| Abstract|| |
Iron deficiency and anemia remain significant health problems worldwide. These may he associated with developmental delay and poor mental development. A source of exogenous iron, is therefore, advisable after four to five months of age for breast-fed babies. Artificiallyfed infants should be given iron-fortified formula from birth.
|How to cite this article:|
MacLean WC. Iron nutrition in infancy. Saudi J Gastroenterol 1996;2:8-10
| Iron Nutrition in Infancy|| |
Anemia is a major health problem worldwide. The World Health Organization estimates that approximately 43% of the world's population is anemic  . In many parts of the world, nonnutritional causes are prominent. Of the nutritional anemias, iron deficiency is the most common. Data from Riyadh, Saudi Arabia, documented that by 12-15 months of age 14.5 % of children were iron deficient  .
The normal full term infant is born with adequate iron stores. Total body iron at birth is approximately 250 mgs. Through recycling and redistribution, this changes little during the first four months of life. By 12 months of age, however, total body iron will nearly double. Thus, a dietary source of iron needs to be assured from at least 4 months of age on.
| Sources of Iron|| |
Iron is absorbed in both heme and nonheme forms. Heme iron from meat and other heme-containing proteins is very well absorbed and is relatively uninfluenced by other aspects of the diet. Nonheme iron, on the other hand, is less well absorbed. The absorption of nonheme iron is affected by other factors in the diet. Factors enhancing the absorption of nonheme iron include: being in the ferrous form, the presence of animal protein, ascorbic acid and fructose in the diet. Factors inhibiting the absorption of nonheme iron are being in the ferric form and the presence of fiber, oxalates, phytates, and high calcium levels in the diet.
During the early months of life, the exclusively breast-fed or formula-fed infant depends on its source of milk for iron. The iron content of breast milk is very low (0.5 mg/L), but the apparent absorption of iron from breast milk is quite high, approximately 50%. It should be noted, however, that when solid foods are added to the diet, the absorption of iron from breast milk decreases dramatically. Absorption of iron from infant formula is lower. Depending on the iron content of the formula, apparent absorption ranges from approximately 5% to 10%, the higher value having been measured in low-iron formula (1-3 mg/L)  . After the age of six months, the recommended dietary allowance of iron in the U.S. is 10 mg per day. The average energy take is approximately 850 calories per day  . When these two estimates are combined, the iron density (mg/1000 kcal) of the diet required to meet these needs is approximately 11.8 mg/1000 kcal. This translates into a minimum of eight mg iron per liter in infant formula.
| Need and Timing of Supplementation|| |
The choice of milk feeding during the first year of life is the major determinant on iron status. Pizarro et al  , studied groups of infants who were fed breast milk, iron-fortified milk, nonfortified milk, or who were given an injection of iron dextran at birth. At nine months of age, approximately 25% of breast-fed infants were iron deficient without anemia; approximately 15% were anemic. In infants fed noniron-fortified milk, over 35% were iron deficient, and approximately 20% were anemic. About 10% of infants fed fortified milk (12 mg/L) were iron deficient, but anemia was almost non-existent. The iron dextran group showed approximately 2% iron deficiency with no anemia. Data such as these, document the need for iron supplementation in breast-fed infants after four months of age and argue for the use of iron-fortified formula rather than low-iron formula  . The American Academy of Pediatrics has stated that whenever infant formula is used, iron- fortified formula is preferred. Despite this fact, approximately 30% of formula sold in the U.S. and over 80% sold in Canada is low-iron.
There are two principal reasons given for not including iron in the diet during the first four to six months of life. The first, is that the infant is born with adequate iron stores. The infant is born with stores of many nutrients. Yet, we do not deprive the infant of the source of these nutrients until stores are depleted. The second reason given for the use of low-iron formula, is that iron causes intolerance. Constipation. gas, fussiness, etc. are often attributed to iron in formula. Whenever this has been studied in an appropriate fashion, no evidence to support these views has been found. Fomon et al  did a double-blind crossover study of infants from seven to 112 days of age. Infants were randomized to receive in two-week alternating blocks, formula containing 1.5 mg iron per liter or 12 mg iron per liter. Parents were asked to record their infant's behavior and stool characteristics. There was no difference between lowiron and iron-fortified formula groups in the frequency of cramps, regurgitation. fussiness, gas or colic. In addition, stool frequency and consistence did not vary by diet. Only stool color showed any change. As has been found in many studies, stools of infants being fed iron-fortified formula tended to be more greenish in color.
| Effects of Iron Deficiency|| |
Our concern about iron deficiency in infancy has been heightened over the last decade by findings in both rats and humans. The first two years after birth is a period of rapid brain development. The brain grows in size, myelinization is occurring, and the complexity of dendritic connections increases. Studies of the brain have shown that the content of iron in specific areas of the brain (globus pallidus, red nucleus, substantia nigra, etc.) is higher than the concentration of iron in liver. Rats who are made iron deficient and anemic during early life show marked decreases of both liver and brain iron. In addition, there are behavioral anomalies such as reversal of sleep cycle and changes in pain threshold. Dopamine (D,) receptors are also affected in the brain in iron deficient rats. Some studies suggest that both the biochemical and behavior changes in rats may be permanent  .
Recent studies in human infants have added to our concerns. In short-term studies, Lozoff et al  documented that infants who had been found to be iron deficient and anemic at 12-23 months of age continued to perform poorly on tests of psychomotor and mental development even after being repleted with iron. Follow-up at five years of age of the cohort who had been iron deficient and anemic in infancy documented a group mean difference in I. Q. of approximately eight points. This difference was highly significant  . Questions were raised in these two studies because of the nonrandomized nature of the subjects. Specifically, it could not be ruled out completely that socioeconomic factors leading to iron deficiency in one group, but not in the other, also accounted for differences in mental function. This question was answered to a large extent by a series of studies by Walter et al , (11,12). Because of feeding practices in Chile at the time, Walter was able to prospectively and blindly study children who were randomized to high-iron or low-iron feedings in infancy. Infants who were found to be anemic at one year of age were treated with iron. No attempt to affect diet following that time was made. When studied at five years of age, the group mean difference in I. Q. of infants who were formerly anemic and those who were not was 5 I. Q. points. This difference was highly significant. Both Lozoff's and Walter's groups did a variety of psychological tests, and there was significant concordance in the sub tests affected by iron deficiency. One study has suggested that the effects of iron deficiency on mental development may be reversible  . All studies to date, however, suggest that during the period of iron deficiency there is inferior mental performance. Consequently, iron deficiency cannot be viewed as a benign condition. Currently, there are large prospective, randomized trials underway to determine the magnitude of the effect of iron deficiency on later mental development and its permanence.
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William C MacLean
Vice President Pediatric Nutrition Research & Development, Ross Products Division, Abbott Laboratories, Columbus, Ohio
Source of Support: None, Conflict of Interest: None