Vitamin K2: A Comprehensive Guide

Written by: Brilliant Staff

Fact checked by: Ellen Landes, MS, RDN, CPT

Vitamin K2: A Comprehensive Guide

Vitamin K2 might not have the same recognition as other headline-grabbing vitamins like vitamins C or D, but this unsung hero of the nutrient world plays a crucial role in our health. While vitamin K2 might be less well-known than vitamin K1, it's starting to get noticed independently.

So, why is everyone suddenly talking about vitamin K2? Let's dive in deep and uncover its marvels in this comprehensive guide.

What is Vitamin K?

Vitamin K is a fat-soluble vitamin that is essential in blood clotting and bone and heart health. 

There are two main types of vitamin K — K1 and K2. 

Vitamin K1, or phylloquinone, is mainly found in leafy green vegetables and makes up about 75-90% of the vitamin K consumed by humans. Vitamin K2, also known as menaquinone, is less well-known. But not because it's less important; in fact, it’s quite the contrary.

Understanding Vitamin K2

While the liver primarily uses vitamin K1 for blood clotting, vitamin K2 seems to be used by other parts of the body, particularly the bones, blood vessels, and other tissues. 

Unlike vitamin K1, which is mainly found in plant foods, vitamin K2 exists in animal foods and fermented plant foods. Several forms or "menaquinones" of vitamin K2 are classified according to the length of their side chains, ranging from MK-4 to MK-13. The most well-studied of these are MK-4 and MK-7.

MK-4 vs MK-7

MK-4 or menaquinone-4 is found in certain animal foods, such as eggs, butter, and meats, particularly organ meats like liver Our bodies can also synthesize it in limited amounts from vitamin K1.

MK-7 (menaquinone-7) is found in high amounts in natto, a traditional Japanese food made from fermented soybeans. Unlike MK-4, MK-7 is not produced in meaningful quantities by animals or humans.

The absorption and usage of these two primary forms of K2 in the body are different. MK-7 is readily absorbed and stays longer in the bloodstream, giving it a more prolonged impact on the body.

The Mighty Powers Of Vitamin K2

Bone Health

One of the critical roles of vitamin K2 is to help keep our bones strong and healthy. It does this by activating a protein called osteocalcin, which binds calcium to the mineral portion of bones. This process helps maintain bone density.

Multiple studies have explored the role of vitamin K2 in bone health. One study shows vitamin K2 supplementation improved bone density in healthy postmenopausal women. 

Heart Health

Another power that vitamin K2 wields is in heart health. Vitamin K2 helps keep calcium out of undesirable places. At the same time, it directs calcium into places your body needs, like bones and teeth. 

Brain Function

Emerging research points towards a role for vitamin K2 in brain health and function. It's believed that vitamin K2 may help to protect neurons in the brain. It is also suggested that vitamin K2 might support cognitive health, specifically in the areas of cognition and behavior.

Dental Health

While more research is needed, some data suggest vitamin K2 may also contribute to good oral health. It is believed that vitamin K2, when combined with vitamin D, helps to ensure calcium is deposited adequately in teeth.

Sources of Vitamin K2

Vitamin K2 can be found in various foods. This includes animal-based foods rich in MK-4, like beef liver, chicken liver, egg yolks, butter, and certain types of cheese. Fermented foods, particularly natto, are packed with MK-7.

The quantity of vitamin K2 in different food sources greatly varies, and in many regular diets, the intake of vitamin K2 is often suboptimal. Dietary supplements can help fill the gap and are available in both MK-4 and MK-7 forms.

Role of Vitamin K2 in the Body

In the body, K2 acts fundamentally as a co-factor for an enzyme called gamma-glutamyl carboxylase, which is involved in "activating" several protein molecules through a process known as carboxylation. By aiding with the carboxylation process, vitamin K2 plays a vital role in regulating calcium metabolism, supporting heart health, and maintaining strong bones.

Activated vitamin K proteins prevent calcium from being deposited in unwanted places. Instead, they ensure that the calcium is sent to areas where it is needed, such as bones and teeth.

The Wrap Up

For some, vitamin K2 might be that missing puzzle piece in the journey towards optimal health. Maintaining an adequate level of this nutrient in your body is crucial, given its significant benefits for bone health and potential contributions to heart health, brain function, and more. While it can be obtained through diet, supplementation might be helpful to fill in any gaps.

Vitamin K2 is generally safe and well-tolerated. However, if you are on medication such as anti-coagulants or have health issues, it's advisable to bring this up with your healthcare provider before starting vitamin K2. As always, it's essential to consult your healthcare professional before adding any new supplement to your routine.


  1. Cao, Yi, et al. Journal of Bone and Mineral Metabolism 39.6 (2021): 1055-1064. doi:10.1007/s00198-013-2325-6. Accessed 23 January 2024.
  2. Cheng, Gong et al. Nutrition and Metabolism 19.1 (2022): 37. doi:10.1186/s12986-022-00696-y. Accessed 23 January 2024.
  3. Mørken, Anne-Lene et al. Journal of Biological Regulators and Homeostatic Agents 31.4 (2017): 1359-1370. doi:10.1177/0973994517696679. Accessed 23 January 2024.
  4. National Institutes of Health. Office of Dietary Supplements, National Institutes of Health, n.d. Accessed 23 January 2024.
  5. Pan, Guo-Hua et al. Frontiers in Cardiovascular Medicine 8 (2021): 539443. doi:10.3389/fcvm.2021.539443. Accessed 23 January 2024.
  6. Panza, Gabriella et al. Indian Journal of Endocrinology and Metabolism 16.3 (2012): 359-363. doi:10.4103/2238-8973.95537. Accessed 23 January 2024.