Vitamin K2 Benefits and Side Effects | A Comprehensive Analysis of Vitamin K2

August 21, 2022 22 mins to read

It is estimated that up to 97% of adults are deficient in Vitamin K2. So there’s a pretty good chance that you and many members of your family are lacking in K2, which can negatively impact your health in a plethora of ways, and reduce your lifespan!

In this article we explain how vitamin K2 differs from vitamin K1 and why K2 MK7 is the most bioavailable form. We list which foods are rich in Vitamin K2 as well as Vitamin K2 benefits and side effects and how much K2 to take per day. Finally we analyze the benefits of Vitamin K2 and D3, and how they work synergistically together (compliment each other) to increase efficacy.

What is Vitamin K2?

Originally discovered in 1929 by a Danish researcher studying cholesterol, vitamin K made it’s debut in a German scientific journal! Because of it’s properties as a coagulator or “koagulationsvitamin” it was labeled Vitamin “K”.

“Vitamin K,” the generic name for a family of compounds with a common chemical structure of 2-methyl-1,4-naphthoquinone and comes in two separate forms: Vitamin K1 and Vitamin K2; both fat soluble vitamins which means they are absorbed more easily when consumed with dietary fats.

How is Vitamin K Used by the Body? | Biochemical Processes

“Like dietary lipids and other fat-soluble vitamins, ingested vitamin K is incorporated into mixed micelles via the action of bile and pancreatic enzymes, and it is absorbed by enterocytes of the small intestine [10]. From there, vitamin K is incorporated into chylomicrons, secreted into the lymphatic capillaries, transported to the liver, and repackaged into very low-density lipoproteins [2,10]. Vitamin K is present in the liver and other body tissues, including the brain, heart, pancreas, and bone [2,3,11].

In the circulation, vitamin K is carried mainly in lipoproteins [2]. Compared to the other fat-soluble vitamins, very small amounts of vitamin K circulate in the blood. Vitamin K is rapidly metabolized and excreted. Based on phylloquinone measurements, the body retains only about 30% to 40% of an oral physiological dose, while about 20% is excreted in the urine and 40% to 50% in the feces via bile [2,11]. This rapid metabolism accounts for vitamin K’s relatively low blood levels and tissue stores compared to those of the other fat-soluble vitamins [11].

Little is known about the absorption and transport of vitamin K produced by gut bacteria, but research indicates that substantial quantities of long-chain menaquinones are present in the large bowel [7]. Although the amount of vitamin K that the body obtains in this manner is unclear, experts believe that these menaquinones satisfy at least some of the body’s requirement for vitamin K [6,7].” More Info.

Why is Vitamin K2 so Important?

An unwanted side effect of aging is calcification of tissues, specifically arteries. Calcium can build up and “calcify” your arteries, making them less elastic and more restrictive of blood flow (harder for blood to flow freely through them). Arteries must remain elastic in order to efficiently transport blood (along with it’s nutrients and oxygen), to all your tissues.

Eating healthy, exercising frequently, and fostering healthy relationship with family and friends can help your arteries stay healthy. While stress, poor diet, lack of exercise, and exposure to toxins can accelerate aging of your arteries; as well as K2 deficiency. It’s estimated that senior age individuals with little to no calcification of their arteries can subtract up to 10 years from their age.

What is Vitamin K2 MK7?

While vitamin K1 only comes in one form, K2 is further broken down, depending on the length of it’s compound chains, into MK4 through MK13.

Vitamin K2 MK7 (aka vitamin K2-7 – the MK7 comes from menaquinone 7) is well researched as being the most efficient, effective, and bioavailable form of vitamin K2.

MK-7 stays in your body much longer with a half-life of about 3 days, which allows consistent blood levels to build, compared to MK-4 or K1. MK-7 is only produced by bacterial fermentation.

