Anthropometric reference data for international use: recommendations from a World Health Organization Expert Committee.

The World Health Organization (WHO) convened an Expert Committee to reevaluate the use of anthropometry at different ages for assessing health, nutrition, and social wellbeing. The Committee's task included identifying reference data for anthropometric indexes when appropriate, and providing guidelines on how the data should be used. For fetal growth, the Committee recommended an existing sex-specific multiracial reference. In view of the significant technical drawbacks of the current National Center for Health Statistics (NCHS)/WHO reference and its inadequacy for assessing the growth of breast-fed infants, the Committee recommended the development of a new reference concerning weight and length/height for infants and children, which will be a complex and costly undertaking. Proper interpretation of midupper arm circumference for preschoolers requires age-specific reference data. To evaluate adolescent height-for-age, the Committee recommended the current NCHS/WHO reference. Use of the NCHS body mass index (BMI) data, with their upper percentile elevations and skewness, is undesirable for setting health goals; however, these data were provisionally recommended for defining obesity based on a combination of elevated BMI and high subcutaneous fat. The NCHS values were provisionally recommended as reference data for subscapular and triceps skinfold thicknesses. Guidelines were also provided for adjusting adolescent anthropometric comparisons for maturational status. Currently, there is no need for adult reference data for BMI; interpretation should be based on pragmatic BMI cutoffs. Finally, the Committee noted that few normative anthropometric data exist for the elderly, especially for those > 80 y of age. Proper definitions of health status, function, and biologic age remain to be developed for this group.

Linking maternal and infant benefits of a nutritional supplement during pregnancy and lactation.

To evaluate the effect of a nutritional supplement on change in women's weight during a reproductive cycle and on the difference in birth weight between one infant and the previous one, we analyzed data on 176 complete reproductive cycles from an experiment that was conducted in rural Guatemala. Women with an initial weight <50 kg were classified as marginally nourished or malnourished. Women whose intake of the supplement was in the top 2 tertiles were distinguished from those whose intake was in the lowest tertile. Linear regression modeling was used to estimate the effect of supplementation on these outcomes and to control for confounding factors. Malnourished women gained weight during the reproductive cycle, but their second (study) infant tended to weigh less at birth than their prior-born infant. Higher intakes of supplement were associated with a less negative difference in birth weight. Marginally nourished women lost weight during the reproductive cycle and their second (study) infant tended to weigh more at birth than their prior-born infant. Higher intakes of supplement were associated with a less negative weight [corrected] trend for the women themselves. Well-nourished women and their infants did not show any of these benefits from supplementation. These findings help explain past contradictory findings on maternal depletion as well as on the benefits of nutritional supplementation for mothers and their infants.

Screening for nutrition interventions: the risk or the differential-benefit approach?

The risk approach has been promoted to improve screening for nutrition interventions on the premise that indicators of risk also predict greater response to interventions. This study tested whether the determinants of the risk of poor growth (eg, low length-for-age) at 36 mo of age were the same as the determinants of differential benefit from food supplementation. The sample included 460 Guatemalan children who were exposed to either a high-energy, high-protein drink (atole) or a low-energy, no-protein drink (fresco) during their first 36 mo of life [INCAP (Institute of Nutrition of Central America and Panama) supplementation trial]. Low maternal stature, poor socioeconomic status, inadequate home diet, high diarrhea rates, and low anthropometry scores at 3 or 6 mo were all determinants of the risk of poor growth. Only indicators of child's thinness at 3 or 6 mo of age (low weight-for-age, weight-for-length, or midupper arm circumference) were determinants of differential benefit from supplementation. Thus, the development of screening indicators should be based on analyses of the predictors of differential benefit, not on conventional risk-factor analysis.

Effect of supplementary feeding on recovery from mild to moderate wasting in preschool children.

