Vitamin K (phylloquinone)

Vitamin K plays a critical role in normal blood clotting.

Although deficiency is rare, adequate intake is key to preventing many diseases.

There are two main types of vitamin K. Vitamin K1 (phylloquinone), or simply vitamin K, is found in plants, while vitamin K2 (menaquinone) is produced by bacteria and is present in animal products and fermented foods.

Thus, vitamin K is necessary for the synthesis of a number of proteins involved in the formation of a clot that stops bleeding.

Whereas vitamin K2 is involved in bone tissue metabolism, promoting the incorporation of calcium into the bone matrix, which is important for maintaining bone strength.

Daily Requirement and Sources of Vitamin K

The daily requirement for vitamin K varies: for adult men about 120 mcg, for women — 90 mcg. Children require less — from 2 to 75 mcg, depending on age.

Sources of vitamin K include green leafy vegetables such as spinach, kale, and broccoli.

Vitamin K is not a water-soluble vitamin. Unlike the B vitamins and vitamin C, vitamin K is fat-soluble. Therefore, it is extremely important to consume sources of vitamin K along with fats for its absorption.

If you consume green leafy vegetables without fats (such as water-based smoothies), the absorption of vitamin K decreases by 80%.

Possible forms and their learnability

Nutrient forms are listed from best to worst:

Phytomenadione (synthetic vitamin K1). This form has high bioavailability and is often used in medical practice for the prevention and treatment of vitamin K deficiency.

Options on iHerb:

Source Naturals, Vitamin K, 500 mcg, 200 Tablets

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≈ $8.89

The Vitamin Shoppe, Vitamin K Complex, 90 Vegetable Capsules

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≈ $19.99

Phylloquinone in the form of dietary supplements. Vitamin K1 in supplement form has good bioavailability, especially when taken with food containing fats, which aids its absorption.

Options on iHerb:

Swanson, Vitamin K1, 100 mcg, 100 Tablets

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≈ $6.59

Nature's Life, Vitamin K, 1,000 mcg, 50 Vegetarian Capsules

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≈ $9.35

Phylloquinone from vegetable oils. Vitamin K1 found in vegetable oils such as soybean and canola has moderate bioavailability.

Phylloquinone from green leafy vegetables. Although these products are rich in vitamin K1, its absorption from them is limited. Without the addition of fats, the bioavailability is only 5-10%, but in the presence of fats, it increases to 15-30%.

Consequences of Vitamin K Deficiency

A deficiency of vitamin K can lead to impaired blood clotting, increasing the risk of bleeding. This is especially dangerous for newborns, as they have not yet fully developed their own vitamin K production system.

A deficiency of this vitamin in adults may be associated with long-term use of antibiotics or issues with the absorption of dietary fats.

Possible Risks of Excess Vitamin K

An excess of vitamin K is rarely observed and usually does not cause problems in healthy individuals. However, taking high doses of vitamin K in the form of dietary supplements may carry a risk of increased blood clotting.

Individuals taking anticoagulants should avoid large fluctuations in vitamin K intake, as this can lead to instability in blood coagulation metrics and potentially dangerous conditions.

Interesting Facts About Vitamin K

Vitamin K got its name from the word “Koagulation.” This name comes from the German word “Koagulation,” as the vitamin was first discovered to be necessary for blood clotting.

Vitamin K also plays a role in maintaining bone health. Studies show that adequate intake of vitamin K is associated with increased bone density. However, the effect of vitamin K is much less pronounced than that of vitamin K2.

Vitamin K deficiency may be especially prevalent in newborns. Therefore, many doctors recommend that newborns receive vitamin K in the form of an injection to prevent hemorrhagic disease of the newborn.

Alcohol abuse can lead to vitamin K deficiency. Alcohol can interfere with the absorption of vitamin K in the intestines.