Vitamin K is a fat-soluble vitamin that plays a key role in blood clotting. It helps the body stop bleeding by supporting the production of proteins that regulate blood clotting. In addition, vitamin K is also important for bone health and the regulation of calcium metabolism, which helps prevent bone fractures. In this article, you'll learn why vitamin K is essential, its health benefits, and how to use it safely.

What is vitamin K?

Vitamin K is a fat-soluble vitamin that exists in two main forms: vitamin K1 (phylloquinone) and vitamin K2 (menaquinone) . Vitamin K1 is found primarily in green leafy vegetables, while vitamin K2 is found in fermented foods and animal products. Both forms play a crucial role in the activation of proteins responsible for blood clotting and calcium metabolism. Vitamin K is essential for bone health and cardiovascular function [1].

Synonyms for vitamin K

In addition to vitamin K1 and vitamin K2, there are other subtypes of vitamin K, such as menaquinone-4 (MK-4) and menaquinone-7 (MK-7) , which have different biological half-lives and are found in various foods. Vitamin K is also called the coagulation vitamin because it is essential for blood clotting [2].

The different forms of vitamin K: K1 and K2

Vitamin K exists in two main forms, each with different functions in the body: vitamin K1 (phylloquinone) and vitamin K2 (menaquinone). Vitamin K1 is found primarily in green leafy vegetables such as spinach and kale and is important for blood clotting, preventing excessive bleeding. In contrast, vitamin K2, which is divided into several subtypes (MK-4 to MK-13), is found in greater quantities in fermented foods and animal products. It is known for its role in bone and heart health, regulating calcium by transporting it to the bones and teeth while preventing plaque buildup in the arteries. Both forms are fat-soluble, meaning they rely on dietary fats for optimal absorption. Together, they contribute to overall health, although each form has specific functions in the body.

Where does vitamin K come from?

Vitamin K1 occurs naturally in green leafy vegetables such as spinach, kale, and broccoli. Vitamin K2, on the other hand, is produced by gut bacteria and is found in fermented foods such as natto (fermented soybeans) and animal products such as cheese and eggs. Because vitamin K is fat-soluble, it is better absorbed when consumed with fat sources [3].

How is vitamin K produced?

Vitamin K1 is derived from plants, while vitamin K2 is produced either by fermentation or synthesis in animal products. In dietary supplements, vitamin K2 is often used as menaquinone-7 (MK-7) because this form has a longer half-life in the body and is more bioavailable than other forms [4].

Health benefits of vitamin K

Vitamin K and blood clotting

The most important health benefit of vitamin K is its role in blood clotting. Vitamin K activates proteins responsible for the production of blood clotting factors. Without sufficient vitamin K, the body cannot produce blood clotting factors, which can lead to excessive bleeding or bruising. People with a vitamin K deficiency are at increased risk for blood clotting disorders, which is why vitamin K is crucial for maintaining normal blood clotting [5].

Vitamin K and bone health

Vitamin K plays a key role in bone health by supporting the activation of osteocalcin, a protein that deposits calcium into the bone matrix. Vitamin K deficiency can lead to reduced bone density and increase the risk of bone fractures. Studies show that adequate vitamin K2 intake can help improve bone health and reduce the risk of osteoporosis, especially in older people [6].

Vitamin K and heart health

Vitamin K is also important for heart health because it helps prevent calcium deposits in the arteries. A vitamin K deficiency can lead to hardening of the arteries (atherosclerosis) because calcium can build up in the blood vessels. Vitamin K2, particularly the form MK-7, has been shown to be effective in reducing arterial calcification and maintaining blood vessel elasticity, reducing the risk of cardiovascular disease [7].

Vitamin K and brain function

Recent studies suggest that vitamin K may also play a role in supporting brain function. Vitamin K is thought to have neuroprotective properties and may reduce the risk of neurodegenerative diseases such as Alzheimer's disease. These benefits may be due to vitamin K's antioxidant properties and its role in regulating inflammatory processes in the brain [8].

