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Indian Pediatr 2017;54:
635-637 |
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Macronutrients in Breastmilk of Mothers of
Preterm Infants
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Shiwani Mahajan, Deepak Chawla, *Jasbinder Kaur and
Suksham Jain
From Departments of Pediatrics and *Biochemistry,
Government Medical College and Hospital, Chandigarh, India.
Correspondence to: Dr Deepak Chawla,
Department of Pediatrics, Government Medical College and Hospital,
Chandigarh, India.
Email:
[email protected]
Received: August 26, 2016;
Initial Review: November 15, 2016;
Accepted: May 16, 2017.
Published online: June 04, 2017.
PII:S097475591600068
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Objectives: To evaluate the
variability in macronutrient and energy content of breastmilk of Indian
women delivering at £34
weeks of gestation. Methods: In this cross-sectional
study, samples of breastmilk expressed manually for feeding of preterm
neonates were collected from 106 mothers at 3±1 (n=26), 7±2 (n=34),
14±2 (n=24), 21±3 (n=12) and 28±3 (n=10) days after
birth. Protein, fat and carbohydrate content were estimated and total
energy content was calculated. Results: Protein content in the
human milk declined from 4.1±2.1 g/dL on the 3rd postpartum day to
2.2±0.6 g/dL by the 28th day postpartum. Lactose (from 2.2±0.7 g/dL to
3.0±0.9 g/dL), fat (1.9±1.8 g/dL to 3.4±2.1 g/dL) and energy (42.3±18.8
Kcal/dL to 51.9±21.5 Kcal/dL) contents increased from day 3 to day 28.
Conclusions: Preterm human milk has high temporal and
inter-individual variation in the macronutrient composition and without
fortification is unlikely to meet the nutritional requirement of preterm
neonates.
Keywords: Lactose, Lipids, Proteins.
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B
reast milk decreases the risk
of late-onset
sepsis and necrotizing enterocolitis in preterm
neonates and is therefore preferred over
formula milk [1]. For adequate growth, enteral nutrition must be able to
provide 110-135 Kcal/kg/day of energy and 3.5-4.5 g/kg/day of proteins
[2]. Breastmilk secreted by mothers of preterm neonates is deficient on
both these counts and therefore needs fortification [3]. However,
neonates fed human milk even after fortification grow slower than the
neonates fed formula milk [4]. One probable reason of this is variation
in composition of human milk. Previous studies, mainly from developed
countries, demonstrated that the breastmilk composition changed as
lactation progressed [3,5]. However, fortification strategies assume a
uniform value of nutrient composition of breastmilk [6]. Evaluation of
the nutritional content of human breastmilk is important to determine
its sufficiency as the source of nutrients for preterm neonate. Data is
sparse about temporal changes and inter-individual variation in
breastmilk composition in Indian mothers delivering prematurely.
Objective of this study was to evaluate variability in macronutrient
composition of human breastmilk of Indian mothers who deliver
prematurely.
Methods
This cross-sectional study was carried out at the
Departments of Pediatrics and Biochemistry of a tertiary care hospital
in Northern India from July, 2014 to September, 2014. Study protocol was
approved by the Institutional Research and Ethics Committee and written
informed consent was obtained from lactating women who participated in
the study. Mothers of preterm neonates born in the hospital were
enrolled if they fulfilled the following criteria: gestation at delivery
£34 completed
weeks, normal blood hemoglobin and glucose levels, normal renal and
liver function tests and milk supply sufficient to meet the the volume
needed by the baby. Mothers who had chronic illness like hypertension,
diabetes mellitus or thyroid dysfunction were excluded. All women
obtained comprehensive instructions about breastfeeding techniques and
milk collection procedures including pumping. Samples of milk for the
study were taken from either or both breasts by manual expression on
3±1, 7±2, 14±2, 21±3 and 28±3 days after birth. To minimize any effect
of diurnal variation, sample collection was done in the morning hours
between 9:00 AM and 11:00 AM 10 mL of milk was collected for analysis.
Total protein estimation was done by the Modified Lowry method [7,8].
Fat content was measured using a commercial enzymatic kit. In this
method, the fat is measured as triglycerides [8]. Lactose content of the
milk sample was measured by Nelson Somogyi method [8]. The coefficient
of variation of these three methods was less than 5%. Energy estimate
was made by using Atwater energy multiplication factors: carbohydrates
(4 Kcal/g), protein (4 Kcal/g) and fat (9 Kcal/g) [9].
Data was entered in a spreadsheet and analyzed with
statistical software R. Variability within each epoch of milk collection
was evaluated by calculating percent variability [10]. Percent
variability was calculated using following formula: Percent variability
= (x - mean) × 100/Mean.
A previous study had reported 15±13% variability in
protein and fat content of non-pooled own mother’s milk [10]. To detect
20±13% variability with alpha error of 0.05 and power of 80% we needed
to enroll 107 mothers. Significance of temporal change in macronutrient
contents was assessed using Kruskal-Wallis rank sum test.
Results
Milk samples were collected from a total of 106
mothers. Of these, 15 delivered at <30 weeks of gestation, 56 at 30-32
weeks and 35 at 33-34 weeks of gestation. Milk samples were collected
from 26 women on postpartum day 3±1, from 34 women on postpartum day
7±2, from 24 women on postpartum day 14±2, from 12 women on postpartum
day 21±3, and from 10 women on postpartum day 28±3. Mothers delivering
prematurely were of the mean (SD) age of 25±4.2 years. The most common
factors responsible for delivery at
£34weeks of gestation were preterm rupture of
membranes (41%) and eclampsia (15%). About one-third women delivered by
a C-section and the median gestational age at delivery was 32 weeks (IQR
31-33).