Three-month recovery rates from moderate wasting (less than 90% weight-for-length) were compared in 6-24-mo-old children in four Guatemalan villages that had been randomly assigned to receive a moderate (Atole) or low (Fresco) energy supplement. The recovery rate (Rr) in the Atole villages was 12% higher than in the Fresco villages (P less than 0.05). This effect was above all due to the children in the Atole villages who consumed greater than or equal to 10% of the daily recommended dietary intake of energy (RDI) from the supplement (high-Atole group) and whose total energy intake (including home diet) was 10.5% of the RDI higher than a comparable high-Fresco group with low supplemental energy intake. All those in the high-Atole group whose wasting was due to malnutrition recovered. Much of this recovery (range 29-52%) was due to the increased supplementation. This proportion rose after potential confounding variables were controlled for.

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.

Iron deficiency and behavior: criteria for testing causality.

The association between iron deficiency and poor behavioral-test performance is well established. The question of causality, however, remains unanswered. This paper presents the essential criteria for a valid test of causality. Internal validity is examined in terms of positive and negative findings. Plausibility of the findings requires analyzing the congruency of the results; for example, those who respond to the iron treatment are also those who respond behaviorally. External validity describes the extent to which inferences may be made about other populations or circumstances.

Influences in child growth associated with poverty in the 1970's: an examination of HANESI and HANESII, cross-sectional US national surveys.

This research examines associations between various measures of child growth (height, weight, triceps skinfold thickness, subscapular skinfold thickness), dietary variables, and poverty status in a sample of 13,750 black and white children aged 1 to 17 yr. The data used in this survey were collected in the National Health and Nutrition Examination Surveys I and II (HANESI, 1971-1975, and HANESII, 1976-1980). In general, lower mean values for all the growth measures examined were found in children living below the defined poverty threshold in comparison with those above the poverty threshold. The magnitude of these poverty-associated differences tended to decrease between the times of the HANESI and HANESII surveys, though not sufficiently to be statistically significant. These differences in growth were not consistently associated with differences in dietary intake of energy between poverty groups or surveys.

Effects of maternal nutritional status and maternal energy supplementation on length of postpartum amenorrhea among Guatemalan women.

To investigate the extent to which better maternal nutrition leads to reduction in length of postpartum amenorrhea, multivariate-logistic and linear-regression analyses were applied to data on 339 mother-infant pairs from the longitudinal Guatemalan Four Village Study, 1969-1977. Maternal triceps skinfold thickness was negatively associated with length of amenorrhea when infant supplementation (a proxy for reduced suckling) was accounted for. However, its effect was small: amenorrhea was only 0.5 mo shorter among women at the 75th percentile than among those at the 25th, equivalent to less than even one additional child during the women's reproductive years. Maternal supplementation was not associated with length of amenorrhea when infant supplementation was controlled. This is in contrast to previous studies in which breast-feeding or infant supplementation was not controlled. These results suggest that infant, not maternal, supplementation influences length of postpartum amenorrhea, and that maternal nutritional status has minimal influence.

Breast milk or animal-product foods improve linear growth of Peruvian toddlers consuming marginal diets.

Although breast-feeding is widely accepted as important for infant health, its benefits during the second year of life have been questioned. We analyzed data from 107 breast-fed and weaned Peruvian children living in a periurban community to determine whether breast milk contributed to improved linear growth between 12 and 15 mo of age. Breast-feeding frequency was self-reported; intakes of complementary foods and animal products were estimated from a food-frequency survey. Multivariate-linear-regression analysis was used to predict the length of the children at 15 mo of age. Determinants of length included length and weight-for-length at 12 mo of age (US National Center for Health Statistics standards), interval between 12- and 15-mo measurements, breast-feeding frequency, incidence of diarrhea, and intakes of complementary and animal-product foods. Complementary foods, animal-product foods, and breast milk all promoted toddlers' linear growth. In subjects with low intakes of animal-product foods, breast-feeding was positively associated (P < 0.05) with linear growth. There was a 0.5-cm/3 mo difference in linear growth between weaned toddlers and children who consumed the average number of feedings of breast milk. Linear growth was also positively associated with intake of animal-product foods in children with low intakes of complementary foods. The negative association between diarrhea and linear growth did not occur in subjects with high complementary-food intakes. When the family's diet is low in quality, breast milk is an especially important source of energy, protein, and accompanying micronutrients in young children. Thus, continued breast-feeding after 1 y of age, in conjunction with feeding of complementary foods, should be encouraged in toddlers living in poor circumstances.

