V

vitamin K A vitamin that is a crucial catalyst, or
coenzyme, in the COAGULATIONprocess (also called
coagulation cascade). Vitamin K (naphtho-
quinone) plays a role in activating seven of the
CLOTTING FACTORSin various stages of coagulation,
helping convert them from the inactive state in
which they circulate in the BLOODto active pro-
teins that form clots. Vitamin K also is important
for new BONEgrowth and BONE DENSITY. The major
forms of vitamin K are phylloquinone (K1),
menaquinone (K2), and menadione (K3, syn-
thetic and cannot be converted into K1).

DIETARY SOURCES OF VITAMIN K

Food Amount of Vitamin K
per 1-Cup Serving

Kale, cooked 1,062 micrograms (mcg)
spinach, cooked 888 mcg
collard greens 836 mcg
parsley 324 mcg
Brussels sprouts, cooked 219 mcg
onions, spring 207 mcg
broccoli, cooked 220 mcg
lettuce, leaf (Bibb, Boston) 167 mcg
asparagus, cooked 144 mcg
prunes, stewed 65 mcg
lettuce, romaine 57 mcg
peas, cooked 40 mcg
blackberries, blueberries (fresh) 28 mcg
lettuce, head (iceberg) 13 mcg
turkey, cooked 5 mcg
strawberries, raw 4 mcg

Source: USDA National Nutrient Database for Standard Refer-
ence, SR17 Nutrients List: Vitamin K (Phylloquinone)

Most of the vitamin K the body uses is in the
form of phylloquinone and comes from plant

foods in the diet, notably leafy green vegetables

such as spinach, kale, and broccoli. Intestinal BAC-

TERIA also synthesize (manufacture) a small

amount of vitamin K (menaquinone). Though

vitamin K is fat soluble, the body does not main-

tain a significant store of it. Consequently, health

experts have established daily adequate intake

values of 90 micrograms per day for women and

120 micrograms per day for men.

The commonly used oral anticoagulant medica-

tion, warfarin, inhibits clotting by blocking the

actions of vitamin K. Doctors may recommend

restricting consumption of foods high in vitamin K

for those who are taking ANTICOAGULATION THERAPY

or maintaining consistent consumption of vitamin

K–containing foods (not to exceed the daily ade-

quate intake value) so the body’s levels of vitamin

K remain stable.

Because infants often have inadequate levels of

vitamin K in their blood at birth, most hospitals in

the United States administer vitamin K supple-

ment injections to newborns within 24 hours of

birth, which is the current recommendation of the

American Academy of Pediatrics. Doctors do not

agree on the value or effectiveness of routine vita-

min K supplements in other circumstances. Most

health experts recommend obtaining the body’s

supply of vitamin K through dietary sources,

which is fairly easy for most Americans to do

because a wide variety of foods contain this nutri-

ent. Menadione is the synthetic supplement form

of vitamin K.

See also ANTICOAGULATION THERAPY; OSTEOPOROSIS;

VITAMINS AND HEALTH.

von Willebrand’s disease A hereditary, genetic

bleeding disorder resulting from a deficiency or

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