Vitamin K2: Benefits, Signs of Deficiency, and Recommended Foods

Vitamin K2, also known as menaquinone, is a fat-soluble vitamin, meaning it dissolves in fat and can be stored by the body. Discovered in the 1930s by a Danish scientist, vitamin K2 gets its name from the German word "Koagulation" (coagulation), with the "K" standing for its essential role in blood clotting. As for the number 2, it distinguishes it from vitamin K1, or phylloquinone, which has different properties and sources. While the main sources of vitamin K2 are animal-based, K1 is found primarily in plants.

How is it produced by our bodies?

Vitamin K2 is produced in part by our gut microbiota, primarily by certain bacteria found in the colon. However, this natural production is often insufficient to meet the body’s needs, hence the importance of dietary intake. A healthy and balanced gut flora plays a key role in the synthesis of vitamin K2.

Where can we find it in our diet?

You can reap the benefits of vitamin K2 primarily by consuming animal-based foods. 

Animal sources: Meat (beef, pork, poultry), organ meats (liver), fatty fish (salmon, mackerel), egg yolks, dairy products (cheese, yoghurt, butter).

Plant sources: Sauerkraut (fermented cabbage), natto (fermented soybeans).

Find out which foods contain vitamin K.

Here are the main reasons to consume vitamin K2, which are the source of its benefits for our bodies:

Regulation of calcium metabolism: Vitamin K2 plays a role in activating certain proteins such as osteocalcin and Matrix Gla Protein (MGP), which promotes better utilisation of calcium by optimising its binding to bones and teeth while simultaneously preventing its deposition in artery walls or on certain organs. This property has a direct impact on the prevention of certain disorders that can affect the skeletal, dental, and cardiovascular systems.

Reduced inflammation: This vitamin inhibits the production of certain pro-inflammatory molecules such as cytokines. Furthermore, its role in calcium metabolism and its prioritisation of calcium transport to bones and teeth helps prevent deposits in certain organs, which could lead to chronic inflammation in these tissues. It also plays a role in protecting cells against free radicals, which, in excessive amounts, could lead to oxidative stress, which triggers inflammatory processes. Vitamin K2 therefore plays a role in preventing certain chronic inflammation-related conditions, such as joint pain associated with osteoarthritis.

Conversion of vitamin D into its active form: Vitamin K2 helps convert vitamin D from its inactive form to its active form. Vitamin D obtained from food or synthesised by the skin upon exposure to the sun’s UV rays is inactive and must be converted by the liver and then the kidneys into calcitriol, its active form, in order to be utilised by the body. Vitamin K2 therefore enables vitamin D to become active so that it can fully perform its various functions, such as promoting calcium absorption for better bone and dental health and actively helping to strengthen our defences against pathogens by activating certain immune cells, such as dendritic cells and white blood cells.

Now let’s discuss the main situations in which the benefits of vitamin K2 are particularly useful:

• Prevention of osteoporosis: Thanks to its role in calcium metabolism, vitamin K2 promotes better bone mineralisation, which reduces the risk of osteoporosis—a condition characterised by a decrease in bone density and strength. This condition increases with age and primarily affects women after menopause

• Prevention of osteoarthritis : Vitamin K2 plays a role in reducing the risk of osteoarthritis in several ways. First, through its anti-inflammatory properties—since osteoarthritis is a degenerative joint disease with an inflammatory component—but also by improving bone density through its effect on calcium, which promotes better joint function

• Contribution to good dental health: Its role in calcium metabolism allows vitamin K2 to promote the transport of calcium not only to the bones, as we have just seen, but also to the teeth, which contributes to their strength

• Prevention of cardiovascular risks: This vitamin helps direct calcium to the tissues where it is needed, such as bones and teeth, thereby preventing its deposition in the arteries, which could lead to cardiovascular disorders. These deposits contribute to arterial stiffness, which increases the risk of atherosclerosis. This condition is characterised by increased stiffness and a narrowing of the arteries, which impacts blood flow; the resulting slowdown reduces the amount of blood—and thus nutrients—reaching the organs. Furthermore, these plaques can lead to the formation of clots that block the arteries and cause cardiovascular disorders. 

