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Optimization of a phytase-containing micronutrient powder with low levels of highly bioavailable iron for in-home fortification of complementary foods^1,2,3

¹ From the Laboratory for Human Nutrition, Institute of Food Science and Nutrition, ETH, Zurich, Switzerland (BT, IE, CZ, RFH, and MBZ); the World Food Program, Rome, Italy (SdP); the Friedman School of Nutrition Science and Policy, Tufts University, Boston, MA (SdP); and the Division of Human Nutrition, Wageningen University, Wageningen, Netherlands (MBZ).

² Supported by the Foundation Nutrition Industry (Basel, Switzerland), established by DSM Nutritional Products Ltd, and the ETH (Zürich, Switzerland).

³ Reprints not available. Address correspondence to B Troesch, Laboratory for Human Nutrition, ETHZ, Zürich ETH Zentrum, Schmelzbergstrasse 7, LFV D19.3, 8092 Zürich, Switzerland. E-mail: barbara.troesch{at}ilw.agrl.ethz.ch.

ABSTRACT

Background: In-home fortification of complementary foods with micronutrient powders containing low levels of iron may be potentially safer than powders containing high levels of iron. However, low iron doses have little nutritional impact, unless iron absorption is high.

Objective: The objective was to maximize iron absorption from a low-iron micronutrient powder for in-home fortification by testing combinations of iron as NaFeEDTA, ascorbic acid, and a microbial phytase active at gut pH. In addition, a recently proposed enhancer of iron absorption, L--glycerophosphocholine (GPC), was tested.

Design: In 6 separate iron-absorption studies using a crossover design, women (n = 101) were fed whole-maize porridge fortified with 3 mg stable isotope–labeled FeSO₄ or NaFeEDTA with different combinations of enhancers added to the meals at the time of feeding. Incorporation of iron isotopes into erythrocytes 14 d later was measured.

Results: The addition of phytase when iron was present as either NaFeEDTA or FeSO₄, with or without ascorbic acid, significantly increased iron absorption. The combined addition of phytase, ascorbic acid, and NaFeEDTA resulted in an absorption of 7.4%, compared with an absorption of 1.5% from FeSO₄ without enhancers in the same meal (P < 0.001). The addition of ascorbic acid did not significantly increase iron absorption from NaFeEDTA, and the addition of calcium did not significantly inhibit iron absorption from NaFeEDTA in the presence of ascorbic acid. The addition of L--glycerophosphocholine did not significantly increase iron absorption.

Conclusion: Optimization of the micronutrient powder increased iron absorption from a highly inhibitory meal 5-fold. This approach may allow for effective, untargeted in-home fortification of complementary foods with low levels of highly bioavailable iron.

Received for publication September 26, 2008. Accepted for publication November 13, 2008.

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