Inclusion of Guava Enhances Non-Heme Iron Bioavailability but Not Fractional Zinc Absorption from a Rice-Based Meal in Adolescents

Assessing the bioavailability of non-heme iron and zinc is essential for recommending diets that meet the increased growth-related demand for these nutrients. We studied the bioavailability of iron and zinc from a rice-based meal in 16 adolescent boys and girls, 13-15 y of age, from 2 government-run residential schools. Participants were given a standardized rice meal (regular) and the same meal with 100 g of guava fruit (modified) with Fe-57 on 2 consecutive days. A single oral dose of Fe-58 in orange juice was given at a separate time as a reference dose. Zinc absorption was assessed by using Zn-70, administered intravenously, and Zn-67 given orally with meals. The mean hemoglobin concentration was similar in girls (129 +/- 7.8 g/L) and boys (126 +/- 7.1 g/L). There were no sex differences in the indicators of iron and zinc status except for a higher hepcidin concentration in boys (P < 0.05). The regular and modified meals were similar in total iron (10-13 mg/meal) and zinc (2.7 mg/meal) content. The molar ratio of iron to phytic acid was >1:1, but the modified diet had 20 times greater ascorbic acid content. The absorption of Fe-57 from the modified meal, compared with regular meal, was significantly (P < 0.05) greater in both girls (23.9 +/- 11.2 vs. 9.7 +/- 6.5%) and boys (19.2 +/- 8.4 vs. 8.6 +/- 4.1%). Fractional zinc absorption was similar between the regular and modified meals in both sexes. Hepcidin was found to be a significant predictor of iron absorption (standardized beta = -0.63, P = 0.001, R-2 = 0.40) from the reference dose. There was no significant effect of sex on iron and zinc bioavailability from meals. We conclude that simultaneous ingestion of guava fruit with a habitual rice-based meal enhances iron bioavailability in adolescents.