people with disorders of the pancreas that interfere
with the absorption of nutrients
people with anorexia nervosa (self-starvation)
people with alcoholism
In the developing world, especially parts of Africa
and Southeast Asia, vitamin A deficiency is common.
The World Health Organization (WHO) estimates
between 100 and 140 million children are at high risk
of developing vitamin A deficiency and that each year
250,000–500,000 children become blind because of
inadequate vitamin A in their diet. These children also
have up to a 50% higher risk of dying from measles,
diarrhea, malaria, and similar infections. These risks
are lowered when vitamin A is added to the diet.
WHO recommends that malnourished and at risk chil-
dren under age five to receive a high-dosage capsule of
vitamin A every six months as a safe and cost-effective
way to prevent blindness and other problems associated
with vitamin A deficiency in children. The excess vita-
min A from the supplement is stored in the liver and
released gradually as it is needed by the body.
InteractionsVitamin A may interact with the following
medications:
antacids, which may be more effective in when used
in combination with vitamin A
birth control pills, which increase the level of vitamin
A in a woman’s blood
blood thinning medicine such as warfarin (Couma-
din), whose effect may be enhanced by long-term use
of vitamin A
cholesterol-lowering drugs, which may reduce the
body’s ability to absorb vitamin A
orlistat, a weight-loss drug marketed as Xenical or
Alli that prevents fat from being absorbed and oles-
tra, substance used to replace fat in some foods.
These may decrease the amount of vitamin A
absorbed from the intestine.
Alcohol, which increases the likelihood of vitamin A
excess possibly because regular use of alcohol dam-
ages the liver and interferes with vitamin A storage
ComplicationsVitamin A is safe when taken in amounts listed
above as recommended by the Institute of Medicine.
Too much or too little vitamin A results in side effects
listed above in the Precautions section.
Parental concerns
Parents should be aware that the RDA and UL for
vitamins and minerals are much lower for children than
for adults. Accidental overdose may occur if children
are give adult vitamins or dietary supplements.Resources
BOOKS
Gaby, Alan R., ed.A-Z Guide to Drug-Herb-Vitamin
Interactions 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.
PERIODICALS
Wolf, George. ‘‘A History of Vitamin A.’’The FASEB
Journal, 10, no. 9 (1996): 1102-8.
ORGANIZATIONS
American Dietetic Association. 120 South Riverside Plaza,
Suite 2000, Chicago, Illinois 60606-6995. Telephone:
(800) 877-1600. Website:<http://www.eatright.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>
Office of Dietary Supplements, National Institutes of
Health. 6100 Executive Blvd., Room 3B01, MSC 7517,
Bethesda, MD 20892-7517 Telephone: (301)435-2920.
Fax: (301)480-1845. Website:<http://dietary-
supplements.info.nih.gov>
OTHER
Eledrisi, Mosheen S. ‘‘Vitamin A Toxicity.’’ emedicine.com,
July 20, 2005.<http://www.emedicine.com/med/
topic2382>
Harvard School of Public Health. ‘‘Vitamins.’’ Harvard
University, November 10, 2006.<http://www.hsph.
harvard.edu/nutritionsource/vitamins.html>
Higdon, Jane. ‘‘Vitamin A.’’Linus Pauling Institute-Oregon
State University, December 12, 2003.<http://lpi.
oregonstate.edu/infocenter/vitamins/VitaminA>
Maryland Medical Center Programs Center for Integrative
Medicine. ‘‘Vitamin A (Retinol).’’ University of Maryland
Medical Center, April 2002.<http://www.umm.edu/
altmed/ConsSupplements/VitaminARetinolcs.html>
Medline Plus. ‘‘Vitamin A (Retinol).’’ U. S. National
Library of Medicine, August 1, 2006.<http://Vitamin A