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Ever heard of vitamin K2?
You’re not alone.
Most have never heard of it which is too bad. It hasn’t enjoyed the spotlight like vitamin D, or omega-3s have, but if there’s one nutrient you need to know about, it’s vitamin K2.
For one, it’s because this vitamin is rare in Western/modern diets and two, you’re probably not getting enough of it.
This is a problem because vitamin K2 is the missing link between diet and several chronic diseases AND it has several potent health benefits.
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What is vitamin K?
In 1929, Danish nutritional scientist Dr. Henrik Dam discovered a factor in food that controlled blood clotting and named it vitamin “K”, for koagulation (Danish for coagulation. Their hard sounding ‘C’ is spelled with a K 🙂 ) (1).
Fast forward to today and we now know that vitamin K (like vitamin E*) is not a single nutrient but a family of fat-soluble vitamins that share similar molecular structures.
The different forms of vitamin K are:
- Vitamin K1 (phylloquinone)
- found in plant foods and leafy greens.
- Vitamin K2 (menaquinones)
- found in animal foods and fermented foods
- found in animal foods and fermented foods
(Note: menaquinone-4 also goes by menatretrenone-MK4 etc.)
For the purposes of this article, the two forms of vitamin K, as they relate to human health, are vitamin K1 and vitamin K2 as MK-4 & MK-7 (2).
Confusion persists to today
When “vitamin K” was discovered for its blood-clotting factors in 1929, no one knew there were several different, yet similar forms. American researcher Edward Doisy ultimately succeeded in isolating vitamin K (from alfalfa) and determining its structure. This form became known as vitamin K1 (3, 4).
In 1943, Drs Dam and Doisy shared a Nobel prize in medicine for this discovery. Unfortunately, this is when things went a bit off the rails.
Around the time they received their Nobel prize, Dam, Doisy, and other researchers (including Canadian dentist Weston A Price) had already discovered and characterized another micronutrient that later became known as vitamin K2.
Because vitamin K is made up of several similarly structured molecules, it didn’t occur to them to treat them as separate nutrients, each with their own unique properties.
In fairness to them, the newly discovered nutrient (K2) does influence blood clotting to a degree so they clumped them all together. Honest mistake.
Because of vitamin K1’s main role in blood clotting, and the similar structures of K1 & K2, understandably the two nutrients became interchangeable and considered as one; two sides of the same coin.
This misclassification persisted for the next several decades. All variations of vitamin K were considered only for their role in blood clotting which ultimately influenced the current recommended daily requirement for “vitamin K”.
Sadly, even today, any discussion about vitamin K from health professionals still defaults to K1 and despite decades of research, K2 is still one of the most misunderstood nutrients in medicine and nutritional sciences today.
What is vitamin K2?
As stated above, vitamin K2 is just one of several different forms (isomers) of vitamin K.
Looking at the diagram above, you can see that K1 & K2 MK-4 are different from each other and K2 MK-7 even more so; this makes all the difference biologically speaking.
All forms of vitamin K activate (turn on) different proteins known as “vitamin K dependent proteins” or VKDPs, that have different functions throughout your body; .
Unlike its K1 sibling, vitamin K2 dependent proteins have a HUGE role in how your body uses calcium and insulin. K2 supports healthy sex hormone levels, influences how your body uses energy, and reduce the risk for several cancers.
In many ways, vitamin K2 has better overall health benefits. Don’t get me wrong, vitamin K1’s role in blood-clotting is a good thing. If you couldn’t clot, then a bruise or accidental cut would be catastrophic, but K2 can much, much more.
Vitamin K1 versus K2
The difference between K1 and K2 isn’t absolute (5). It’s not as if K1 is limited to the liver where it’s only used to make clotting factors.
Some of the K1 that you eat reaches other tissues throughout your body where it will be converted to K2 (MK-4). And, some K1 will also be converted to K2 (MK-7) by your intestinal bacteria, and then absorbed into your bloodstream. Like K1, K2 MK-7 can also be converted to MK-4 by other tissues
K1 ==> K2 MK-4 (tissues)
K1 ==> K2 MK-7 (instestines)
K2 MK-7 ==> K2 MK-4 (tissues)
Can’t we just consume lots of K1?
That would be nice given that K1 makes up about 90% of the total vitamin K in a typical Western diet.
Although humans can convert a whiff of vitamin K1 to vitamin K2, there are a number of lines of evidence strongly suggesting that humans require preformed K2 from their diet, either from fermented or animal foods, for optimal health.