PIP: The contribution of prolonged breast feeding to linear growth at 12-15 months of age was investigated in 107 breast-fed and weaned toddlers from a low-income neighborhood in Lima, Peru. The median duration of breast feeding in this sample was 17.1 months; by 15 months, 46 children had been weaned. The prevalence of stunting (length-for-age score -2 SD below the reference standard) was 17.8% at 12 months and 24.3% at 15 months; no child was wasted. Complementary foods, animal product foods, and breast milk all promoted toddlers' linear growth. In children with low intakes of animal product foods, breast feeding was positively associated with linear growth at 15 months (p 0.05). There was a 0.5 cm/3 months difference in linear growth between weaned toddlers and those who consumed the average number (6.3/day) of breast feeds. Linear growth was further positively associated with intake of animal product foods in children with low intakes of complementary foods. The negative association between diarrhea and linear growth did not occur in children with high intakes of complementary foods. When the household diet is of poor quality, breast feeding is an especially important source of energy, protein, and micronutrients in toddlers and should be continued beyond 12 months of age in conjunction with the provision of complementary foods. Breast milk not only added to the total diet of these young children, but also potentiated the beneficial effects of complementary foods consumed by increasing their growth promotion capacity.

Influence of maternal nutrition on birth weight.

This paper discusses some conditions necessary to detect an effect of maternal nutrition on birth weight and the relative contribution of calories and protein to such an effect. The expected dose- and time-response relationships for nutritional interventions aimed at the improvement of birth weight are also discussed. There appears to be a minimal level of nutrients which must be available in order to obtain adequate birth weight. However, above this minimum level, pregnant women can adapt themselves to a wide variety of food intake, both in quantity and quality, without affecting birth weight. The relative contribution of calories and protein to an increase in birth weight depends on the limiting nutrients of the home diet in the population under study. Other factors like physical activity, prevalence of disease and magnitude of the maternal nutritional stores before pregnancy are also important determinants of the relative contribution of calories and protein to birth weight. The anticipated input of a nutritional intervention on birth weight should range between 25 and 84 g of birth weight/10,000 kcal ingested during pregnancy. This estimate was computed from analyses based on four sources of published data: weight gain during pregnancy, prepregnant weight, fetomaternal body composition, and food intake during pregnancy. The expected reduction in proportion of low birth weight (LBW less than 2.5 kg) babies following a nutritional intervention will depend not only on the estimated range of fetal weight increase but also on the total amount of supplemented calories ingested during pregnancy as well as on the existent proportion of low birth weight babies prior to the intervention. The offspring of women who have low prepregnant weight, poor diet, low level of replacement of the home diet by the supplement, low physical activity during pregnancy and good health status will show larger increase in birth weight per unit of supplemented calories. Finally, nutritional interventions during pregnancy as opposed to earlier in the life of the mother, should have the higher impact on birth weight. In consequence, interventions as of pregnancy are recommended.

PIP: This paper discusses some conditions necessary to detect an effect of maternal nutrition on birthweight and the relative contribution of calories and protein to such an effect. The expected dose- and time-response relationships for nutritional interventions aimed at the improvement of birthweight are also discussed. There appears to be a minimal level of nutrients which must be available in order to obtain adequate birthweight. However, above this minimum level, pregnant women can adapt themselves to a wide variety of food intake, both in quantity and quality, without affecting birthweight. The relative contribution of calories and protein to an increase in birthweight depends on limiting nutrients of the home diet in the population under study. Other factors like physical activity, prevalence of disease, and magnitude of the maternal nutritional stores prior to pregnancy are also important determinants of the relative contribution of calories and protein to birthweight. The anticipated input of a nutritional intervention on birthweight should range between 25-84 g of birthweight/10,000 kcal ingested during pregnancy. This estimate was computed from analyses based on 4 sources of published data: weight gain during pregnancy, prepregnant weight, fetomaternal body composition, and food intake during pregnancy. The expected reduction in proportion of low birthweight (LBW or= 2.5 kg) babies following a nutritional intervention will depend not only on the estimated range of fetal weight increase but also on the total amount of supplemented calories ingested during pregnancy as well as on the existent proportion of low birthweight babies prior to the intervention. The offspring of women who have low prepregnant weight, poor diet, low level of replacement of home diet by the supplement, low physical activity during pregnancy, and good health status will show larger increase in birthweight/unit of supplemented calories. Finally, nutritional interventions during pregnancy as opposed to earlier in the life of the mother, should have the highest impact on birthweight. Consequently, interventions as of pregnancy are recommended.