What is Vitamin K2 MK4? | K2 MK4 Supplements

MK-4 acts very much like vitamin K1 as it remains mostly in your liver after reaching your intestines. It has a biological half-life of about one hour, which makes it a poor candidate for a vitamin K2 supplement.

Many vitamin K2 supplements use MK-4, but it’s not the same wholesome MK-4 that you find in grass-fed dairy products. The MK-4 in supplements is a synthetic form of MK-4, made from the extract of the tobacco plant. It’s cheaper to produce than the natural form from grass-fed sources, which is why it’s used.

However MK-4 has a shorter chain length than MK-7. Because it only remains in the blood stream at useful levels for a short time, its effectiveness is limited. This means you’d need to take frequent MK-4 supplements throughout the day for it to be effective.

On the other hand, MK-7 supplements only require once daily dosing because MK-7 stays in therapeutic doses in the blood much longer than synthetic MK-4, and is able to build up to healthy levels.

What is Vitamin K3?

“Menadione, which is sometimes called “vitamin K3,” is another synthetic form of vitamin K. It was shown to damage hepatic cells in laboratory studies conducted during the 1980s and 1990s, so it is no longer used in dietary supplements or fortified foods [3].” More Info.

Are Vitamin K and Vitamin K2 the same?

No! For starters Vitamin K and K2 are found in different foods; K is a phylloquinone Vs K2 is a menaquinone. Also Vitamin K1 plays a role in blood coagulation and clotting, while K2 has a much wider range of benefits including: regulating calcium, supporting hearth health, lowering blood sugar levels, and more.

  • A recent study revealed that of all the K2 vitamins, vitamin K2-MK7 is the version with the highest bioavailability (it is more easily absorbed and stays active for a longer time). 

Vitamin K

  • phylloquinone found mostly in leafy green vegetables
  • Role in blood coagulation, supports clotting, prevents excessive bleeding, bruising and in extreme cases hemorrhaging

Vitamin K2

  • menaquinone found in some animal products and fermented foods (and in small amounts by gut bacteria).
  • Regulates calcium
  • Boosts heart hearlth
  • lowers blood sugar levels
  • Assists in blood clotting (less so than vitamin K1)
  • and more

Vitamin K2 Foods | K1 & K2 Food Sources

  1. Vitamin K1 is a phylloquinone, meaning it’s found mostly in green leafy vegetables. Food sources of phylloquinone include vegetables, especially green leafy vegetables, vegetable oils, and some fruits. Meat, dairy foods, and eggs contain low levels of phylloquinone but modest amounts of menaquinones. The most common sources of vitamin K in the U.S. diet are spinach; broccoli; iceberg lettuce; and fats and oils, particularly soybean and canola oil.
  2. Vitamin K2 is a menaquinone, which means it occurs in some animal products (especially organ meats) and fermented foods. It is also produced, in a smaller amount, by gut bacteria.

These dietary sources are rich in K2

(based on 100-gram servings unless otherwise indicated):

Please Note: Generally speaking, the foods on this list derived from animal products will contain MK4, while the fermented foods will contain MK5–MK14. 

  • Natto (fermented soybeans): 108 micrograms
  • Eel: 63 micrograms
  • Cheeses
    • Munster: 100 micrograms
    • Camembert: 68 micrograms
    • Edam and aged Gouda: 63 micrograms’
    • Cheddar: 24 micrograms
  • Organ meat, such as beef liver: 11 micrograms
  • Chicken: 10 micrograms
  • Butter: 2.1 micrograms per tablespoon
  • Sauerkraut: 2.75 micrograms per half-cup
  • Egg yolks: 67-192 micrograms per yolk (depending on the hen’s diet)

Do I need K2 Supplements? Can’t I Get Enough K2 from Food Sources?

Although many people prefer to obtain nutrients through dietary sources rather then supplements, this can be difficult for some vitamins such as K2. Because K2 is rich in foods such as natto beans, which are not common to most diets (including the western diet), most people will not obtain adequate K2 from food.

