Infants, metal absorption

This pilot study with a small number of infants does not permit firm conclusions about metal absorption in infants However we have learned that bottle-fed infants tolerate the metal isotope solutions better than breast-fed infants In a subsequent study many (6/20) breast-fed babies spit up the milk-isotope mixture within 30 minutes of feeding Two others refused it entirely In contrasty all bottle-fed babies (12/12) drank the isotope-formula mixture and none had emesis The doses of isotopes could probably be reduced by at least half without sacrificing analytical sensitivity and this would probably reduce gastrointestinal intolerance ... 

In a review of data on occupational chemicals that may contaminate breast milk (Byczkowski et al. 1994), it is stated that lead may be excreted in milk in amounts lethal to the infant and that the metal may be mobilized from bone stores to milk during the lactation period. Even when the concentration of lead in mother s milk is low, the absorption of metals into the systemic circulation of infants is generally high when they are on a milk diet. To better understand the sensitivity of the nursing infant to chemicals, epidemiological studies, chemical monitoring, and model development and application are needed. 

Much else is known about GI absorption. Individuals vary in the extent to which they can absorb the same chemical, and absorption can be influenced by individual factors such as age, sex, health status, and even dietary habits. People who consume large amounts of fiber may absorb less calcium and iron than those who eat less. The GI tract is not fully developed until about 24 months after birth, and infants absorb metals such as lead and certain organic chemicals more readily than do adults. 

Nutritional Effects Due to the Presence of the Maillard Products. Many physiological or antinutritional effects have been attributed to the Maillard products. Specific effects have been attributed to the Amadori products deoxyfructosylphenylalanine (a model substance not likely to be present in large quantities in foods) appears to depress the rate of protein synthesis in chicks (32) and to partially inhibit in vitro and in vivo the absorption of tryptophan in rats (33). The compound e-deoxyfructosyllysine inhibits the intestinal absorption of threonine, proline, and glycine and induces cytomegaly of the tubular cells of the rat kidneys (34) as does lysinoalanine. In parenteral nutrition the infusion of the various Amadori compounds formed during sterilization of the amino acid mixture with glucose is associated with milk dehydration in infants and excessive excretion of zinc and other trace metals in both infants and adults (35,36,37). 

Water treatment Reduction of lipid absorption Production of single cell protein Antigastritis agent Infant food ingredient Recovery of metal ions, pesticides, phenols, and PCBs Removal of dyes, radioisotopes... 

Human Toxicity Ingestion or absorption may cause nausea, vomiting, diarrhea, abdominal cramps, erythematous lesions on skin and mucous membranes, circulatory collapse, tachycardia, cyanosis, delirium, convulsions, coma. Death has occurred from < 5 g in infants and from 5 to 20 g in adults. Chronic use may cause borism (dry skin, eruptions, gastric disturbances) E. Browning, Toxicity of industrial Metals (Appleton-Century-Crofts, New York, 2nd ed., 1969) pp 90-97. 

Many aspects of heavy metal tolerance differ in an infant as compared to an adult. As far as absorption, retention, distribution, interactions with other nutrients or toxic effects are concerned, the specific influences of age have been discovered and evaluated by other contributors to this volume who present their view more competently than this presentation by pediatric nutritionists could possibly do it. 

In order to take intelligent decisions concerning possible remedies it is necessary to understand the principles regulating the intake of heavy metals by infants via different routes, especially in the case of oral intake. There may be significant differences in the absorption processes. It still has to be determined whether there are different toxicokinetic conditions in the growing organism at all, so that different patterns of distribution have to be assumed. In that case the elimination and accumulation processes should be evaluated differ-... 

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