Vitamin K deficiency
Vitamin K deficiency is extremely rare in healthy
people. It can, however, occur in individuals who have
disorders that interfere with the absorption of
nutrients from the intestine. Signs of vitamin K defi-
ciency include easy bruising, excessive bleeding, and
slow clotting. People who are at higher risk for vitamin
K deficiency include:
people with gastrointestinal diseases such as Crohn’s
disease, cystic fibrosis, inflammatory bowel disease,
or ulcerative colitis
people who have had part of their stomach or intes-
tine surgically removed for weight loss or other
reasons
people with liver damage
people with alcoholism
people who take high doses of antibiotics over a long
period.
Precautions
People who are taking blood-thinning drugs,
especially warfarin (Coumadin), should discuss their
vitamin K needs with their healthcare provider. They
may need to restrict their intake of vitamin K. The
purpose of blood-thinning drugs is to keep the blood
from forming clots in the veins and arteries. Since
vitamin K helps blood to clot, high levels of vitamin
K in the diet may work against blood-thinning drugs
and reduce their effect. Individuals taking these drugs
are encouraged to keep their daily intake of vitamin K
steady at or slightly below the IA level. In addition,
they should have their international normalized ratio
(INR) and prothrombin time (PT), both measures of
blood clotting potential, checked regularly.
Injections of vitamin K 3 (menadione) are banned
in the United States because they can cause liver dam-
age and rupture of red blood cells in infants and
children.
Interactions
In addition to interfering with blood-thinning
drugs mentioned above, vitamin K may interact with
the following:
Some broad-spectrum antibiotics (antibiotics that
kill a wide variety of bacteria) may decrease the
amount of vitamin K 2 produced in the intestines.
Aspirin (salicylates) taken in high doses over a long
time may increase the body’s need for vitamin K.
Cholestyramine (Questran) and mineral oil may
decrease vitamin K absorption.
Quinine may increase the body’s need for vitamin K
Orlistat (Xenical, Alli) is likely to decrease Vitamin K
absorption.
Vitamin K may decrease the effectiveness of blood
thinning herbs such as American ginseng (P. quinque-
folius), alfalfa (Medicago sativa), and angelica (Angelica
archangelica).
Olestra, a compound that reduces fat absorption,
decreases the absorption of vitamin K. The FDA
requires all foods containing olestra to be fortified
with the fat-soluble vitamins A, D, E, and K.AftercareComplicationsNo complications are expected from vitamin K,
especially when most of the vitamin K comes from
dietary sources. However, pregnant and breastfeeding
women should avoid taking vitamin K supplements. In
addition, people taking blood-thinning drugs should
carefully monitor their intake of vitamin K so that
they do not increase the chance of developing blood
clots.Resources
BOOKS
Food and Nutrition Board, Institute of Medicine.Dietary
Reference Intakes for Vitamin A, Vitamin K, Arsenic,
Boron, Chromium, Cooper, Iodine, Iron, Manganese,
Molybdenum, Nickel, Silicon, Vanadium, and Zinc.Wash-
ington, DC: National Academy Press, 2001, pp. 162-177.
<http://books.nap.edu/books/0309072794/html>.
Gaby, Alan R., ed.A-Z Guide to Drug-Herb-Vitamin Inter-
actions Revised and Expanded 2nd Edition: Improve
Your Health and Avoid Side Effects When Using Com-
mon Medications and Natural Supplements Together.
New York: Three Rivers Press, 2006.
Lieberman, Shari and Nancy Bruning.The Real Vitamin and
Mineral Book: The Definitive Guide to Designing Your
Personal Supplement Program,4th ed. New York:
Avery, 2007.
Pressman, Alan H. and Sheila Buff.The Complete Idiot’s
Guide to Vitamins and Minerals,3rd ed. Indianapolis,
IN: Alpha Books, 2007.
Rucker, Robert B., ed.Handbook of Vitamins.Boca Raton,
FL: Taylor & Francis, 2007.
ORGANIZATIONS
American Cancer Society. 1599 Clifton Road NE, Atlanta
GA 30329-4251. Telephone: 800 ACS-2345. Website:
http://www.cancer.org.
Linus Pauling Institute. Oregon State University, 571
Weniger hall, Corvallis, OR 97331-6512. Telephone:
(541) 717-5075. Fax: (541) 737-5077. Website: http://
lpi.oregonstate.edu/Vitamin K