Iron deficiency in minority groups in Australia

Although iron deficiency is not a major health problem in developed countries, it still affects about 2−3% of young children, particularly certain at risk groups1,2. Among these groups are young children and disadvantaged minority groups, such as refugees, recent migrants and indigenous people. At the other end of the spectrum are those at risk of iron overload, including about 10% of the Caucasian population who carry the mutation for hereditary haemochromatosis. This means that measures to prevent iron deficiency need to be targeted specifically to population groups at risk. The current issue of the Journal features a study on the iron status of young Vietnamese children in Sydney. At 18 months of age, the prevalence of iron depletion (low ferritin) was 19.4%; of iron deficiency without anaemia (low ferritin and MCV) was 2.3%; and of iron deficiency anaemia was 3.9% among 129 children out of a cohort of 321 mothers recruited antenatally. This high prevalence of iron depletion occurred despite appropriate infant feeding practices during infancy, but correlated with high cows milk intake (≥ 650 mL/day), low meat/fish/poultry intake, and high weight gain. See related article, p 424. Another group in Australia with a high prevalence of iron deficiency is the Aboriginal population in northern Australia, but the risk factors in this group are very different. The true prevalence of iron deficiency anaemia among Aboriginal children from remote communities is unclear because of the high prevalence of infections, which make haemoglobin and ferritin levels difficult to interpret. In a Northern Territory (NT) study of 11 communities, the prevalence of anaemia was 39% on a school screening of 774 Aboriginal children3. Out of 408 Aboriginal children admitted to Royal Darwin Hospital, 55% had microcytosis with a blood film suggestive of iron deficiency and 35% were anaemic, whereas the comparable figures for non-Aboriginal children were 16% and 6%, respectively4. This implies that about 27% of Aboriginal children have iron deficiency anaemia in hospital compared to 8.5% of non-Aboriginal children. A high prevalence of iron deficiency anaemia has also been documented in indigenous Canadian children between 6 and 24 months5. Thus, many Aboriginal children in the NT have iron deficiency (± anaemia), which in combination with wasting and microcephaly, are likely to be important contributors to the health disadvantage which Aboriginal children suffer. Iron deficiency anaemia has been correlated with poor cognitive function and deficits in psychomotor development, especially in children under 2 years. However, iron deficiency is associated with socio-economic disadvantage which may be a confounder. The latest Cochrane review on this issue is equivocal and calls for more studies6. The major risk factor for iron deficiency in Aboriginal children is an inadequate weaning diet in partially breastfed children from 4 to 24 months, which is also the key risk factor for poor growth. Many Aboriginal mothers in the NT continue breastfeeding for about 18 months, but do not introduce iron rich solids from 4 to 6 months of age in sufficient amounts to supply iron and growth needs. Cows milk does not seem to be an important risk factor since its intake is very low in children of this age and the small amount added to tea is probably not a significant contributor to iron deficiency. It is also likely that the combination of a high burden of infections and tropical enteropathy syndrome result in greater requirements and less absorption7−9. Another important risk factor for iron deficiency is low birthweight, particularly with prematurity or twins. There has been considerable debate about the optimal time of introduction of weaning foods to infants, including in Australia. A Cochrane review on the optimal duration of exclusive breastfeeding concluded that infants exclusively breastfed for 6 months experience less morbidity from gastrointestinal infection than those in whom weaning foods are started by 3−4 months, and ‘no deficits have been demonstrated in growth among infants from either developing or developed countries who are exclusively breastfed for six months or longer.’ Although infants should still be managed individually so that insufficient growth or other adverse outcomes are not ignored, the available evidence demonstrates no apparent risks in recommending exclusive breastfeeding for the first 6 months of life10. However, this review found that the data are conflicting with respect to iron status, so suggested that exclusive breastfeeding without iron supplementation until 6 months may compromise haematological status. The high prevalences of iron deficiency, growth failure and late introduction of weaning foods in NT Aboriginal community children means that it would be unwise to delay introduction of weaning foods until 6 months in this setting. Introduction of weaning foods at 4 months of age is still recommended for Aboriginal community infants, however, urban indigenous infants who are thriving may safely continue exclusive breastfeeding until 6 months. The accurate diagnosis of iron deficiency is based upon a venous haemoglobin, mean cell volume (MCV) and thin film. Serum ferritin gives falsely elevated values in children with even trivial infections (ferritin is an acute phase reactant) and is unreliable even in a community setting11. The soluble transferrin receptor measures tissue iron, unaffected by infection, but it does not significantly improve the diagnosis in Aboriginal children12. The newly described hormone, hepcidin, is an acute phase reactant made by hepatocytes which appears to regulate iron homeostasis, including enterocyte iron absorption and iron sequestration in macrophages13,14. Inappropriate expression of hepcidin with the high burden of infection seen in Aboriginal children may mediate the anaemia of inflammation and high prevalence of iron deficiency in these children from early infancy, along with the dietary risk factors. Daily iron medication is problematic due to poor compliance and side-effects11. Most paediatricians might be surprised if they knew the true frequency of iron injections in Aboriginal children in NT. There are technological solutions such as sprinkles15,16 and ready-to-use foods of high energy fortified with micronutrients and which do not support bacterial growth17,18. It remains a mystery why it is acceptable to give out antibiotics for infections whereas giving out food supplements to malnourished children is denounced as increasing dependency. The new breed of food supplements developed for Africa could potentially have major benefits for Aboriginal community children in managing growth failure, iron and zinc deficiency.

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