A systematic review of 55 studies on the effect of iron supplementation on haemoglobin concentration in children showed that iron supplementation resulted in a haemoglobin concentration that was 7•4 g/L higher than in children who had no supplementation (weighted mean difference 7•4 g/L, 95% CI 6•1–8•7; random effects) (Gera et al, 2007). Reductions in the occurrence of anaemia with iron supplementation alone ranged from 38% to 62% in non-malarial regions and 6% to 32% in malarial hyper endemic areas. The incidence of diarrhoea was increased in the iron-supplemented group (incidence rate ratio 1•11, 95% CI 1•01–1•23; random effects), and overall there was noted no benefit of iron supplementation on growth. Some studies have recommended that untargeted iron supplementation should not be given to children in malaria-endemic areas as iron supplementation can have adverse effects with regard to infectious diseases (Black et al, 2006).

A pooled analysis of data from eight studies of iron-folate supplementation during pregnancy suggested an increase of 12 g/L (95% CI 2•93–21•07, random effects) in hemoglobin at term and a 73% reduction in the risk of anaemia at term (relative risk 0•27, 95% CI 0•12–0•56) (Pena-Rosas JP, 2006).

Micro-nutrient supplementation via home fortification (sachets that contain iron and other micronutrients in microencapsulated form, which can be added to prepared food). has also been shown to be effective. An analysis of studies of these dispersible micronutrient preparations (Zlotkin et al, 2006; Hirve et al, 2007; Christofides et al, 2006; Menon et al, 2007; Giovannini et al, 2006; Sharieff et al, 2006) showed that, in children younger than 2 years,123,124 hemoglobin concentrations increased by 5•68 (95% CI 1•78–9•57) g/L and iron-deficiency anemia was reduced compared with controls (relative risk 0•54, 95% CI 0•42–0•70).

In a global review, Vitamin A supplementation was seen to reduce childhood mortality in children aged 6–59 months. These were testing trials from Indonesia, Ghana, India, Nepal and Sudan (Beaton et al, 1993; Grotto et al 2003). A pooled estimate showed a 24% reduction in the risk of all-cause mortality (relative risk 0•76, 95% CI 0•69–0•84). Vitamin A supplementation did not affect morbidity from infectious diseases (Barreto et al, 1997; Sempertegui et al, 1999; Villamor et al, 1992) or anthropometric measures. Also identified were three reported trials of vitamin A supplementation in the neonatal period in low-income countries, showing a 20% reduction in mortality in babies younger than 6 months (relative risk 0•80, 95% CI 0•66–0•96). (Humphrey et al, 1996; Rahmathullah et al, 2003). However, much of the evidence regarding neonatal Vitamin A supplementation comes from Asia.