Intake and growth of breast-fed and formula-fed infants in relation to the timing of introduction of complementary foods: the DARLING study. Davis Area Research on Lactation, Infant Nutrition and Growth.

We examined if the timing of introduction of solid foods was related to growth, intake, morbidity, activity or motor development among infants either breast fed or formula fed until > or = 12 months of age. Breast-fed infants given solids before 6 months of age (earlysol) consumed less breast milk at 6 and 9 months of age than those given solids > or = 6 months (latesol); thus total energy intake did not differ between groups. Z scores for weight, length and weight-for-length at 1-18 months did not differ between groups. Latesol infants gained less weight from 6 to 9 months but not during any other interval. Neither activity level nor morbidity differed between groups, but several developmental milestones occurred earlier in the earlysol versus the latesol group, probably due to reverse causation. Among formula-fed infants, timing of introduction of solid foods was not related to intake, growth, activity or morbidity. We conclude that solid foods given before 6 months of age generally replace the milk source among breast-fed but not formula-fed infants.

Use of growth models to describe patterns of length, weight, and head circumference among breast-fed and formula-fed infants: the DARLING Study.

Nine mathematical models were applied to 24-month length, weight, and head circumference growth curves of 39 breast-fed and 31 formula-fed infants from the DARLING study. For both breast-fed and formula-fed infants, the Karlberg infancy-childhood-puberty (ICP) model best describes the relationship between recumbent length and age and the Jenss model best describes the relationship between head circumference and age. For formula-fed infants several models appropriately describe the relationship between weight and age, and we recommend the Jenss model. However, none of the models suitably describes the shape of the weight curve for breast-fed infants.

Energy and protein intakes of breast-fed and formula-fed infants during the first year of life and their association with growth velocity: the DARLING Study.

Intake and growth were compared between matched cohorts of infants either breast-fed (BF) or formula-fed (FF) until > or = 12 mo of age. Total energy intake at 3, 6, 9, and 12 mo averaged 0.36, 0.34, 0.35, and 0.38 MJ.kg-1.d-1 (85.9, 80.1, 83.6, and 89.8 kcal.kg-1.d-1) among BF infants vs 0.41, 0.40, 0.39, and 0.41 MJ.kg-1.d-1 (98.7, 94.7, 93.6, and 98.0 kcal.kg-1.d-1) among FF infants, respectively. Protein intake was 66-70% higher in the FF than in the BF group during the first 6 mo. Differences in energy and protein intakes were significant at 3, 6, and 9 mo. Gains in weight and lean body mass were lower in BF than in FF infants from 3 to 9 mo. BF infants gained more weight and lean body mass per gram protein intake but not per megajoule intake. Although growth differences between groups were related to differences in intake, there is no evidence of any functional advantage to the more rapid growth of FF infants.

Maternal weight-loss patterns during prolonged lactation.

Weight and triceps-skinfold thickness were measured until 24 mo postpartum in matched cohorts of women who breast-fed for > or = 12 mo (BF; n = 46) or < or = 3 mo (FF; n = 39). In the BF group, breast-feeding frequency and breast-milk energy output were determined every 3 mo until 18 mo. Weight loss from 1 to 12 mo postpartum was significantly greater in BF than in FF women (4.4 vs 2.4 kg, P < 0.05), due primarily to differences in weight loss from 3 to 6 mo. BF mothers had a net loss in triceps-skinfold thickness whereas FF mothers gained fat at this site (-0.4 vs 2.4 mm, P < 0.05). Breast-feeding frequency and total time breast-feeding were related to weight loss in the BF group from 6 to 12 mo. Maternal weight did not differ significantly between 12 and 24 mo in either group. We conclude that lactation enhances weight loss postpartum if breast-feeding continues for at least 6 mo.

Energy expenditure in lactating women: a comparison of doubly labeled water and heart-rate-monitoring methods.

