Serum concentrations of insulin, insulin-like growth factor-I and insulin-like growth factor binding proteins are different between white and African American girls.

OBJECTIVES: To determine whether serum insulin-like growth factor (IGF)-I and IGF binding protein (IGFBP) concentrations are different between African American and white girls. STUDY DESIGN: Serum glucose and hormone concentrations were measured in blood samples collected after a 12-hour fast from 79 white and 57 African American healthy girls between 9 and 17 years of age. Tanner stages of pubic hair development were evaluated by physical examination, and body composition by dual energy x-ray absorptiometry. RESULTS: The African American girls were older and sexually more mature and had higher fat mass, higher serum insulin and free IGF-I concentrations, higher serum free IGF-I to total IGF-I ratio, but lower serum IGFBP-1 concentrations than the white girls. After controlling for sexual maturation and fat mass, the serum concentrations of total IGF-I, bound IGF-I, and IGFBP-3 in the white girls became significantly higher than those in the African American girls. The higher concentrations of total IGF-I in the white girls were due to a proportional increase in the concentrations of bound IGF-I that coincided with a similar increase in serum IGFBP-3 concentrations. CONCLUSIONS: Higher serum insulin concentrations in the African American girls are associated with lower serum IGFBP-1 concentrations and increased bioavailability of free IGF-I, which may contribute to their accelerated growth compared with their white counterparts.

Increased energy expenditure associated with repetitive involuntary movement does not contribute to growth failure in girls with Rett syndrome.

OBJECTIVE: To determine whether increased total daily energy expenditure (TDEE) associated with repetitive, involuntary movements contributes to growth failure in girls with Rett syndrome (RS). STUDY DESIGN: Fourteen girls with RS and 11 healthy girls were studied for 10 days to obtain measurements of height, weight, body circumference, and skin-fold thickness with stadiometric and anthropometric methods; whole-body potassium by potassium 40 counting; 72-hour dietary energy intakes by test weighing; 24-hour activity patterns using observational methods; and TDEE using the doubly-labeled water technique. RESULTS: TDEE, when adjusted for differences in lean body mass, did not differ significantly between girls with RS and healthy girls. Although girls with RS spent more waking hours in physical activity than their healthy counterparts (85%+/-10% vs. 73%+/-11% awake time per day, p < 0.05), their repetitive movements were not sufficiently intense to increase TDEE. However, girls with RS had significantly less lean body mass, but not body fat, which contributed to their lower absolute TDEE in comparison with that of healthy girls (845+/-251 vs. 1453+/-534 kcal/day, p < 0.01). Dietary energy intake, when adjusted for differences in body weight, was not significantly different in girls with RS compared with healthy girls. CONCLUSIONS: Increased TDEE as a result of repetitive, involuntary movements does not explain the alterations in growth and body composition of girls with RS.

Total energy expenditure and physical activity level of lactating Mesoamerindians.

Energy-sparing mechanisms may be elicited to meet increased energy requirements imposed by lactation on women who reside in poor, rural communities in developing countries. The objectives of this study were to measure total energy expenditure and its components, basal and activity energy expenditure, and to investigate their relationships with lactation performance in a total of 40 rural Mesoamerindians stratified according to postpartum body mass index. Total energy expenditure and fat-free mass were measured by the doubly labeled water method, and basal metabolic rate was determined by indirect calorimetry at 3 and 6 mo postpartum. Physical activity level was taken as the ratio of total energy expenditure to basal metabolic rate. Milk energy output, which is not included in total energy expenditure, was computed from 24-h milk intake (test-weighing) and energy concentration of milk (bomb calorimetry). Anthropometric measurements revealed negligible mobilization of tissue stores. Mean (+/- SD) total energy expenditures were 8912 +/- 1296 kJ/d and 9253 +/- 1298 kJ/d for the lower and higher body mass index groups, respectively. Adjusted for fat-free mass, total energy expenditure was higher in the lower body mass index group (P = 0.05). Adjusted for fat-free mass, basal metabolic rate did not differ between groups. Physical activity level was significantly higher in the lower body mass index group (P = 0.03). Lactation performance did not differ between groups and was not associated with total energy expenditure or its components. Despite the maintenance of energy balance and heightened energy requirements of lactation, energy-sparing mechanisms were not evident in these lactating Mesoamerindians.

