JACN Did you know that you can get alerts when a new issue is online?
HOME HELP FEEDBACK SUBSCRIPTIONS ARCHIVE SEARCH TABLE OF CONTENTS
QUICK SEARCH:   [advanced]


     

This Article
Right arrow Figures Only
Right arrow Full Text
Right arrow Full Text (PDF)
Services
Right arrow Similar articles in this journal
Right arrow Similar articles in PubMed
Right arrow Alert me to new issues of the journal
Right arrow Download to citation manager
Right arrow reprints & permissions
Citing Articles
Right arrow Citing Articles via Google Scholar
Google Scholar
Right arrow Articles by Heaney, R. P.
Right arrow Articles by Bendich, A.
Right arrow Search for Related Content
PubMed
Right arrow PubMed Citation
Right arrow Articles by Heaney, R. P.
Right arrow Articles by Bendich, A.
Journal of the American College of Nutrition, Vol. 22, No. 2, 142-146 (2003)
Published by the American College of Nutrition

Original Research Paper

Calcium Absorption Varies within the Reference Range for Serum 25-Hydroxyvitamin D

Robert P. Heaney, MD, FACN, M. Susan Dowell, PhD, Cecilia A. Hale, PhD and Adrianne Bendich, PhD, FACN

Creighton University, Omaha, Nebraska (R.P.H., M.S.D.)
GlaxoSmithKline, Parsipanny, New Jersey (C.A.H., A.B.)

Address reprint requests to: Robert P. Heaney, M.D., Creighton University, 601 N. 30th St., Suite 4841, Omaha, NE 68131. Email: rheaney{at}creighton.edu

ABSTRACT

Background: Calcium absorption is generally considered to be impaired under conditions of vitamin D deficiency, but the vitamin D status that fully normalizes absorption is not known for humans.

Objective: To quantify calcium absorption at two levels of vitamin D repletion, using pharmacokinetic methods and commercially marketed calcium supplements.

Design: Two experiments performed in the spring of the year, one year apart. In the first, in which participants were pretreated with 25-hydroxyvitamin D (25OHD), mean serum 25OHD concentration was 86.5 nmol/L; and in the other, with no pretreatment, mean serum concentration was 50.2 nmol/L. Participants received 500 mg oral calcium loads as a part of a standard low calcium breakfast. A low calcium lunch was provided at mid-day. Blood was obtained fasting and at frequent intervals for 10 to 12 hours thereafter.

Methods: Relative calcium absorption at the two 25OHD concentrations was estimated from the area under the curve (AUC) for the load-induced increment in serum total calcium.

Results: AUC9 (± SEM), was 3.63 mg hr/dL ± 0.234 in participants pretreated with 25OHD and 2.20 ± 0.240 in those not pretreated (P < 0.001). In brief, absorption was 65% higher at serum 25OHD levels averaging 86.5 nmol/L than at levels averaging 50 nmol/L (both values within the nominal reference range for this analyte).

Conclusions: Despite the fact that the mean serum 25OHD level in the experiment without supplementation was within the current reference ranges, calcium absorptive performance at 50 nmol/L was significantly reduced relative to that at a mean 25OHD level of 86 nmol/L. Thus, individuals with serum 25-hydroxyvitamin D levels at the low end of the current reference ranges may not be getting the full benefit from their calcium intake. We conclude that the lower end of the current reference range is set too low.

Key words: vitamin D, calcium absorption, 25-hydroxyvitamin D, vitamin D status, parathyroid hormone, vitamin D requirement






HOME HELP FEEDBACK SUBSCRIPTIONS ARCHIVE SEARCH TABLE OF CONTENTS
Copyright © 2003 by the American College of Nutrition.