Biofortified orange maize is as efficacious as a vitamin A supplement in Zambian children even in the presence of high liver reserves of vitamin A: a community-based, randomized placebo-controlled trial

Abstract

Background: Biofortification is a strategy to relieve vitamin A (VA) deficiency. Biofortified maize contains enhanced provitamin A concentrations and has been bioefficacious in animal and small human studies.

Objective: The study sought to determine changes in total body reserves (TBRs) of vitamin A with consumption of biofortified maize.

Design: A randomized, placebo-controlled biofortified maize efficacy trial was conducted in 140 rural Zambian children. The paired (13)C-retinol isotope dilution test, a sensitive biomarker for VA status, was used to measure TBRs before and after a 90-d intervention. Treatments were white maize with placebo oil (VA-), orange maize with placebo (orange), and white maize with VA in oil [400 μg retinol activity equivalents (RAEs) in 214 μL daily] (VA+).

Results: In total, 133 children completed the trial and were analyzed for TBRs (n = 44 or 45/group). Change in TBR residuals were not normally distributed (P < 0.0001); median changes (95% CI) were as follows: VA-, 13 (-19, 44) μmol; orange, 84 (21, 146) μmol; and VA+, 98 (24, 171) μmol. Nonparametric analysis showed no statistical difference between VA+ and orange (P = 0.34); both were higher than VA- (P = 0.0034). Median (95% CI) calculated liver reserves at baseline were 1.04 (0.97, 1.12) μmol/g liver, with 59% >1 μmol/g, the subtoxicity cutoff; none were <0.1 μmol/g, the deficiency cutoff. The calculated bioconversion factor was 10.4 μg β-carotene equivalents/1 μg retinol by using the middle 3 quintiles of change in TBRs from each group. Serum retinol did not change in response to intervention (P = 0.16) but was reduced with elevated C-reactive protein (P = 0.0029) and α-1-acid glycoprotein (P = 0.0023) at baseline.

Conclusions: β-Carotene from maize was efficacious when consumed as a staple food in this population and could avoid the potential for hypervitaminosis A that was observed with the use of preformed VA from supplementation and fortification. Use of more sensitive methods other than serum retinol alone, such as isotope dilution, is required to accurately assess VA status, evaluate interventions, and investigate the interaction of VA status and infection. This trial was registered at clinicaltrials.gov as NCT01814891.

Keywords: 13C-retinol dilution; Zambia; biofortified maize; plant carotenoids; retinol.

FIGURE 1

Study design. Baseline assessment comprised blood draw 1, isotope dose 1, the 14-d mixing period, and blood draw 2. This was followed by 90 d of intervention and a 7-d washout period. The endline assessment procedure was repeated identically to baseline and comprised blood draw 3, isotope dose 2, the 14-d mixing period, and blood draw 4. Sample size: n = 44, 44, and 45 for VA−, orange, and VA+ groups, respectively. White maize VA– = received placebo oil (214 μL) daily during treatment period and was fed white maize throughout (white shading). Orange maize VA– = received placebo oil (214 μL) daily and orange maize during the treatment period and white maize during mixing and washout periods (light gray shading). White maize VA+ = received VA in oil (400 μg retinol activity equivalents/d in 214 μL) during the treatment period and was fed white maize throughout (dark gray shading). VA, vitamin A.

FIGURE 2

Trial profile for a randomized, controlled efficacy study that fed orange maize to Zambian children for 90 d compared with positive and negative controls. VA− group received white maize throughout and placebo oil (214 μL) daily during the treatment period. Orange group received white maize during mixing/washout periods and orange maize and placebo oil (214 μL) daily during the treatment period. VA+ group received white maize throughout and VA in oil (400 μg retinol activity equivalents/d in 214 μL) during the treatment period. ¹All 4 blood draws for the subject were analyzed for ¹³C-retinol content with adequate signal. VA, vitamin A.

FIGURE 3

A: Schematic boxplot (SAS Institute, version 9.2) of change in TBRs of VA (in μmol) by treatment group. Line is the median; box is first through third quartiles; whiskers are to the most extreme point within fences; lower and upper fences are first or third quartile plus or minus 1.5 times the interquartile range, respectively; and points outside the fences are represented individually. Treatment groups with uncommon lowercase letters are statistically different (nonparametric analysis). Overall ANOVA P = 0.0034. Sample size: n = 44, 44, and 45 for VA−, orange, and VA+ groups, respectively. VA− group received white maize with placebo oil (white shading). Orange group received orange maize with placebo oil (light gray shading). VA+ group received white maize with VA in oil (400 μg retinol activity equivalents/d in 214 μL) (dark gray shading). B: Individual raw data ranked by treatment group. TBR, total body reserve; VA, vitamin A.