Also because 90% of the vitamin K we receive from our diet is vitamin K1, we need vitamin K2 supplements to help us ensure we’re doing the most for our bones and heart health.

Vitamin K2 Produced in the Colon | Gut Microbiome

It is now well researched that a large potion of immune regulation takes place in the gut. In other words your gut health plays a key role in your immune system function and overall health. One way the gut promotes health is by producing small amounts of vitamin K2. Beneficial bacteria is responsible for the production of K2 in the colon. This can play a significant role in the presence of vitamin K2 in your body, especially during short lapses in dietary consumption (through supplements or food). But only in small quantities well below the optimal amount of K2 required by your body.

Vitamin K2 Supplements

If these foods are not standard to your diet (as they are not common to a western diet), it is recommended you supplement your K2 intake. Cheese for example is common to a western diet, but can be high in fat (especially toxic trans fats), and for that reason, isn’t a very good source of K2. If you’re a vegan and can’t consume cheese or eggs, then soybeans would be your only dietary source of K2.

  • Only buy from reputable brands with all the necessary nutritional info clearly indicated on the packaging
  • Concentration levels can vary, and your body may not absorb 100% of the supplement, therefore getting a slightly higher dose will ensure you get adequate intake of K2
  • Pharmaceutical Grade Supplements are ideal because they are guaranteed to be > 99% pure
  • K2 supplements can deteriorate quickly on the shelf – look for formulations that extend shelf life and ensure the package you receive hasn’t been sitting on the shelf for long before reaching you.

What Does Vitamin K2 do?

We go over this more in the section on Vitamin K2 Benefits, but essentially K2 helps regulate calcium to reduce calcification of arteries and extend your life! As you age your arteries can calcify (become less elastic), meaning they have reduced blood flow to tissues which can shorten your lifespan ad lead to a host of age related diseases. Vitamin K2 helps to prevent this calcification of your arteries, largely through it’s ability to help direct calcium into your bones and away from your soft tissues.

In addition Vitamin K2 has the following benefits: boosts heart health, lowers blood sugar levels, assists in blood clotting and has a host of other health benefits, primarily due to it’s ability to reduce arterial calcification, which supports blood flow to bodily tissues.

Vitamin K2 and Calcium | The Calcium Controller

Calcium is vital to strong healthy bones and teeth, but it requires considerable help getting there (where it belongs), and away from your soft tissues where it can cause vascular calcification (hardening of tissues) which can lead to: bone spurs, liver and kidney stones, stiffened blood vessels, cardiovascular disease, and major cardiac events. You want calcium in your skeleton, and not in the linings of your arteries, heart valves, and organs.

K2 steps in to prevent vascular calcification by directing calcium where it belongs (in your bones and teeth), therefore preventing calcium deposits from forming in your blood vessels, kidneys, liver, or other soft tissues. It can even help extract existing calcium from your arteries helping them become more elastic ensuring smoother, easier blood flow and boosting circulation!

Vitamin K, K2 and Blood Clotting

“Vitamin K functions as a coenzyme for vitamin K-dependent carboxylase, an enzyme required for the synthesis of proteins involved in hemostasis (blood clotting) and bone metabolism, and other diverse physiological functions [3,5]. Prothrombin (clotting factor II) is a vitamin K-dependent protein in plasma that is directly involved in blood clotting.” More Info.

Although K2 also plays a role in blood clotting, it is secondary and significantly less than it’s counterpart Vitamin K1.

Benefits of Vitamin K2 and D3 | The Perfect Team

Vitamin D’s primary role is to help your body absorb calcium, by ensuring your body draws the maximum amount of calcium from your diet. However vitamin D doesn’t direct where calcium is deposited, which can create a toxic situation where high levels of calcium go into your soft tissues (detrimental to your health), instead of into your bones and teeth where it can benefit your health.

So while Vitamin D raises your calcium levels, Vitamin K2 helps to safely route that calcium where it belongs, making it a cofactor in maintaining an optimal balance of Vitamin D and Calcium.

