Vitamin K

Vitamin K is another fat-soluble vitamin that exists in two forms of vitamin K: vitamin K1 (phylloquinone, mainly found in green leafy vegetables) and vitamin K2 (menaquinone, a small amount produced by lactic acid bacteria in the colon, where there is no bile for absorption). Our diet should provide the rest, but dietary sources can be limited and or not available for everyone to consume, such as dietary restrictions - vegans. The highest intake of vitamin K2 is in natto -998 microgram/100g, but this food is not widely available everyone and it also does not taste nice, so it can be difficult to get daily intake of vitamin K2 just from the dietary sources. The most widely used vitamin K form for supplementation is vitamin K2 and more specifically menaquinone-4 and menaquinone-7. Menaquinone-4 is more used in trials with bone outcomes, while menaquinone-7 is more in trials with cardiovascular outcomes.

 Function of vitamin K2

activated vitamin K – dependent proteins (VKDPs) – osteocalcin – calcium is deposit into the bones. If the osteocalcin in the bone is not properly activated, then calcium in the bloodstream can adhere to cartilage, causing arthritis or rheumatoid arthritis.  It can also calcify blood vessels, causing cardiovascular diseases.  Matrix GLA protein (MGP) – binds to calcium and it is taken away from arteries and other soft tissues (musculoskeletal joints)

 Vitamin K antagonists

Antagonists are type of medication (usually prescribes for people with DVT such as warfarin) that blocks the action of vitamin K in the process of blood clotting. This helps keep clots from becoming larger and preventing new ones from forming. They do not stop clotting completely but help the blood flowing through a vein more easily.

 Vitamin K2 MK- 7

This type of vitamin K has the most supporting evidence for support of bone health, calcium metabolism and cardiovascular health. It does remain within the body for the longest time and can reach vessels and bones, activating the key proteins.

 Vitamin D3 and K2

Growing evidence in studies suggest, that optimal concentration of both vitamin D3 and vitamin K2 are beneficial for bone and cardiovascular health. However, long-term high dose vitamin D3 supplementation could create an imbalance. If vitamin D3 concentrations are constantly high, there might not be enough vitamin K2 for activation of vitamin K-dependent proteins. Consequently, excess vitamin D3 diminishes the ability of vitamin K-dependent proteins to function properly, and   more calcium is absorbed into the blood stream than the vitamin K2 – dependent proteins can process direct safely to bones.

There is no need to take vitamin D3 and K2 together at the same meal or in the same capsule, because they do not help each other with the absorption (as vitamin D helps calcium) as long they are taken synergistically daily. Some people might prefer to supplement separately in order to adjust the dose of D3 according to the time of year – taking less or no vitamin D3 supplements in Spring/Summer and more in Autumn/Winter. It is important to note, that not all studies observed synergistic effects of vitamin D3 and K2 supplementation.

 Dietary sources of vitamin K2

Mainly found in certain animal and fermented foods (natto, hard cheeses, sauerkraut), high fat dairy products, pork/beef liver and organ meats. Low fat and lean animal products do not contain much of K2.

 Benefits of supplementing with K2  

Vegans may not get any dietary K2 (unless they eat natto)

Ageing and digestive/gallbladder issues can compromise absorption

Antibiotics and proton pump inhibitors are associated with lower K2

Lack of microbial diversity in the gut due to unhealthy eating habits

Statins can inhibit K2 (MK-4) synthesis from vitamin K1

Postmenopausal women (low bone density – osteoporosis)

May help with nocturnal leg cramps if vitamin K2 deficiency

(recommended dose for a healthy person is around 200 mcg)