people living in northern latitudes who cover almost
all their body for much of the year due to climate or
religious requirements
people with gastrointestinal diseases such as Crohn’s
disease, celiac disease, or inflammatory bowel dis-
ease that interfere with the absorption of nutrients
from the intestine
people with disorders of the pancreas that interfere
with the absorption of nutrients
people with anorexia nervosa (self-starvation)
people who have had part of their stomach or intestine
surgically removed for weight loss or other reasonsVitamin D excess
Vitamin D excess in healthy individuals occurs
only when large quantities of vitamin D are taken as a
dietary supplement over several months. This can result
in high calcium levels in the blood (hypercalcemia).
Symptoms of vitamin D excess include nausea, vomit-
ing, excessive thirst, weakness, and high blood pressure.
Calcium deposits may develop in the kidneys, blood
vessels, heart, and lungs. The kidneys may be perma-
nently damaged and eventually fail completely.InteractionsResearch suggests that the following types of med-
ications may increase the available amount of vitamin
D in the body. People taking these drugs should not
take a vitamin D supplement without consulting their
healthcare provider.
birth control pills
hormone replacement therapy/estrogen replacement
therapy
isoniazid (INH) used to treat tuberculosis
thiazide diuretics
Research suggests that the following types of med-
ications may decrease the available amount of vitamin
D in the body. People taking these drugs should dis-
cuss with their healthcare provider whether a vitamin
D supplement is right for them.
antacids taken daily for long periods
calcium-channel blockers used to treat heart condi-
tions and high blood pressure
certain cholesterol-lowering medications that block
fat absorption
phenobarbitol and similar anticonvulsants
mineral oil taken on a daily basis
orlistat, a weight loss drug marketed as Xenical or AlliComplicationsNo complications are expected when vitamin D is
used in the recommended amounts. The complications
resulting from insufficient or excess use are discussed
above.Parental concernsParents 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 Inter-
actions Revised and Expanded 2nd Edition: Improve Your
Health and Avoid Side Effects When Using Common
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
Carpenter, Kenneth J. and Ling Zhao. ‘‘Forgotten Mysteries
in the Early history of Vitamun D.’’Journal of Nutri-
tion, 129 (1999):923-7.
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
American Cancer Society. ‘‘Can Vitamin D Prevent Can-
cer?’’ American Cancer Society, December 29, 2005.
<http://www.cancer.org/docroot/NWS/content/
NWS_1_1x_Can_Vitamin_D_Prevent_Cancer.asp>
Finberg, Laurence. ‘‘Rickets.’’ emedicine.com, April 25,
2006.<http://www.emedicine.com/ped/topic2014.htm>Vitamin D