Macrosomia is associated with high weight-for-height in children aged 1-3 years in Shanghai, China.

OBJECTIVE: To investigate the association between macrosomia and high weight-for-length/height in 1-3 years old Chinese infants. DESIGN: A retrospective longitudinal study. SUBJECTS: 918 children aged 1-3 years in Shanghai, China. MEASUREMENTS: Body weight and length/height, illness status and feeding modalities were obtained during follow-up. Macrosomia was defined as birth weight >/=90th percentile of sex specific birth weight distribution. High weight-for-length/height was defined as a weight-for-length/height z-score >/=1.68 using the WHO growth reference. RESULTS: The odds ratios (ORs) for high weight-for-length/height were 3.60 (95% confidence interval (CI), 1.74-7.42) for boys and 1.39 (95% CI, 0.51-3.81) for girls who were macrosomic compared with the nonmacrosomic counterparts after adjustment for age. The ORs were attenuated to 3.48 (95% CI, 1.63-7.43) for boys and were still nonsignificant for girls (OR, 1.38; 95% CI, 0.49-3.91) after further controlling for illness status, the age of breast-feeding cessation and the age at introduction of complementary foods. From the analysis of boys and girls combined, the ORs were 2.48 (95% CI, 1.40-4.40) with adjustment for age and sex and 2.33 (95% CI, 1.29-4.22) with all covariates. CONCLUSION: Macrosomia is an important predictor for high weight-for-length/height in Chinese children aged 1-3 years.

Ultrasound measurement of fetal size in rural Guatemala.

OBJECTIVES: To describe the fetal growth pattern of a population from rural Guatemala and determine when during gestation growth faltering becomes evident. METHODS: Ultrasound examinations were conducted for 319 women. Femur length (FL), biparietal diameter (BPD), abdominal (AC) and head circumference (HC) were compared with reference values. RESULTS: FL and AC were similar to reference values throughout gestation. BPD and HC were below the 50th percentile by 30 weeks' gestation and below the 10th percentile later in gestation. We expected all four dimensions to show marked growth restriction during gestation. Measurement differences may explain the results but would call into question the value of cross-study comparisons. Infants born small for gestational age were small in all measures as early as 15 weeks. CONCLUSIONS: Fetal growth faltering begins in early gestation among infants who were born small. The lack of deviation from reference data for FL and AC requires further clarification.

Iron deficiency and reduced work capacity: a critical review of the research to determine a causal relationship.

The causal relationship between iron deficiency and physical work capacity is evaluated through a systematic review of the research literature, including animal and human studies. Iron deficiency was examined along a continuum from severe iron-deficiency anemia (SIDA) to moderate iron-deficiency anemia (MIDA) to iron deficiency without anemia (IDNA). Work capacity was assessed by aerobic capacity, endurance, energetic efficiency, voluntary activity and work productivity. The 29 research reports examined demonstrated a strong causal effect of SIDA and MIDA on aerobic capacity in animals and humans. The presumed mechanism for this effect is the reduced oxygen transport associated with anemia; tissue iron deficiency may also play a role through reduced cellular oxidative capacity. Endurance capacity was also compromised in SIDA and MIDA, but the strong mediating effects of poor cellular oxidative capacity observed in animals have not been demonstrated in humans. Energetic efficiency was affected at all levels of iron deficiency in humans, in the laboratory and the field. The reduced work productivity observed in field studies is likely due to anemia and reduced oxygen transport. The social and economic consequences of iron-deficiency anemia (IDA) and IDNA have yet to be elucidated. The biological mechanisms for the effect of IDA on work capacity are sufficiently strong to justify interventions to improve iron status as a means of enhancing human capital. This may also extend to the segment of the population experiencing IDNA in whom the effects on work capacity may be more subtle, but the number of individuals thus affected may be considerably more than those experiencing IDA.

Higher arterial oxygen saturation during submaximal exercise in Bolivian Aymara compared to European sojourners and Europeans born and raised at high altitude.

