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University, November 10, 2006.http://www.hsph.
harvard.edu/nutritionsource/vitamins.html
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Shows High-dose Vitamin E Supplements May
Increase Risk of Dying.’’ Johns Hopkins University,
November 10. 2004.http://www.hopkinsmedicine.
org/Press_releases/2004/11_10_04.html
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Tish Davidson, A.M.Vitamin K
Definition
Vitamin K is a fat-soluble organic compound that
the body needs to remain healthy. Although bacteria in
the human intestine make some vitamin K, it is not
nearly enough to meet the body’s needs, so people must
get most of their vitamin K from foods in their diet.
Purpose
The liver needs vitamin K to make factors that
regulate blood clotting. Vitamin K may also play a
role in maintaining strong bones and preventing
osteoporosis.
Description
Vitamin K is not a single substance but a collec-
tion of chemically similar compounds called naphtho-
quinones. Vitamin K 1 , called phylloquinone, is the
natural form of vitamin K. It is found in plants and
is the main source of vitamin K in the human diet.
Vitamin K 2 compounds, called menaquinones, are
made by bacteria that live in the human intestine.
Researchers originally thought that bacteria in the
gut provided a substantial percentage of human vita-
min K needs, but more recent research suggests that
these bacteria provide only a small amount and that
people should get most of their vitamin K from diet.
Vitamin K 1 is manufactured synthetically and sold
many brand names as a dietary supplement. Vitamin
K is also included in many multivitamins. In addition,
a synthetic water-soluble form of vitamin K called K 3
or menadione is not allowed indietary supplementsin
the United States because of its association with seri-
ous side effects.Normal vitamin K requirements
The United States Institute of Medicine (IOM) of
the National Academy of Sciences has developed val-
ues calledDietary Reference Intakes(DRIs) forvita-
minsandminerals. The DRIs consist of three sets of
numbers. The Recommended Dietary Allowance
(RDA) defines the average daily amount of the
nutrient needed to meet the health needs of 97–98%
of the population. The Adequate Intake (AI) is an
estimate set when there is not enough information to
determine an RDA. The Tolerable Upper Intake Level
(UL) is the average maximum amount that can be
taken daily without risking negative side effects. The
DRIs are calculated for children, adult men, adult
women, pregnant women, andbreastfeedingwomen.
The IOM has not set RDA values for vitamin K
because of incomplete scientific information. Instead, in
2000, it set AI levels for all age groups. AI and levels for
vitamin K are measured in by weight (micrograms orVitamin KAge Adequate intake (mcg/day)
Children 0–6 mos. 2
Children 7–12 mos. 2.5
Children 1–3 yrs. 30
Children 4–8 yrs. 55
Children 9–13 yrs. 60
Children 14–18 yrs. 75
Men 19 yrs. 120
Women 19 yrs. 90
Pregnant women 18 yrs. 75
Breastfeeding women 18 yrs. 75
Pregnant women 19 yrs. 90
Breastfeeding women 19 yrs. 90
Food Vitamin K (mcg)
Kale, cooked, ½ cup 530
Spinach, cooked, ½ cup 445
Swiss chard, cooked, ½ cup 285
Turnip greens, cooked, ½ cup 265
Parsley, fresh, 2 tbsp. 120
Brussels sprouts, cooked, ½ cup 110
Broccoli, cooked, ½ cup 77
Asparagus, cooked, ½ cup 46
Celery, raw, ½ cup 18
Carrots, raw, ½ cup 8
Milk, 2%, 1 cup 5
Miso, 1 oz. 4
mcg microgram(Illustration by GGS Information Services/Thomson Gale.)Vitamin K