The Journal of Clinical Endocrinology & Metabolism February 5, 2013 jc.2012-3106
J. Christopher Gallagher, Munro Peacock, Vinod Yalamanchili and Lynette M. Smith
Bone Metabolism Unit (J.C.G., V.Y.), Creighton University School of Medicine, Omaha, Nebraska 68131; Department of Endocrinology (M.P.), Indiana University School of Medicine, Indianapolis, Indiana 46202; and Department of Biostatistics (L.M.S.), College of Public Health, University of Nebraska Medical Center, Omaha, Nebraska 68198
Address all correspondence and requests for reprints to: Dr J. C. Gallagher, MD, Bone Metabolism Unit, Creighton University School of Medicine, 601 North 30th Street, Suite 6718, Omaha, Nebraska 68131. E-mail: jcg at creighton.edu.
Context: Serum 25-hydroxyvitamin D (25OHD) is lower in women with darker skin color. Is it due to lower skin production, lower absorption, or different metabolism of vitamin D?
Objectives: The objective of the study was to measure the effect of vitamin D3 on serum 25OHD and serum PTH in older African American women with vitamin D insufficiency and the serum 25OHD 20 ng/mL or less (<50 nmol/L). The results can be used to estimate the Recommended Dietary Allowance (RDA).
Design and Setting: This was a randomized, double-blind placebo trial at Creighton University Medical Center and Indiana University Medical Center.
Participants: Participants were 110 healthy older African American women.
Interventions: The intervention consisted of participants randomly assigned to placebo, vitamin D3 400, 800, 1600, 2400, 3200, 4000, or 4800 IU daily; calcium supplements were given to maintain total calcium intake of 1200–1400 mg/d.
Main Outcome Measurements: Change in serum 25OHD and serum PTH levels at 12 months was measured.
Results: Mean baseline serum 25OHD was 13 ng/mL (33 nmol/L).
On 4800 IU, serum 25OHD averaged 50 ng/mL (125 nmol/L) compared with 47 ng/mL (117 nmol/L) in Caucasian women.
Serum PTH at 12 months decreased significantly (P = .008) when related to serum 25OHD but not dose.
Hypercalcemia occurred in 7% and hypercalciuria in 15%. Events were unrelated to vitamin D dose.
Conclusion: Vitamin D3 800 IU increased serum 25OHD greater than 20 ng/mL (>50 nmol/L) in 97.5% of the African American women just as it did in the Caucasian women, and therefore, the RDA is the same for both groups. Because absorption and metabolism of oral vitamin D absorption is similar in both groups, lower levels of serum 25OHD in African Americans must be due to lower production of vitamin D in skin.
Received August 16, 2012. Accepted December 17, 2012.
PDF is attached at the bottom of this page
- nice confirmation of assumption. Not a surprise
- It appears that 10% of all participants had too much Calcium - indepedant of dose (e.g. 400 IU to 4800 IU) - strange