Arterial oxygen saturation (SaO(2)) was measured at 3,600-3,850 m by pulse oximetry at rest and during submaximal exercise in three study groups: 1) highland Aymara natives of the Bolivian altiplano (n = 25); 2) lowland European/North American sojourners to the highlands with at least 2 months of acclimatization time to 3,600 m (n = 27); and 3) subjects of European ancestry born and raised at 3,600 m (n = 22). Aymara subjects maintained approximately 1 percentage point higher SaO(2) during submaximal work up to 70% of their maximal work capacity, and showed a smaller rate of decline in SaO(2) with increasing work compared to both European study groups. The higher-exercise SaO(2) of Aymara compared to Europeans born and raised at 3,600 m suggests genetic adaptation. The two European study groups, who differed by exposure to high altitude during their growth and development period, did not show any significant difference in either resting or exercise SaO(2). This suggests that the developmental mode of adaptation is less important than the genetic mode of adaptation in determining exercise SaO(2). A weak correlation was detected (across study groups only) between the residual forced vital capacity (FVC) and the residual SaO(2) measured at the highest level of submaximal work output (P = 0.024, R = 0.26). While firm conclusions based on this correlation are problematic, it is suggested that a part of the higher SaO(2) observed in Aymara natives is due to a larger lung volume and pulmonary diffusion capacity for oxygen. Results from this study are compared to similar studies conducted with Tibetan natives, and are interpreted in light of recent quantitative genetic analyses conducted in both the Andes and Himalayas.

Iron supplementation improves endurance after training in iron-depleted, nonanemic women.

Our objective was to investigate the effects of iron depletion on adaptation to aerobic exercise, assessed by time to complete a 15-km cycle ergometer test. Forty-two iron-depleted (serum ferritin <16 microg/l), nonanemic (Hb >12 g/dl) women (18-33 yr old) received 100 mg of ferrous sulfate (S) or placebo (P) per day for 6 wk in a randomized, double-blind trial. Subjects trained for 30 min/day, 5 days/wk at 75-85% of maximum heart rate for the final 4 wk of the study. There were no group differences in baseline iron status or in 15-km time. Iron supplementation increased serum ferritin and decreased transferrin receptors in the S compared with the P group. The S and P groups decreased 15-km time and respiratory exchange ratio and increased work rate during the 15-km time trial after training. The decrease in 15-km time was greater in the S than in the P group (P = 0.04) and could be partially attributed to increases in serum ferritin and Hb. These results indicate that iron deficiency without anemia impairs favorable adaptation to aerobic exercise.

Effect of developmental and ancestral high-altitude exposure on VO(2)peak of Andean and European/North American natives.

Peak oxygen consumption (VO(2)peak) was measured in 150 adult males (18-35 years old) in Bolivia, using a complete migrant study design to partition developmental from ancestral (genetic) effects of high-altitude (HA) exposure. High-altitude natives (HANs, Aymara/Quechua ancestry, n = 75) and low-altitude natives (LANs, European/North American ancestry, n = 75) were studied at high altitude (3,600-3,850 m) and near sea level (420 m). HAN and LAN migrant groups to a nonnative environment were classified as: multigeneration migrants, born and raised in a nonnative environment; child migrants who migrated to the nonnative environment during the period of growth and development (0-18 years old); and adult migrants who migrated after 18 years of age. Variability in VO(2)peak due to high-altitude adaptation was modeled by covariance analysis, adjusting for fat-free mass and physical activity (training) differences between groups. A trend for increased VO(2)peak with increasing developmental high-altitude exposure in migrant groups did not reach statistical significance, but low statistical power may have limited the ability to detect this effect. HANs and LANs born, raised, and tested at high altitude had similar VO(2)peak values, indicating no genetic effect, or an effect much smaller than that reported previously in the literature. There was no functional correlation between forced vital capacity and VO(2)peak, within or across groups. These results do not support the hypothesis that Andean HANs have been selected to express a greater physical work capacity in hypoxia.

The comparison of mixed distribution analysis with a three-criteria model as a method for estimating the prevalence of iron deficiency anaemia in Costa Rican children aged 12-23 months.