Estimates of total daily energy expenditure (TDEE) by heart-rate (HR) monitoring were compared with those made by the doubly labeled water (DLW) method in nine exclusively breast-feeding women. Subjects recorded HR and dietary intake daily during the 8-d, isotope-measurement period. Milk energy output was determined by 3-d test weighing and analysis of 24-h milk samples. Total energy output (milk energy and TDEE) averaged 12.36 +/- 1.03 MJ/d with DLW compared with 11.74 +/- 1.3 MJ/d with HR monitoring, a 5.8% difference (NS). Individual differences ranged from -27.1% to +17.6%. The high water turnover and relatively low level of activity during lactation made the slopes of deuterium and 18O disappearance more similar, resulting in increased error in estimates of TDEE by DLW. Therefore, the DLW method may not be appropriate for use in lactating women. There are considerable individual deviations in estimating TDEE by HR monitoring, but it is satisfactory for estimating TDEE of groups.

Breast-fed infants are leaner than formula-fed infants at 1 y of age: the DARLING study.

Anthropometric indexes from 1 to 24 mo were compared between matched cohorts of infants either breast-fed (BF, n = 46) or formula-fed (FF, n = 41) until > or = 12 mo. Neither group received solid foods before 4 mo. Weight-for-length was significantly greater among FF infants from 7 to 24 mo. In both groups, skinfold thickness (triceps, biceps, subscapular, flank, and quadriceps) and estimated percent body fat (%FAT) increased rapidly during the first 6-8 mo and declined thereafter. At all sites except biceps, FF infants had larger skinfold thicknesses in later infancy (particularly 9-15 mo) than did BF infants; %FAT was significantly higher from 5 to 24 mo. Lower energy intake among BF infants explained the difference between groups. Maternal and infant fatness were positively correlated at 12-24 mo. Breast-milk lipid and energy concentration were unrelated to infant fatness. These results indicate that infants BF for > or = 12 mo are leaner than their FF counterparts.

Growth patterns of breast-fed infants in affluent (United States) and poor (Peru) communities: implications for timing of complementary feeding.

We compared growth, dietary intake, and morbidity of infants breast-fed for > or = 12 mo from two populations: Davis, CA (n = 46) and Huascar, Peru (n = 52). When compared against WHO reference data (based primarily on formula-fed infants), Huascar infants appeared to falter as early as 3-4 mo, but when compared with Davis breast-fed infants, the curves for weight and length were very similar in girls until 10-12 mo and in boys until 6-9 mo. Thereafter, Huascar infants grew less rapidly than did Davis infants. Breast milk intake was very similar between groups, but in Huascar the amount and nutrient density of complementary foods consumed after 6 mo were lower and morbidity rates were much higher than in Davis. These results indicate that growth faltering of Huascar infants, when judged against breast-fed infants in the United States, occurs primarily after the first 6 mo of life and is not due to poor lactation performance.

Growth of breast-fed and formula-fed infants from 0 to 18 months: the DARLING Study.

Anthropometric data were collected monthly from birth to 18 months as part of the Davis Area Research on Lactation, Infant Nutrition and Growth study, which followed infants who were either breast-fed or formula-fed during the first 12 months. The two cohorts were matched for parental socioeconomic status, education, ethnic group, and anthropometric characteristics and for infant sex and birth weight, and neither group was given solid foods before 4 months. While mean weight of formula-fed infants remained at or above the National Center for Health Statistics median throughout the first 18 months, mean weight of breast-fed infants dropped below the median beginning at 6 to 8 months and was significantly lower than that of the formula-fed group between 6 and 18 months. In contrast, length and head circumference values were similar between groups. Weight-for-length z scores were significantly different between 4 and 18 months, suggesting that breast-fed infants were leaner. The groups had similar weight gain during the first 3 months, but breast-fed infants gained less rapidly during the remainder of the first year: cumulative weight gain in the first 12 months was 0.65 kg less in the breast-fed group. Length gain was similar between groups. These results indicate that weight patterns of breast-fed infants, even in a population of high socioeconomic status, differ from current reference data and from those of formula-fed infants. Thus, new growth charts based on breast-fed infants are needed.

