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Calcium in blood (tightly regulated) did not increase when increase vitamin D to 40 ng – RCT Oct 2013

Vitamin D does not Increase Calcium Absorption in Young Women: A Randomized Clinical Trial

Journal of Bone and Mineral Research, DOI: 10.1002/jbmr.2121
Christopher J Gallagher MD1, jcg at creighton.edu
PS Jindal MBBS 1,
M Smith Lynette MS 2
1 Bone Metabolism Unit, Creighton University Medical Center, Omaha, Nebraska
2 Department of Biostatistics, University of Nebraska Medical Center, Omaha, Nebraska

VitaminDWiki Summary

1 year RCT with women
Ca with Vitamin D3 of 0, 400, 800, 1600, and 2400 IU
    (2400 IU resulted in 40 ng vitamin D blood level)
Ca absorption (radioactive) measured before and after
This disagrees with what is commmonly said
Note 1: They appear to be measuring the Calcium level in the bloodstream
Calcium level in the bloodstream is tightly regulated.
Calcium absorption can be increased by vitamin D without its showing up in the bloodstream.
Increased Calcium will show up in bone density, bone-like arteries, increased Calcium in Urine, etc.

Note 2: Calcium absorption increases a lot during pregnancy.
PDF shows they did not have any pregnant women

It is commonly said that vitamin D should be used to increase calcium absorption.
We tested this statement in a dose response study of vitamin D on calcium absorption.

198 Caucasian and African American women, ages 25–45 years, with vitamin D insufficiency, serum 25OHD < 20ng/ml, were randomized in a double blind study to vitamin D3 400, 800, 1600, 2400 IU or placebo. A calcium supplement was given to increase mean calcium intake at baseline from 706 mg/day to 1031 mg/day. Calcium absorption was measured at baseline and after 12 months using a single isotope method with radiocalcium45 and 100 mg of calcium.

Mean baseline serum 25OHD was 13.4 ng/ml (33.5nmol/L) and increased to 40 ng/ml (100nmol/l) on the highest dose of 2400 IU.

Using a multivariate regression analysis with significant predictors, baseline absorption, calcium intake and weight there was no increase in 12-month calcium absorption compared to baseline on any dose of vitamin D in either Caucasians or African Americans.

There was no significant relationship between 12-month calcium absorption and final serum 25OHD. In an analysis of calcium absorption and serum 25OHD at baseline, serum 25OHD levels were divided into groups 0-5, > 6–10, > 11–15, > 16–20ng/ml. There was no evidence of a threshold decrease in calcium absorption nor serum 1,25(OH)2D amongst the lowest groups.

Vitamin D doses upto 2400 IU daily did not increase calcium absorption. No threshold level of serum 25OHD for calcium absorption was found at baseline or in the longitudinal study suggesting that active transport of calcium is saturated at very low serum 25OHD levels< 5ng/ml. There is no need to recommend vitamin D for increasing calcium absorption in normal subjects. Very efficient calcium absorption at very low levels of serum 25OHD explains why people do not develop osteomalacia provided that dietary intake of calcium and phosphorus is adequate.
© 2013 American Society for Bone and Mineral Research

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see wikipagehttp://www.vitamindwiki.com/tiki-index.php?page_id=1936

See also web

  • Calcium metabolism Wikipedia
    The plasma level of calcium is closely regulated with a normal total calcium of 2.2-2.6 mmol/
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