BACKGROUND: A maximum likelihood method of mixed distribution analysis (MDA) is presented as a method to estimate the prevalence of iron deficiency anaemia (IDA) in Costa Rican infants 12-23 months old. MDA characterizes the parameters of the admixed distributions of iron deficient anaemics and non-iron-deficient-anaemics (NA) from the frequency distribution of haemoglobin concentration of the total sample population. METHODS: Data collected by Lozoff et al. (1986) from 345 Costa Rican infants 12-23 months old were used to estimate the parameters of the IDA and NA haemoglobin distributions determined by MDA and the widely used three-criteria model of iron deficiency. The estimates of the prevalence of IDA by each of the methods were compared. The sensitivity and specificity of MDA compared to diagnosis by the three-criteria method were assessed. Simulations were carried out to assess the comparability of MDA and the three-criteria method in low and high prevalence scenarios. RESULTS: The mean and standard deviation (SD) of the NA haemoglobin distribution determined by both methods was 12.1 +/- 1.0 g/dL. The IDA haemoglobin distribution determined by MDA had a mean and SD of 10.2 +/- 1.3 g/dL while the IDA distribution by the three-criteria method had a mean and SD of 10.4 +/- 1.3 g/dL. The prevalences of IDA as estimated by MDA and the three-criteria method were 24% and 29%, respectively. The sensitivity and specificity of MDA were 95% and 97%, respectively. The performance of MDA was similar to the three-criteria method at a simulated high prevalence of IDA and less similar at a low prevalence of IDA. CONCLUSIONS: Compared to the reference three-criteria method MDA provides a more accurate estimate of the true prevalence of IDA than the haemoglobin cutoff method in a population of children aged 12-23 months with a moderate to high prevalence of IDA. MDA is a less costly method for estimating the severity of IDA in populations with moderate to high prevalences of IDA, and for assisting in the design, monitoring and evaluation of iron intervention programmes.

PIP: A maximum likelihood method of mixed distribution analysis (MDA) is presented as a method to estimate the prevalence of iron deficiency anemia (IDA) in Costa Rican infants aged 12-23 months old. MDA characterizes the parameters of the ad-mixed distributions of iron deficient anemics and non-iron-deficient anemics (NA) from the frequency distribution of hemoglobin concentration of the total sample population. Data collected by Lozoff et al. from 345 Costa Rican infants aged 12-23 months old were used to estimate the parameters of the IDA and NA hemoglobin distributions determined by MDA and the 3-criteria model of iron deficiency. The mean and standard deviation (SD) of the NA hemoglobin distribution determined by both methods was 12.1 +or- 1.0 g/dl. The IDA hemoglobin distribution determined by MDA had a mean and SD of 10.2 +or- 1.3 g/dl, while the IDA distribution by the 3-criteria method had a mean and SD of 10.4 +or- 1.3 g/dl. The prevalences of IDA as estimated by MDA and the 3-criteria method were 24% and 29%, respectively. The sensitivity and specificity of MDA were 95% and 97%, respectively. MDA performed similarly to the 3-criteria method at a simulated high prevalence of IDA and less similar at a low prevalence of IDA.

Hemoglobin correction factors for estimating the prevalence of iron deficiency anemia in pregnant women residing at high altitudes in Bolivia.

This study had two primary objectives: 1) to derive a method to determine hemoglobin cutoffs that could be used to better estimate the prevalence of iron deficiency anemia in pregnancy at high altitudes and 2) to estimate the prevalence of anemia in a sample of pregnant women residing in two cities in Bolivia, La Paz (3,600 meters) and El Alto (4,000 meters). We derived a hemoglobin-altitude curve from previously published data on the mean hemoglobin concentrations of nonanemic women of childbearing age at various altitudes. In addition, we abstracted data on hemoglobin concentration during pregnancy from medical records of women from La Paz and El Alto who had given birth at a maternity hospital in La Paz between January and June of 1996. Using our approach and two other previously published, currently used methods, we calculated and compared prevalences of iron deficiency anemia in this population using hemoglobin cutoffs determined from a hemoglobin-altitude curve corrected for pregnancy. The hemoglobin-altitude curve derived in this study provided a better fit to data for women of childbearing age than the two other models. Those models used cutoffs based on non-iron-replete populations of children or men, both of which were residing below 4,000 m, and then extrapolated to women and higher altitudes. The estimated prevalences of iron deficiency anemia in pregnancy using the hemoglobin cutoffs determined in this study were higher than those estimated by the two other approaches.

Altered metabolic response of iron-depleted nonanemic women during a 15-km time trial.

