Catherine Pieltain

Reference values of body composition obtained by dual energy X-ray absorptiometry in preterm and term neonates

BACKGROUND As previously reported, dual-energy x-ray absorptiometry provides reliable and accurate values for bone mineralization in piglets and infants, but overestimates fat content in small infants. The purpose of the current study was to determine an appropriate equation of correction for fat mass measurement and to establish reference values of body composition of preterm and term neonates. METHODS Fat mass and chemical whole-body fat content were evaluated by dual-energy x-ray absorptiometry in eight piglets with a body weight between 1408 and 5151 g. The results were combined with previous data obtained in 13 piglets, and two correction equations were determined according to fat mass content. Close to birth, 106 healthy appropriate-for-gestational-age preterm and term infants were scanned by dual-energy x-ray absorptiometry to determine bone mineral content, bone area, and fat mass. Fat mass content determined by dual-energy x-ray absorptiometry was corrected using the equations obtained in piglets after which lean body mass was recalculated. RESULTS Multivariate analysis showed that dual-energy x-ray absorptiometry body weight was the best predictor of bone mineral content (r2 = 0.94), bone area (r2 = 0.95), lean body mass (r2 = 0.98), and fat mass (r2 = 0.84). Gender was an additional significant independent variable for fat mass and lean body mass. Body weight related curves of percentiles for bone mineral content, bone area, fat mass, and lean body mass, were constructed. In vivo dual-energy x-ray absorptiometry values of fat mass and calcium content estimated from bone mineral content were in accordance with previously reported whole-body carcass reference values in preterm and term neonates. CONCLUSION Normative data of dual-energy x-ray absorptiometry body composition for healthy preterm and term infants are provided and can therefore be used in research and in clinical practice.

Bone mineral metabolism in the micropremie.

Environmental factors, nutritional supplies, hormonal status, diseases, and treatments appear to affect postnatal skeletal growth and mineralization in VLBW infants. Compared with their term counterparts, ELBW infants are at risk of postnatal growth deficiency and osteopenia at the time of hospital discharge. From recent data, DXA is becoming one of the reference techniques to evaluate mineral status, whole-body composition, and effects of dietary manipulations on weight gain composition and mineral accretion in preterm infants. Weight gain and length increases need to be evaluated carefully during the first weeks of life, in the intensive care unit and out of it, in the step down unit. Nutritional survey is required to improve the nutritional supply and to maximize linear growth. As the critical epoch of growth extends, during the first weeks or months after discharge, follow-up and nutritional support need to be provided during the first years to promote early catch-up growth and mineralization. Further studies need to determine precisely the most optimal feeding regimen during this period but also need to evaluate the long-term implications of such a policy on stature, peak bone mass, and general health at adulthood.

Enteral calcium, phosphate and vitamin D requirements and bone mineralization in preterm infants

With major advances in life‐support measures, nutrition has become one of the most debated issues in the care of very low birth‐weight (VLBW) infants. Current nutritional recommendations are based on healthy premature infants and designed to provide postnatal nutrient retention during the ‘stable‐growing’ period equivalent to the intrauterine gain of a normal foetus. However, this reference is still a matter of discussion, especially in the field of the mineral requirements.

Weight gain composition in preterm infants with dual energy X-ray absorptiometry.

