Worldwide, 170 million children 5 or younger are not growing appropriately because they lack proper nutrition, according to the World Health Organization.

“Though undernutrition is not a big problem in the United States or Europe or Japan or Australia—the high-income countries—from a global perspective, it’s a huge problem,” says Jere Behrman, the William R. Kenan, Jr. Professor of Economics in the School of Arts & Sciences.

Previous research proved associations between undernourishment during early life, particularly a child’s first 24 months, and areas like cognitive skills, schooling levels, wage rates in adulthood, and next-generation birth weights.

Now, work from Behrman and colleagues from the Universidad de Chile, the University of Houston, and others, verified the importance of protein intake during this period. Analyzing data from more than 3,500 children from Guatemala and the Philippines, they found that upping protein by just one egg per week positively affected growth, which could lead to better outcomes later.

The scientists published their findings in the journal Economics and Human Biology.

Behrman and colleagues are not the first to study the connection between nutrient input and child development. However, Behrman says their research is unique because of their datasets and the fact that they control for dietary choices.

Overall, the study looked at 3,591 children. In four rural Guatemalan villages between 1969 and 1977, the Institute of Nutrition of Central America and Panama gathered height, weight, and dietary information for 878 babies 24 months or younger every three months. For two years starting in 1983 in 33 Filipino communities, the Cebu Longitudinal Health and Nutritional Survey collected that same information from 2,713 children every two months. Both data sets also included information about breastfeeding, infectious diseases, and factors affecting dietary choices.

Guatemala and the Philippines may be almost 10,000 miles apart and have very different diets—one based on corn, the other on rice—but the study results were strikingly alike.

“It’s provocative,” Behrman says. “That we found very similar relations in two fairly different contexts reinforces that this is probably a more general phenomena.”

To ensure their work’s validity, the researchers accounted for other factors that could result in undernourishment, something few such studies have done. Some of these factors include infectious disease, which could prevent proper food processing or lead to decreased appetite; breastfeeding, if a mother and child aren’t successful in this realm; and children who simply require more attention, leaving their siblings with less.

Behrman says he hopes to eventually ask similar questions in other parts of the world such as India and sub-Saharan Africa, where many call the childhood malnutrition problem a crisis, though rich and long-standing datasets don’t yet exist in those places. For now, he’s focusing on the “catch-up question,” whether a child with nutritional deficits in the first 1,000 days of life can ever catch up. 

It’s still an open query, he says.

“Why do we care? Because as humans we care about other humans,” he says. “It’s not good to be undernourished. But we also care because undernourishment early in life has been shown to be strongly associated, probably causally, with important outcomes later.”