In this double-blinded study, 37 women with iron depletion without anemia (age 19-36 yr) were randomly assigned to receive either an iron supplement (135 mg/day) or a placebo. Endurance capacity was assessed during a 15-km simulated time trial (TT) on a cycle ergometer before and after the 8-wk treatment. After the treatment, although the iron-supplemented group did not have shorter time to finish the TT (time), it had 2.0 kJ/min lower energy expenditure and 5.1% lower fractional utilization of peak oxygen consumption during the TT compared with the placebo group, after controlling for work rate (P < 0.05). Time, fractional utilization of peak oxygen consumption, and plasma lactate concentration at the 5th km of the TT were all negatively associated with hemoglobin levels, after controlling for work rate (P < 0.05). In conclusion, repletion of iron stores to women with iron depletion without anemia increased their energetic efficiency, and oxygen transport capacity of the blood was found to be an important determinant of endurance capacity and energy metabolism in nonanemic women.

Response of serum transferrin receptor to iron supplementation in iron-depleted, nonanemic women.

Serum transferrin receptor (sTfR) concentration has been recognized recently as a reliable indicator of functional iron deficiency, but its response to iron supplementation has not been investigated in marginally iron-deficient women. In this randomized, double-blinded trial, 37 female subjects aged 19-35 y with iron depletion without anemia (hemoglobin > 120 g/L and serum ferritin < 16 microg/L) received an iron supplement or placebo for 8 wk. Iron status was measured before treatment, after 4 wk of treatment, and posttreatment (ie, after 8 wk of treatment). Iron supplementation of these iron-depleted, nonanemic women resulted in a progressive and significant decrease in sTfR and a significant increase in serum ferritin, and prevented a fall in hemoglobin. The responsiveness of sTfR to iron treatment indicated that sTfR is a sensitive indicator of marginal iron deficiency in iron-depleted, nonanemic women, even when their body iron stores were being replenished.

Iron depletion without anemia and physical performance in young women.

Studies in laboratory animals found that iron deficiency without anemia decreased oxidative capacity and increased reliance on carbohydrate as the substrate for energy, thereby causing impaired endurance. The purpose of this cross-sectional study was to investigate the relation between iron deficiency without anemia and physical performance in healthy active women aged 19-36 y. Iron-status assessment included determination of hemoglobin, hematocrit, transferrin saturation, and serum ferritin values. Dietary iron intake was assessed by frequency questionnaires and physical activity level was estimated by frequency questionnaires and 2-wk records. Fifteen women with normal iron status and 15 women with iron depletion (serum ferritin < 12 micrograms/L) were chosen randomly from a group of 69 nonanemic women and given physical-performance tests, including determinations of maximum oxygen consumption (VO2max), ventilatory threshold, and delta-efficiency. There were no significant differences between the two groups in body size, body composition, physical activity level, dietary iron intake, delta-efficiency, or ventilatory threshold. Compared with the iron-depleted group, the iron-sufficient group had significantly higher hemoglobin, transferrin saturation, and serum ferritin values and a significantly greater tendency to use iron supplements. When physical activity level and fat-free mass were controlled for, the iron-depleted group had a significantly lower VO2max. The difference in VO2max was significantly associated with serum ferritin concentration; hemoglobin value was not a significant confounder. Therefore, reduction of VO2max in nonanemic women with iron depletion was likely caused by factors related to reduced body iron storage but was unrelated to decreased oxygen-transport capacity of the blood.

Evidence of a role for fat-free body mass in modulation of plasma carotenoid concentrations in older men: studies with hydrodensitometry.

We examined the relationship between body composition and changes in plasma carotenoid concentration in response to dietary carotenoid restriction or beta-carotene (betaC) supplementation in healthy older men. Subjects (mean age 65 y) were assigned randomly to supplement (30 mg betaC/d) or placebo groups, and all subjects consumed a standard low carotenoid basal diet plus 1.5 mg betaC/d as carrots. Body composition was measured at baseline by hydrodensitometry, and plasma carotenoids were measured at baseline and after 28 d of treatment by HPLC. Baseline plasma total carotenoid concentration was significantly and negatively correlated with body mass index (BMI) and fat-free mass (FFM) but not with fat mass, whereas baseline betaC concentration was negatively associated with all three variables. The increase in plasma betaC concentration in response to betaC supplementation was significantly and inversely correlated with BMI and FFM but not with fat mass. Likewise, the decline in plasma total carotenoid concentration in the placebo group was also significantly and inversely related to BMI and FFM but not to fat mass. Thus, FFM seems to be an important determinant of plasma carotenoid concentrations and to explain a substantial portion of the often-observed relationship between BMI and blood carotenoid levels. Fat-free mass seems to represent a dynamic reservoir that dampens short-term changes in plasma carotenoid concentrations during fluctuation in carotenoid intake.

