ENERGY REQUIREMENTS (ER) DURING INFANCY

To evaluate the ER of infants, 20 formula-fed and 20 breast-fed infants (10 ea at 1 mo and 10 ea at 4 mo) from the USA and 8 4-mo-old breast-fed infants from Mexico were studied. Energy expenditures (EE) were estimated by the 2H2 18O method. After collection of a predose urine sample, each infant received by mouth 200 mg 2H2O and 300 mg 18O/kg body wt. One daily Dostdose utine sample was collected from each infant for 7-10 d. H and 18O content of urine samples were measured by isotope-ratio mass spectrometry. CO2 expiration rates (rCO2) were calculated from the fractional turnover rates and isotope dilution spaces of 2H and 18O. Oxygen consumption rates (rO2) were calculated from rCO2, using the measured respiratory quotient or the estimated food quotient values. EE was calculated from the rCO2 and rO2 using Weir's equation. Energy deposited for growth (EDG) was calculated from fat and protein gained by these infants using Fomon's reference data and gross energy equivalents of 9.25 kcal/g for fat and 5.65 kcal/g for protein. Energy requirement (ER) was the sum of EE and EDG. ER of the 1-mo-old infants were 103±17 kcal/kg/d. At 4 mo of age, no difference in ER was observed between the American and Mexican infants. However, ER of the 4-mo-old infants (79±15 kcal/kg/d) were significantly lower than the current recommendation for energy intake (105-115 kcal/kg/d) during infancy. Therefore, revision of the current recommendation is warranted.