The RDA ranges from 5 micrograms for infants to 80 micrograms for adult men.
Little is stored in the body.
Too much sugar, over-use of antibiotics, excess vitamin E and too much calcium can all cause decreased absorption of vitamin K.
Where do you get vitamin K?
Vitamin K is found in green vegetables, cereals, cheese and liver, and in eggs and beef.
Bacteria in your gut are also an important source.
You need vitamin K for blood to clot properly, and for teeth and bones to form correctly.
Too much vitamin K
Toxicity is rare, but can happen if large amounts of synthetic vitamin K are taken. Symptoms include flushing, sweating and anaemia.
Too little vitamin K
Deficiency is rare in adults unless they suffer from conditions that disrupt absorption such as Crohn’s disease, cystic fibrosis and ulcerative colitis.
Vitamin K supplements
Multivitamin preparations usually contain small amounts of vitamin K; the rest should come from the diet and intestinal bacteria.
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