Nuclear scientists use isotope to measure fat in babies, a marker of long-term health

25 May 2023 --- Researchers supported by the International Atomic Energy Agency (IAEA) had the insight to use a nuclear isotopic technique, as well as other methods, to assess body composition in infants between 3 and 24 months.

The study, published in The American Journal of Clinical Nutrition, tries to overcome the “lack of global reference data” on children’s body compositions. Previously, infant nutrition data was based only on body proportions.

“While length and weight are core components of early childhood measurements, these measurements do not provide information on a child’s body composition, in other words, the fat and fat-free mass,” says Alexia Alford, nutrition specialist at the IAEA and corresponding author of the infant body composition study. 

“The amount of fat or fat-free mass a person has, has important implications for long-term health, so it is important to measure body composition during childhood,” she highlights.

Combating a double burden
Researchers gathered body composition data from Africa, Asia, Oceania and South America. Collecting from 1,496 children between 2013 and 2019, the scientists obtained the “most diverse collection available of infant body composition data.”

“These reference body composition charts will give clinicians and researchers the tools to interpret infant body composition data, which can inform and evaluate interventions to combat the double burden of malnutrition and set up healthier childhood trajectories,” Alford explains.

Early life nutrition and how it affects our microbiota can predict obesity by the age of five.The double burden of malnutrition refers to the prevalence, especially in low- and middle-income countries, of high levels of undernutrition alongside increasing obesity levels.

“In this way, the data can contribute to enhancing nutrition programs and strengthening the global efforts to prevent malnutrition in infants and young children and related longer-term poor health into adulthood,” she underscores.

Infants with poor body composition are at higher risk of developing obesity and related non-communicable diseases like Type 2 diabetes and heart disease.

Early life nutrition and how it affects our microbiota can predict obesity by the age of five, according to a study released this week. 

Nuclear techniques in nutrition
The IAEA explains that the nuclear stable isotope technique of deuterium dilution can measure the amount of water in one’s body. Knowing this, fat mass can be estimated as “it is assumed that fat mass contains no water,” unlike fat-free mass, which is composed of water, minerals and proteins.

Deuterium is a stable – therefore non-radioactive – isotope of hydrogen.

The baby’s saliva was collected using a cotton swab before they drank a small amount of water labeled with deuterium. The deuterium-labeled water swallowed by the infant was mixed with the water in the baby’s body, and after a few hours, the isotope was evenly spread throughout the body. 

A second saliva sample was collected from the baby. The amount of deuterium in the saliva was measured then using isotope ratio mass spectrometry. The total amount of water in the body was calculated from the measured isotope enrichment and the weight and enrichment of the deuterium-labeled water consumed.

Following this, the fat-free mass was estimated using an appropriate hydration factor. 

Healthy Eating Index for toddlers
In another study on infant nutrition, last week, researchers created an index to assess how well foods align with the new guidance in the Dietary Guidelines for Americans for toddlers 12 through 23 months old.

The research, published in the Journal of the Academy of Nutrition and Dietetics, is adapted to new recommendations on salt, sugar and saturated fats, among others. 

“Toddlers have lower energy intake relative to high nutrient needs and added sugars should be avoided. Another distinctive difference is that there is no recommendation to limit saturated fats to less than 10% of energy intake in this age group. However, saturated fats cannot be unlimited without displacing the energy available to achieve other food group and subgroup goals,” explain the scientists.

By Marc Cervera