My point? While some K1 is converted into K2, it’s not reliable. We simply don’t convert it that well. Getting ‘premade’ K2 from food (or supplements) is much, much better.
Also, when it comes to reaping the benefits of K2, dose matters. Relying on the conversion of K1 to K2 is as futile as relying on the conversion of the plant form of omega-3 (ALA) into EPA and DHA, or beta-carotene into retinol.
Vitamin K2 metabolism
All vitamins activate proteins called enzymes. Enzymes then facilitated and direct biochemical reactions that ‘run’ your body (an estimated 1 trillion reactions per second). Specifically to K vitamins, they activate enzymes through a process called carboxylation.
When we talk about VKDPs, they are either carboxylated (a good thing) or under-carboxylated (not so good). Under-carboxylated just means the vitamin K dependent enzymes haven’t been activated so they can’t do their jobs of preventing disease and promoting health. But that’s easy to fix.
As mentioned, the liver preferentially uses vitamin K1 to activate enzymes that make clotting factors. Most other tissues in your body preferentially use vitamin K2 to activate the other enzymes that influence heart health, insulin metabolism, energy production, skin health, and more.
For the health issues below, the discussion will focus on the two main vitamin K2 dependent proteins/enzymes osteocalcin (a hormone found in bone and dentin/teeth) and matrix Gla protien (MGP) (a protein found in blood vessels, cartilage, muscle, skin, ligaments, tendons).
Vitamin K requirements
Here’s the crux of the problem. As a victim of historical circumstances, vitamin K1 and K2 were considered to be the same thing.
Given K1’s role in blood clotting, vitamin K1 as a nutrient of concern was given priority AND still today, vitamin K requirements are based on the amount of K1 to prevent bleeding.
The official recommendations, therefore, are only given generically as “vitamin K” with no distinction between K1 and K2. “vitamin K” (K1) recommendations are 90 mcg for adult women and 120 mcg for adult men.
By treating K vitamins as a single nutrient, there’s been a lack of research done on K2 so we don’t have a sense of how much people are eating. We also don’t know how much is needed by different parts of the body for the best health or how best to assess a person’s K2 status.
But, there’s a reasonable way to determine how much K2 people might need to thrive. One way is to measure the degree of carboxylation (activation) of VKDPs circulating in the blood. Most of the VKDPs are activated with 100 mcg of K2 per day. At 200 mcg per day, nearly all (>90-95%) of them are activated and performing well.
200 mcg is also an amount that reasonably could have been consumed with traditional and ancestral diets. In the present day, people in Northern Japan, who eat a lot of natto, are getting an average of about 250 mcg per day. Food for thought.
Are we deficient in vitamin K2?
Unlike K1 where a deficiency directly and immediately affects blood clotting, a deficiency in K2 doesn’t have acute (immediate and obvious) signs.
A deficiency in K2 is a long-term concern and contributes over years to poor bone, dental, cardiovascular health.
Determining a deficiency in vitamin K2 is rather straightforward. Remember that K2 ‘carboxylates’ vitamin K2 dependent proteins (VKDPs). If you’re getting adequate amounts of K2, then all of your VKDPs will be carboxylated. The more deficient you are, the greater the amount of uncarboxylated VDKPs you have in your blood.
So….studies show that vitamin K2 deficiency is very common. A greater degree of deficiencies are seen in children, adults over 40, and those with high blood pressure, type 2 diabetes, chronic kidney disease, cardiovascular disease, and bone disease/osteoporosis (6, 7, 8, 9, 10).
Deficiency is on a spectrum, the more deficient a person is, the greater the number of VKDPs that are uncarboxylated. The VKDPs that are most vital for health/life with get what little K2 you’re eating. Other organs and tissues will be denied; ergo increase heart disease, wrinkles, bone disease, and more.
Vitamin K2 benefits
The benefits of vitamin K2 are plenty but underappreciated. Ongoing research has confirmed that vitamin K2’s role in human health extends beyond what’s possible with K1. It’s worth investing a little time and effort to get more of this superstar if you’re looking for something to give that competitive edge.
Dr. Kate Rheaume-Bleue, the author of the Calcium Paradox, writes, “when it comes to skin, it seems that a K2 deficiency might be written all over your face”.
Research has found a strong association between excessive skin wrinkling and vitamin K2 deficiency. In fact, the severity of a postmenopausal woman’s facial wrinkles predicts her risk of osteoporosis.
Why? The greater the deficiency of vitamin K2, the greater the calcium content of the skin which leads to ‘cross-linking’ of skin proteins (elastin). This contributes to irregular folding, a.k.a. wrinkles (11).
