Causes of Iron Deficiency

Reference from the joint report of FAO/WHO expert consultation on Human Vitamins and Minerals verbatim.

Nutritional iron deficiency implies that the diet cannot cover physiologic iron requirements. Worldwide this is the most common cause of iron deficiency. In many tropical countries, infestations with hookworms lead to intestinal blood losses that may be considerable. The severity of the infestations with hookworms varies considerably between subjects and regions. The average blood loss can be well estimated by egg counts in stools. Usually the diet in these populations is also limited with respect to iron content and availability.

In clinical practice a diagnosis of iron deficiency must always lead to a search for pathologic causes of blood loss (e.g., tumours in the gastrointestinal tract or uterus, especially if uterine bleedings have increased or changed in regularity). Patients with achlorhydria absorb dietary iron less well (a reduction of about 50 percent) and patients who have undergone gastric surgery, especially if the surgery was extensive, may eventually develop iron deficiency because of impaired iron absorption. Gluten enteropathy is another possibility to consider, especially in young patients.

Prevalence of iron deficiency

81. DeMaeyer, E ., Adiels-Tegman, M. & Raystone, E. 1985. The prevalence of anemia in the world. World Health Stat Q., 38: 302-316.

Iron deficiency is probably the most frequent nutritional deficiency disorder in the world. Arecent estimate based on World Health Organization (WHO) criteria indicated that around600-700 million people worldwide have a marked iron deficiency anaemia (81). 

In industrialized countries, the prevalence of iron deficiency anaemia is much lower and usually varies between 2 percent and 8 percent. However, the prevalence of iron deficiency, including both anaemic and non-anaemic subjects (see definitions above), is much higher. In industrialized countries, for example, an absence of iron stores or subnormal serum ferritinvalues is found in about 20–30 percent of women of fertile age. In adolescent girls the prevalence is even higher. 

It is difficult to determine the prevalence of iron deficiency more exactly because representative populations for clinical investigation are hard to obtain. Laboratory methods and techniques for blood sampling need careful standardization. One often neglected source of error, for example, when materials in different regions or at different times are compared, is the fact that there are still reagent kits on the market for determining serum ferritin which are not adequately calibrated at different concentrations against the international WHO standards.

In addition, seasonal variations in infection rates influence the sensitivity and specificity of most methods used. Worldwide, the highest prevalence figures for iron deficiency are found in infants, children, teenagers, and women of childbearing age. Thanks to better information and access to fortified cereals for infants and children, the iron situation has markedly improved in these groups in most industrialized countries, where the highest prevalence today is observed in menstruating women and adolescents of both sexes.

72. Yip, R., Stolzfus, R.J. & W.K.S. 1996. Assessment of the prevalence and the nature of iron deficiency for populations: the utility of comparing haemoglobin distributions. In: Hallberg L, Asp, N-G., eds. Iron nutrition in health and disease. London, John Libby & Company Ltd. 

In developing countries, where the prevalence of iron deficiency is very high and the severity of anaemia is marked, studies on the distribution of haemoglobin in different population groups can provide important information as a valuable basis for action programmes (72). A more detailed analysis of subsamples may then give excellent information for the planning of more extensive programmes.