Adequacy of energy intake among breast-fed infants in the DARLING study: relationships to growth velocity, morbidity, and activity levels. Davis Area Research on Lactation, Infant Nutrition and Growth.

Breast-fed infants grow less rapidly after the first 2 to 3 months of age than current standards. The DARLING study (Davis Area Research on Lactation, Infant Nutrition and Growth) was designed to evaluate whether this pattern should be considered "faltering" or is a normal outcome even under optimal conditions. Data on intake, growth, morbidity, activity, and motor development were collected longitudinally from infants who were breast fed for at least 12 months. Gross energy intake, calculated from 4-day records of milk and food intake at 3, 6, 9, and 12 months, averaged 91.4, 84.1, 86.7, and 91.8 kcal/kg per day, respectively, well below recommended amounts of metabolizable energy. Nevertheless, infants usually left some food unconsumed. Growth velocity was also below current reference data and was weakly correlated with energy intake. There were no significant negative associations between energy intake at any time and incidence, prevalence, or duration of any category of morbidity during the subsequent 3 months. There were no consistent associations between energy intake and activity level, time spent sleeping, or achievement of key developmental milestones. Similarly, infants with slower growth velocity were just as active and were ill no more often in subsequent months than infants who were growing more rapidly. Thus the deviation from current recommendations for energy intake and growth can be considered a normal pattern with no apparent deleterious consequences in our population of breast-fed infants.

Maternal versus infant factors related to breast milk intake and residual milk volume: the DARLING study.

Factors related to milk volume and sources of variance in intake were examined using data at 3 months from the longitudinal Davis Area Research on Lactation, Infant Nutrition and Growth study. Milk intake of 73 exclusively breast-fed infants was measured by 4-day test-weighing, correcting for insensible water loss. Total volume extracted was assessed by a combination of test-weighing and expression of breast contents during a subsequent 24-hour period. Residual milk volume was calculated as volume extracted minus intake. Intake, volume extracted, and residual milk volume averaged 818, 914, and 109 g/d, respectively. The interindividual coefficient of variation in intake (16.3%) was greater than within-individual day-to-day variation (8.9%). In comparing those with low (less than 650 g/d) vs average intake, there was no significant difference in residual milk volume between groups (85 vs 111 g/d), indicating that infants with low intakes left as much milk unconsumed as those with higher intakes. There were no differences between groups in maternal age, parity, or anthropometric indices. Infants with low intakes were smaller and spent less time nursing, even though their mothers reportedly nursed on demand. In linear regressions, none of the maternal variables was significantly correlated with intake, volume extracted, or residual milk volume. Infant birth weight, weight at 3 months, and total time nursing were positively associated with intake. The results suggest that infant demand is the main determinant of lactation performance in populations such as this.

Determinants of energy, protein, lipid, and lactose concentrations in human milk during the first 12 mo of lactation: the DARLING Study.

Factors associated with concentrations of energy-yielding nutrients in human milk were examined at 3, 6, 9, and 12 mo postpartum in the DARLING (Davis Area Research on Lactation, Infant Nutrition and Growth) Study. Samples were obtained by complete expression of alternate breasts over 24 h. Milk energy density was highly correlated with lipid concentration; both were positively related to maternal percent of ideal body weight (%IBW) at 6, 9, and 12 mo and negatively related to milk volume at 3 mo and to parity at 12 mo. Milk protein concentration was negatively related to milk volume at 6 and 9 mo and positively related to nursing frequency at 6 mo and %IBW at 9 mo. Milk lactose concentration was positively related to milk volume at 6 and 9 mo and to continued amenorrhea at 9 mo. In a subsample who completed dietary records, protein intake was positively associated with lipid concentration after 16 wk postpartum but not before. These findings suggest that milk composition is more sensitive to maternal factors such as body composition, diet, and parity during later lactation than during the first few months.