Patterns of infant weight gain in developing countries

Body composition by 2H dilution in Gambian infants: comparison with UK infants and evaluation of simple prediction methods

Gambian infants show growth faltering, but the underlying body composition is unknown. The present study aimed to compare body composition in Gambian and UK infants using 2H dilution; and to evaluate accuracy of bioelectrical impedance analysis (BIA) and creatinine excretion for estimating lean mass (LM), using 2H as the reference. Body composition was measured in thirty Gambian infants, aged 3-18 months, using (1) anthropometry, (2) 2H, (3) BIA (equation of Fjeld et al. Pediatr Res (1990), 27, 98-102) and (4) 5 h urinary creatinine excretion. Compared with UK reference data, Gambian infants were light, short and had reduced BMI and skinfolds. The subscapular skinfold standard deviation score (SDS) was greater than the triceps SDS (P < 0.01), indicating central fat preservation. Both LM and fat mass were reduced in Gambian infants, with or without adjustment for length. However, whereas the Gambia-UK difference in LM increased with age, that in fat mass decreased. Average creatinine excretion was similar to that expected (95.5 (sd 23.2) % recovery), but LM estimates showed unacceptable error in individuals. BIA using Fjeld's equation overestimated total body water and LM (P < 0.001), hence a new equation was developed, with standard error of 0.47 kg LM. In conclusion, Gambian infants characterised by growth faltering had LM deficits that increased with age. However, adiposity increased with age, and showed indications of a more central distribution than in the reference infants. A new BIA equation for LM prediction is presented; however, creatinine excretion is not recommended for LM estimation in this population.

Nutritional status of low-birthweight ethnic minority infants in Backan province, Vietnam

BACKGROUND

Birthweight and length have been reported to be important determinants of infant growth and future nutritional status. The study aims to describe the weight and length growth patterns during the first year of life of low-birthweight (LBW) ethnic minority infants in the mountainous province Backan, Vietnam.

METHODS

A total of 64 LBW and normal birthweight infants of ethnic minority mothers were recruited from 2001 to 2002 into a prospective cohort study. The weight and length of infants were measured monthly for 1 year. Data on nutritional status and feeding practices of the infants were collected from monthly health records and face-to-face interviews with mothers while their infants were 6 and 12 months of age.

RESULTS

Most of the increase in weight, length and catch-up to the 10th percentile for LBW infants occurred during the first 3 and 6 months for boys and for girls, respectively. After these ages, the mean weight and length diverged from National Center for Health Statistics (NCHS) reference curves to below the 10th percentile. LBW infants' weight-for-age z-scores was below the NCHS standard at birth (-2.16 SD), caught up after birth, became sustainable by 4 months, fell rapidly from the sixth month, then decreased to -2 SD at 12 months of age. LBW infants' length-for-age z-scores increased in the first month after birth, decreased in the second month and sharply increased again until 5 months of age before decreasing.

CONCLUSIONS

For LBW infants, it is difficult to achieve the same weight or length curves at 12 months of age as the NCHS standard.

Intestinal parasites increase the dietary lysine requirement in chronically undernourished Indian men

BACKGROUND

We previously used the 24-h indicator amino acid balance method to show that the lysine requirement in undernourished Indian men from low socioeconomic and unsanitary environments is approximately 50% higher than the mean requirement of 30 mg lysine. kg(-1). d(-1) in well-nourished men.

OBJECTIVE

It is possible that this higher lysine requirement in persons with chronic undernutrition is due to environmental influences, including the presence of intestinal parasites. We assessed this possibility by using 24-h indicator amino acid balance (with leucine) at both the "normal" requirement for lysine intake and the higher requirement, before and after successful treatment to eradicate intestinal parasites in affected, undernourished men.

DESIGN

Fourteen chronically undernourished men were studied before and after treatment for intestinal parasites, during each of two 7-d (6-d dietary adaptation plus 1-d tracer experiment) diet periods supplying either 30 (n = 7) or 45 (n = 7) mg lysine. kg(-1). d(-1) from an L-amino acid diet. Twenty-four-hour indicator amino acid balance was estimated on day 6 by [(13)C]leucine tracer infusion.

RESULTS

Before the parasite treatment, subjects were in neutral 24-h leucine balance at both lysine intakes. After the eradication of intestinal parasites, there was a significant (P < 0.001) improvement in 24-h leucine balances, which were positive at both lysine intakes.

CONCLUSIONS

On the basis of the 24-h indicator amino acid balance approach, it appears that intestinal infestation with parasites increases the requirement for lysine and that this may be one factor responsible for the higher lysine requirement observed in persons with chronic undernutrition.

Parent-offspring conflict theory, signaling of need, and weight gain in early life

Human growth in early life has major implications for fitness. During this period, the mother regulates the growth of her offspring through placental nutrition and lactation. However, parent-offspring conflict theory predicts that offspring are selected to demand more resources than the mother is selected to provide. This general issue has prompted the development of begging theory, which attempts to find the optimal levels of offspring demand and parental provisioning. Several models have been proposed to account for begging behavior, whether by biochemical or behavioral pathways, including: (1) blackmail of parents; (2) scramble competition between multiple offspring; (3) honest signaling of nutritional need; and (4) honest signaling of offspring worth. These models are all supported by data from nonhuman animals, with species varying according to which model is relevant. This paper examines the evidence that human suckling and crying signal nutritional demand, need, and worth to the mother. While suckling provides hormonal stimulation of breast milk production and signals hunger, crying fulfills a different role, with evidence suggesting that it signals both worth and need for resources (nutrition and thermoregulation). The role of signaling in nutritional demand is examined in the context of three common health problems that have traditionally been assumed to have physiological rather than behavioral causes: excess weight gain, failure to thrive, and colic. The value of such an evolutionary approach lies in its potential to enhance behavioral management of these conditions.

