ExtractInfants of two groups, one of 16, one of 14 infants, who weighed < 1.3 kg at birth (mean 1.01 ± 0.05 kg), were studied from age 14 days until they reached 1.8 kg body weight. Infants were pair-matched for gestational age and birth weight and one member was randomly allocated to two treatment groups. Infants ingroup Areceived no calcium supplement and those ingroup Breceived calcium lactate, 800 mg/kg/24 hr, in divided doses with each feed. All were fed “Improved” SMA, 200 ml/kg/24 hr, 160 cal/kg/24 hr, and were given a multivitamin preparation containing 500 IU vitamin D2/dose.The infants' weekly length gain did not differ between groups (1.08 ± 0.04 cm/week vs 1.11 ± 0.04 cm/week; mean ± SEM). Mean weight and head cercumference increments also were similar (group A, 163 ± 6 g/week; 1.12 ±0.03 cm/week;group B, 170 ± 6 g/week and 1.18 ± 0.03 cm/week).An increase in blood pH from 7.33 ± 0.01 to 7.41 ± 0.01 (P< 0.01) ingroup Ababies was associated with a decrease in PCO2from 44.2 ± 1.0 to 38.9 ± 1.4 mm Hg. Values remained unchanged with age ingroup Bbabies. After institution of calcium supplementation, base excess values differed transiently between groups (at age 5 weeks,group A−0.16 ± 0.56 mEq/liter,group B−1.17, ± 0.76 mEq/liter;P< 0.05).Mean ionic calcium values remained unchanged ingroup A(2.37 ± 0.06 mEq/liter), but increased slightly from 2.42 ± 0.06 to 2.57 ±0.04 mEq/liter ingroup B(P< 0.05).Total plasma calcium differed transiently between groups after calcium supplementation had started ingroup B(Group A, 4.53 ± 0.08 mEq/liter;group B, 4.82 ± 0.12 mEq/liter;P< 0.05), and plasma Mg and P levels were lower ingroup Bbabies than ingroup Ababies (P< 0.01). All infants remained somewhat hypoproteinemic throughout the study; mean values of plasma total protein averaged 4.5 g/100 ml.Mean urinary excretion rates of calcium initially were 0.17 mEq/kg/24 hr ingroup Ababies and 0.18 mEq/kg/24 hr ingroup Binfants, and no increase was seen with calcium supplementation.Fecal excretion of calcium (percentage of intake) decreased from 70% to 33% ingroup Bbabies after calcium supplementation. Calcium retention rates (mEq/kg/24 hr) were similar in both groups initially but increased subsequently ingroup Bfrom 1.20 to 7.33 mEq/kg/24 hr and were 3 times as high ingroup Bthan ingroup Aduring the second and third balances.Urinary phosphorus excretion was initially similar in both groups (group A, ISA ± 2.2 mg/kg/24 hr;group B, 32.4 ± 5.5 mg/kg/24 hr), but decreased to half this value in infants ofgroup Bafter calcium supplementation had started (P< 0.02).Group Binfants showed a higher percentage fecal fat excretion thangroup Ainfants during the second and third balance.In 9 of 10 paired radiographs of the knee and tibiagroup Binfants showed better defined bone texture and/or wider cortices than didgroup Ainfants.We suggest that prevention of the “bone disease of very low birth weight (VLBW) infants” may be accomplished by suitable calcium supplements.SpeculationAs a consequence of their special requirements and the unavailability of appropriately constituted infant formulas, infants born very prematurely fail to achieve intrauterine accretion rates for many minerals. Postnatal growth may also be jeopardized. We believe that for optimal postnatal growth infants born very prematurely require sufficient nutrients to parallel intrauterine accretion rates.SpeculationAs a consequence of their special requirements and the unavailability of appropriately constituted infant formulas, infants born very prematurely fail to achieve intrauterine accretion rates for many minerals. Postnatal growth may also be jeopardized. We believe that for optimal postnatal growth infants born very prematurely require sufficient nutrients to parallel intrauterine accretion rates.