Effects of daily iron supplementation in 2- to 5-year-old children: systematic review and meta-analysis

Iron Intake and Status of Children Aged 6-36 Months in Europe: A Systematic Review

Background: Iron deficiency is the most common nutritional disorder in the world. Young children are particularly vulnerable to the consequences of iron deficiency because of their rapidly developing brain. This review evaluates the prevalence of inadequate iron intake and iron deficiency (anaemia) in European children aged 6-36 months. Summary: Computerized searches for relevant articles were performed in November 2013. A total of 7,297 citations were screened and 44 studies conducted in 19 European countries were included in this review. In both infants (6-12 months) and young children (12-36 months), the mean value of iron intakes in most countries was close to the RDA. Nevertheless, proportions of inadequate intakes were considerable, ranging from about 10% in the Netherlands up to 50% in Austria, Finland and the United Kingdom. The prevalence of iron deficiency varied between studies and was influenced by children's characteristics. Two to 25% of infants aged 6-12 months were found to be iron deficient, with a higher prevalence in those who were socially vulnerable and those who were drinking cow's milk as a main type of drink in their first year of life. In children aged 12-36 months, prevalence rates of iron deficiency varied between 3 and 48%. Prevalence of iron deficiency anaemia in both age groups was high in Eastern Europe, as high as 50%, whereas the prevalence in Western Europe was generally below 5%. Key Messages: In most European countries, mean iron intakes of infants and children aged 6 to 36 months were found to be close to the RDA. Nevertheless, high proportions of inadequate intakes and high prevalence rates of iron deficiency were observed. Health programs should (keep) focus(ing) on iron malnutrition by educating parents on food choices for their children with iron-rich and iron-fortified foods, and encourage iron supplementation programmes where iron intakes are the lowest.

Meeting iron needs for infants and children

PURPOSE OF REVIEW

Iron deficiency early in life is associated with impaired neurological development. This study reviews the latest research on how to best meet iron requirements in infants and children.

RECENT FINDINGS

There is concurrent evidence that delayed cord clamping is well tolerated and improves infant iron stores. Iron supplements or enriched complementary foods starting before 6 months of life do not reduce iron deficiency prevalence in low-risk populations. However, for low birth weight infants, iron supplements before 6 months of life have long-term benefits. Iron deficiency anaemia (IDA) during the second half year of life is rare in countries with high compliance to iron-rich complementary foods, but remains a major problem globally. In high-risk populations, iron supplementation reduces IDA and possibly improves growth. However, increased risk of infections is a concern and optimal preventive strategies have not yet been determined. Finally, there is concurrent evidence that iron supplementation of anaemic school-aged children reduces IDA and possibly improves neuropsychological outcomes.

SUMMARY

Interventions for prevention of iron deficiency should be prioritized in risk groups. However, the unclear long-term benefits and possible risk of adverse effects, particularly increased infections in developing countries, prompt further large-scale, double-blinded trials.

Iron deficiency and cognitive functions

Micronutrient deficiencies, especially those related to iodine and iron, are linked to different cognitive impairments, as well as to potential long-term behavioral changes. Among the cognitive impairments caused by iron deficiency, those referring to attention span, intelligence, and sensory perception functions are mainly cited, as well as those associated with emotions and behavior, often directly related to the presence of iron deficiency anemia. In addition, iron deficiency without anemia may cause cognitive disturbances. At present, the prevalence of iron deficiency and iron deficiency anemia is 2%-6% among European children. Given the importance of iron deficiency relative to proper cognitive development and the alterations that can persist through adulthood as a result of this deficiency, the objective of this study was to review the current state of knowledge about this health problem. The relevance of iron deficiency and iron deficiency anemia, the distinction between the cognitive consequences of iron deficiency and those affecting specifically cognitive development, and the debate about the utility of iron supplements are the most relevant and controversial topics. Despite there being methodological differences among studies, there is some evidence that iron supplementation improves cognitive functions. Nevertheless, this must be confirmed by means of adequate follow-up studies among different groups.

Effect of daily iron supplementation on health in children aged 4-23 months: a systematic review and meta-analysis of randomised controlled trials

BACKGROUND

About 47% of preschool children worldwide are anaemic. Daily oral iron supplementation is a commonly recommended intervention for treatment and prevention of anaemia, but the efficacy and safety of iron supplementation programmes is debated. Thus, we systematically reviewed the evidence for benefit and safety of daily iron supplementation in children aged 4-23 months.

METHODS

We searched Scopus and Medline, from inception to Feb 5, 2013, WHO databases, theses repositories, grey literature, and references. Randomised controlled trials that assigned children 4-23 months of age to daily oral iron supplementation versus control were eligible. We calculated mean difference (MD) or standard MD (SMD) for continuous variables, risk ratios for dichotomous data, and rate ratios for rates. We quantified heterogeneity with the I(2) test and synthesised all data with a random-effects model. This review is registered with the International Prospective Register of Systematic Reviews, number CRD42011001208.

FINDINGS

Of 9533 citations identified by the search strategy, 49 articles from 35 studies were eligible; these trials included 42,306 children. Only nine studies were judged to be at low risk of bias. In children receiving iron supplements, the risk ratio for anaemia was 0·61 (95% CI 0·50-0·74; 17 studies, n=4825), for iron deficiency was 0·30 (0·15-0·60; nine studies, n=2464), and for iron deficiency anaemia was 0·14 (0·10-0·22; six studies, n=2145). We identified no evidence of difference in mental (MD 1·65, 95% CI -0·63 to 3·94; six studies, n=1093) or psychomotor development (1·05, -1·36 to 3·46; six studies, n=1086). We noted no significant differences in final length or length-for-age, or final weight or weight-for-age. Children randomised to iron had slightly lesser length (SMD -0·83, -1·53 to -0·12; eight studies, n=868) and weight gain (-1·12, -1·19 to -0·33) over the course of the studies. Vomiting (risk ratio 1·38, 95% CI 1·10-1·73) and fever (1·16, 1·02-1·31) were more prevalent in children receiving iron.

INTERPRETATION

In children aged 4-23 months, daily iron supplementation effectively reduces anaemia. However, the adverse effect profile of iron supplements and effects on development and growth are uncertain. Adequately powered trials are needed to establish the non-haematological benefits and risks from iron supplementation in this group.

FUNDING

Victoria Fellowship (Government of Victoria, Australia); CRB Blackburn Scholarship (Royal Australasian College of Physicans); Overseas Research Experience Scholarship, University of Melbourne.