Vitamin K2 Benefits

  1. Prevents Vascular Calcification – K2 helps route calcium into your bones and away from your soft tissues where it can do damage.
  2. Supports Cardiovascular (Heart) Health – By preventing vascular calcification and arterial disease, vitamin K2 takes the pressure off the heart. It ensures your heart doesn’t have to work extra hard to push blood through clogged arteries (aka arteriosclerosis). This means your heart doesn’t have to pump as hard, so it can function more effectively and longer!
    1. In one study on dietary intake of menaquinone, participants with high vitamin K2 intake had a 57% lower risk of dying from heart disease.
    2. Another study showed that for every 10 micrograms of K2 consumed per day, the risk of heart disease was lowered by 10%.
  3. Promotes Bone Health – K2 is an “osteo-powerhouse” which helps activate GLA protein (MGP) and osteocalcin, the two proteins which help bind calcium to your bones through the process of bone mineralization and calcium homeostasis.
    1. Some research indicates that high serum levels of undercarboxylated osteocalcin are associated with lower bone mineral density [5,28].
    2. Some, but not all, studies also link higher vitamin K intakes with higher bone mineral density and/or lower hip fracture incidence [29-34].
    3. Japanese researchers found vitamin K2 to be especially beneficial for postmenopausal women, who are more likely to suffer from decreased bone density.  Clinical trial participants with increased K2 intake significantly decreased their risk of fractures. As a result, vitamin K2 is regularly prescribed in Japan to prevent and treat osteoporosis.
  4. Regulates Blood Sugar – Studies have shown K2 can normalize blood glucose levels. This is due to the protein osteocalcin, activated by K2, which acts like a hormone and reduces both insulin sensitivity and blood glucose. A high blood glucose level is also associated with an elevated risk of diabetes and mood disorders.
    1. Studies show that when K2 lowers blood sugars, it also works to reduce the possibility of type 2 diabetes and minimize depression and anxiety.
  5. Promotes Blood Clotting – Your body utilizes all the “K” vitamins to produce the prothrombin protein, crucial to blood clotting. This reduces both excessive bleeding and severe bruising, and promotes wound healing. It also prevents potentially dangerous—even fatal—hemorrhages. Some patients on blood thinning medications are monitored to ensure vitamin K levels are adequate.
  6. Supports Cardiac Health – K2 MK7 Fuels Mitochondria. Mitochondria are the cells “batteries” which supply energy to all of the cells in your body, including muscles; especially the heart with the highest concentration of mitochondria! Unlike other organs, the heart is the one organ in your body that is unable to re-generate cells. Therefore it is vital not just for athletes, but for everyone to take as much stress off the heart as possible to ensure it’s long-term effective function.
    1. In a study of athletes who took vitamin K2 for eight weeks, their cardiac output (the amount of fresh oxygenated blood pumped by the heart) increased by 12%
  7. Promotes Oral (Dental) Health – One of the less researched health benefits of K2 is it’s possitive effect on dental health. Vitamin K2 promotes activation of osteocalcin, a protein believed to stimulate the growth of dentin, the calcified tissue underneath your tooth enamel.
  8. Helps Combat (liver and Prostate) Cancer – Several new studies have shown a possible link between K2 and recovery from two specific types of cancer: liver and prostate cancer. Although it’s important to note these are preliminary studies, and more research is required.
    1. Liver Cancer: Two separate clinical studies found that a high vitamin K2 intake seemed to reduce the recurrence of liver cancer and increased the participants’ survival times.
    2. Prostate CancerAnother study found that participants who increased their K2 levels had a 63% lower risk of advanced prostate cancer.
  9. Prevents Muscle Cramps – Muscle mass typically declines with age (similar to bone mass). Age related muscle wasting usually results in impaired muscle function. As part of this muscle cramping can occur. Studies show 30% of seniors over 60 and 50% over 80 experience muscle cramps.
    1. A group of 19 elderly men and women experiencing leg cramps on a daily or weekly basis was given a daily dose of 100 mcg per day of vitamin MK-7 for three months. At the end of the study, the researchers found that this low dosage level of MK-7 resulted in “dramatic improvement of frequency, duration, and severity of pain during cramping”. When the subjects stopped taking the supplement, the cramping tended to return within days or weeks.

