Extent of thermal processing of infant formula affects copper status in infant rhesus monkeys

Infant rhesus monkeys are excellent models in which to study the effect of infant formulas on trace element absorption and status. Infants fed powdered formula from birth exhibit normal growth and have blood variables similar to those of breast-fed infants.

The objectives were to evaluate the effects of feeding ready-to-feed (RTF) formulas exposed to different heat treatments to infant monkeys, and, for one of these formulas, to compare the effect of fortification with 2 iron concentrations.

From birth to age 5 mo, infant monkeys (n = 6/group) were fed one of the following formulas exclusively: 1) 12 mg Fe/L processed in cans (RTF-12), 2) formula in glass bottles with 12 mg Fe/L and manufactured by an ultrahigh-temperature (UHT) process (UHT-12), or 3) formula manufactured by a standard thermal process (STP), containing either 8 (STP-8) or 12 (STP-12) mg Fe/L. All formulas had similar copper concentrations (0.6 mg Cu/L). Anthropometric measures and venous blood samples were taken monthly.

Weight and length gain did not differ among groups; however, the STP-12 group weighed less than the UHT-12 group at ages 2, 4, and 5 mo. Hemoglobin values were significantly lower in the RTF-12 group than in all other groups at ages 4 and 5 mo and serum ferritin was lower in the RTF-12 group than in the STP-12 group at age 5 mo. Copper status was lower in STP-12 infants than in STP-8 infants. There was a progressive and significant decline in plasma copper, ceruloplasmin, and Cu/Zn superoxide dismutase activity in infants fed canned formula (RTF-12). Furthermore, coat color changed from normal brown to silver. These outcomes suggest that the canned formula induced copper deficiency in infant monkeys.

Excessive heat treatment of formula can have a pronounced negative effect on copper status. High iron concentrations did not improve iron status but may adversely affect copper status.