Whole body composition was investigated using dual energy x-ray absorptiometry in 54 healthy preterm infants, birth weight < 1750 g, who were fed fortified human milk (n = 20) and preterm formula (n = 34) when full enteral feeding was attained and then again 3 wk later at around the time of discharge. Weight gain composition was calculated from the difference between the earlier and later measurement. The minimal detectable changes in whole body composition over time according to the variance of the population (within groups of 20 infants) and the minimal detectable changes according to the dietary intervention (between two groups of 20 infants) were determined at 5% significance and 80% power. Whole body composition was similar in the two groups at the initial measurement, but all the measured variables differed at the time of the second measurement. Formula-fed infants showed a greater weight gain (19.9 ± 3.2 versus 15.9 ± 2.2 g·kg-1·d-1, p < 0.05), fat mass deposition (5.1 ± 1.9 versus 3.3 ± 1.3 g·kg-1·d-1, p < 0.05), bone mineral content gain (289 ± 99 versus 214 ± 64 mg·kg-1·d-1, p < 0.05), and increase in bone area (1.6 ± 0.4 versus 1.3 ± 0.3 cm2·kg-1·d-1, p < 0.05) compared with the fortified human milk group. From these data, a minimal increase from the first measurement of 111 g lean body mass, 68 g fat mass, and 3.1 g bone mineral content is needed to be detectable in a longitudinal study that includes 20 infants. For significance between two groups of 20 infants around the time of discharge, dietary intervention needs to achieve minimal differences of 160 g lean body mass, 86 g fat mass, and 4.1 g bone mineral content. With respect to weight gain composition, the minimal differences required to reach significance are 2.1 g·kg-1·d-1 for gain in lean body mass, 1.2 g·kg-1·d-1 for gain in fat mass, and 76 mg·kg-1·d-1 for gain in bone mineral content. We conclude that dual energy x-ray absorptiometry allows evaluation of the effects of dietary intervention on whole body and weight gain composition in preterm infants during the first weeks of life.

Effect of fortification on the osmolality of human milk

AIM To evaluate the effect of fortification on the osmolality of human milk. METHODS The osmolality of 47 samples of human milk was determined at baseline, just after, and 24 hours after supplementation with five different human milk fortifiers (HMF) at 4°C. RESULTS Ten minutes after HMF supplementation the osmolality of human milk was significantly higher than the sum of the respective values of HMF dissolved in water and human milk, measured separately at baseline (p<0.0001), with the exception of the HMF containing only proteins. After 24 hours a further increase in osmolality was observed. Linear regression analysis showed that total dextrin content (r=0.84) was the main determinant of the increase. CONCLUSIONS Human milk and HMF interact to induce a rapid increase in osmolality higher than would be expected from composition alone. This rise could be explained by the amylase activity of human milk, inducing hydrolysis of the dextrin content of HMF, leading to small osmotically active molecules of oligosaccharides. The high osmolality of fortified human milk should be considered in the nutritional management of preterm infants.

Prematurity and bone health

Recent advances in neonatal care significantly increases survival rate in preterm and particularly in extremely low birth weight infants (ELBW infants) and nutrition is becoming one of the most challenging issue to improve short and long term health and developmental outcomes. Nutrition is also relevant for bone development and mineralization reducing the risk of osteopenia and metabolic bone disease (MBD). Osteopenia of prematurity is a multifactorial disease including predominantly nutritional but also biomechanical and environmental factors. At birth, the fetal active mineral transfer is interrupted and the preterm becomes related to the parenteral and enteral mineral supplies. On the other hand, physiological adaptation of bone to extra uterine life leads to an increase in bone resorption. This process occurring earlier in preterm than in term infants can be accompanied by an increased risk of bone fragility and fractures. Early provision of highly bioavailable mineral supplies, correction of vitamin D deficiency and the screening of serum phosphorus concentration combined to urinary mineral excretion appears to be helpful for the prevention of MBD. When available, DEXA is more sensitive than ultrasound for quantifying osteopenia in VLBW infants at the time of discharge. Catch-up of mineralization is rapidly observed during the post term period and osteopenia of prematurity seems to be a self-resolving disease although the potential long-term consequences on the attainment of peak bone mass remains uncertain.

Software and scan acquisition technique-related discrepancies in bone mineral assessment using dual-energy X-ray absorptiometry in neonates.

