Meta-analysis of efficacy of iron and iodine fortified salt in improving iron nutrition status.

Background: Salt fortification with iron is a potential strategy to increase population-level iron intake. The current evidence regarding double-fortified salt (DFS) in improving iron nutrition status is equivocal.

Objective: To study the efficacy of DFS as compared to iodine fortified salt (IS) in improving iron nutrition status.

Methods: Randomized controlled trials comparing DFS and IS until August 2016 were systematically searched across multiple databases to assess for change in mean hemoglobin (Hb), prevalence of anemia, iron deficiency (ID), ID anemia (IDA), serum ferritin, and serum transferrin receptor (TfR). Meta-analysis was performed using R software.

Results: Of the initial 215 articles retrieved using the predetermined search strategy, data from 10 comparisons of DFS and IS across 8 randomized controlled trials are included. There was significant heterogeneity across included studies and the studies were of low to very low quality as per GRADE criteria. DFS significantly increased mean Hb by 0.44 g/dl (95% confidence interval [CI]: 0.16, 0.71) and significantly decreased anemia (risk difference -0.16; 95% CI: -0.26, -0.06) and ID (risk difference -0.20; 95% CI: -0.32, -0.08) as compared to IS. There was no statistically significant difference in change in ferritin levels (mean difference 0.62 μg/L; 95% CI: -0.12, 1.37), serum TfR levels (mean difference -0.23 mg/dL; 95% CI: -0.85, 0.38), and IDA (risk difference -0.08; 95% CI: -0.28, 0.11).

Conclusion: DFS is a potentially efficacious strategy of addressing anemia as a public health problem at population level. There is a need for effectiveness trials before DFS can be scaled up in program mode at population level.