Vitamin K is a fat-soluble vitamin that plays an important role
in blood clotting.
Vitamin K is known as the clotting vitamin, because without it blood
would not clot. Some studies indicate that it helps in maintaining strong
bones in the elderly. Vitamin K helps make six of the 13 proteins needed
for blood clotting. Its role in maintaining the clotting cascade is so
important that people who take anticoagulants such as warfarin (Coumadin)
must be careful to keep their vitamin K intake stable.
Vitamin K is also involved in building bone. Low levels of circulating
vitamin K have been linked with low bone density, and supplementation
with vitamin K shows improvements in biochemical measures of bone health.
A report from the Nurses' Health Study suggests that women who get at
least 110 micrograms of vitamin K a day are 30% less likely to break a
hip as women who get less than that. Among the nurses, eating a serving
of lettuce or other green leafy vegetable a day cut the risk of hip fracture
in half when compared with eating one serving a week. Data from the Framingham
Heart Study also shows an association between high vitamin K intake and
reduced risk of hip fracture.
The recommended daily intake for vitamin K is 80 micrograms for men and
65 for women.
Vitamin K deficiency is very rare and occurs when there is an inability
to absorb the vitamin from the intestinal tract. Vitamin K deficiency
can also occur after prolonged treatment with oral antibiotics.
Food Sources: Vitamin K is found in cabbage, cauliflower, spinach and
other green leafy vegetables, cereals, soybeans, and other vegetables.
Vitamin K is also made by the bacteria that line the gastrointestinal
tract.
It is important for people taking warfarin (a blood thinner) to know
that vitamin K or foods containing vitamin K may reduce the effectiveness
of this medication. Ask your health care provider before increasing intake
or for advice on maintaining proper levels of vitamin K if you are taking
warfarin.