Wrinkling is associated with less bone mineralization as a lack of K2 leads to a lack of activated Matrix GLA protein: less calcium goes into bones and teeth where it belongs and gets deposited into the skin.
Japanese women have less skin wrinkling than those in North America even after controlling for smoking, alcohol, and sun exposure (12). Natto, a fermented soybean product is one of the best sources of vitamin K2 MK-7. Natto is consumed more so in the northern part of the country and a regional difference in wrinkles & skin quality is seen within Japan.
You might be wondering how vitamin K2 can help to prevent and manage diabetes? Turns out that our bones help to control diabetes. What?
Bones produce the hormone osteocalcin which also improves both insulin secretion and sensitivity; a major underlying factor in the development of insulin resistance, a.k.a. “pre-diabetes” and Type 2 diabetes.
Since osteocalcin in a vitamin K2-dependent protein, researchers are now asking and focusing on the current prevalent vitamin K2 deficiency as one of the underlying risk factors for the epidemic of Type 2 diabetes we’re now facing.
By optimizing levels of osteocalcin produced by bone in the presence of an adequate vitamin K2 intake, this underappreciated nutrient is likely yet another piece in the big picture as to why the Standard American Diet (SAD), and Western diets, in general, are a major risk factor for developing diabetes in the first place (13, 14).
Vitamin K2 supplements might also prove to be an effective way to increase insulin sensitivity and support pancreatic function in Type 2 diabetes (like vitamin D*) and maybe, one day, an adjunctive treatment (15, 16).
Via its activation (carboxylation) of osteocalcin, vitamin K2 enables osteocalcin to transport and integrate calcium into the bone matrix. K2 ensures that bones (and teeth) pull in all the calcium they possibly can AND helps them to hold on to it (17).
FUN FACT: While vitamin D increases the amount of calcium your body can absorb, that’s only part of the story. Vitamin K2 ensures that calcium makes its way into your bones.
In this way, K2 improves bone mineralization and supports calcium metabolism within bone tissue (18, 19). Because bones are largely protein (collagen), K2 strikes again. By activating osteocalcin, K2 helps the bones form strands of collagen which give bones their flexibility.
Taking vitamin K2 supplements has been shown to slow down decreases in age-related bone mineral density (20). Supplements have been shown to reduce spinal fractures by 60%, hip fractures by 77%, and all non-spinal fractures by 81% (21).
To be fair, like all things in research, some studies didn’t find a benefit (22, 23).
Heart health for the most part is about blood vessel health. Yes, the heart muscle can be damaged and diseased but by and large, the concern for the majority of the population is the health of their vessels. By extension, the whole cardiovascular system (brain, limbs, etc.). One of the major concerns for blood vessel health is atherosclerosis, an inflammatory disorder that involves plaque formation.
Most probably don’t realize that plaque composition is consistently about 20% calcium. Calcium build-up in plaque is a significant risk factor for heart disease (24, 25, 26). In fact, the coronary calcium score is far more accurate in predicting cardiac disease risk than LDL. Therefore, anything that can reduce calcium build up in your blood vessels is a very good thing.
This is where vitamin K2 (not K1) comes into play. Via vitamin K2 activation, Matrix Gla protein is able to bind calcium. This directs calcium to where it’s needed like the bones and teeth where 99% of all body calcium is stored. This binding of calcium by MGP also prevents calcium from building up in soft tissues like blood vessels, including the heart (27, 28).
Proper calcium use. K2 as promoter of bone and cardiovascular health
Studies have shown that those with the highest intakes of vitamin K2 (not K1) have less heart disease. For every 10 mcg of K2 they consumed, subjects of one study reduced their heart disease risk by 9% (29, 30). Many think K2, and not red wine, is the explanation for the so-called French Paradox. Despite higher intakes of fat (including saturated fat), the French have much less vessel disease. Traditional French food staples are rich in vitamin K2.
The Rotterdam Study was one of the first studies to demonstrate the association of dietary vitamin K2 and reduced risk for coronary heart disease back in 2004 (31). To reiterate, vitamin K1 (phylloquinone from plants) was not related to any heart disease reduction benefits.
BONUS: vitamin K2 has been shown to pull pre-existing calcium out of soft tissues like blood vessels, skin, etc. where it doesn’t belong (32, 33). In this sense, reverse some of the problems.
As with bones, K2 helps your teeth. Teeth contain osteocalcin which, when activated by K2, pulls calcium into teeth and helps the teeth hold on to it. Like in bone, osteocalcin in teeth is activated by K2 (34).