Early nutrition and later physical work capacity.

PIP: Several important studies within the past 20 years have examined the impact of acute nutrient deficiencies upon physical work capacity. Spurr et al. and Satyanarayana et al. extended that line of research to explore the apparent effects of chronic or lifelong undernutrition upon the work capacity of adolescent males. These studies conducted in Colombia and India, as well as others in Tanzania and Guatemala, are discussed. The authors believe that there is enough evidence to conclude that poor early childhood nutritional status, as indicated by the low dietary energy intakes and subsequent stunted growth, leads to many undesirable functional consequences. The studies of physical work capacity, together with other measures such as cognitive functioning and reproductive performance, provide strong evidence in support of policies and programs designed to eliminate the causes of environmental stunting in poor populations.^ieng

Nutritional supplementation during the preschool years influences body size and composition of Guatemalan adolescents.

Effects of supplementary feeding during early childhood on body size and composition at adolescence are examined in a population with marked growth failure in the first 3 y of life. The data came from a supplementation trial conducted in rural Guatemala from 1969 to 1977 and a 1988-89 follow-up study of the same subjects at adolescence. Two pairs of villages participated in the trial. One village from each pair received a high protein-energy supplement (Atole), which significantly improved dietary intakes, whereas the other village of the pair received a low-energy, no-protein supplement (Fresco), which did not impact appreciably on dietary intakes. Children from Atole villages grew better during the preschool period than children from Fresco villages. At adolescence, subjects from Atole villages were taller, weighed more and had greater fat-free masses than subjects from Fresco villages. Differences in height at adolescence were slightly reduced in magnitude relative to differences at 3 y of age. However, differences in weight were increased in adolescence relative to 3 y of age.

Nutritional supplementation during the preschool years and physical work capacity in adolescent and young adult Guatemalans.

A follow-up study (1988-89) was carried out in 364 rural Guatemalans, 11-27 y of age, who earlier had participated in a nutritional supplementation experiment. Among its objectives was the assessment of the long-term effects of the nutrition intervention on physical work capacity. Subjects and their mothers from two villages had available a high-energy, high-protein supplement (Atole: 163 kcal/682 kJ and 6.4 g protein per serving or 180 mL), whereas in two other villages a low-energy, no-protein supplement (Fresco: 59 kcal/247 kJ per 180 mL) was provided. Consumption was ad libitum. Maximum oxygen consumption (VO2max) at follow-up was significantly greater in Atole compared with Fresco subjects of both sexes. In subjects 14-19 y, exposed to supplementation throughout gestation and the first 3 y of life, Atole males had a significantly higher VO2max (2.62 L/min) than Fresco males (2.24 L/min), the differences remaining significant even after controlling for body weight and fat-free mass; also, there was a significant positive relationship between amount of supplement consumed and VO2max. The supplementation effect in females of similar age was not statistically significant. It is concluded that early nutritional improvements can have long-lasting effects on physical performance.

Early nutritional supplementation and skeletal maturation in Guatemalan adolescents.

The effect of early childhood nutritional supplementation on skeletal maturation at adolescence was investigated in 663 rural Guatemalans, aged 11-18 y. Skeletal maturation was assessed by the Tanner-Whitehouse-2 method. The subjects were former participants in the Institute of Nutrition of Central America and Panama longitudinal study of growth and development (1969-77) residing in four villages (two large and two small) in eastern Guatemala. The villages were randomized within pairs to receive either a high energy, high protein supplement (Atole) or a low energy supplement with no protein (Fresco). Skeletal maturity was observed across all villages to be delayed significantly relative to a British reference for boys < 14 y of age, but not for older boys or for girls < 14 y of age. Delays in girls > 14 years could not be determined reliably because many had reached maturity. Girls < 14 years from Atole villages were more advanced in skeletal maturity than similar age girls from Fresco villages but these differences were found only in comparisons of the large villages. The relationship between early nutrition and biological maturation at adolescence may be obscured in this sample by the advanced age at which the subjects were examined in adolescence.