Serum retinol concentrations in children are affected by food sources of beta-carotene, fat intake, and anthelmintic drug treatment.

The provision of vitamin A in food sources of beta-carotene is an alternative to the distribution of high-dose capsules. To examine factors that may influence the success of food-based programs, a study was carried out in Sumatra, Indonesia, of the effect of food sources of beta-carotene, extra dietary fat, and Ascaris lumbricoides infection on serum retinol concentrations in children. Meals and snacks with various amounts of beta-carotene and fat were fed at midday to children 3-6 y of age for 3 wk. Some groups of children were dewormed with the anthelmintic levamisole before the feeding period, whereas others remained infected. Results showed that the incorporation of beta-carotene sources (mainly in the form of red sweet potatoes) into the meal significantly increased serum retinol concentrations. The greatest rise in serum retinol occurred when meals contained added beta-carotene sources and added fat and the children were dewormed. Adding more fat to the meal and deworming the children caused a rise in serum retinol similar to that seen when feeding additional beta-carotene sources. Moreover, the effects of fat and deworming together were additive to the effects of additional beta-carotene sources. When the meal contained additional beta-carotene sources, added fat caused a further improvement in serum retinol concentrations but only if A. lumbricoides infection was low. These studies indicated that food-based interventions in vitamin A-deficient areas might be successful and that other interventions such as increasing dietary fat concentrations and anthelmintic treatment should be considered along with increasing consumption of beta-carotene-rich food.

Head and chest circumferences in rural Guatemalan Ladino children, birth to seven years of age.

Growth patterns in head and chest circumferences are reported for a mixed-longitudinal sample of rural Guatemalan Ladino children from birth to 7 years of age. The sample is representative of a population with suboptimal nutrition. Both circumferences show similar rapid growth from birth through 9 months, after which chest circumference continues to increase more rapidly, while head circumference increases at a slower rate. Chest circumference provides nutritional information apparently not contained in length and weight. Compared to a sample of well-nourished children from Denver, the head circumferences of Guatemalan children are consistently smaller. Differences are relatively small at birth, are well established by 6 months, and become progressively greater through 24 months. After 2 years the mean smaller head circumference of the Guatemalan children also reflects stunted growth during the first 2 years of life. Similarly, among 5-year-old Guatemalan children of similar stature, head circumference at 5 years of age indicates which of these children were more stunted in stature at 2 years of age.

Nutritional supplementation: effects on child stunting because of diarrhea.

Research has shown that the positive effect of nutritional supplementation on child growth in malnourished populations is small relative to the large negative effect of diarrheal disease. To test the hypothesis that the effects of supplementation and diarrhea are synergistic in that supplementation modifies the negative effect of diarrhea on linear growth, length and diarrheal morbidity were compared at 36 mo of age for two cohorts of Colombian children: supplemented from birth and unsupplemented. Among unsupplemented children diarrhea was negatively associated with length. Among supplemented children diarrhea had no effect on length and differed from that of unsupplemented children. Thus, supplementation completely offset the negative effect of diarrheal disease on length. Targeting supplementation programs to the critical period of high diarrheal prevalence among infants and young children should increase the effectiveness of such programs in preventing growth retardation associated with diarrhea.

