Copper absorption from human milk, cow's milk, and infant formulas using a suckling rat model

Abstract

Since copper deficiency is known to occur during infancy, it becomes important to assess copper uptake from various infant diets. We have investigated the uptake of copper from human milk, cow's milk, cow's milk formulas, cereal/milk formula and soy formula, compensating for the decay of 64Cu and using the suckling rat as a model. Radiocopper was added to the diet in trace amounts. Ultracentrifugation, ultrafiltration, and gel filtration were used to show that the added 64Cu bound to milk fractions and individual binding compounds in a manner analogous to the distribution of native copper, thus validating the use of extrinsically labeled diets. Labeled diets were intubated into 14-day-old suckling rats. Animals were killed after 6 h and tissues removed and counted. Liver copper uptake was 25% from human milk, 23% from cow's milk formula, 18% from cow's milk, 17% from premature (cow's milk based) infant formula, 17% from cereal/milk formula and 10% from soy formula. These results show that the rat pup model may provide a rapid, inexpensive, and sensitive method to assay bioavailability of copper from infant foods.

Heat Processing in Infant Formulas Induces Changes in Copper Tissue Levels in Suckling and Weanling Rats

“…Olivares et al [21] described in young infants a high variability, ranging from 46 to 95%, using 65 Cu as a tracer and the fecal monitoring technique, pointing to copper absorption not being downregulated within the range of copper intake tested and to the trapping of copper in the intestine and an incomplete release through desquamation over the study period. The suckling rat mucosa retains a considerable fraction of absorbed copper, but this fraction decreases considerably with increasing age [1,10] , in agreement with the results of the present study.…”

“…Infant formulas can provide either less copper than breast milk or substantially more, depending on manufacturer and type of formula, but the copper absorption from infant formulas is not as effective as that from breast milk [1,2] .…”

Does Dietary Fiber Affect the Levels of Nutritional Components after Feed Formulation?

“…Davis, et al [39] reported that dietary supplementation of crude soybean proteins decreased the bioavailability and deficiency of copper in broilers. In addition, Lönnerdal, et al [40] reported about 90% decrease in copper bioavailability in infants after feeding on purified soybean protein. Moreover, after feeding different fiber forms to adolescent males, Drews, et al [41] observed a decrease in copper balance among subjects that were fed hemicellulose, though pectin and intact cellulose had no effect on the copper concentration.…”

Copper Deficiency in Infancy

“…A few patients [17,24,26] had been fed mainly on cow's milk, which contains slightly less copper than human milk [57] and this may have been a contributory factor. Only four patients were breast-fed [27,28], and two of the infants reported by Sutton et al [1] received naso jejunal feeding with expressed breast milk during the period in which the copper deficiency was probably developing.…”