A Longitudinal Study of Total Body Potassium in Normal Breastfed and Bottle-fed Infants

Abstract

ExtractIn a previous publication we predicted that growth as measured by ' OK is best described by comparison of the semilog function of total body potassium (TBK) vs. length with a slope that differs in infants from that of children aged 3-18 years. Data for 84 infants having three or more measurements during the first year of life attest to this hypothesis, with a regression line for TBK and length: log, K, g = -0.265 + 0.04112 length in centimeters. SpeculationThe increasing rate of ' OK accumulation between birth and the age of 1-2 years is compatible with the hypothesis that changes of body composition from that of the neonate to that of the adult is a steady process and that it is completed by the time the infant reaches a length of about 90 cm. This process is independent of sex and initial feeding within the conditions of this study. Further methodology refinements will be needed to determine the events occurring in low birth weight infants. The role of protein-calorie malnutrition in this process warrants study.In a previous publication (5) we predicted that growth as measured by ' OK is best described by comparison of the semilog function of total body potassium (TBK) vs. length with a slope that differs in infants from that of children aged 3-18 years.In this longitudinal study we have attempted to document that prediction by measuring total body potassium in the first 1.5 years in 84 normal infants who grew within the 16th and 84th percentiles of the Iowa Growth Charts. The relationship between TBK and height (or length) has been well established by several investigators (3,5,7,13,15,16). The uniqueness of this study is its assessment of the effects of type of feeding during the study and its attempt to delineate sex-related differences within two feeding regimens. SUBJECTS A N D METHODSFrom body composition studies of 153 normal, healthy term infants recruited with informed consent of their parents, and receiving care from the University of Missouri Medical Center and community pediatricians, 84 infants had three or more measurements of TBK, length, and weight and therefore qualified for a statistical analysis of their longitudinal data. Approximately half of the babies were breastfed. About half of the babies on each diet were female. The three or more measurements of weight, height, and TBK were usually spaced at 3 weeks, 4 months, 8 months, and 10-14 months. Infants of middle socioeconomic families were admitted to the study regardless of ethnic group. The mothers were advised to follow the same feeding schedule, used the same quantity of solid food additions (21), and recorded the type and amount actually consumed each week (no solid foods were permitted before 3 months of age.)Infants whose mothers breastfed them for 4 months o r more were grouped as "breastfed" in this study. Breast and bottle feedings were ad libitum. The bottle-fed infants consunled a variety of milk-based prepared commercial infant formulas (22). Records of illnesses and physician visits were reported by the mothers. N o ...

Influence of Early Feeding Mode on Body Composition of Infants

“…Formula feeding promoted greater fat accretion in boys and greater FFM accretion in girls. Rutledge et al [9] found no feeding-related differences in FFM based on TBK counting.…”

“…The limited information from in vivo body composition techniques also is conflicting. Based on total body potassium (TBK) content, Rutledge et al [9] reported no significant differences in FFM between breast-fed and formula-fed infants studied from birth through 10-14 months of age. In another study using TBK counting and skinfold measurements, formula feeding was associated with greater fat deposition in boys and greater FFM accretion in girls at 3 months of age [10].…”

Human Body Composition

“…The latter instrument was designed so that the scintillation fluid tanks could be arranged to fit subjects of various size. The imprecision of 4°K assays for infants is evident from the fact that the coefficient of variation of body K was greater than that for body weight in the infants studied by Rutledge et al (1976), who used the instrument designed by Graham (1969 'Sk6ldborn et al (1972). 930 of several infants studied at each of several specific ages Rutledge et al (1976) and Novak et al (1973) were able to show a progressive increase in body K during the first 12 months of life.…”

Comparison of body composition measured by total body potassium and infrared interactance.

“…Women naturally contain more body fat. The efficiency correction for our counter is based on body weight because fat, which is K poor, can be bypassed in comparison of male and female subjects [14,23,24]. We have regarded data obtained from human weighing more dian 113 kg as less accurate.…”

“…In our longitudinal studies, we prefer to relate TBK to height rather than weight because fat, which is K poor, can be bypassed in comparison of male and female subjects [20][21][22][23][24]. Women naturally contain more body fat.…”