PIP: To test the hypothesis that supplementation modifies the negative effect of diarrhea on linear growth, body length and diarrheal morbidity were compared at 36 months of age for 2 cohorts of Columbian children: those receiving supplements from birth and those not receiving supplements. The sample was a subset from a longitudinal study that took place in Bogota, Columbia, between 1973 and 1980 and consisted of 456 families randomly assigned to 6 experimental groups. There were 148 children in the unsupplemented group. The 140 children from the supplemented group received supplements from the 6th month of pregnancy until they were 36 months old. The supplementary feeding included 30 g of protein daily, and 7.5 mg or 15 mg of ferrous sulphate daily as well as vitamin A every 6 months. Supplemented children had a mean 16 episodes of diarrhea, compared with a mean of 18 episodes of the unsupplemented cohort, and they spent a total of 73 days ill, compared with 83 days ill for unsupplemented children. Linear regression analysis showed that the slopes for unsupplemented children were significantly different from 0 (p 0.001). Each day with diarrhea was associated with a reduction of about 0.03 cm in attained length at age 36 months. In contrast, for supplemented children diarrhea had no effect on attained length at age 36 months. 2-way analysis of variance showed that the difference between supplemented and unsupplemented children in attained length in the lowest quartile of diarrhea was small, but the difference in the highest quartile was almost 5 cm. Cumulative growth patterns of children in the high quartile of diarrheal disease revealed that the difference between unsupplemented children was a median of 13 cm, thus supplementation made up nearly 40% of the deficit, compared with the reference standard (5 cm/13 cm). Targeting supplementation programs to the critical period of high diarrheal prevalence among infants and young children should help prevent growth retardation associated with diarrhea.

Adherence to iron supplementation during pregnancy in Tanzania: determinants and hematologic consequences.

Limited adherence to iron supplementation is thought to be a major reason for the low effectiveness of anemia-prevention programs. In rural Tanzania, women at 21-26 wk of gestation were randomly given either 120 mg of a conventional (Con) iron supplement or 50 mg of a gastric-delivery-system (GDS) iron supplement for 12 wk. Adherence was assessed by using a pill bottle equipped with an electronic counting device. Adherence in the GDS group was 61% compared with 42% for the Con group. In both groups, women experiencing side effects had about one-third lower adherence. Fewer side effects were observed in the GDS group. In a subgroup of women with a low initial hemoglobin concentration (< or = 120 g/L), the response to the iron supplements suggested that both of the applied doses were unnecessarily high for adequate hematologic response in a population with a marginal hemoglobin concentration. The GDS group appeared to require a dose one-fourth as high as that of the Con group for an equal effect on improving hemoglobin to normal concentrations.

Nutritional status and the timing of deciduous tooth eruption.

The number of deciduous teeth in a sample of rural Ladino Guatemalan children was counted every 3 months through 24 months of age, and at 6-month intervals from 24 to 36 months. Nutritional status at birth, whether expressed as full-term birth weight or as maternal caloric supplementation during pregnancy, influences the timing of deciduous tooth eruption. Furthermore, the timing of deciduous tooth eruption seems more closely associated with postnatal weight than with birth weight. Although indices of nutritional deficiencies are associated with retarded tooth eruption, the use of mean number of deciduous teeth erupted as an estimate of mean chronological age in populations living under conditions of mild-to-moderate malnutrition is relatively accurate because errors of age estimation based on mean values for the present sample only vary between 1 and 2 months.

Age-specific responsiveness of weight and length to nutritional supplementation.

Evaluation of the responsiveness of weight and length to supplementary feeding shows that the two periods of greatest response coincide with weaning (ages 3-6 mo) and peak incidence and duration of diarrheal disease (ages 9-12 mo). Analyses were done for seven consecutive nonoverlapping intervals comparing children randomly assigned to receive supplemental feeding from birth to age 36 mo or to serve as control subjects. Absolute responsiveness was greatest between ages 3-6 mo; supplemented infants grew 0.61 cm more and gained 162 g more than did unsupplemented infants (p less than 0.005). Relative to rates of growth, responsiveness was greatest between ages 9 and 12 mo (the period of peak diarrheal prevalence), followed by ages 3-6 mo (the period of weaning). Responsiveness to supplementation is thus directly related to age-dependent risk patterns for malnutrition. Targeting supplementation programs to coincide with periods of high nutritional risk should maximize their effectiveness in reducing malnutrition, though caution should be exercised to avoid disruption of breast-feeding.

Body composition and energy intake: do overweight women overeat and underreport?