The 2004 Rotterdam Study

A 2004 Rotterdam Study from 2004, a 10-year study on 4,807 healthy individuals, age 55+ showed consumption of more than 32 mcg of dietary vitamin K2 from mostly fermented foods led to a 50 percent reduction of arterial calcification, 50 percent reduction of cardiovascular risk, and a 25 percent reduction of all-cause mortality.

And those who consumed 45 mcg of K2 from foods lived 7 years longer than those getting only 12 mcg per day! Most importantly, these results were only seen in groups consuming high levels of vitamin K2, and not vitamin K1.

The Prospect Study

In a study labeled the Prospect Study, 16,000 healthy women were followed for 8 years. The results were similar to those of the Rotterdam study: High intake of natural vitamin K2, but not vitamin K1, over an 8-year period promoted cardiovascular health.

For every 10 mcg of vitamin K2 consumed, cardiovascular risk was reduced by 9 percent.

Vitamin K2 Deficiency Symptoms

According to estimates, 97% of adults are deficient in Vitamin K2. Here are some general symptoms to be aware of:

Note: most of these symptoms occur in the more advanced stages of K2 deficiency. Once K2 deficiency symptoms display it may be too late to undo some of the damage. In light of this it’s essential you keep up adequate K2 intake daily either through diet, supplements or a combination of both.

  • Delayed blood clotting
  • Prolonged prothrombin time (the time it takes for a blood sample to form clots, as measured by a physician)
  • Excessive bleeding or bruising
  • Hemorrhaging
  • Osteopenia (the precursor to osteoporosis)
  • Osteoporosis – a disorder characterized by porous and fragile bones, is a serious public health problem that affects more than 10 million U.S. adults, 80% of whom are women

Groups at Risk of Vitamin K2 Deficiency

  1. Newborns not treated with vitamin K at birth
  2. People with malabsorption disorders or other gastrointestinal disorders such as cystic fibrosis, celiac disease, ulcerative colitis, and short bowel syndrome, might not absorb vitamin K properly
  3. Patients who have undergone bariatric surgery
  4. Individuals taking antibiotics
  5. Individuals on blood thinning medications
  6. Individuals cholesterol lowering drugs – Statins can deplete your body of both vitamins K1 and K2.

Infants and K2 Deficiency

Newborns who do not receive a vitamin K shot at birth are 81x more likely to experience severe bleeding than those who do! Infants are particularly susceptible to a vitamin k deficiency, due to the fact that K2 is unable to cross the placenta and only negligible amounts are found in breast milk. This can create a serious and sometimes fatal situation. In newborns and infants, even minor bleeding will be dangerous because the lack of K2 can cause issues with blood clotting. Therefore as a safety precaution infants are typically administered a vitamin K shot before they leave the hospital, which protects them until they are roughly 6 months of age, at which point they’ll have enough vitamin K in their system. 

Antibiotics and K2 Deficiency

Antibiotics can decimate the gut microbiome and it’s ability to manufacture vitamin K2 in the colon. As a result individuals prescribed antibiotics are especially susceptible to vitamin K2 deficiency deficiency.

Blood Thinning (anticoagulant) Medications and K2 Deficiency

Some blood thinning medications (anticoagulants such as Warfarin) are known to antagonize vitamin K. Patients who take these medicines are monitored to make sure their vitamin K levels remain consistently high.

