A quarter of the world's children may need more protein to promote their growth.
Globally, 150 million children are malnourished, and around 25% of all children under 5 years experience stunted growth and development.
The most obvious feature is short stature, but other problems relate to cognitive development and the ability to resist disease and infection. Stunted growth can also shorten the life span.
Essential amino acids are the building blocks of proteins. They are necessary for human health, but they must come from dietary sources, as the body cannot produce them.
Animal sources such as eggs and dairy products can provide the necessary nutrients.
Nutritional interventions have helped to reduce deaths from acute malnutrition, but they have barely reduced the prevalence of stunted growth.
Researchers from Washington University School of Medicine in St. Louis, MO, partnered with colleagues from Johns Hopkins University in Baltimore, MD, and scientists at the National Institute of Aging of the National Institutes of Health (NIH), the University of Malawi and other institutions to look for clues.
15-20% lower level of amino acids in children who are small for their age
Using a metabolomic approach, which examines the metabolites present in an organism, the team evaluated blood samples of 313 children aged 12-59 months, from rural Malawi, in sub-Saharan Africa.
The children who were enrolled in the study did not have evidence of severe acute malnutrition, congenital or chronic disease or diarrhea.
However, height and weight measurements revealed that 64% of the participants were small for their age, based on curves defined by the World Health Organization (WHO).
Blood samples showed that over 80% of the children with stunted growth had 15-20% lower levels of all nine essential amino acids, compared with those who were growing normally.
They also had significantly lower concentrations of other substances: conditionally essential amino acids, nonessential amino acids and six sphingolipids.
Sphingolipids are found in cell membranes, and they keep cell membranes strong and impermeable, which reduces exposure to microbes.
The children also had unusual concentrations of another lipid linked to cell membranes in the brain and nervous tissue.
Targets for nutritions should focus on amino acids
The findings suggest that the children who are at risk of stunting may not be receiving adequate essential amino acids and choline, which is needed for the synthesis of lipids.
The authors explain that the children have low levels of "all of these amino acids and all of these kinds of fats," each of which is needed to turn on a switch for growth.
The team believes that the lack of amino acids could cause a certain protein complex, which functions as a nutrient sensor inside cells, to hinder the synthesis of proteins and lipids and cellular growth. The same function regulates bone growth, which determines height.
Senior co-author, Dr. Mark J. Manary, from John Hopkins University, who spends several months a year in Africa treating children with malnutrition, says:
"Stunting affects half of the children in rural Africa and millions more elsewhere in the world. Many efforts have been undertaken to reduce stunting's impact, from introducing various food supplements to reducing exposure to infections, but we haven't really gotten anywhere. But these new findings, obtained with the help of cutting-edge technology, shed light on the biological reasons for this age-old, globally-significant problem."
Dr. Richard Semba, of John Hopkins University, says: "This challenges the widespread assumption that children are getting enough protein in developing countries. This could cause a huge shift in the aid community. We have to really think about trying to improve the diet. Children are not getting quality food."
The team hopes that further research will help to create a means, whether as a food product or an additive, to reduce stunting.
Dr. Manary, who has been working for decades to develop and deliver nutrient-rich ready-to-eat food (RUTF) in Africa, Asia and Central America, suggests that the findings may lead to "something analogous to RUTF, but for stunting."
Medical News Today reported last year that some asthma medication could lead to stunted growth.