Introduction
Vitamin K is another fat-soluble vitamin essential for body functions. It comes in 2 forms: phylloquinone (vitamin K1) and menaquinone (vitamin K2). [2]
Vitamin K1 is the main dietary form of vitamin K and is present abundantly in plant sources, whereas K2 is available through fermented foods and animal sources, but only in small quantities. [2]
Vitamin K helps to make various proteins that are needed for blood clotting and the building of bones. [2]
Vitamin K is found throughout the body including the liver, brain, heart, pancreas, and bone. It is broken down very quickly and hence rarely reaches toxicity level. [2]
Compared to the other fat-soluble vitamins, very small amounts of vitamin K circulate in the blood. [1]
- Vitamin K is absorbed in the small intestine. The body retains only about 30% to 40% of a vitamin k oral physiological dose, while about 20% is excreted in the urine and 40% to 50% in the faeces via bile. [1]
- The absorption rate from vegetables is enhanced by the presence of dietary fats. [3]
- This rapid metabolism is responsible for low vitamin K levels in the blood and tissue stores. [5]
- Vitamin K is found throughout the body including the liver, brain, heart, pancreas, and bone. [1]
- Human liver stores normally comprise about 90% menaquinones and 10% phylloquinone and in case of severe dietary depletion, liver concentration can possibly reduce to 25% of their initial levels within 3 days, [5]
- Like other fat-soluble vitamins, vitamin K is absorbed in the intestine and transported to the liver which then repackages it to low-density lipoproteins. [1]
- Vitamin K is excreted primarily in the bile, but also, to a lesser extent, in the urine. [3]
- Vitamin K is rapidly metabolised and broken down in the body very quickly, hence it rarely reaches toxic levels even with high intakes. [1]
- Therefore, about 60-70% of vitamin K1 absorbed through meals might be lost through excretion. [5]
Body Functions
Recommended Daily Intake
Deficiency Symptoms
Symptomatic vitamin K deficiency and impairment of normal haemostatic control in healthy adults may take more than 2–3 weeks to develop at ‘low’ phylloquinone intake (i.e. < 10 mcg/day). [8]
Vitamin K Food Sources
Excessive Intake/ Toxicity Side Effects
Vitamin K toxicity is uncommon overall but is more prevalent in formula-fed infants. Hence, no Upper tolerable limits have been established for vitamin K because of its low toxicity potential. [3]
Groups At Risk of Vitamin K Deficiency
Vitamin K Interaction With Other Nutrients
Nutrient Profiles For Food Groups
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