Comparing body composition of preterm infants on human breast milk or cow milk diet

When comparing preterm babies’ diets that consisted of either exclusively human milk or 1 that contained cow milk products, investigators of a randomized, controlled study published in Early Human Development found no important differences in body composition at term.

The study authors stated preterm infants that receive only human milk, compared to infants that receive mostly preterm formula, have lower weight and non-adipose tissue mass (N-ATM) by term. Seeking to determine if these respective diets would affect body composition, the investigators conducted a randomized, multicenter, open-label, controlled study in 4 United Kingdom centers. The study’s primary endpoint was body composition (adipose tissue mass [ATM] and N-ATM) at term.

From March 2018 to September 2019, preterm infants below 30 weeks gestation were enrolled. Major or life-threatening abnormalities, inability to randomize within 72 hours of birth, bovine milk exposure prior to randomization, or likelihood of transfer to a different hospital before 34 weeks postmenstrual age were exclusion criteria.

Infants received their own mother’s milk (OMM) and were randomized to exclusive human milk (“Ready to Feed Human Preterm 26” formula, RTF 26; Prolacta Biosciences), the intervention arm, or preterm formula, the control arm, making up for shortfalls until an enteral feed volume of 150 ml / kg per day was reached. The human milk-based fortifier (Prolacta Biosciences) was added after the feed volume of 150 ml / kg per day was reached (at least 50 ml was OMM) in the intervention arm. Enteral intake maximum was 165 ml / kg per day, providing a protein intake of 3.7–4.6 g /kg per day, carbohydrate intake of 8.2–12.2 g / kg per day and fat intake of 8.2–9.2 g / kg per day.

Standard cow milk-based fortifier was added in the control arm once an enteral feed volume of 150 ml / kg per day was reached. In this group, the maximum enteral intake was 165 ml / kg per day, which provided a protein intake of 3.7 to 4.6 g / kg per day, a fat intake of 6.3 to 6.4 g / kg per day, and a carbohydrate intake of 13 to 14.7 g /kg per day. Trial intervention ended at 34 weeks postmenstrual age.

After randomization, exclusions or those lost to follow-up, 12 infants from the control arm and 15 infants from the intervention arm were analyzed. Magnetic resonance imaging was used to assess body composition, carried out in natural sleep at term. Total adipose tissue volume was defined as the sum of 6 discrete depots: superficial-subcutaneous non-abdominal, superficial-subcutaneous abdominal, deep-subcutaneous abdominal, deep-subcutaneous non-abdominal, internal-abdominal, and internal non-abdominal.

Results demonstrated that N-ATM at term (kg) was 2.25 (2.015, 2.492) for the intervention arm and 2.255 (2.105, 2.459) for the control arm (P = 0.97). ATM at term (kg) for the intervention arm was 0.8 (0.565, 1.05) and 0.755 (0.66, 0.828) for the control arm (P = 0.27).

In both arms, there were no differences in feed tolerance, exclusive breast feeding at discharge, days of parenteral nutrition, total length of stay in neonatal unit, postmenstrual age at discharge from neonatal unit, or change in weight standard deviation scores (SDS) between birth and discharge. There was no impact on body composition of source of protein in human milk fortifier.

No suggestions of important differences in body composition at term were observed when comparing an exclusive human milk-based diet to a diet containing cow milk products, with macronutrient fortification in both arms. Sample size was a limitation of the study. The authors concluded that an exclusive human milk diet was well tolerated, though they acknowledged “the pressing and as yet unresolved issue for neonatal practice is whether an exclusive human milk diet results in functional benefits for very preterm babies.” A randomized, controlled trial that can detect clinically relevant differences in outcomes for infants and their parents is needed for this data. Until then, authors stated “the optimal diet for very preterm babies remains uncertain.”

Reference:

Uthaya S, Jeffries S, Andrzejewska I, Vasu V, Embleton ND, Modi N. Randomised controlled trial of human derived breast milk fortifier versus bovine milk fortifier on body composition in very preterm babies. Early Human Development. 2022;171:105619. doi:10.1016/j.earlhumdev.2022.105619