slather of good quality butter on my kale is the right move.”
Better still are the higher concentrates of K2 found in fermented foods. Not something prevalent in the American diet. But we can learn, can’t we? Here is where I’m going to recommend one of my favorite cookbooks which I believe is a fun and easy introduction to the world of fermentation for health. Wild Fermentation: The Flavor, Nutrition, and Craft of Live-Culture Foods by Sandor Ellix Katz. In the meantime, taking a trustworthy supplement eases my mind when I find its been three weeks since I’ve had a good sausage smothered in my homemade kraut.
A quick word for K3 or menadione which is the synthetic form. I certainly understand the dynamic of how this synthetic supplement came about as vitamin K deficiency is a serious matter. If you do not have the necessary bile for K absorption the water soluble alternative must seem like a rescue, but for someone who does not have this issue why would you consider the more inferior, man made substitute which has a toxicity level whereas K2 supplementation is natural and non toxic even at 500 times the RDA. I don’t take very many supplements because a dietary source is usually a superior idea with a natural balance of minerals and vitamins suited for health, however, when I know it is probable I’ll have trouble obtaining enough (like vitamin D in the dead of winter for northern folk) that’s when I cross the line.
Written by a nutrition investigator just like you, Linda Saffer. May 2018.