Infants' growth charts for southern Iran

Currently there are no growth charts based on local norms available for infants in Iran, and their growth is assessed by the National Centre for Health Statistics (NCHS) reference data, which is misleading. Growth charts for a cohort of 317 infants (164 girls and 153 boys) born in Shiraz (Southern Iran) in 1996 and followed for 2 years from birth are presented. All the centiles of length and weight charts are slightly above those of the NCHS charts under the age of 6 months and fall substantially below those over the age of 6 months. However, the spread is similar, so there is no suggestion that the difference is due to the prevalence of gross malnutrition. The difference shows that the use of locally based growth charts are essential for assessing the growth of children in Iran. The representativeness of our data leads us to conclude that the charts presented here are likely to be applied to the urban infant population of Iran.

Environmental temperature and human growth in early life

A link between adult human body size and environmental temperature, evolved through adaptation to heat stress, was first recognized a century ago and is now well accepted in human biology. Increasing heat stress favours smaller body size and an increased ratio of surface area to mass. However, possible effects of temperature on growth in early life have not been considered. Many developing country populations inhabit relatively hot environments compared to industrialized populations, but growth faltering in developing countries is invariably attributed to the combination of poor nutrition and infection. The aim of this study was to model the theoretical effect of growth faltering on cooling capacity in early life. Data on weight, length and total energy expenditure were selected from the literature. Three types of growth (normal growth, stunting and wasting) were considered, and the relationship between body size and heat production investigated. Relative to normal growth, stunting causes little increase in the area-to-mass ratio until 2 years of age, and results in little increase in cooling capacity during infancy. Wasting increases the area-to-mass ratio by > 15% in early infancy, and by 10% thereafter, equivalent to a similar increase in cooling capacity. These findings demonstrate theoretically that growth faltering can relieve heat stress in both infancy and childhood. The hypothesis that heat stress plays a role in human growth faltering in hot environments therefore merits empirical investigation.

Natural selection and sex differences in morbidity and mortality in early life

Both morbidity and mortality are consistently reported to be higher in males than in females in early life, but no explanation for these findings has been offered. This paper argues that the sex difference in early vulnerability can be attributed to the natural selection of optimal maternal strategies for maximizing lifetime reproductive success, as modelled previously by Trivers and Willard. These authors theorized that males and females offer different returns on parental investment depending on the state of the environment. Natural selection has therefore favoured maternal ability to manipulate offspring sex in response to environmental conditions in early life, as shown in variation in the sex ratio at birth. This argument can be extended to the whole period of parental investment until weaning. Male vulnerability in response to environmental stress in early life is predicted to have been favoured by natural selection. This vulnerability is most evident in the harsh conditions resulting from pre-term birth, but can also be seen in term infants, and manifests as greater morbidity and mortality persisting into early childhood. Malnutrition, interacting with infection after birth, is suggested as the fundamental trigger mechanism. The model suggests that whatever improvements are made in medical care, any environmental stress will always affect males more severely than females in early life.

A minimally invasive tracer protocol is effective for assessing the response of leucine kinetics and oxidation to vaccination in chronically energy-deficient adult males and children

In disadvantaged populations, recurrent infections lead to a loss of body nitrogen and worsen nutritional status. The resulting malnutrition, in its turn, produces a greater susceptibility to infection. This study aimed to examine the ability of a new minimally invasive tracer protocol to measure leucine oxidation, and then to use it to quantify the effect of vaccination on leucine kinetics and oxidation. Undernourished men (n = 5; body mass index 16.3 +/- 0.9 kg/m(2)) and children (n = 9; age 4.1 +/- 0.6 y; weight-for-age Z-score -2.3 +/- 0.7) underwent metabolic studies 6 d before and 1 d after vaccination with diphtheria, pertussis and tetanus (DPT). The tracer protocol was performed in the fed state and involved two 3-h sequential periods of frequent (20 min) oral doses of NaH(13)CO(3) or [1-(13)C] leucine. Frequent breath samples and urine collections were made. Blood samples were obtained from the men and used for the determination of the isotopic enrichment of alpha-ketoisocaproic acid. The prevaccination oxidation of leucine (percentage of dose +/- SD) was 18.1 +/- 2.3 (men) and 16.7 +/- 3.8 (children). One day after vaccination, these values had risen to 19. 9 +/- 1.9 (P < 0.05) in the men and to 19.5 +/- 4.6 (P < 0.01) in the children. In the adults, vaccination was associated with a rise in whole-body protein breakdown [mg protein/(kg.h)] from 200 +/- 40 to 240 +/- 10 (P < 0.05). A minor simulated infection increases leucine catabolism in undernourished humans and this new, minimally invasive protocol is sufficiently sensitive to measure these changes.

Growth patterns of breastfed infants and the current status of growth charts for infants

In summary, numerous studies have indicated that the pattern of growth during infancy is influenced by feeding mode. Compared to formula-fed infants, breastfed infants generally gain less weight, particularly after the first few months of life. This appears to be a normal pattern among healthy, thriving infants. Although true growth faltering can certainly occur among breastfed infants, it is difficult to evaluate using the NCHS growth chart, which is based on a sample of predominantly formula-fed infants. This situation has prompted WHO to begin the process of creating a new growth chart based on breastfed infants.