PIP: The authors measured total energy expenditure and its components, basal and activity energy expenditure, and investigated their relationships with lactation performance among 40 rural Mesoamerindians stratified according to postpartum body mass index. Total energy expenditure and fat-free mass were measured by the doubly-labeled water method, and basal metabolic rate was determined by indirect calorimetry at 3 and 6 months postpartum. The ratio of total energy expenditure to basal metabolic rate identified the physical activity level, while milk energy output was computed from 24-hour milk intake test and the energy concentration of milk. Anthropometric measurements identified negligible mobilization of tissue stores. Mean total energy expenditures were 8912 kJ/day and 9253 kJ/day for the lower and higher body mass index groups, respectively. Adjusted for fat-free mass, total energy expenditure was higher in the lower body mass index group, although the basal metabolic rate did not differ between groups. The physical activity level was significantly higher in the lower body mass index group. Lactation performance did not differ between groups and was not associated with total energy expenditure or its components. Despite the maintenance of energy balance and heightened energy requirements of lactation, energy-sparing mechanisms were not evident in these lactating Mesoamerindians.

Higher total energy expenditure contributes to growth faltering in breast-fed infants living in rural Mexico.

To investigate the energy requirements of infants living under unfavorable environmental conditions in rural Mexico, we measured the total energy expenditure (TEE) of 40 Otomi infants at approximately 4 or approximately 6 mo of age. Total energy expenditure was estimated by the doubly labeled water method: 100 mg 2H2O/kg and 250 mg 18O/kg were administered orally, after which urine was collected serially for 7 or 10 d. Isotopic enrichment of urine samples was analyzed by gas-isotope-ratio mass spectrometry. Weight and length were measured monthly from birth to 6 mo. Fat free mass was estimated from 18O dilution spaces. Total energy expenditures (mean +/- SD) were 310 +/- 58 and 318 +/- 29 kJ.kg-1 x d-1 at approximately 4 and approximately 6 mo, respectively. Total energy expenditure was higher than that previously observed for breast-fed infants reared under more protected environments (268 +/- 29 kJ.kg-1 x d-1). Weight, length and weight gain were 5.9 +/- 0.8 kg, 60 +/- 2 cm and 2.9 +/- 2.4 g.kg-1 x d-1 at 4.25 mo and 7.1 +/- 0.8 kg, 65 +/- 2 cm and 1.0 +/- 1.2 g.kg-1 x d-1 at 6.27 mo. Growth faltering was evident at 6 mo by clinically significant declines in growth velocities and National Center for Health Statistics Z-scores. Body fat of the Otomi infants averaged 21 +/- 6 and 18 +/- 5 g/100 g at approximately 4 and approximately 6 mo, respectively. Higher rates of TEE narrowed the margin of energy available for growth and thereby contributed to growth faltering in the Otomi infants.

Human milk intake and growth faltering of rural Mesoamerindian infants.

To determine whether growth faltering during early infancy was attributable to inadequate intake of human milk, the nutrient intakes and growth of 30 Otomi infants from Capulhuac, Mexico, were studied at 4 or 6 mo of age. Growth was monitored monthly from 1 through 6 mo of age. The 2H dose-to-the-mother method was used to measure human milk intake. Energy, protein, lactose, and fat concentrations in milk were analyzed by standard techniques. Mean (+/- SD) human milk intakes were 885 +/- 145 and 869 +/- 150 g/d at 4 and 6 mo, respectively. Protein and lactose concentrations in milk were normal but fat and consequently energy concentrations were abnormally low. Energy intakes averaged 81 +/- 14 kcal.kg-1.d-1 at 4 mo and 72 +/- 14 kcal.kg-1.d-1 at 6 mo. Growth faltering by 6 mo was evidenced by the significant decline in growth velocities and National Center for Health Statistics Z scores. Weight gain at 6 mo was 8.1 +/- 3.5 g/d and length gain was 1.0 +/- 0.34 cm/mo. Weight-for-age and length-for-age Z scores were -0.81 +/- 0.94 and -1.51 +/- 0.83, respectively. Growth velocities were not significantly correlated with nutrient intakes. Growth faltering among the Otomi infants despite energy intakes comparable to those of breast-fed infants in more protected environments may have resulted from an increase in the need for nutrients or from a growth-limiting nutrient, other than energy, in their diet.

Lactation performance of rural Mesoamerindians.