K2 has been found to improved dental health via the salivary glands which excrete it. In fact, the salivary glands have the second-highest concentration of K2, second only to the pancreas. Vitamin K2 has been shown to stimulate the growth and remineralization of dentin with calcium & phosphorus (35, 36).
Working with two of the other fat-soluble vitamins A and D3, K2 is a key player in maintaining dental health (37).
Cancer risk reduction
While very preliminary, vitamin K2 has shown some promise when it comes to reducing the risk of certain cancers. One study found that K2 was able to reduce the risk of liver cancer recurrence post-liver surgery (38).
Another study found that K2 increased the survival time of subjects with liver cancer by increasing the length of time it took for cancer to return. At 36 months post-treatment, 64% of subjects getting vitamin K2 had their cancer return to 91.6% of those not getting the vitamin (39).
One observational study found those with higher intakes of K2 had a lower risk of advanced prostate cancer – K1 had no effect (40).
Controlling vascular calcification is important for those with chronic kidney disease (CKD). Calcification is very common for a variety of reasons beyond the scope of this post (altered vitamin D, calcium & phosphate metabolism), coumadin use, and a renal diet that is restrictive in phosphate which is found in many K2-rich foods.
Vitamin K deficiency in chronic kidney Disease. Evidence is building up.
K2 has been studied in CKD with some positive outcomes (41, 42). A four-week trial showed improvement in vascular calcification with K2 MK-7 supplementation with a higher dose (360 mcg/day) showing the greatest benefit. This amount was demonstrated to be safe as well (43).
Varicose vein reduction
Via its role in preventing vascular calcification, vitamin K2 even shows promise for our legs. Greater intakes are associated with fewer varicose veins (44).
Vitamin K2 supports glucose metabolism (energy use by exercising muscles) and cardiovascular health. Optimal fuel use, and having a great delivery system of nutrients (blood vessels), will help with athletic performance.
A small 8-week, double-blind, placebo trial with 26 males and female athletes showed a 12% increase in maximal cardiac output after daily supplementation with vitamin K2 as MK-7 (45)
Emerging research is showing a role for vitamin K2 in the prevention of vascular dementia, and other forms such as Alzheimer’s disease. After all, anything that’s good for blood vessel health is great for overall brain health (46, 47, 48).
Of note, vitamin K2 is highly concentrated in the brains of healthy individuals, especially the myelin sheath that surrounds neurons (49, 50).
Of interest is the lower levels of K2 in patients with multiple sclerosis, a disease of the neuron’s myelin. Whether a low intake of vitamin K2 is a risk factor in those who are genetically at risk for MS is unknown.
Lower amounts of K2 seen in MS may be due to depletion, lower production in the gut (but gut production isn’t a reliable source even in healthy people), reduced dietary consumption and absorption (51).
Regardless, vitamin K2 is important for the entire central nervous system, which the brain is part of, as well as the spinal cord (52). Getting more K2 can only be a good thing.
Vitamin K2 foods
MK-4 is exclusively made by animal tissues and is therefore found in foods like butter, cheeses, eggs, dark meat in some fowl, liver and liver pate. Ideology aside, pastured versions of these foods have more vitamin K2 (53).
Modern farming practices, while safe, provide a nutritious and relatively inexpensive food supply, but has resulted in decreased amounts of a couple of nutrients, K2 being one of them. Cows, pigs, chickens have bacteria that can normally turn vitamin K1, found in grasses, into ample amounts of vitamin K2-MK-4. An unintended consequence of livestock not being grass-fed is a decrease in the amount of K1 in their diets.
MK-7 is found abundantly in fermented foods such as natto, tempeh, miso, sauerkraut, and aged cheeses (54).
FACT: Although cows’ milk is low in vitamin K2, aged cheeses are still a good source. The bacteria that are used to make cheese are able to convert vitamin K1 into K2.
|Natto||1103 (100% MK-7)|
|Goose Liver Paste||369 (100% MK-4)|
|Hard Cheeses||76 (6% MK-4, 94% MK-7)|
|Soft Cheeses||56 (6% MK-4, 94% MK-7)|
|Egg Yolk (Netherlands)||32 (98% MK-4, 2% MK-7)|
|Goose Leg||31 (100% MK-4)|
|Curd Cheeses||24 (1.6% MK-4, 99.4% MK-7)|
|Egg Yolk (United States)||15 (100% MK-4)|
|Butter||15 (100% MK-4)|
|Chicken Liver||14 (100% MK-4)|
|Salami||9.0 (100% MK-4)|
|Chicken Breast||8.9 (100% MK-4)|
|Chicken Leg||8.5 (100% MK-4)|
|Ground Beef (Medium Fat)||8.1 (100% MK-4)|
|Bacon||5.6 (100% MK-4)|
|Calf Liver||5.0 (100% MK-4)|
|Sauerkraut||4.8 (8% MK-4, 92% MK-7)|
Persons taking anticoagulant (“blood-thinning”) medications such as warfarin (Coumadin®) should talk to their doctors before supplementing with vitamin K2 as there’s a theoretical risk it may interfere with the activity of medication.