Overweight schoolchildren in New York State: prevalence and characteristics.

OBJECTIVES: Childhood overweight is an increasing public health concern. This study was undertaken to determine the prevalence of overweight in elementary school children in New York State and to identify characteristics associated with child fatness. METHODS: Weight, height, triceps skinfold, midarm circumference, and a 24-hour dietary recall were taken on 1797 second- and fifth-grade students from 51 randomly selected schools in New York State outside of New York City. Parents completed a brief questionnaire. RESULTS: In comparison with 1974 and 1980 national reference data, up to twice the expected percentages of children had values above the 85th, 90th, and 95th percentiles for body mass index, triceps skinfold, and arm fat area. Regression analyses suggested that children who tended to be fatter were members of low socioeconomic status, two-parent (but not single-parent) households; those with few or no siblings; those who ate school lunch; and those who skipped breakfast. CONCLUSIONS: The findings suggest that overweight is a problem among many elementary school children in New York State and that sociodemographic characteristics may be useful for targeting preventive efforts.

Testing the effects of nutrient deficiencies on behavioral performance.

The association between specific nutrient deficiencies and poor performance on behavioral tests has been documented for several nutrients. The determination of causality, however, remains elusive. This paper presents the essential criteria for a valid test of causality. Findings from experimental studies in which a nutritional treatment was randomly allocated can be summarized in a statistical statement about the probability that the nutrient treatment caused the behavioral response. Criteria for assessing the internal validity of these studies are examined in terms of whether alleviation of a nutrient deficiency did or did not produce a detectable behavioral response. The plausibility of such a causal inference is dependent on its congruency with known or theorized biological and behavioral mechanisms. External validity describes the extent to which inferences from internally valid studies may be applicable to other populations or circumstances. In addition to these scientific considerations, some of the ethical issues of nutrient-treatment trials are also discussed. All of these considerations provide a better basis for judging whether public health action would be worthwhile than do observed associations that could actually be due to other causes.

Serum alkaline phosphatase activity and skeletal maturation in Guatemalan adolescents.

Serum alkaline phosphatase activity (AP), stature and Tanner-Whitehouse-2 RUS skeletal age (SA) were determined for 873 rural Guatemalan youth and young adults 11-25 years of age. Mean AP decreases systematically with chronological age (CA) in girls, while an adolescent increase in mean AP occurs at 14 years in boys. When mean AP is calculated within SA groups, clear adolescent increases are apparent in girls, peaking at 11 years SA, and at 14 years SA in boys. Correlations between AP and relative skeletal age (SA-CA) decrease systematically from moderately positive at the youngest CA groups to moderately negative at the older ages, crossing zero at the chronological ages of maximum adolescent AP values. Analyses suggest the patterns of mean AP in adolescence follow closely the timing and patterns of growth velocity in stature in each sex, and are only indirectly related to SA as it is a proxy for the maturational timing of the adolescent spurt in stature.

Predicting body composition from anthropometry and bioimpedance in marginally undernourished adolescents and young adults.

Body-composition prediction equations were developed using data from a sample of 201 female and male Guatemalan ladinos (ie, people of Amerindian-European descent) aged 11-25 y. Fat-free mass (FFM) values were estimated from body density by using the two-component model and age- and sex-specific values for the density of FFM. The root-mean-square error (RMSE) of the best model predicting FFM from a set of simple anthropometric variables was 1.59 kg for females and 1.90 kg for males. The addition of more extensive anthropometry to the set of candidate predictors reduced the RMSE to 1.42 kg for females and 1.88 kg for males. The subsequent addition of a bioelectrical impedance measure (Ht2/R) further reduced the RMSE to 1.32 kg for females and 1.82 kg for males. These results suggest that for a marginally undernourished population with relatively little body fat, simple anthropometrics are as useful as more sophisticated measures for the prediction of body composition.