Infant and young child nutrition

Appropriate feeding practices in the early months and years of life are important to achieve optimal health outcomes, and intellectual and social development. Stable isotope techniques are used to evaluate activities to improve infant and young child feeding practices.

A child’s future is shaped mainly within the first 1,000 days between conception and age two. This is why the World Health Organization recommends exclusive breastfeeding from birth to six months of age, followed by the introduction of appropriate complementary foods and continued breastfeeding for up to two years. During infancy and early childhood, inappropriate infant feeding practices, nutrient deficiencies and frequent infections result in underweight and stunting, which affects about 159 million children under five years of age in low and middle income countries. There is strong evidence linking early life undernutrition and increased risk of chronic, non-communicable diseases (NCDs) in adulthood, including cardiovascular disease, diabetes and cancer.

The IAEA supports the application of stable isotopes to assess activities to improve infant and young child feeding practices:

  • Objectively measure whether a child is exclusively breastfed or not, and the amount of breast-milk is consumed by the child. This measurement can be used to assess accuracy of information reported by the mothers, and the impact of breastfeeding promotion campaigns.
  • Body composition in terms of the relative amounts of fat and lean tissues as an indicator of the nutritional status reflecting the quality of the diet. Poor quality diets in infancy can lead to obesity later in life. Monitoring body composition is important, because changes in body composition are associated with physiological changes that can eventually lead to disease or death, in the case of severe wasting (loss of muscle mass).
  • Quality of complementary foods and feeding practices: absorption and retention of provitamin A, iron and zinc from fortified foods, or biofortified foods (accumulation of higher levels of minerals and vitamins during plant growth), or mixed diets; and protein bioavailability from plant foods.
  • The infants’ micronutrient intake can be estimated when human milk intake is measured and this information is combined with the micronutrient content of human milk (e.g. vitamin A).
  • Changes in vitamin A body stores reveal the success of interventions to prevent vitamin A deficiency (see also: Maternal and Adolescent Nutrition).

The IAEA also supports the application of stable isotope techniques to assess the success of refeeding programmes for severely undernourished children. Rapid catch-up weight gain could be associated with disproportionally higher amounts of body fat gain, which could lead to higher risk of non-communicable diseases during adult life. Assessing body composition gives important information on the amount of fat and lean tissue in the body.

By supporting the use of isotopic techniques, the IAEA’s work aligns with the World Health Assembly’s aim to increase the rate of exclusive breastfeeding in the first six months up to at least 50 per cent by 2025, and with the Sustainable Development Goal 2.1 to end hunger and ensure access by all people to safe, nutritious and sufficient food all year round.

Measuring breastfeeding patterns using stable isotopes


  • The mother consumes an accurately weighed dose of deuterium oxide. 
  • The deuterium mixes with the mother’s body water.
  • The baby consumes deuterium in its mother’s milk.
  • Saliva is sampled from the mother and from the baby for 2 weeks.
  • The amount of deuterium in the saliva is analysed.


  • Volume of human milk consumed by the baby.
  • Volume of non-milk water consumed by the baby.
  • Deuterium in the baby’s body comes only from the milk consumed during breastfeeding.
  • As the deuterium is eliminated from the mother’s body, the enrichment in her milk declines and therefore the enrichment in the baby’s body also falls.
  • A mathematical model is used to determine how much of the deuterium given to the mother appears in the baby’s saliva. From this information, the amount of human milk the baby has consumed can be calculated. The technique also shows if the baby has ingested water from sources other than its mother’s milk over the test period.

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