I first learned about vitamin K2 when I was going to a cardiologist for aortic stenosis. He had sent me for a calcium score test, which I flunked. Supposedly this means severe calcification of the coronary arteries, as I described in my posts about my heart valve saga. Later I found this was a false alarm in my case. But my cardiologist had casually mentioned at one visit that “excess calcium goes to the heart”. I became curious and did research on the subject, which led me to vitamin K2. Specifically to the book Vitamin K2 And The Calcium Paradox: How a Little-Known Vitamin Could Save Your Life by Dr. Kate Rheaume-Bleue. It was here that I learned about the important connection between K2 and calcium.
Many people have heard of vitamin K, which helps with blood clotting (the discovery of which led to the 1943 nobel prize in medicine). The letter K comes from the German Koagulationsvitamin for “vitamin for coagulation”. It turns out that vitamin K comes in multiple forms, of which the first two, K1 and K2 are important. K1 (phytonadione) is the one that helps coagulation, but K2 (menaquinone), a different substance from different sources, is involved in how the body processes calcium. This has not been understood until much more recently. It has now been shown that K2, which is actually the substance menaquinone, is helpful in preventing fractures [1,2,3] and in preventing vascular calcification, thus improving cardiovascular health [1,4]. Many doctors are unaware of the distinction between K1 and K2 and the importance of K2 for bone and cardiovascular health.
K1 (comes from dark green leafy vegetables and deficiency of it is rare. There is some evidence discussed in Dr. Rheaume-Bleue’s book that deficiency of K2 may be more common. K2 comes in two important forms MK-4 (or menaquinone-4) and MK-7. MK-4 is present in some animal sources, including milk butterfat, while the best source of MK-7 is natto, a fermented soybean food popular in Japan. Mk-4 has a relatively short life so it’s more difficult to get it from supplements. MK-7 has a longer life and can readily extracted in supplment form from natto. This is fortunate because Westerners may find natto unappealing. There is an amusing section in Dr. Rheaume-Bleue’s book where she describes her heroic (and unsuccessful) efforts to make it palatable for her.
As I mentioned in my post on health aspects of animal foods, there are some differences between how arteries calcify and how heart valves calcify, so I don’t know if K2 helps slow down the progression of heart valve calcification. Not enough research, lamentably, has been done on understanding calcification of heart valves. But a colloquial way of describing the action of K2 is that is helps calcium go to the right places, like bones and teeth, and not the wrong places, like arteries and (hopefully) heart valves. For that reason I continue to take it. It is inexpensive and has no side effects I am aware of. Anyone who is concerned about possible bone loss (osteopenia which can advance to osteoporosis) or progression of heart disease might want to read Dr. Rheaume-Bleue’s book and decide for themselves whether K2 is a good idea. There’s also a pretty good review article here.
- Schwalfenberg, G, “Vitamins K1 and K2: The Emerging Group of Vitamins Required for Human Health”,, J Nutr Metab. 2017.
- Cockane, S, et al, “Vitamin K and the prevention of fractures: systematic review and meta-analysis of randomized controlled trials.”, Arch Intern Med 2006.
- Knapen, N, et al, “Three-year low-dose menaquinone-7 supplementation helps decrease bone loss in healthy postmenopausal women”, Osteoporosis International, 2013.
- Spronk H, et al, “Tissue-specific utilization of menaquinone-4 results in the prevention of arterial calcification in warfarin-treated rats.”, J Vasc Res. 2003.