Vitamin K commonly refers to a group of five structurally similar fat-soluble vitamins. Only two of the five types of vitamin K occur naturally.
Phylloquinone, also known as vitamin K1, is found in plants and performs the traditional functions of vitamin K. Phylloquinone is an active factor in photosynthesis and is found in high amounts in leafy green vegetables like kale and Swiss chard.
Vitamin K1 can be converted to its storage form, Vitamin K2, by bacteria in the large intestine. Vitamins K3-5 are synthetic and can be purchased as supplements.
Vitamin K plays a major role in blood clotting, bone metabolism and the regulation of blood calcium levels. It is absorbed in the small intestine and stored in fatty tissue and the liver. Vitamin K is utilized by the liver in the production of prothrombin (clotting factor).
However, vitamin K is also a nutrient of concern for many people as it can alter the effects of several common medications such as warfarin.
Vitamin K deficiency is rare and typically only occurs in people with malabsorptive conditions or after long-term treatment with antibiotics. Symptoms of deficiency include prolonged clotting time, hemorrhage and excessive bleeding.
This MNT Knowledge Center feature provides an in-depth look at the recommended intake of vitamin K and a breakdown of its possible health benefits, how to incorporate more vitamin K into your diet and any potential health risks of consuming vitamin K.
Contents of this article:
Recommended vitamin K intake
The recommended adequate intake for vitamin K depends on age and gender:
|0-6 months||2 mcg/day|
|7-12 months||2.5 mcg/day|
|1-3 years||30 mcg/day|
|4-8 years||55 mcg/day|
|9-13 years||60 mcg/day|
|14-18 years||75 mcg/day|
|19+ years, females||90 mcg/day|
|19+ years, males||120 mcg/day|
Vitamin K supplements are available but it is best to obtain any vitamin or mineral through food first. It is not the individual vitamin or mineral alone that makes certain foods an important part of our diet but the synergy of nutrients working together.
Experts have proven time and again that isolating certain nutrients in supplement form will not provide the same health benefits as consuming that same nutrient from a whole food. Focus on obtaining your daily vitamin K requirement from food and use supplements only when necessary.
Possible health benefits of consuming vitamin K
Vitamin K may help individuals maintain low blood pressure by preventing several minerals from accumulating in the arteries.
There is a correlation between low intake of vitamin K and osteoporosis.2 Although several studies have suggested that vitamin K supports the maintenance of strong bones, improves bone density and decreases the risk of fractures, others have shown no improvement in bone density associated with vitamin K.2
Increased blood levels of vitamin K have been linked with improved episodic memory in older adults.3 In one study, healthy individuals over the age of 70 with the highest blood levels of vitamin K-1 had the highest verbal episodic memory performance.
Vitamin K may help keep lower blood pressure by eliminating the build-up of several minerals in the arteries (mineralization), allowing the heart to freely push blood through the body. Mineralization naturally occurs with age and is a major risk factor for heart disease. Adequate intake of vitamin K has also been shown to lower the risk of stroke.4
On the next page we look at how to incorporate more vitamin K into your diet and the potential health risks of consuming vitamin K.