Aim: In adults, whole‐body mineralization assessment by dual‐energy X‐ray absorptiometry can be affected by the densitometer and/or the software used. As there are no published data on neonates, the aim of this study was to evaluate the magnitude of such effects in growing preterm infants. Methods: We analysed the absorptiometry results obtained from 44 preterm infants scanned at discharge and again 6 wk later using densitometers from the same manufacturer equipped with “Pediatric” (Group A, n= 24) or with “Infant” (Group B, n= 20) packages. Results of bone mineral content assessment were compared using an unpaired f‐test and a linear regression analysis. Results: At the time of the first absorptiometry (body weight = 2119 ± 144 g, n= 44), the bone mineral content was three times lower in Group A (10 ± 3 g) than in Group B (29 ± 4 g) (p < 0.001). Subsequently, on the second absorptiometry (body weight = 4037 ± 236 g, n= 44) such significant differences in bone mineral content (A: 65 ± 19 g, B: 66 ± 9 g, p= 0.85) were no longer in evidence. The differences in bone mineral content were related to differences in analysis algorithms between the two programs, which can lead to an overestimation of bone mineral content accretion when two successive measurements are made using the “Pediatric” package.

Evaluation of weight gain composition during the first 2 months of life in breast- and formula-fed term infants using dual energy X-ray absorptiometry

Healthy term breast- and adapted formula-fed infants show similar weight gain and weight gain composition during the first months of life.

Electrolyte and mineral homeostasis after optimizing early macronutrient intakes in VLBW infants on parenteral nutrition

Objectives: The aim of the present study was to evaluate electrolyte and mineral homeostasis in very-low-birth-weight (VLBW) infants who received high protein and energy intakes with a unique standardized parenteral nutrition solution containing electrolytes and minerals from birth onward. Methods: Prospective cohort study in 102 infants with birth weight <1250 g. The evolution of plasma biochemical parameters was described during the first 2 weeks of life. Results: During the first 3 days of life, mean parenteral intakes were 51 ± 8 kcal · kg−1 · day−1 with 2.7 ± 0.4 g · kg−1 · day−1 of protein, 1.1 ± 0.2 mmol · kg−1 · day−1 of sodium and potassium, and 1.3 ± 0.2 mmol · kg−1 · day−1 of calcium and phosphorus. Afterwards, most nutritional intakes (parenteral and enteral) met growth requirements. No infant developed a hyperkalemia >7 mmol/L, and a hypernatremia >150 mmol/L occurred only in 15.7% of the infants. In contrast, hyponatremia <130 mmol/L and hypokalemia <3 mmol/L occurred in 30.4% and 8.8% of the infants, respectively. The initial neonatal metabolic acidosis rapidly resolved in most infants and only 2.0% developed a base deficit >10 mmol/L after day 3 of life. Early hypocalcemia <1.8 mmol/L occurred in 13.7% of the infants. In contrast, hypophosphatemia <1.6 mmol/L occurred in 37.3% and hypercalcemia >2.8 mmol/L occurred in 12.7% of the infants. Conclusions: Increasing early protein and energy intakes in VLBW infants in the first week of life improves electrolyte homeostasis. It also increases the phosphorus requirements with a calcium-to-phosphorus ratio ⩽1.0 (mmol/mmol) and the potassium and sodium requirements to avoid the development of a refeeding-like syndrome. These data suggest that the parenteral nutrition guidelines for VLBW infants for the first week of life need to be revised.

Use of donor milk in the neonatal intensive care unit

Own mothers milk is the first choice in feeding preterm infants and provides multiple short- and long-term benefits. When it is unavailable, donor human milk is recommended as the first alternative. Donor milk undergoes processing (i.e. pasteurization) to reduce bacteriological and viral contaminants but influences its bioactive properties with potentially fewer benefits than raw milk. However, there is no clinical evidence of health benefit of raw compared to pasteurized human milk, and donor milk maintains documented advantages compared to formula. Nutrient content of donor and own mothers milk fails to meet the requirements of preterm infants. Adequate fortification is necessary to provide optimal growth. There are significant challenges in providing donor milk for premature infants; therefore, specific clinical guidelines for human milk banks and donor milk use in the neonatal intensive care unit should be applied and research should focus on innovative solutions to process human milk while preserving its immunological and nutritional components. In addition, milk banks are not the only instrument to collect, process and store donor milk but represent an excellent tool for breastfeeding promotion.