The relationship between energy consumption and body composition was evaluated in 63 women by use of energy-intake values that were precisely measured in a metabolic unit and corrected for deviations from energy balance. Energy requirement for the maintenance of body weight was not significantly correlated with adiposity expressed as percent body fat. However, energy requirement was positively associated with lean mass (p less than 0.0001) whereas fat mass added no predictive value to the same multivariate regression equation. Self-reported energy intake (before the experiments) was not correlated with lean mass and was underestimated by lean subjects at least as much as by obese subjects. Discrepant findings in the literature concerning relationships between obesity and energy intake may be explained by reporting error and by the relative lean mass of obese vs nonobese women but not by systematic underreporting unique to obese subjects.

Mother's milk and sewage: their interactive effects on infant mortality.

If they lived in households without piped water or a toilet, Malaysian infants who did not breast-feed were five times more likely to die after 1 week of age than those who breast-fed, when other significant factors affecting infant mortality were taken into account. This is double the relative risk associated with not breast-feeding for infants born into households with toilets, whether or not they had piped water. Analogously, improvements in toilet sanitation appear to have reduced mortality twice as much among infants who did not breast-feed as among those who did. These findings, from a retrospective survey of infants born to a probability sample of 1,262 women in peninsular Malaysia, confirm the pernicious synergistic effect of poor sanitation and nonbreastfeeding that was postulated previously on theoretical grounds. Promoting and maintaining high initiation of breast-feeding is thus particularly important where poor sanitation is prevalent. Even more affluent areas should not be neglected, however, because socioeconomic improvement, including improved environmental sanitation, is often accompanied by decreased breast-feeding. Although the risk to each nonbreast-fed infant was less in those areas, infants there were less likely to breast-feed in Malaysia, and hence they made up a significant proportion of lives that could be saved by breast-feeding.

Effect of food supplementation during pregnancy on birthweight.

The high prevalence of low-birthweight (less than or equal to 2,500 gm) babies in many poor communities is a major public health problem. Studies in humans in situations of acute starvation suggest an effect of maternal nutrition on birthweight, but less clear results appear under situations of moderate maternal malnutrition. We studied the effects of food supplementation during pregnancy on birthweight in four rural villages of Guatemala, in which two types of supplements were distributed: protein-caloric and caloric. The caloric supplementation increased the total caloric intake during pregnancy. In both supplements, the amount of calories supplemented during pregnancy showed a consistent association with birthweight. In the combined sample the proportion of low-birthweight babies in the high-supplement group (G greater than or equal to 20,000 supplemented calories during pregnancy) was 9% compared with 19% in the low-supplement group (less than 20,000 supplemented calories during pregnancy). The relationship between caloric supplementation and birthweight (29 gm of birthweight per 10,000 supplemented calories) was basically unchanged after controlling for the maternal home diet, height, head circumference, parity, gestational age, duration of disease during pregnancy, socioeconomic status, and different rates of missing data. Moreover, a similar association was found in consecutive pregnancies of the same mother. We concluded that caloric supplementation during pregnancy produced the observed increase in birthweight.

Use of positive-negative deviant analyses to improve programme targeting and services: example from the TamilNadu Integrated Nutrition Project.

This paper describes the characteristics of southern rural Indian children who grow best (positive deviants) and worst (negative deviants) as compared to median growers. A 100 each of positive and negative deviants and 120 median growers were selected after analysing the 12-month growth patterns (weight-for-age) of 2954 children enrolled in the TamilNadu Integrated Nutrition Project (TINP), a major health and nutrition intervention project covering nearly one million children in rural south India. The determinants of poor growth that have been left unaddressed by 6 years of TINP exposure are delineated to address the question of what more needs to be done. Further, the rationale for differential targeting of services to negative deviants and to median growers is discussed, as are the implications for programme evaluation. Data indicate that the next generation of projects targeted at the most needy (negative deviants) should address the issues of gender discrimination in childcare, of breastfeeding, of diarrhoeal disease, and of maternal empowerment. Such interventions will, however, not improve the growth of median growers in the direction of positive deviance. Instead, programmes targeted at the median growers need to support the hygienic use of nonbreast milk supplements. Improving family wealth will also improve the nutritional status of the median growers, but less so than for the negative deviants.