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Vitamin K - naphthoquinoids

Vitamin K is a group of structurally similar, fat-soluble vitamins that are vitamin K for blood coagulation and strong bones needed to modify certain proteins required for blood coagulation and in metabolic pathways in bone and other tissue.

This group of vitamins includes two natural vitamins: vitamin K1 and vitamin K2.

Vitamin K1, phylloquinone or phytomenadione (also called phytonadione), is synthesized by plants, and is found in highest amounts in green leafy vegetables because it is directly involved in photosynthesis.

Vitamin K2 (menaquinone) has several subtypes, one of which is involved in bone metabolism. Bacteria in the large intestine can produce a range of vitamin K2 forms. The amount absorbed may be small.


Vitamin K1 is found chiefly in leafy green vegetables such as dandelion greens, parsley, spinach, Swiss chard, cabbage, kale, cauliflower, broccoli, brussels sprouts, avocado, kiwifruit and grapes.

Vitamin K2 is synthesized by animal tissues and is found in meat, eggs, and dairy products.

Freezing foods may destroy vitamin K, but heating does not affect it. Here is a list of foods having the highest content of vitamin K.

Daily intake

The recommended daily intake is 120 micrograms for adult males and 90 micrograms for adult (including pregnant or lactating) females. No tolerable upper intake level (UL) has been set.


Vitamin K deficiency is uncommon in healthy adults. Newborn infants are at an increased risk of deficiency. Vitamin K deficiency may develop in bulimics, those on stringent diets, and those taking anticoagulants.

Vitamin K1 deficiency can result in coagulopathy, which is a bleeding disorder. Symptoms of K1 deficiency include anemia, bruising, and bleeding of the gums or nose, and in women also heavy menstrual bleeding.

Osteoporosis (weak, porous bones) and coronary heart disease are strongly associated with lower levels of K2 (menaquinone).


Although allergic reaction from supplementation is possible, no known toxicity is associated with high doses of the phylloquinone (vitamin K1) or menaquinone (vitamin K2) forms of vitamin K.

However, a synthetic form of vitamin K, vitamin K3 (menadione), is demonstrably toxic. This form has been banned from over-the-counter supplements because large doses have been shown to cause allergic reactions, hemolytic anemia, and cytotoxicity in liver cells.

References: 1 , 2 , 3

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