Donor breastmilk doesn’t contain enough zinc

A new equation based on how long ago the milk donor gave birth can predict the milk's zinc level. (Credit: Getty Images)

Levels of zinc in pooled donor breastmilk do not meet the nutritional requirements of preterm infants and term newborns, according to a new study.

The finding could have implications for how milk banks prepare milk and distribute it to infants across the country.

The study analyzes the nutrient and caloric profile of 138 samples of donated human milk from The Mother’s Milk Bank in Colorado, which is a member of the Human Milk Banking Association of North America (HMBANA). Researchers used a Miris Human Milk analyzer, the only FDA-approved product available for testing breast milk.

The results from the analysis also confirmed previous research finding lower caloric density in donor milk than expected.

“It’s important to note that the majority of donor milk is given to NICUs, which use fortifiers to ensure that premature babies receive the energy and nutrients they need,” says study author Bridget Young, a research assistant professor in the pediatrics department who co-founded the University of Rochester Human Milk and Lactation Research Consortium. “However, our study could change the ways donor milk is used in other settings, such as in nurseries or at home.”

Donor milk is increasingly provided to healthy term infants in the hospital, and is used by 18 percent of level 1 nurseries, according to a national study led by the Boston Medical Center.

Parents are also increasingly purchasing donor milk privately or directly from milk banks. In those settings, milk is generally not fortified with extra nutrients or calories. This is one of the reasons HMBANA milk banks encourage parents’ close consultation with the baby’s doctor if they use donor milk long term or as a large portion of the baby’s total.

Standardizing levels of zinc in donor milk is difficult, says Young, because the measurement process is time intensive. Zinc also dramatically decreases over the course of lactation and donor milk banks often face limited availability of milk donations when generating pools of donor milk.

To address this challenge, Young’s study presented a new equation, based on the milk donor’s “post-partum time,” (or how long it has been since she delivered her baby and began nursing), that can predict the level of zinc in donor milk.

This equation could provide a method for standardization across milk banks.

“This is still an emerging field of research and sets the stage for further work on this topic,” says Young. “But, we’ve taken an important step by demonstrating new findings about the composition of donor milk and the way we might be able to optimize this important form of nutrition for infants.”

The findings appear in The Journal of Pediatrics. Coauthors are from the University of Colorado.

Source: University of Rochester