Variations in human donor milk present critical considerations for preterm infants worldwide

A recent study has revealed significant variations in the nutritional composition of donor human milk across different countries. These findings could transform how hospitals support critically ill preterm infants worldwide.

The work is published in the American Journal of Clinical Nutrition and was led by Dr. Maryanne Perrin at UNC Greensboro (UNCG).

“Donor human milk serves as a lifesaving feeding alternative for preterm infants when a mother’s own milk is unavailable, significantly reducing the risk of necrotizing enterocolitis—a devastating intestinal condition,” said Perrin, an associate professor of nutrition. “Our study reveals current clinical protocols around donor human milk may require substantial revisions that vary based on the profile of a milk bank’s donors.”

The researchers collected and analyzed 600 milk samples from approved donors across eight milk banks in Chile, Kenya, Poland, Vietnam, and the United States.

“We found that the nutritional profile of donor human milk varies dramatically depending on whether milk banks predominantly recruit donors in early versus mature lactation stages, with implications for how we feed our most vulnerable infants,” said Perrin. “This is in line with other studies of human breast milk.”

Almost all the countries studied used a mature donation model, where donations occurred an average of 14–21 weeks after delivery. These donations had higher concentrations of lactose and several B-vitamins, including thiamine, niacin, B6, and pantothenic acid.

However, Kenya used an early donation model with milk donations sourced from donors at an average of 1.6 weeks after delivery. These samples had 30–50% higher protein concentrations, an especially important nutrient for preterm infant growth. They also had higher concentrations of several minerals, including potassium, sodium, copper, iron, selenium, and zinc, and increased human milk oligosaccharides. It is important to note that over half of donors in Kenya had experienced preterm deliveries.

The researchers also noted other regional differences in vitamins that may be related to the dietary patterns of the donors. Among the countries using mature donation models, they found relatively higher riboflavin and lower choline levels in samples from the United States, lower B12 in Poland, and lower thiamine in Vietnam.

“Donor human milk is usually fortified to ensure vulnerable preterm infants receive the best possible nutrition,” said Perrin. “Our findings imply that these fortification strategies could be optimized according to specific regions and milk-banking models.”

These findings are a first step, but the researchers say there is still much more to be discovered.

“Over 60% of nutrient variation we saw in donor milk remains unexplained by lactation stage, birth term, maternal age, donation volume, or storage duration,” said Perrin. “In addition to fortification, we must investigate other strategies, such as multi-donor pooling to reduce variation. For now, the unpredictability means continuing challenges to ensuring consistent nutrition for the 15 million preterm infants born each year, many of whom are nutritionally vulnerable.”

Study authors included researchers and practitioners from PATH in Seattle, Wash., the University of California San Diego, the University of California Davis, the USDA Western Human Nutrition Research Center, the Complejo Asistencial Dr. Sótero del Rio in Chile, Pumwani Maternity and Referral Hospital in Kenya, Da Nang Hospital for Women and Children in Vietnam, Vietnam University of Da Nang, and Medical University of Warsaw in Poland.

“This represents the largest and most geographically diverse study of donor human milk composition to date,” said Perrin. In particular, the study fills knowledge gaps by including low- and middle-income countries with high preterm birth rates.

“This is a population that didn’t exist 30 years ago—babies that were born around 24 weeks didn’t survive,” said Perrin. “There’s so much work to be done.”