Anthropometry, body composition and dietary intake of 30 lactating Otomi Indians of Capulhuac, Mexico, were studied to identify maternal factors which potentially limit lactation and thereby infant growth. Human milk production, milk composition, and maternal dietary intake, body weight, skinfold thicknesses, and body composition were measured at 4 and 6 months postpartum. The 2H2O dose-to-mother method was used to estimate milk production and maternal total body water (TBW). Fat-free mass (FFM) was calculated as TBW/0.73. Body fat was computed as body weight minus FFM. Human milk samples were analyzed for energy, nitrogen, lactose and fat using standard analytical methods. Maternal diet was assessed by three 24-h intake recalls. Mean (SD) milk production was 885 (146) and 869 (150) g/d at 4 and 6 months, respectively. Milk concentrations of protein nitrogen (1.23 (0.17) mg/g) and lactose (66.6 (2.8) mg/g) were comparable to, but the concentrations of fat (22.2 (6.7) mg/g) and energy (0.54 (0.06) kcal/g) were lower than, values observed in economically privileged populations. Maternal height, weight, and BMI were 1.47 (0.06) m, 50.3 (6.0) kg, and 23.4 (3.1) kg/m2, respectively. Maternal TBW, FFM and body fat were 55.8 (4.6)%, 76.4 (6.3)%, and 23.6 (6.4)%, expressed as a percentage of body weight, respectively. Maternal energy and protein intakes averaged 1708 (338) kcal/d and 40 (10) g/d, respectively. Milk production was negatively correlated with maternal body fat (P = 0.006). Energy and fat concentrations in the milk of the Otomi women were positively related to their weight (P = 0.002), BMI (P = 0.05), and body fat (P = 0.004). Energy concentrations in milk were not related to rates of milk production (r = 0.24; P = 0.23). Nor was milk production or composition significantly associated with maternal dietary intake. Lactation performance of these Otomi women correlated significantly with maternal body size and composition, but not current dietary intake.

PIP: Researchers analyzed data on 30 postpartum women from the Otomi Indian community living in rural Capulhuac, Mexico to examine interrelationships among lactation performance, maternal body size/composition, and dietary intake to learn which maternal factors limit lactation and thus infant growth. Infant food supplementation was minimal. Current diet did not affect milk production or levels of energy and fat in milk. Even though the body mass index (BMI) was lower than the normal range (19.8-26 kg/sq meter) for only 2 women, 8 women had 20% body fat indicating considerable undernutrition. Women consumed a mean of 68% and 80% of energy and protein requirements. Mean energy intakes (kcal/kg/day) at 4 and 6 months postpartum were 33.8 and 35.1 respectively, compared with the recommended 51. Mean protein intakes (g/kg/day) were 0.75 and 0.84 respectively compared with the recommended 1.1 3-day intake records based on memory, estimation of portion sizes, food preparation, and food composition data led to the above energy intake results, but they may not have been accurate since a mean of 35 would not allow much physical activity. Fats and carbohydrates mainly from maize made up 17% and 76% respectively of the Otomi diet suggesting a suboptimal diet. Yet human milk production rates (885 g/day at 4 months and 869 g/day at 6 months) tended to equal or be higher than those of women of higher socioeconomic status (711-925 g/day) and other poor women (525-789 g/day). The greater the levels of maternal body fat the smaller the amount of milk women produced (p=.006). Total nitrogen, protein nitrogen, lactose, and nonprotein nitrogen levels fell within the range of that of privileged women. Fat and energy levels in the milk were lower than those of privileged women, however heavy women (p=.002) with high BMI (p=.05) and body fat (p=.004) levels tended to have high levels of energy and fat in the milk. Energy levels in milk were not linked with milk production. Neither milk production nor composition were related to dietary intake.

Utilization of dietary cereal by young infants.

The direct demonstration of cereal utilization by 16 healthy 1-month-old infants was achieved by tracing the appearance in breath CO2 of carbon derived from the fed cereal. These oxidation rates were compared with rates obtained from the feeding of glucose and glucose polymers. Fermentation of unabsorbed carbohydrate by the colonic flora was assessed by measurement of breath H2. Stools from four infants were analyzed for the quantity of carbon that originated from the cereal. Oxidation rates were not significantly different (mean = 31.2% of the dose fed). Mean peak hydrogen production was 39.8, 29.1, and 18.6 ppm for cereal, glucose polymers, and glucose, respectively. Cereal carbon was detected in the stools of two infants (3.7% and 13.1% of the ingested load). We conclude that young infants can utilize cereal, although absorption is not always complete. Hydrogen production increases with carbohydrate complexity; participation of colonic bacterial fermentation increases the net absorption of cereal.