Infection, Nutritional Status, and Body Composition in Infants from Birth to Six Months

Many infants in South Africa face poor nutrition, frequent infections, and limited access to clean water and sanitation. These issues can slow their growth, weaken their immune systems, and raise the risk of long-term health problems. Infections can make infants lose weight or grow slowly because their bodies must work hard to fight illness. At the same time, poor nutrition can make it harder for them to recover from infections.

Most studies measure child growth by looking at weight and height, but these do not show how an infant’s body stores fat and muscle. Fat mass (FM) helps infants store energy, while fat-free mass (FFM), which includes muscles and bones, is important for their development.

A research study funded by the NRF explored the relationship between infection, nutritional status, and body composition in infants from birth to six months in Soweto. The goal was to see how infections influence body composition, focusing on fat-free mass (FFM), fat mass (FM), fat-free mass index (FFMI), and fat mass index (FMI). Understanding these interactions is crucial to shape early childhood health interventions.

To achieve the research goals, the study monitored a cohort of mother-infant pairs weekly from birth to six months. Recruitment took place at Chris Hani Baragwanath Academic Hospital (CHBAH) in Soweto, a township in Johannesburg with a population of 1.3 million residents. Many residents face economic difficulties and have limited access to quality healthcare and sanitation. 156 mother-infant pairs were recruited, based on the following criteria:

  • Mothers aged 18 years or older
  • Singleton pregnancies
  • Full-term infants (born between 38 and 42 weeks)
  • Birth weight between 2.5 kg and 4 kg
  • No congenital disorders
  • HIV-negative mothers

By six months, a total of 92 mother-infant pairs remained in the study, and 78 completed body composition tests. Fat mass (FM) and fat-free mass (FFM) were measured using a specialised water-based technique. Additionally, they recorded information about income level, education, mothers’ BMI, and access to clean water.

After the six-month period, weekly tests of the infants revealed the following data:

  • 80.5% had colds (sneezing or runny nose)
  • 70.5% had skin rashes
  • 68.6% had coughs or wheezing
  • 27.9% had diarrhoea

Key findings from scientific analysis revealed that:

  1. Infants with more infections had lower fat mass (FM). For every increase in the infection rate, infants lost 1.77 kg/m² of fat. By six months, these infants had 0.61 kg less body fat.
  2. More infections were linked to higher muscle mass (fat-free mass, or FFM). Infants gained 0.94 kg of muscle and other fat-free tissue when they experienced frequent infections.
  3. Height and weight were not significantly affected by infections, indicating that traditional growth measurements may not adequately reflect how illness impacts body composition.
  4. Infants with higher birthweights showed better growth outcomes. Those born heavier had increased muscle mass (an average increase of 0.66 kg per unit of birthweight), better height-for-age scores (an increase of 1.14 units), and improved weight-for-height scores (an increase of 0.87 units).
  5. Infants living in households with clean water and proper sanitation facilities had better height-for-age (HAZ) scores. Poor sanitation increased the risk of infections, making it more difficult for infants to grow properly

The study indicates that frequent infections can decrease infant fat while increasing muscle mass. This suggests that infants may use fat stores to fight infections, which could leave them with less energy available for healthy growth and brain development. Additionally, birth weight significantly influences subsequent growth, indicating that ensuring healthier pregnancies could contribute to better growth outcomes for infants after birth.

From a public health perspective, these results imply that it is important to intensify efforts to prevent infection in infants in the first 6 months postnatally, and that these efforts should concentrate on access to safely managed sanitation facilities.