Degradation of phytic acid in cereal porridges improves iron absorption by human subjects

Abstract

Background: Phytic acid in cereal-based and legume-based complementary foods inhibits iron absorption. Low iron absorption from cereal porridges contributes to the high prevalence of iron deficiency in infants from developing countries. Objective: The objective was to measure the influence of phytic acid degradation on iron absorption from cereal porridges. Design: An exogenous phytase was used to fully degrade phytic acid during the manufacture of 9 roller-dried complementary foods based on rice, wheat, maize, oat, sorghum, and a wheat-soy blend. Iron absorption from the phytate-free and native phytate porridges prepared with water or milk (wheat only) was measured in adult humans with an extrinsic-label radioiron technique. Ascorbic acid was added to some porridges. Results: When the foods were reconstituted with water, dephytinization increased iron absorption from rice porridge from 1.73% to 5.34% (P < 0.001), from oat from 0.33% to 2.79% (P < 0.0001), from maize from 1.80% to 8.92% (P < 0.0001), from wheat from 0.99% to 11.54% (P < 0.0001), from the wheat-soy blend without ascorbic acid from 1.15% to 3.75% (P < 0.005), and from the wheat-soy blend with ascorbic acid from 2.40% to 8.46% (P < 0.005). Reconstituting wheat porridge with milk instead of water markedly decreased or completely removed the enhancing effect of dephytinization on iron absorption in the presence and absence of ascorbic acid. Dephytinization did not increase iron absorption from high-tannin sorghum porridge reconstituted with water but increased iron absorption from low-tannin sorghum porridge by ≈2-fold (P < 0.01). Conclusions: Phytate degradation improves iron absorption from cereal porridges prepared with water but not with milk, except from high-tannin sorghum. © 2003 American Society for Clinical Nutrition.