What is Vitamin K?

In 1929 a Danish scientist discovered what was to later become identified as vitamin K. Henrik Dam was studying the effects of cholesterol by feeding chickens a diet lacking in it. He observed that after a few weeks the chickens started bleeding and he could not reverse this by adding purified cholesterol back into their diet. At that point he realized that there was another element in the unpurified cholesterol which he referred to as the “coagulation vitamin”.


This substance later became known as vitamin K simply because in German coagulation begins with a K. At that point it was determined that serious vitamin K deficiencies would manifest as bleeding disorders, or malfunction in blood clotting functions.


It is now known that vitamin K is a family of vitamins that exists in various forms including K1 (phylloquinone), K2 (menaquinone) and K3. Vitamin K3 is a synthetic form that is toxic in high doses, and has already been banned by the FDA from over-the-counter sales, due to side effects, though it may still be prescribed as a drug. Since it is of no value to us here we will speak of it no more.


Vitamin K1

Vitamin K1 is the most commonly available form in the modern diet and is found in plant foods. The foods richest vitamin K1 include avocado, broccoli, Brussels sprouts, cabbage, cauliflower, kale, kiwi, grapes, parsley, spinach and Swiss chard.  While the absorption of K1 from green plants is usually fairly low (cooked spinach is 5% bio-available) it can be improved by adding fat to the greens (with added fat the bio-availability of K1 jumps to 13%). This is because vitamin K is a fat-soluble vitamin.


While the famed Framingham Study showed a lower risk for hip fracture in those who consumed the most K1 from food, another study that attempted to get the same results with supplemental K1 showed no benefits. Therefore, K1 is not really recommended for use in supplemental form.


Vitamin K2

We now know that the type of vitamin K that is most utilized by the body is the K2 form, found mostly in butter, eggs yolks and meat products, especially organ meats, from animals fed grass. In North America most food animals are fed grains because it is cheaper, so deficiency of K2 in humans has become widespread.


Vitamin K2 (menaquinone) is usually found in the forms known as MK4 and MK7, though it does exist in other forms as well. For our purposes we will focus on these two forms since they are the most studied and the ones that are available in supplemental form.


Vitamin K2 as MK7 is also created during fermentation, so some is found in cheese and a lot in the soybean product called Natto, a Japanese food that is considered quite unpalatable by most North Americans.


Why is K2 So Important?

The critical importance of vitamin K2 for us in the modern age is due to its link to two widespread ailments: osteoporosis and heart disease, in the form of atherosclerosis (calcification of the arteries). It is well established that vitamin K develops bones during growth by directing calcium where to go in the skeleton and in cells. When we have enough vitamin K it will direct calcium to the bones and teeth and keep it away from the areas where it could do harm, such as the cardiovascular system and soft tissues.


A European study of more than 8,000 people over the age of 55 found that those with the highest intake of vitamin K2 had a 50% reduction in death by coronary heart disease. (Geleijnse J.M., et al, “Dietary intake of menaquinone is associated with a reduced risk of coronary heart disease, The Rotterdam study,” Journal of Nutrition, 143 (11): Nov; 2004) Furthermore, studies done on animals have indicated that calcification of the arteries can even be reversed with supplemental vitamin K2. Vitamin K1 was also tested but shown to not prevent arterial calcifications.


K2 Deficiency

Up until recently, it was believed that vitamin K deficiency only occurred if the intestinal tract was damaged, forbidding absorption of the nutrient. Since K2 (in the MK7 form) is mostly produced from K1 by friendly bacteria in the gut, a deficiency was also often found in people who had been on long term broad spectrum antibiotic use. Heavy antibiotic use has been shown to reduce vitamin K2 production in the body by almost 75%.


Vitamin K2 production is also reduced as we get older, much like B-12 production. Since much of the K2 in the body is converted from K1, a diet too low in the plant foods containing K1, will also reduce the amounts of K2 in the body. The ability of supplemental K2 to keep bones healthy and strong has even been demonstrated in people experiencing bone loss from steroid use, dialysis and/or paralysis.