Vitamin A, D3, and calcium all work best together when they play with vitamin K2. The fact of the matter is that the correct form of these vitamins is key.
Vitamin D3 and NOT D2 is what’s needed. Retinol/retinal and NOT beta/alpha-carotene provides balance to D3* and by now you know, K2 and NOT K1 are what we need to get more of.
When these three vitamins are present in optimal amounts, your body can use calcium the way it was meant to be: keeping your teeth and bones strong while not damaging your soft tissues.
Vitamin K2 dosage
How much vitamin K2 should I take? Currently, there are no official recommendations about vitamin K2 but as mentioned, a look at ancestral diets and some of the current research gives us a ballpark figure.
I recommend 100-200 μg per day of vitamin K2 for healthy adults. Although most of the benefit probably comes from the first 100 μg, 200 μg is harmless and may provide additional benefit.
MK-7 is nearly completely absorbed and it stays in the blood longer. It also appears to be the more active form compared to MK-4 which is cleared much quicker which is why more MK-4 is needed is benefits.
Vitamin K2 MK-4 is found in food but in much smaller amounts compared to what has been used in research. The MK-4 dose for therapeutic use is in the 5 – 15 mg (5000 – 15,000 mcg) range per day. An amount that is not available in Canada given that the limit for vitamin “K” in supplements is 120 mcg per dose.
While both forms have been shown to have a benefit on their own, there are no studies available comparing the efficacy of MK-7 found in fermented foods to that of the MK-4 found in animal products.
Supplements of either form are readily available. Most provide vitamin K2 in amounts that are similar to those found in foods per the table above.
Vitamin K2 supplements
Striving to include more vitamin K2-rich foods is paramount. Sadly, most of use are not likely to eat them daily, let along weekly, so supplementation is strongly recommended.
Because Health Canada limits the total amount of vitamin “K” to 120 mcg per day, it’s hard to get enough of the K vitamins in one supplement.
Most multivitamins only include K1. Those that contain both K1 & K2 will include an amount that is at or below the limit of 120 mcg. You can buy vitamin K2 as an individual supplement; typically with doses in the 50 – 120 mcg range.
Below are a few of my favourites:
Natural Factors* – derived from natto bean (fermented soybeans). This supplement provides a usable form of vitamin K2 as MK-7 at 100 mcg per capsule. The capsules are small, easy to swallow. Available in either 60 or 120 vegetarian capsules sized bottles.
Prairie Naturals* – this also provides vitamin K2 as MK-7 at a dose of 100 mcg per capsule. Available in 60 vegetarian capsules sized bottles.
Naka Professional* – vegetarian, non-GMO, gluten-free and non-irradiated. It also provides vitamin K2 as MK-7 at a dose of 100 mcg per capsule. Available in 150 or 300 vegetarian capsules sized bottles.
Now Foods* – vitamin K-2 as MK-7, 100 mcg dose. Available in either 60 or 120 vegetarian capsules sized bottles. Uses the brand version MenaQ7.
* Remember, look for vitamin K2 and not K1.
I’ve been as obsessed with Vitamin K2 almost as long as I have been with vitamin D*. I was waiting patiently for Health Canada to lift it’s overly-conservative and unsubstantiated ban on allowing vitamin “K” to be added to supplements.
As soon as they did, and companies started adding K2, I started using a vitamin D supplement with added K2, such as CanPrev D3 & K2*, back in the mid-2000s.
This unspoken hero is something most of us could use a lot more of. It’s health benefits are significant. Given its role in many of the disorders and diseases we attribute to ‘old age’; I’ll gladly make sure I’m getting my daily dose and lets the chips fall where they may.
The best way to get more is to consume K2-rich foods more often in the context of a well-rounded, nutrient-dense diet (remember it likes to play with vitamins A, D3, and calcium and phosphorus).
Supplements can be very helpful, as long as they are used to support a good diet rather than as replacements for it.
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Doug Cook RDN is a Toronto based integrative and functional nutritionist and dietitian with a focus on digestive, gut, mental health. Follow me on Facebook, Instagram and Twitter.