Vitamin K is an essential nutrient for the clotting of blood and the healthy mineralization of bone. Found in leafy green vegetables, oils and vitamins, most forms of vitamin K have little side effects with moderate overuse. Those with kidney, liver or heart disease or those taking certain synthetic forms of vitamin K may be at risk for side effects of excessive vitamin K consumption.
Vitamin K Function
Vitamin K is a fat-soluble vitamin that is needed to modify proteins involved in blood clotting and bone structure so they can bind calcium. The ability to bind calcium allows these proteins to signal blood to clot and your bones to strengthen by absorbing minerals.
Vitamin K deficiency is rare in the modern diet. The daily allowance for adults of 90 to 120 mcg per day is easily obtained.
Though results have been mixed, some recent studies suggest that supplementing with up to 1,000 mcg of vitamin K per day decreases the risk of bone fracture but does not necessarily increase bone mineral density, according to the Linus Pauling Institute.
Drug Interactions
Warfarin and other anti-clotting drugs may be affected by changes in vitamin K intake. The dietary intake of those prescribed drugs should be done under the supervision of a doctor. Large doses of vitamins A and E may inhibit the absorption and action of vitamin K. Long-term use of antibiotics may deplete vitamin K levels in the body. Drugs that inhibit the intestinal absorption of fats may inhibit vitamin K absorption.
Side Effects
No tolerable upper limit has been established for vitamin K intake in adults. A synthetic form of vitamin K3, menadione and its derivates, caused liver damage and hemolytic anemia in infants and has been removed from the market. Vitamin K intake may worsen bleeding in those with liver disease and interfere with dialysis in those with kidney disease.
Caution
If you suspect you may have overdosed on a drug or dietary supplement, seek medical help. Vitamin K should not be substituted for a prescription medication without the instruction of your doctor.
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