The Nutrition of a Preterm Infant
Premature birth is a world-wide health concern where, the earlier in gestation that babies are born, the higher the risk of death, serious disability, or other health issues. More than 15 million infants are born preterm (before 37 weeks of pregnancy) every year. In the United States, more than one in 10 children are born preterm.
ARS is funding research to study human nutrition and the health risks for these preterm infants. One common risk is the inability for a preterm infant to be given food orally. Instead, preterm infants must be nourished intravenously by infusing purified nutrients, such as glucose and amino acids, directly into the blood.
Researchers are using preterm pigs as a model for the human preterm infant, with the primary goal of identifying the mechanisms whereby foods and nutrients promote healthy growth and development. The neonatal pig is considered the best model for the human infant because of similarities in the metabolism, anatomy, and stage of development in both.
“When preterm infants are given intravenous nutrition for long periods of sometimes more than 2 to 3 weeks, they get a condition called cholestasis,” explained Douglas Burrin, research physiologist at the Children's Nutrition Research Center (CNRC) in Houston, TX. “Cholestasis is a form of liver disease, where bile produced in the liver builds up and spills into the blood. These babies can get jaundice or yellowish appearance.” Burrin’s research with preterm pigs is providing important clues about how parenteral fat emulsions, recently approved by the FDA can prevent cholestasis. Burrin and his research group are also focused on how to prevent a major disease in preterm infants, called necrotizing enterocolitis or NEC, which is an inflammatory disease in the intestine.
“NEC is the number one gastrointestinal emergency in infants,” said Burrin. “And usually, it happens when they're in the hospital and especially when they’re fed formula.”
Burrin noted that the current guidelines from pediatric professionals recommend the use of human milk for feeding preterm babies. Particularly beneficial is colostrum, the milk that the new mother produces in the first 24 hours after giving birth. It's a very concentrated form of milk that is especially rich in nutrients and immune proteins to protect the developing immature intestine. A new project in Burrin’s laboratory is aimed at discovering how these immune proteins or antibodies can fight infection and reduce the risk of NEC in preterm infants.
“Although the nutritional support of preterm infants has improved in recent years, many infants born prematurely are lighter, shorter, and have less muscle mass than infants born at term,” explained Teresa Davis, nutrition scientist and professor of pediatrics nutrition at Baylor College of Medicine. “This different body composition likely contributes to their increased risk of developing type two diabetes, obesity, and glucose intolerance later in life.”
Knowing how to properly feed an infant at this stage is essential to helping them grow and develop normally. Studies using the preterm piglet model suggest that the body’s ability to mount a growth response after feeding is reduced in the preterm infant.
“The food ingested doesn’t cause as profound an increase in the synthesis of protein in their muscles,” explained Davis. “So, they appear to be resistant to the simulation of protein synthesis by feeding. However, simply increasing the total food intake of preterm infants does not completely reverse their limited muscle growth. And excess catch-up growth can promote obesity.”
Davis and colleagues at the CNRC are currently testing whether supplementing their diet with additional leucine can promote muscle growth following preterm birth. Leucine is an essential amino acid that cannot be synthesized in the body but must be consumed in the diet.
“Leucine also can act as a signaling molecule to tell the muscle to make more protein,” said Davis.
These nutritional management strategies could be used by both parents and pediatricians to lower the risk of disease and other health issues through the early years of a preterm baby.– By Olga Vicente, ARS's Office of Communications
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