Vitamin K is a fat-soluble vitamin for the overall health and wellness of the body. A fat-soluble vitamin is generally defined as a type of vitamin that can dissolve in fat and be stored in the body's fatty tissues. 

Vitamin K may help support the functions of the circulatory system in the body.* The vitamin K family has a different set of subtypes of vitamin K, which will explore in more detail.

What does vitamin K do?

Vitamin K is a nutrient that may support the circulatory system.* Vitamin K may also play a role in blood cells, the bones, heart and a series of other important functions.* 

Sources of vitamin K

Foods rich in vitamin K include broccoflower, broccoli, brussels sprouts, cabbage, celery, cilantro, collard greens, kale, velvet kale, green onions, parsley, spinach, and cucumbers. Vitamin K is also found in smaller amounts in other foods such as eggs, dairy yogurt, and vegan cashew yogurt. 

It's generally recommended to eat a diet that includes foods rich in vitamin K as a healthy amount of vitamin K is important for overall wellness (study).*

Vitamin K's natural form

Two of the naturally occurring forms of vitamin K are known as phylloquinone (vitamin K1), which can come from plants, and menaquinone (vitamin K2), which is produced by certain bacteria during a process called "anaerobic respiration". 

What are menaquinones?

Menaquinones are a group of vitamin K2 compounds. They are fat-soluble and support the body in absorbing calcium.* Menaquinones are mostly found in fermented foods such as cheese, yogurt, natto (fermented soybeans), and some meats.

Different variants of menaquinone

We may differentiate the family of menaquinone variants based on the number of certain types of prenyl units on their side chains. 

A prenyl unit is a type of hydrocarbon molecule that is often found in the cell membranes of plants and animals. Prenyl units are composed of five carbon atoms, and they are typically attached to other molecules via a sulfur atom.

Scientists have used the different variations in the structure of the menaquinones produced by bacteria to classify these bacteria. Several of them, which have been isolated from the human intestine during studies, have previously been identified as making menaquinones of various chain lengths. 

We believe today that these bacteria can help define and contribute to the vitamin K necessary conditions to be processed and used by the human body.

How many forms of vitamin K are there in total?

Vitamin K exists in different forms: 

• Phytonadione, a synthetic and man-made form of vitamin K1 
• Vitamin K1, or phylloquinone, is the natural form of vitamin K1. Phylloquinone is a prenylated naphthoquinone that may be synthesized exclusively by plants or green algae.
• Menaquinone, which is vitamin K2. Vitamin K2 has a few subtypes, the two most common being MK4 and MK7.
• Menadione, or vitamin K3, is a synthetic form of vitamin K.

What is vitamin K1?

Vitamin K1, also known as phylloquinone when in natural form, may play a role in supporting the circulatory and musculoskeletal systems.* 

What is vitamin K2?

Vitamin K2 is a nutrient that may play a role in supporting bodily functions, including the circulatory and musculoskeletal systems, as well as the skin and nails.*

What is vitamin MK4? 

Vitamin MK-4, also known as menatetrenone, is a vitamin that can be found in food and used by the body to support circulatory and musculoskeletal systems as well.*

What is vitamin MK7?

Vitamin MK-7 is a nutrient that may play a role in supporting blood cells in the body, bones, and heart.* You may want to read more about different Vitamin K MKs.

What is vitamin K3?

Vitamin K3 is a type of vitamin found in plant-based foods. Vitamin K3 is often associated with the circulatory system.*

Vitamin K and the circulatory system

Vitamin K may play a role in supporting the activation of certain protein factors necessary for specific coagulation factors (study).*

Vitamin K and the heart

Vitamin K may be an essential vitamin that plays a role in supporting our heart health.* This nutrient may also positively support calcium from being deposited in the arteries, which could lead to plaque buildup in certain populations.* 

Vitamin K may also support artery flexibility to be more adaptable to differences in blood pressure, which may differentiate effects on the heart (study).*

Vitamin K and the musculoskeletal system

Overall, vitamin K may play a role in supporting bone health. This vitamin may help positively support the deposit of calcium into the bones and "naturally select" the right type of calcium to be deposited so that the bones might stay strong and healthy (study).* 

Vitamin K is an essential nutrient that may support health and wellness.* Its benefits have been studied with different populations in many studies. While science around vitamin K is well established, new studies are often underway to try to understand other roles and benefits this vitamin can offer.

As always, talk to your doctor before taking any supplements. Get professional advice if you think you might need a vitamin K supplement or are already taking one to ensure you're not exceeding the amounts you may need.* 

Read more about other fat-soluble vitamins such as vitamin A and vitamin D, as well as the role of vitamin K in sport recovery.