Myths & Facts
Fact: Vitamin K actually consists of a group of essential fat-soluble vitamins. The vitamin K family is divided into vitamin K1, one molecule (phylloquinone), and vitamin K2, a group of molecules (menaquinones). Vitamin K2 exists in several forms, the most common ones are the synthetic menaquinone-4 (MK-4) and the natural or synthetic menaquinone-7 (MK-7).
Fact: While vitamin K1 is found in green leafy vegetables, vitamin K2 is not. A small amount of vitamin K2 is present in the colon, where it is synthesized by the intestinal microflora. Vitamin K2 is primarily found in animal products, such as meat, dairy, and eggs, and fermented foods like cheese, yogurt, and natto, a Japanese traditional dish of fermented soybeans.
Fact: Just as vitamins K1 and K2 come from different sources, they also deliver different benefits. Vitamin K1 is known for blood coagulation, as it is processed in the liver. Vitamin K2, on the other hand, is transported beyond the liver so it is available to other tissues in the body, which is why it has been shown beneficial for bone and heart health.
Fact: K2 is only found in “real” cheese, that is, rind cheeses that are sliced from a wheel, not processed cheese, or “cheeze” foods. Food processing strips the vitamin out (and some of these chemical “cheezes” never had nutrients such as K2 to begin with.) Cultured cheese like Gouda can provide up to 50 mcg of menaquinone-7 (vitamin K2) per 100 g of cheese consumed.
Fact: Current daily recommendations for K vitamins are based exclusively on vitamin K1 and the requirement for proper blood clotting, which is 1 mcg vitamin K1 per kg of body weight (daily). But this amount of vitamin K1 is insufficient for the optimal function of vitamin K-dependent proteins in other tissues like bone and vasculature – since vitamin K1 has a short half-life time, the recommended dose will not reach these peripheral tissues.
Fact: Oral anticoagulants work by a mechanism that inhibits vitamin K. Vitamin K1, due to its ability to support healthy blood clotting, may interact or interfere with anti-coagulants such as warfarin. Researchers concluded in one study that K2 (MK-7) supplementation at doses as low as 10 μg (lower than usual retail dose of 45 μg) significantly influenced anticoagulation sensitivity in some individuals. Thus, the researchers recommended avoiding use of MK-7 supplements if on vitamin K-antagonist therapy.
However, it has been shown that patients on oral anti-coagulant therapy who take up to 50 mcg of MK-7 per day have more complete activation of osteocalcin without interfering with the effect of the blood thinner. In other words, taking a small amount of MK-7 allows one to avoid the side effects of these medications without interfering with their intended benefits.
On the basis of the latest insights and in order to remain on the safe side, it is recommended that patients on conventional blood thinners consult with their doctor before taking a K2 supplement, since taking more than 50 mcg of K2 might interfere with the prescription.
Fact: A vitamin K insufficiency does not lead to dramatic, intensely painful, debilitating or disfiguring symptoms of deficiencies of other vitamins, such as vitamins C (scurvy), B1 (beri beri), or D (rickets). While insufficient vitamin K1 can lead to improper blood clotting, or bleeding more than one should after a cut, insufficient levels of K2 can lead to the decline in bone health status (potentially osteoporosis) and calcification of the cardiovascular arteries, making them stiff and inelastic – symptoms that are not immediately or obviously detectable.
There are three factors that can increase vitamin K2 insufficiency: poor nutrition and use of antibiotics that deteriorate gut flora; poor absorption of K2 from the gut due to aging or chronic gastrointestinal (GI) infections; and age-related compromised bioavailability of K2. If any of these factors correlate with one’s lifestyle, they should consider the possibility that they are vitamin K2 deficient.