Unfortunately, the amount of the MK7 form that is made in the intestines may not be sufficient to meet the needs of the body. The MK4 version of K2, unlike MK7, does not appear to be dependent on friendly bacteria to be created in the body. It is also converted from K1 but that conversion occurs in the arterial walls, pancreas and testes (for guys).


Supplemental Forms of K2

Both the MK4 and MK7 version of K2 are available in supplemental form, though the effective dosages are very different. While K2 may not make claims for preventing osteoporosis in North America, in Japan it has been recommended by the health authorities since 1995 for this purpose. Japanese studies have indicated that MK4 can reduce fractures by up to 87%.  (Sato, Y; Kanoko T, Satoh K, Iwamoto J (2005). “Menatetrenone and vitamin D2 with calcium supplements prevent nonvertebral fracture in elderly women with Alzheimer’s disease”. Bone 36 (1): 61–8.)


The problem for those of us in Canada, is that the recommended dosage of MK4 is 45mg daily, but in this country the maximum amount of K2 allowed in a product is 120mcg (a mcg being one thousandth of a mg).


Since MK4 is not effective in microgram doses, we in Canada can only use MK7, which does appear to be effective in these low doses. The recommended amount of MK7 is about 120mcg for maintenance and twice that much for therapeutic use.Certainly there is much more science on the MK4 version of vitamin K2 but there are a couple of studies supporting MK7, and there are currently more studies underway. The MK7 form of K2 showed effectiveness in stimulating bone formation and inhibiting bone decline in one Japanese study. (Yamaguchi M (November 2006). “Regulatory mechanism of food factors in bone metabolism and prevention of osteoporosis”. Yakugaku Zasshi 126 (11): 1117–37)


And another MK7 study showed elevation in biomarkers of bone formation, along with inhibition of bone-reabsorbing factors found in parathyroid hormones. (Tsukamoto Y (2004). “Studies on action of menaquinone-7 in regulation of bone metabolism and its preventive role of osteoporosis”. BioFactors 22 (1-4): 5–19) As well, in 2011, the Singapore government approved a health supplement that contains the MK7 form of vitamin K2, along with vitamin D3, for increasing bone density.


These bits of data indicate that, while we Canadians do not have the choice as to which form of K2 we can purchase, we can at least rest comfortable in the knowledge that the form that the government is so kind as to allow us to buy, does have some scientific validity behind it.


It is currently believed that vitamin K2 maintains the teeth as well as the rest of the skeletal system, and this seems to be confirmed by the fact that, after the pancreas, the highest amount of K2 found in the tissues is found in the salivary glands.


Don’t Forget Vitamin D

Combining vitamin D3 with K2 has been shown to be more effective on building bones than either one alone. (Weber P., “Vitamin K and Bone Health,” Nutrition, 17: 880-887; 2001) While vitamin D helps us to absorb the calcium, the vitamin K directs it into the skeletal structure.


Other Benefits of K2

It is beyond the scope of this article to cover the other potential benefits of vitamin K2 but I will mention that it appears to function both as an antioxidant and anti-inflammatory. As well, some studies have indicated the potential of vitamin K2 to aid in the treatment and/or prevention of Alzheimer’s disease, diabetes (indicated by the large amounts found in the pancres) and liver and prostate cancer.


There is no known toxicity associated with high doses of vitamin K2 in the forms of MK4 or MK7. While the body uses vitamin K2 for purposes of blood clotting studies have indicated that doses of MK4 at 135mg daily (divided dose) showed no risk of abnormal blood clotting. Blood thinning drugs, such as Warfarin and Coumadin, work by inhibiting the actions of vitamin K, therefore K1 and K2 can block the action of these types of drugs. People on these drugs are even told not to eat too many greens.


Deficiency of vitamin K2 has been linked to birth defects and it is generally considered safe to take during pregnancy and lactation.

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