Vitamin K & K2 Side Effects

According to Vitamin K side effects can include:

Check with your doctor immediately if any of the following side effects occur while taking phytonadione:

Incidence not known

  • Bluish color of the fingernails, lips, skin, palms, or nail beds
  • blurred vision
  • chest tightness
  • confusion
  • cough
  • difficulty swallowing
  • dizziness, faintness, or lightheadedness when getting up suddenly from a lying or sitting position
  • fast heartbeat
  • hives, itching, skin rash
  • puffiness or swelling of the eyelids or around the eyes, face, lips, or tongue
  • rapid and weak pulse
  • sweating
  • trouble breathing
  • unusual tiredness or weakness
  • yellow eyes or skin
  • While an allergic reaction is possible, vitamin K-2 supplements are generally safe and nontoxic, according to the Linus Pauling Institute.

Side Effects NOT Requiring Immediate Medical Attention

Some side effects of phytonadione may occur that usually do not need medical attention. These side effects may go away during treatment as your body adjusts to the medicine. Also, your health care professional may be able to tell you about ways to prevent or reduce some of these side effects.

Check with your health care professional if any of the following side effects continue or are bothersome or if you have any questions about them:

Incidence not known

  • Change in taste
  • feeling of warmth
  • redness of the face, neck, arms and occasionally, upper chest

Vitamin K2 Specific Side Effects

  • Vitamin K2 supplements are considered safe for the average person to take. They generally do not result in any adverse side effects, and the side effects that can occur are typically mild.
  • There is little danger of K1 or K2 overdosing, because excess K1 and K2 is quickly broken down by the body and excreted in both the urine and feces.
  • Upset stomach 
  • Diarrhea
  • Dizziness
  • Shortness of breath

Vitamin K2 Drug Interactions | Medications Known to Interact with Vitamin K2

Who Should Avoid K2 Supplements

A few sensitive groups may need to avoid vitamin k supplements. This includes pregnant or breastfeeding women and anyone taking the following medications:

  • Blood thinners – Some blood thinning medications (anticoagulants such as Warfarin) are known to antagonize vitamin K. Patients who take these medicines are monitored to make sure their vitamin K levels remain consistently high.
  • Phenytoin
  • Certain antibiotics – Antibiotics can decimate the gut microbiome and it’s ability to manufacture vitamin K2 in the colon. As a result individuals prescribed antibiotics are especially susceptible to vitamin K2 deficiency deficiency.
  • Orlistat
  • Bile acid sequestrants

How Much Vitamin K2 per Day

The recommended daily amount of K2 varies depending on country or health authority and age of the individual:

  • In Canada the DRI (Dietary Reference Intake) for K2 can be found here
    • 120mcg/day for Males over 18
    • 90mcg/day for Females over 18 (not pregnant or lactating)
  • The recommended intake for K2 by the NIH (National Institutes of Health) found here is 90mcg
  • The upper recommended limit is 320mcg
  • There is little danger of K1 or K2 overdosing, because excess K1 and K2 is quickly broken down by the body and excreted in both the urine and feces.
  • Always consider your diet when supplementing. For example if you are a vegetarian with a diet high in leafy greens rich in K2, or one day you consume allot of veggies, a lower supplemental dose of K2 is ideal.
AgeK2 Dose (mcg)
Children 7-12 months2.5 mcg/day
Children 4-8 years55 mcg/day
Adults90-400 mcg/day
Seniors 50+ years100-200 mcg/day
Recommended Vitamin K2 Dose (mcg

Best Way to Take Vitamin K2 Supplements

K2 is best taken with adequate water and a protein containing meal, or with a supplement containing fatty acids which will help increase absorption. It does not matter what time of day you take vitamin K2, and there is no particular benefit to taking K2 in the morning or at night.

Best Vitamin K2 Supplement


Many dietary supplements, including vitamin k2, have not been evaluated by the United States Food and Drug Administration (FDA) and are not intended to treat, cure, or prevent any disease. They may help to lower risk factors of certain conditions, but they shouldn’t be used as a substitute for professional medical treatment or prescribed medication. 

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