Elsevier

The Lancet

Volume 370, Issue 9586, 11–17 August 2007, Pages 511-520
The Lancet

Seminar
Nutritional iron deficiency

https://doi.org/10.1016/S0140-6736(07)61235-5Get rights and content

Summary

Iron deficiency is one of the leading risk factors for disability and death worldwide, affecting an estimated 2 billion people. Nutritional iron deficiency arises when physiological requirements cannot be met by iron absorption from diet. Dietary iron bioavailability is low in populations consuming monotonous plant-based diets. The high prevalence of iron deficiency in the developing world has substantial health and economic costs, including poor pregnancy outcome, impaired school performance, and decreased productivity. Recent studies have reported how the body regulates iron absorption and metabolism in response to changing iron status by upregulation or downregulation of key intestinal and hepatic proteins. Targeted iron supplementation, iron fortification of foods, or both, can control iron deficiency in populations. Although technical challenges limit the amount of bioavailable iron compounds that can be used in food fortification, studies show that iron fortification can be an effective strategy against nutritional iron deficiency. Specific laboratory measures of iron status should be used to assess the need for fortification and to monitor these interventions. Selective plant breeding and genetic engineering are promising new approaches to improve dietary iron nutritional quality.

Section snippets

Epidemiology

Estimates of occurrence of iron deficiency in industrialised countries are usually derived from nationally representative samples with specific indicators of iron status.1 By contrast, estimates from developing countries are often based only on haemoglobin measurements from restricted regions or target populations, and should be interpreted with caution. Prevalence estimates of iron deficiency anaemia (ie, iron deficiency and low haemoglobin) based on haemoglobin alone are overestimations

Physiology

Human beings are unable to excrete iron actively, so its concentration in the body must be regulated at the site of iron absorption in the proximal small intestine (figure). Diets contain both haem and non-haem (inorganic) iron; each form has specific transporters. A putative intestinal haem iron transporter (HCP1) has been identified, which is upregulated by hypoxia and iron deficiency, and might also transport folate.11, 12 Transport of non-haem iron from the intestinal lumen into the

Causation

Nutritional iron deficiency arises when physiological requirements cannot be met by iron absorption from diet. Dietary iron bioavailability is low in populations consuming monotonous plant-based diets with little meat.32 In meat, 30–70% of iron is haem iron, of which 15–35% is absorbed.33 However, in plant-based diets in developing countries most dietary iron is non-haem iron, and its absorption is often less than 10%.32, 33 The absorption of non-haem iron is increased by meat and ascorbic

Adverse effects

The high frequency of iron deficiency anaemia in the developing world has substantial health and economic costs. In an analysis of ten developing countries, the median value of physical productivity losses per year due to iron deficiency was about US$0·32 per head, or 0·57% of the gross domestic product.54 In the WHO African subregion, it is estimated that if iron fortification reached 50% of the population, it would avert 570 000 disability adjusted life years (DALYs) every year.55 During the

Laboratory diagnosis

Table 2 shows useful indicators for diagnosis of iron deficiency anaemia in population studies. The major diagnostic challenge is to differentiate between iron deficiency anaemia in otherwise healthy individuals and anaemia of chronic disease. Inflammatory disorders increase circulating hepcidin concentrations,90 and hepcidin blocks iron release from enterocytes and the reticuloendothelial system,17 resulting in iron-deficient erythropoiesis. If chronic, inflammation can produce anaemia of

Strategies

Three main strategies for correcting iron deficiency in populations exist, alone or in combination: education combined with dietary modification or diversification, or both, to improve iron intake and bioavailability; iron supplementation (provision of iron, usually in higher doses, without food); and iron fortification of foods. A new approach is biofortification via plant breeding or genetic engineering. Although dietary modification and diversification is the most sustainable approach,

Conclusions

Nutritional iron deficiency is still common in young women and children in developing countries where monotonous, plant-based diets provide low amounts of bioavailable iron. The high prevalence of iron deficiency in the developing world has substantial health and economic costs. However, more data are needed on the functional consequences of iron deficiency; for example, the effect of iron status on immune function and cognition in infants and children needs to be clarified. Continuing rapid

Search strategy and selection criteria

We searched PubMed, Current Contents Connect, and ISI Web of Science for articles in English, French, German, and Spanish. We searched for “iron”, “iron deficiency”, “anaemia”, “nutrition”, “haemoglobin”, “bioavailability”, “supplementation”, “fortification”, “plant breeding”, and “genetic engineering”. We mainly selected publications from the past 5 years, but did not exclude highly regarded earlier publications.

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