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Everything you need to know about Vitamin K2

| APR 28, 2023

Vitamin K, like many vitamins, is a group of three related substances which form part of the family of fat-soluble vitamins (also including A, D & E). This nutrient, both found in nature and made in the body, has the primary role of helping blood clotting and coagulation. It’s also involved in bone health. 

What is Vitamin K2?

So, what are the 3 substances and more importantly what is vitamin K2.

Phylloquinone, also known as K1, found in alfalfa, broccoli, collard greens and other foods was discovered in Denmark and named vitamin K for the Danish word koagulation (coagulation).

Menaquinone labeled vitamin K2 is made by our very own intestinal bacteria. It’s also found in animal foods including liver and cheese and certain fermented dishes such as the Japanese natto. K2 can also be further divided into several different subtypes based on whether they are short or long-chain. The ones found in supplements are called MK-4 and MK-7.

Finally, K3 is a synthetic substance made with the basic structure of the above and can be used therapeutically for people who may not use natural vitamin K very well due to health issues.

Now let’s explore in more detail.

What does Vitamin K2 actually do? 

As mentioned above it’s needed for blood clotting as it’s involved in the synthesis of prothrombin and other proteins involved in blood coagulation. In simple terms let’s imagine you get a paper cut and start bleeding. Immediately your body will begin to try and stop the bleed by mounting a response of these coagulation proteins. If after a while you begin to see the blood thickening and the bleed stops, this is coagulation in action. Common anti-coagulants (blood-thinners) compete with vitamin K at its active sites.

People with low vitamin K levels may experience a much longer time before the bleed stops or may not stop bleeding on their own at all. People who bruise easily or whose blood clots slowly after injury may benefit from supplementation. It’s also sometimes given to women with heavy period bleeding. In the UK, vitamin K is routinely given to newborns. Vitamin K isn’t transferred from the mother and there are no colon bacteria present yet to make it in newborns because the digestive tract is sterile at birth. 

But coagulation is not its only role. One of its most important functions is to regulate calcium deposition as it promotes the calcification of bones and prevents the calcification of blood vessels and kidneys.

What are the benefits of Vitamin K2?

In controlled studies, researchers have observed that vitamin K2 supplements generally improve bone and heart health. More specifically it may help prevent heart disease through reducing calcium build up around the heart and may help improve bone health and lower the risk of osteoporosis. Calcium is the main mineral found in your bones and teeth. K2’s central role in calcium metabolism therefore makes it crucial in this area. In fact, a 3-year study in 244 postmenopausal women found that those taking vitamin K2 supplements had much slower decreases in age-related bone mineral density. In line with these findings, vitamin K supplements are officially recommended for preventing and treating osteoporosis in Japan.

By a similar mechanism, K2 may well play a role in improving dental health though more studies are needed in this area. It is however clear that vitamin K2 has many benefits and plays an important role in human health. 

How much Vitamin k2 should you be taking?

Most adults need between 90 and 120 mcg of K2 per day although up to 300mcg may be optimal. As discussed above, many foods contain vitamin K1 and it’s easily obtained from a balanced diet, especially if you eat your veg. K2 however is far less common and found in foods in much smaller amounts. Few people regularly consume organ meats and fermented foods such as sauerkraut and miso. Additionally, as it’s fat-soluble, it’s only available to the body when consumed with fat. Therefore, modern low-fat diets may further contribute to people not getting enough vit K. 

Your body can convert K1 to K2 which is great but current evidence indicates that this process is far from efficient and may not provide adequate amounts. As mentioned, gut bacteria also provide vitamin K2, however it’s unclear how much of this can be used by the body and many of us have a far from optimal microbiome. There may also be poor absorption of this nutrient due to other intestinal health issues. 

Therefore, taking a supplement is a valid alternative. Overall, more studies have used K2 than K1 so there is more evidence on its effects. Additionally, while all the different forms of vitamin K have a similar function in the body, vitamin K2 is better absorbed and tends to stay in the body for longer. This means even relatively low doses of vitamin K2 in supplemental form can be an effective aid to health.

Vitamin D3 + K2 combination 

The benefits of supplementing with K2 may be enhanced even further when combined with a vitamin D3 supplement. These two vitamins have synergistic effects, which means they work together. In a nutshell, vitamin D promotes the production of vitamin K-dependent proteins. Current evidence suggests that joint supplementation of vitamins D and K might be more effective than the consumption of either alone for bone and cardiovascular health.

Vitamin D also has positive effects on bone health in general as it’s needed for calcium absorption and is associated with bone-mineral density. It therefore makes sense to combine the 2 if used for bone health. 

Can Vitamin K2 be toxic?

Toxicity rarely occurs. It’s virtually impossible from food and production by bacteria as well as from supplements, especially where these are from natural sources. In fact the only known cases are from the synthetic form (K3), usually used in medical treatment. You should never supplement K2 if you’re on blood-thinning medication such as warfarin. In fact, if you have any medical diagnoses or are on any prescription medication it’s best to check with your GP before supplementing. 

Toxicity rarely occurs from natural sources (food and production by bacteria) and the only known cases are from the synthetic form (K3), usually used in medical treatment. However, side effects are possible from Vitamin K2 use in supplement form if you’re on certain medications. 

Is Vitamin K2 good for you?

It’s clear that Vitamin K2 plays an essential role in our health. Whilst it can be found in some foods, you may not be getting enough of these or may not always be able to absorb it well. Due to its crucial role in bone health, it may be particularly important for women during and after menopause and if taken in supplement form it’s best combined with vitamin D3.

Written by Uta Boellinger DipNut DipNCFED mBANT rCNHC 

Uta Boellinger is a registered nutritional therapist and lecturer who specialises in helping busy women balance their hormones, feel re-energised and optimise their health.

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