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Bioavailability of enteric-coated microencapsulated calcium during pregnancy: a randomized crossover trial in Bangladesh.

The American journal of clinical nutrition (2014-11-21)
Daniel E Roth, Brendon Pezzack, Abdullah Al Mahmud, Steven A Abrams, Munirul Islam, Ashley Aimone Phillips, Jo-Anna B Baxter, Michelle C Dimitris, Keli M Hawthorne, Tahmeed Ahmed, Stanley H Zlotkin
ABSTRACT

Prenatal calcium and iron supplements are recommended in settings of low dietary calcium intake and high prevalence of anemia. However, calcium administration may inhibit iron absorption. To overcome calcium-iron interactions, we developed a multi-micronutrient powder containing iron (60 mg), folic acid (400 μg), and calcium carbonate granules microencapsulated with a pH-sensitive enteric coating to delay intestinal release. We aimed to establish in vivo evidence that enteric-coated (EC) calcium is bioavailable in pregnant women and to explore the dose-responsiveness of fractional calcium absorption (FCA) in pregnancy. This was a randomized crossover trial in pregnant women (26-28 wk of gestation) in Dhaka, Bangladesh. Participants were allocated to 1 of 3 dose groups (500, 1000, or 1500 mg elemental Ca). FCA was estimated in random order for EC and non-EC (control) granules by a dual-stable-isotope method ((44)Ca-labeled granules and intravenous (42)Ca) on the basis of the relative recovery of (44)Ca compared with (42)Ca in urine over 48 h. Forty-nine participants with FCA for both EC and non-EC granules were included in the primary analyses. FCA geometric means were as follows: 21.8% (500 mg), 9.2% (1000 mg), and 11.7% (1500 mg) for non-EC granules compared with 3.3% (500 mg), 1.2% (1000 mg), and 2.1% for EC granules. Cumulative 48-h FCA of EC calcium was 85% lower (P < 0.001) than that of non-EC calcium, after adjustment for dose. In comparison to 500 mg, the FCA for the 1000-mg dose was 61% lower (P < 0.001) and was 42% lower (P = 0.002) for the 1500-mg dose, after adjustment for formulation. A pH-sensitive enteric coating substantially reduced calcium absorption from a prenatal multi-micronutrient powder. In its current formulation, this novel supplement is not suitable for clinical use. FCA was highly dose-dependent, such that doses of 1000 and 1500 mg delivered only negligibly more bioavailable calcium than the 500-mg dose. This trial was registered at clinicaltrials.gov as NCT01678079.

MATERIALS
Product Number
Brand
Product Description

Supelco
Folic acid, Pharmaceutical Secondary Standard; Certified Reference Material
USP
Folic acid, United States Pharmacopeia (USP) Reference Standard
Folic acid, European Pharmacopoeia (EP) Reference Standard
Supelco
Folic acid, analytical standard
Sigma-Aldrich
Folic acid, ≥97%
Sigma-Aldrich
Folic acid, BioReagent, suitable for cell culture, suitable for insect cell culture, suitable for plant cell culture, ≥97%
Sigma-Aldrich
Folic acid, meets USP testing specifications