Improved micronutrient status and health outcomes in low- and middle-income countries following large-scale fortification: evidence from a systematic review and meta-analysis

Abstract

Background: Micronutrient malnutrition is highly prevalent in low- and middle-income countries (LMICs) and disproportionately affects women and children. Although the effectiveness of large-scale food fortification (LSFF) of staple foods to prevent micronutrient deficiencies in high-income settings has been demonstrated, its effectiveness in LMICs is less well characterized. This is important as food consumption patterns, potential food vehicles, and therefore potential for impact may vary substantially in these contexts.

Objectives: The aim of this study was to determine the real-world impact of LSFF with key micronutrients (vitamin A, iodine, iron, folic acid) on improving micronutrient status and functional health outcomes in LMICs.

Methods: All applicable published/unpublished evidence was systematically retrieved and analyzed. Studies were not restricted by age or sex. Meta-analyses were performed for quantitative outcomes and results were presented as summary RRs, ORs, or standardized mean differences (SMDs) with 95% CIs.

Results: LSFF increased serum micronutrient concentrations in several populations and demonstrated a positive impact on functional outcomes, including a 34% reduction in anemia (RR: 0.66; 95% CI: 0.59, 0.74), a 74% reduction in the odds of goiter (OR: 0.26; 95% CI: 0.16, 0.43), and a 41% reduction in the odds of neural tube defects (OR: 0.59; 95% CI: 0.49, 0.70). Additionally, we found that LSFF with vitamin A could protect nearly 3 million children per year from vitamin A deficiency. We noted an age-specific effect of fortification, with women (aged >18 y) attaining greater benefit than children, who may consume smaller quantities of fortified staple foods. Several programmatic/implementation factors were also reviewed that may facilitate or limit program potential.

Conclusions: Measurable improvements in the micronutrient and health status of women and children are possible with LSFF. However, context and implementation factors are important when assessing programmatic sustainability and impact, and data on these are quite limited in LMIC studies.

Keywords: developing countries; effectiveness; folic acid; fortification; functional outcomes; iodine; iron; micronutrient status; systematic review; vitamin A.

FIGURE 1

Summary of study selection.

FIGURE 2

Change in distribution of global vitamin A deficiency (serum retinol <70 μmol/L) in children (0–9 y) after 14 mo of LSFF with vitamin A. LSFF, large-scale food fortification.

FIGURE 3

Reduction (74%) in the odds of goiter prevalence (OR: 0.26; 95% CI: 0.16, 0.43) following salt iodization. Analysis model: random effects; statistical method: Mantel-Haenszel (M-H).

FIGURE 4

Reduction in anemia prevalence for children aged <7 y (RR: 0.61; 95% CI: 0.38, 0.96), children 6–18 y (RR: 0.68; 95% CI: 0.52, 0.90), WRA (RR: 0.66; 95% CI: 0.58, 0.76), and pregnant women (RR: 0.73; 95% CI: 0.64, 0.84), with a combined 34% reduction in anemia across all ages (RR: 0.66; 95% CI: 0.59, 0.74) following LSFF with iron. Analysis model: random effects; statistical method: Mantel-Haenszel. LSFF, large-scale food fortification; WRA, women of reproductive age.

FIGURE 5

Reduction (41%) in NTD prevalence (OR: 0.59; 95% CI: 0.49, 0.70) following LSFF with folic acid. Analysis model: random effects; statistical method: Mantel-Haenszel (M-H). LSFF, large-scale food fortification; NTD, neural tube defect.