Frozen and thawed breast milk can limit nutrients for babies with CF

Poorer digestion seen even when PERT used at high recommended dose in study

Lindsey Shapiro, PhD avatar

by Lindsey Shapiro, PhD |

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Freezing and thawing breast milk negatively affected how nutrients are digested under lab conditions mimicking the gastrointestinal environment of an infant with cystic fibrosis (CF), scientists report.

The addition of pancreatic enzyme replacement therapy (PERT) at sufficient doses was able to restore more normal fat breakdown under CF digestive conditions, restoring them to levels similar to what might be observed with digestion in a healthy infant.

“Breast milk is the only source of energy and nutrients for breast-fed infants, so to prevent the loss of nutrient absorption, those with CF should not be fed with frozen-thawed breast milk,” the researchers wrote.

The study, “Impact of refrigeration and freezing-thawing of breast milk on in vitro digestibility and liposoluble vitamin bioaccessibility in breast-fed infants,” was published in LWT.

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Breastfeeding can be sole nutrient source for babies with CF

Many CF patients have pancreatic insufficiency, where the pancreas does not release enough of certain enzymes needed for digestion. Poor digestion is considered a disease symptom, with patients failing to adequately absorb nutrients from their food.

Infants with CF also may not digest nutrients in breastmilk — early in life, their only source of nutrition — as well as healthy babies, limiting their nutrition and slowing their growth. These factors contribute to a worse prognosis later on.

People with CF with pancreatic insufficiency, regardless of age, are given PERT before a meal to supplement the missing enzymes. Still, its recommended dose for infants — 5 to 25 lipase units/mL (UL/mL) of breast milk or infant formula — is “supported by little scientific evidence,” the scientists wrote, meaning that breast milk fed to babies with CF “may not be optimally digested.”

Moreover, breast milk that can’t be used immediately often is preserved by being refrigerated or frozen, then thawed before use. While short-term freezing and thawing does not significantly alter the nutrient composition of breast milk, the digestibility of its nutrients might change.

Infants with gastrointestinal issues, including those with CF, particularly would be affected.

“In CF, non-digested lipids are known to be excreted in feces, along with fat-soluble vitamins, leading to a loss of energy and vitamin deficiency,” the scientists wrote.

Researchers in Spain assessed how breast milk refrigeration or freezing affected its digestibility via in vitro, or laboratory, experimentsBreast milk was obtained from a healthy 29-year-old woman, then refrigerated or frozen for 24 hours.

Fat globules, or pieces of fat, are found in breastmilk, and various proteins, vitamins, and other nutrients deposited on their surface.

Frozen and thawed milk samples showed an increased size of these fat globules relative to refrigerated samples. The researchers believed this is likely due to multiple fat globules clumping together as a result of freezing, which could limit the ability of digestive fluids to break them down adequately.

These milk samples then were incubated with lab-made intestinal or gastric (stomach) digestive fluids that mimicked what would be found in healthy infants and in infants with CF.

Digestion of fats and proteins significantly poorer under CF-like conditions

Nutrient digestion, including of fats (lipolysis) and proteins (proteolysis), generally was significantly lower under CF conditions than healthy ones.

When PERT was added at a dose of 25 LU/mL of breast milk, lipolysis under CF conditions “achieved” that observed under healthy conditions, the scientists noted. Some restoration also was seen at PERT doses in the 15-20 LU/mL range.

“Therefore, the recommended dose would seem to be in the range 15–25 LU/mL,” the researchers wrote. Still, PERT given at 25 LU/mL of breast milk dose did not reverse all proteolysis deficits seen in the CF environment.

Under healthy digestive conditions, no significant effect was observed for refrigeration versus freezing of breast milk on the breakdown of fats or proteins.

But under CF digestive conditions, freezing and thawing had a negative impact relative to refrigeration. Specifically, freeze-thaw conditions were associated with poorer lipolysis and proteolysis than refrigerated milk.

The bioavailability — the amount of a substance available for absorption in the body — of vitamins A and E also diminished with frozen milk in the CF gastrointestinal environment relative to refrigerated milk.

Study “results suggest that infants with CF being fed frozen-thawed breast milk will have reduced lipolysis, proteolysis, and vitamin A and E bioaccessibility,” the researchers wrote, adding they also “could also encourage the avoidance of freezing as a preservation method for breast milk for infants with CF.”

Likewise, findings regarding PERT “could lead to the early development of evidence-based criteria to recommend the dose of [PERT] in breast-fed infants with CF,” they added.