The Evidence for Estimating the Recommended Nutrient Intake for Iron...continued.

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

100. Galan, P. 1990. Iron absorption from typical West African meals containing contaminating Fe. Br. J. Nutr., 64: 541-546.

101. Acosta, A. 1984. Iron absorption from typical Latin American meals. Am. J. Clin. Nutr., 39: 953-962.

102. Rao, B.S.N., Vijayasarathy, C. & Prabhavathi, T. 1983. Iron absorption from habitual diets of Indians studied by the extrinsic tag technique. Indian J. Med.. 77: 648-657.

Iron absorption data (Table 44) are also available from several population groups in Africa (100), South America (101), India, and Southeast Asia. The bio-availability of different Indian diets after an adjustment to a reference dose absorption of 56.5 percent was 1.7–1.8 percent for millet-based diets, 3.5–4.0 percent for wheat-based diets, and 8.3-10.3 percent for rice-based diets (102).

103. Aung-Than-Batu, Thein-Than & Thane-Toe. 1976. Iron absorption from SoutheastAsian rice-based meals. Am. J. Clin. Nutr., 29: 219-225. 

In Southeast Asia, iron absorption data has been reported from Burma and Thailand. In Burma, iron absorption from a basal rice-based meal was 1.7 percent, when the meal contained 15 g of fish the bio-availability of iron was 5.5 percent, and with 40 g of fish it was 10.1 percent (103).

104. Hallberg, L. 1974. Iron absorption from Southeast Asian diets. Am. J. Clin. Nutr., 27:

826-836.

105. Hallberg, L. 1977. Iron absorption from Southeast Asian diets. II. Role of various factors that might explain low absorption. Am. J. Clin. Nutr., 30: 539-548. 

In Thailand, iron absorption from a basal ricebased meal was 1.9 percent; adding 100 g of fresh fruit increased absorption to 4.8 percent and adding 80 g of lean meat increased non-heme iron absorption to 5.4 percent (104, 105).

106. Hallberg, L. 1978. Iron absorption from South-East Asian diets and the effect of iron fortification. Am. J. Clin. Nutr., 31: 1403-1408. 

In three other studies serving basal meals with vegetables rich in ascorbic acid, the absorption figures were 5.9 percent, 10 percent, and 10.8 percent, respectively (106).

107. Hallberg, L., Björn-Rasmussen, E. & Rossander, L.R.S. 1979. The measurement of food iron absorption in man. A methodological study on the measurement of dietary non-haem-Fe absorption when the subjects have a free choice of food items. Br. J. Nutr. 41: 283-289.

In a further study in Thailand, 60 g of fish were added to the same meal, which increased absorption to 21.6percent. An even more realistic field study was done in Central Thailand to examine the reproducibility of dietary iron absorption measurements under optimal field conditions for 20 farmers and labourers (16 men, 4 women). The subjects had a free choice of foods (rice, vegetables, soup, a curry, and fish). All foods consumed were weighed and the rice was labelled with an extrinsic radioiron tracer. The mean absorption was 20.3 percent (adjusted to reference dose absorption of 56.5 percent) (107).

8. FAO/WHO. 1988. Requirements of vitamin A, iron, folate and vitamin B12. Report of a Joint FAO/WHO Expert Consultation.. Rome: FAO. (FAO Food and Nutrition Series No. 23). 

It is obvious that absorbed iron requirements need to be adjusted to different types of diets, especially in vulnerable groups. The Food and Agriculture Organization of the United Nations (FAO) and WHO recommended, for didactic reasons, three bio-availability levels of 5 percent, 10 percent, and 15 percent (8).

For developing countries, it may be realistic to use the figures of 5 percent and 10 percent. In populations consuming more Western-type diets, two levels would be adequate – 12 percent and 15 percent – mainly depending on meat intake. The amount of dietary iron absorbed is mainly determined by the amount of body stores of iron and by the properties of the diet (iron content and bio-availability). In anaemic subjects the rate of erythrocyte production also influences iron absorption. In a 55-kg woman with average iron losses who consumes a diet with an iron bio-availability of 15 percent, the mean iron stores would be about 120 mg.

69. Hallberg L., Hulthén L. & Garby L. 1998. Iron stores in man in relation to diet and iron requirements. Eur. J. Clin. Nutr., 52: 623-31.

Under these circumstances approximately 10–15 percent of women would have no iron stores. When a diet with a bio-availability of 12 percent is consumed by a 55-kg woman, iron stores would be approximately 75 mg and about 25–30 percent of women would have no iron stores at all. When the bio-availability of iron decreases to 10 percent, mean iron stores are reduced to about 25 mg and about 40–50 percent of women consuming this diet would have no iron stores. Those consuming diets with an iron bio-availability of 5 percent have no iron stores and they are iron deficient. These calculations are based on a recent study (69).

Recommendations for iron intake for infants, children, younger and older adults, and pregnant and lactating women Tables 39 and 40 showed both the physiologic absorbed iron requirements and the dietary iron requirements. All these figures are for the 95th percentile of iron requirements. The figures are given for women with a body weight of 55 kg and men with a body weight of 70 kg. For example, women with a body weight of 45 kg and men with a body weight of 55 kg have iron requirements that are 20 percent lower than those given in Table 39. 

No figures are given for dietary iron requirements in pregnant women because the iron balance in pregnancy depends not only on the properties of the diet but also and especially on the amounts of stored iron.