• Promotes healthy ageing and longevity: The benefits of vitamin K2 for bone density, cardiovascular protection, and the prevention of chronic inflammation—all factors in premature ageing—make it one of the pillars of long-term good health. It also plays an indirect role in the immune system by helping to activate vitamin D, which plays an active role in our natural defences. Thanks to the many benefits of vitamin K2, it helps provide a better quality of life for older adults and promotes greater longevity.

What can cause a deficiency?

A vitamin K2 deficiency can be caused by a diet low in fermented foods or high-quality animal fats, which are the main sources of this vitamin. Certain digestive disorders, such as inflammatory bowel disease or an imbalanced gut flora, can also reduce its absorption. In addition, prolonged use of antibiotics or certain medications, such as anticoagulants, can disrupt the natural synthesis of vitamin K2 by the gut microbiota.

What are the effects of a deficiency?

Signs that may indicate a vitamin K2 deficiency are related to its main functions, namely calcium metabolism, blood clotting, and its anti-inflammatory role:

• Signs related to blood clotting: These manifest as unexpected bleeding, such as nosebleeds or bleeding gums; difficulty stopping bleeding from injuries because the blood does not clot properly; or the appearance of bruises on the skin after minor impacts that would not normally cause them.

• Signs related to calcium metabolism : These include a higher risk of developing osteoporosis, with increased bone fragility that can raise the risk of fractures even from minor impacts. Dental problems may also arise, such as cavities or increased tooth fragility. Additionally, there is an increased risk of cardiovascular disease due to plaque buildup on the walls of the arteries.

• Signs related to its anti-inflammatory function: These are primarily inflammatory conditions such as joint pain associated with arthritis or osteoarthritis.

To maintain optimal vitamin K2 levels, it is essential to follow a varied diet that includes foods rich in K2. The best sources are fermented foods such as natto (fermented soybeans), aged cheeses, and certain fermented dairy products. Eggs, liver, and meat from grass-fed animals are also good sources. Additionally, maintaining a balanced gut flora by consuming foods rich in fibre promotes the natural production of K2 by the microbiota.

Good to know: Alcohol consumption impairs the proper absorption of this vitamin, as well as that of other nutrients. It is therefore recommended to limit alcohol intake.

In addition, certain nutrients promote better absorption of vitamin K2:

Vegan Vitamin D3:   

Vitamin D and vitamin K2 work synergistically. Vitamin D improves calcium absorption, while K2 helps direct this calcium to the bones and prevent it from accumulating in the arteries. Combined supplementation can therefore be particularly beneficial.

Probiotics for gut health:

A healthy gut microbiome contributes to the natural production of K2. Consuming dietary supplements rich in probiotic strains can therefore effectively support this process.

An excess of vitamin K2 is rare, as it is generally well regulated by the body. However, if excessive supplementation is suspected, it is advisable to consult a doctor to adjust the dosage and avoid any imbalance, particularly if you are on anticoagulant therapy. A blood test can be helpful in assessing exact levels and guiding necessary adjustments.

The specific Recommended Daily Allowance (RDA) for vitamin K2 has not yet been clearly established, but for total vitamin K (K1 and K2 combined), the general recommendations are as follows:

• Adults: approximately 75 to 120 µg per day, depending on the country.

• Children: adjusted according to age, generally between 10 and 75 µg per day.

Since vitamin K2 is fat-soluble, it is better absorbed when consumed with foods rich in healthy fats. However, if taking supplements, it is advisable to consult a healthcare professional to adjust the dose to your specific needs.

Vitamin K2 is contraindicated for children. Pregnant or breastfeeding women, as well as people with chronic conditions, coagulation disorders, or those taking medication, should consult a healthcare professional before taking any supplements. More generally, people on anticoagulant therapy should limit their intake of vitamin K2 and seek medical advice.

Before starting vitamin K2 supplementation, it is recommended that you ask your doctor for a blood test to assess your actual needs. This is particularly important if you are taking anticoagulant medication or have a bleeding disorder.

After completing a Master’s degree in Management, Christine spent 20 years working for leading companies in the food supplement and natural cosmetics sectors. She then turned her passion for nature into a career. Today, she practises naturopathy for people and animals, as well as sophrology, and mentors aspiring naturopaths and sophrologists at various schools.