mcg). No UL levels have been set for vitamin K. Large
amounts of vitamin K 1 do not appear to cause blood
clotting or other side effects. However, K 3 is associated
with health risks especially to children. It is banned by
the United States Food and Drug Administration.
The following are the AIs for vitamin K for
healthy individuals:
children birth–6 months: 2 mcg
children 7–12 months: 2.5 mcg
children 1–3 years: 30 mcg
children 4–8 years: 55 mcg
children 9–13 years: 60 mcg
children 14–18 years: 75 mcg
men age 19 and older: 120 mcg
women age 19 and older: 90 mcg
pregnant and breastfeeding women age 18 and
younger: 75 mcg
pregnant and breastfeeding women age 19 and older:
90 mcgSources of vitamin K
Vitamin K is found in the largest quantities in
green, leafy vegetables. The following list gives the
approximate vitamin K 1 content or some commonfoods. Little vitamin K is lost during cooking, but
more is lost when foods are frozen.
parsley, fresh, 2 Tablespoons: 120 mcg
spinach, cooked 1/2 cup: 445 mcg
kale, cooked, 1/2 cup: 530 mcg
turnip greens, cooked, 1/2 cup: 265 mcg
Swiss chard, cooked, 1/2 cup: 285 mcg
brussels sprouts, cooked 1/2 cup: 110 mcg
broccoli, cooked, 1/2 cup: 77 mcg
asparagus, cooked, 1/2 cup: 46 mcg
celery, raw, 1/2 cup: 18 mcg
carrots, raw, 1/2 cup: 8 mcg
miso, 1 ounce: 4 mcg
milk, 2% 1 cup: 5 mcg
dietary supplements: 10–120 mcgVitamin K’s role in health
Vitamin K is necessary for normal blood clotting
(coagulation). In the liver, it is converted into more
than half a dozen coenzymes that are essential to the
complex cascade of events that result in the formation
of a blood clot.
Vitamin K is routinely given to newborns in order
to prevent bleeding known as hemorrhagic disease of
the newborn (HDN) or vitamin K deficiency bleeding
(VKDB) that can occur during the early weeks of life.
Although this type of bleeding occurs only in 0.25–
1.7% of untreated newborns, it can be fatal. Since
1961, the American Academy of Pediatrics has recom-
mended that all newborns receive a single 0.5–1.0 mg
injection of vitamin K1 immediately after birth. As of
2007, there was no equivalent oral (by mouth) supple-
ment available in the United States. A few researchers
have questioned whether this early injection of vitamin
K increases the risk of developing childhoodcancer.
In the view of the American Academy of Pediatrics,
well-designed research does not support this link.
There is some growing evidence that vitamin K
plays a role in maintaining strong bones. Certain pro-
teins that regulate the cells(osteoblasts) that deposit
calcium and other minerals in bone appear to be
dependent on vitamin K. If this is true, vitamin K may
play a role in preventing osteoporosis. Clinical trials are
currently underway to determine safety and effectiveness
of vitamin K in a variety of situations. Individuals inter-
ested in participating in a clinical trial at no charge can
find a list of open trials at http://www.clinicaltrials.gov.KEY TERMS
Coenzyme—Also called a cofactor, a small non-
protein molecule that binds to an enzyme and cat-
alyzes (stimulates) enzyme-mediated reactions.
Dietary supplement—A product, such as a vitamin,
mineral, herb, amino acid, or enzyme, that is intended
to be consumed in addition to an individual’s diet
with the expectation that it will improve health.
Enzyme—A protein that change the rate of a chem-
ical reaction within the body without themselves
being used up in the reaction.
Fat-soluble vitamin—A vitamin that dissolves in
and can be stored in body fat or the liver.
Osteoporosis—A condition found in older individ-
uals in which bones decrease in density and become
fragile and more likely to break. It can be caused by
lack of vitamin D and/or calcium in the diet.
Vitamin—A nutrient that the body needs in small
amounts to remain healthy but that the body cannot
manufacture for itself and must acquire through diet.Vitamin K