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Vitamin K and skin health

Vitamin K is also used to support skin health, particularly in wound healing and scar reduction. It is often used in topical creams to treat bruises, stretch marks, and redness. Vitamin K may help improve blood circulation and accelerate skin healing processes [9].

How does vitamin K work in the body?

Vitamin K works in the body by supporting the activation of proteins necessary for blood clotting, calcium metabolism, and bone health. It helps transport calcium from the blood to the bones while preventing calcium deposition in the arteries. Furthermore, vitamin K supports normal cell function and acts as an antioxidant, protecting cells from damage [10].

Recommended dosage and use of vitamin K

What is the recommended dosage?

The recommended daily intake (RDA) of vitamin K is approximately 120 micrograms per day for men and 90 micrograms per day for women. Pregnant and breastfeeding women do not have increased needs. When taking vitamin K supplements to support bone health or prevent arteriosclerosis, higher doses of vitamin K2 (MK-7) are often recommended, ranging from 100 to 200 micrograms per day [11].

When should you take vitamin K?

Vitamin K should ideally be taken with a meal containing fat, as it is fat-soluble and requires fats for proper absorption. Vitamin K supplements are available in capsule, drop, and tablet form. It is important to consume vitamin K regularly to support blood clotting and bone health [12].

Side effects and safety of vitamin K

Is vitamin K safe?

Vitamin K is considered safe and well-tolerated when taken in recommended amounts. Because it is a fat-soluble vitamin, it can be stored in the body, but there are no reports of toxic effects from excessive dietary intake of vitamin K1 or K2. However, people taking blood-thinning medications such as warfarin should monitor their vitamin K intake, as vitamin K may interfere with the effectiveness of these medications [13].

What are the side effects of vitamin K?

Rare side effects of vitamin K supplements include stomach upset or skin reactions. People taking blood thinners should consult their doctor before taking vitamin K supplements, as high vitamin K intake can affect blood clotting. It is recommended to always consult a doctor before taking vitamin K supplements, especially if there are health concerns [14].

Vitamin K compared to other fat-soluble vitamins

Vitamin K vs. Vitamin D

Both vitamin K and vitamin D are fat-soluble vitamins that play an important role in calcium metabolism and bone health. While vitamin D promotes calcium absorption in the intestines, vitamin K helps deposit calcium into the bones and prevent plaque buildup in the arteries. These two vitamins work synergistically and are often used together in supplements to support bone health [15].

Vitamin K vs. Vitamin E

Vitamin K and vitamin E are both fat-soluble vitamins with antioxidant properties. While vitamin K is primarily responsible for blood clotting and calcium metabolism, vitamin E protects cell membranes from oxidative damage. Both vitamins are important for overall health but function differently in the body. Vitamin E has no direct effect on blood clotting, which is why it can be taken alongside vitamin K without interfering with its function [16].

Natural sources of vitamin K

Vitamin K1 is found primarily in green leafy vegetables such as spinach, kale, broccoli, and Brussels sprouts. Vitamin K2, on the other hand, is found in fermented foods such as natto, sauerkraut, and cheese, as well as in animal products such as eggs and chicken. To ensure adequate vitamin K intake, a balanced diet with a variety of green vegetables and fermented foods should be considered [17].

Vitamin K in dietary supplements

Vitamin K supplements are available in various forms, including capsules, drops, and tablets. Vitamin K2 (especially MK-7) is often preferred because of its longer half-life in the body and greater bioavailability. This form of vitamin K is often used to support bone health and prevent arteriosclerosis. It is important to discuss the use of vitamin K supplements with a doctor, especially if you are taking blood-thinning medications [18].

Final thoughts on vitamin K

Vitamin K is an essential fat-soluble vitamin that is vital for blood clotting, bone health, and heart function. It helps retain calcium in the bones and prevents calcium deposits in the arteries. For people who want to promote bone health, support blood clotting, or protect heart health, vitamin K is a valuable supplement that can be obtained either through food or supplements.