I've been looking for an answer to this for a while. Does anyone know what the accepted dosage recommendation for K2 (menatetrenone) is? Most of what I find is between 90 and 200mcg, and there's a Carlson Labs product containing 5mg ($44.75 @ vitacost.com!). Is the 5mg one overkill? Can anyone recommend a good menatetrenone supplement w/a better bang/buck ratio?
Thorne Research's K2 is the only cost-effective MK4 supplement I know of. $60 for what appears to be 1200 1mg drops. 1 mg/day is far more than almost everyone gets from their diet (typical intakes are on the level of a few dozen MICROgrams per day) but as someone else pointed out, there isn't a known toxicity and dosages in the 15-45mg range have shown benefits for osteoporosis.
I take the same Thorne Research drops that Stephan Guyenet mentions in his Vitamin K2 article which are around $50 per bottle but I take 3 drops per day and the bottle lasts months.
Your question about "accepted dosage" is tricky to answer in that the RDA for Vitamin K is in the micrograms but many of the intervention studies, especially those dealing with osteoporosis, use dosages of up to 15 milligrams per day. There is no known toxicity for Vitamin K2 either (per Wikipedia's entry for Vitamin K) and no "Tolerable Upper Limit" (TUL) has been set. I suppose that if you are concerned with over-dosing you could take one drop (one drop = 1 milligram) per day of the Thorne product in which case the bottle will probably last 6 months and your K2 needs would be covered for about $8 per month.
There are three major forms of “vitamin K.” Phylloquinone (vitamin K1) is produced by plants, and is primarily used in humans and other mammals in the liver to support blood clotting. A wide range of “menaquinones” are produced by different organisms; collectively, these are termed “Vitamin K2.” Bacteria primarily produce a menaquinone called MK-7. Most supplements labeled “vitamin K2” or “menaquinone” contain this form. But mammals synthesize a different menaquinone, known as “Menatetrenone” or MK-4, which is concentrated in the brain, bone, and the vasculature.
It has long been suspected that humans and other mammals produce this form of vitamin K for specialized functions not shared by phylloquinone or bacterial menaquinone. The first such function was shown to be a role in bone health. After extensive preclinical studies, Menatetrenone (and not other forms of vitamin K) is now used as a “drug” against osteoporosis in Japan. These studies show that Menatetrenone has unique bone-shielding effects which are independent of its role in gamma-carboxylation of proteins.
For several years now, evidence has ac***ulated to show that Menatetrenone also plays a specific role in cardiovascular health, by preventing the calcification of the arteries – a role not shared by other forms of vitamin K. This evidence is reviewed below. This latest study in experimental animals confirms these previous findings, and suggests some possible mechanisms underlying Menatetrenone’s unique heart-healthy powers.
J Vasc Res. 2003 [Epub ahead of print]. Epub 2003 Dec 03.
I take the Thorne K2 drops now because I figured 1mg a day + the cost savings was good. I used to take the 5mg you mentioned. It is a good product and the stuff is animal derived, I believe, while the Thorne stuff is made in a lab. I am not sure I am getting quite the same efficacy, but it isn't a really fair comparison because I am taking a lower dosage of the Thorne stuff and I don't even remember to take it every day anymore. I may return to Carlsons at some point, especially if the idea of saving money stops being as pertinent as it seems to be now.
In the book "Vitamin K2 and the calcium paradox", summarized in this video: http://www.youtube.com/watch?v=fYMExQNosTQ the book author Kate Rheaume-Bleue explains that there are two types of vit K, namely K1 and K2. K1 has to do with blood clotting and no other function, it recycles in the body/is used again and again and we get it easily from veggies. K2 is not made from K1 in the body, that is an old misconception, it has to come from food or supplement, it is used for bone and tooth health, it does not recycle and most ppl have a deficiency!!! In the past K2 was found in grass fed beef, milk and cheese but now cows are fed grains and the meat and milk lack K2 (unless you are neighbor with a farmer who does have grass fed cows and nutrient rich grass, not depleted land)! There are two sources of K2: fermented soy (MK7 menaquinone) and MK4 menatetrenone which is derived from tobacco plant. Somebody here mentioned a research study where patients got 45 mg of K2 for osteoporosis. I read about the study also (sorry, didn't save the link). Amazon sells Carlson brand, MK4, 5 mg strength, 60 capsules for $15 (March 2013). MK7 (soy) is in most supplements (caps, tabs, liquid and sublingual). To my knowledge soy of any kind is not recommended for patients with estrogen positive breast cancer diagnosis b/c soy contains phytoestrogens/plant estrogens. Also most soy is genetically modified, leading to disease and death thanks to Monsanto company which thinks it is okay to play God and genetically modify anything and everything (no, I am not religious, I only want to survive)!