Quick guide to Vitamin K
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- blood clotting
- bone metabolism
- kidney function
Absorption and metabolism
Vitamin K requires the presence of fats and bile in the gut in order to be absorbed.
Deficiency
Vitamin K deficiency in adults is rare and is usually limited to those who have liver or food absorption disorders. Symptoms include prolonged clotting time, easy bleeding and bruising. It may contribute to osteoporosis. Deficiency can occur in premature babies.
Sources
Good sources include dark leafy greens, oils from green plants and some dairy products. Vitamin K is also produced by gut bacteria.
Daily recommended dietary intakes
- Men - 80 mcg
- Women - 65 mcg
- Pregnancy - 65 mcg
- Lactation - 65 mcg
Toxic effects of excess intake
Reports of toxic effects are rare. Some forms of supplements may cause anemia. Some studies suggest links between vitamin K injections and an increased risk of childhood cancer.
Therapeutic uses of supplements
Vitamin K supplements are used to prevent hemorrhages and may also be useful in the treatment of osteoporosis.
Interactions
X-rays, aspirin, mineral oil, cholestyramine and anticonvulsant drugs, such as phenytoin, can raise vitamin K requirements. Long-term use of antibiotics can produce vitamin K deficiency.
Cautions
Vitamin K can interfere with the action of anticoagulant drugs such as warfarin.