Over the first 4 weeks postpartum, there was a
significant decline (P=0.006) in the protein content from
4.1±2.1g/dL on the 3rd day to 2.2±0.6 g/dL by the 28th day. The fat
content of colostrum (3rd day) was lower than the fat content of
transitional milk (7th day) and mature milk (14th, 21st, 28th day, P=0.03).
The lactose content also increased from 2.2 g/dL in the first week to
3.0 g/dL by the fourth week. The energy content of milk escalated
progressively from 42.3 kcal/dL in the first week to 52 kcal/dL by the
fourth week (P=0.01). High degree of variability was observed in
macronutrient composition even when milk expressed at each time-point
was assessed (Table I).
TABLE I Composition of Breast Milk of Preterm Mothers
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Age |
Protein (g/dL) |
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Fat (g/dL) |
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Lactose (g/dL) |
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Energy (kcal/dL) |
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Post-partum |
Mean (SD) |
Percent |
Mean (SD) |
Percent |
Mean (SD) |
Percent |
Mean (SD) |
Percent |
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Variability |
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Variability |
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Variability |
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Variability |
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Day 3±1 (n=26) |
4.1 (2.1) |
43.7 |
1.9 (1.8) |
24.4 |
2.2 (0.7) |
68.2 |
42.3 (18.8) |
29.7 |
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Day 7±2 (n=34) |
2.8 (0.7) |
20.7 |
2.6 (1.4) |
29.9 |
2.4 (0.9) |
39.9 |
44 (12.4) |
21.0 |
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Day 14±2 (n=24) |
2.6 (1.0) |
24.7 |
3.2 (1.1) |
14.5 |
2.8 (0.5) |
28.0 |
50.5 (11.9) |
19.3 |
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Day 21±3 (n=12) |
2.3 (0.6) |
21.8 |
3.3 (0.8) |
19.4 |
3.0 (0.3) |
43.2 |
50.7 (8.2) |
25.8 |
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Day 28±3 (n=10) |
2.2 (0.6) |
47.5 |
3.4 (2.1) |
79.9 |
3.0 (0.9) |
53.0 |
51.9 (21.5) |
33.8 |
To determine whether the nutritional requirements of
the preterm neonate were being adequately met, the recommended and
actual values for protein and energy intake was calculated for each
neonate assumed to be receiving either 150mL/kg/day or 180mL/kg/day of
breastmilk. It was observed that in 102 (96.2%) neonates the minimum
prescribed energy intake of 110 Kcal/kg was not met even with 180 mL/kg
of breastmilk. With intake of 180 mL/kg of breast milk, the minimum
prescribed protein intake of at least 3.5 g/kg was not met in 67 (63.2%)
neonates.
Discussion
This study reiterates significant inter-individual
and temporal variation in the macronutrient content of human breastmilk
and inability of preterm milk to meet macronutrient requirement of
preterm neonates. The preterm milk is rich in protein initially and with
increase in postpartum age there is a decline in protein content and an
increase in the amount of lactose, fat and energy. Although
multicomponent fortification of milk can improve the macronutrient
profile, wide inter-individual variation reported in the present study
highlights the inappropriateness of use of fixed-composition
commer-cially available milk fortifiers. Large variability in the
protein and fat content of human milk has also been observed in a
systematic review of the studies which have reported macronutrient
composition of human milk [3]. Although studies from developing
countries were excluded from this review to exclude mothers with
suboptimal nutrition, protein content reported is lower than the present
study at all the postnatal age time-points. The increase in fat content
with postnatal age and stabilization of the content by second postnatal
week are comparable with the present study. Lactose content observed in
the present study is lower than levels reported by many other studies
[8,11,12]. However, lactose content of the milk decreases with degree of
prematurity and similar low levels have been reported previously by
Narang, et al. [13] in the milk obtained during first week after
birth. In addition, it is possible that some of milk samples in the
present study consisted predominantly of hind-milk which is relatively
rich in fat and contains less of proteins and lactose.
Decrease in protein and inadequate fat content of
breastmilk can compromise the physical and brain growth of preterm
neonates. Small studies from developed countries have demonstrated the
feasibility of targeted and individualized fortification [6,14]. This
consists of adding medium-chain triglycerides and/or protein
hydrolysates to meet the prescribed range of protein and energy intake.
However, influence of individualized fortification on long-term growth
and neuro-developmental outcomes has not been investigated.
The milk analyzed in this study was collected by a
standardized procedure designed to minimize variations and sample
collection was restricted to 2 hours in the morning to prevent any
diurnal variation. Although, a 24-hour pooled sample would have
minimized the effect of diurnal variation in the fat content, this
approach would have deprived the infant of mother’s milk for a day.
Another limitation of the study is the cross-sectional samples of
breastmilk instead of longitudinal follow-up of all the enrolled
mothers. The modified Lowry method used for measurement of proteins is
susceptible to interference by other compounds like carbohydrates,
calcium, magnesium and other chemicals used as buffers in the
laboratory.
In conclusion, this study suggests that the
macronutrient composition of breastmilk is highly variable and may not
be able to meet the energy and protein demands of growing preterm
neonates. In view of large inter-individual variation observed, further
studies are needed to evaluate the role of routine measurement of
content of macronutrients and individualized fortification of the
breastmilk.
Acknowledgement: ICMR-STS-2014 program for
providing a student fellowship to complete the project.
Contributors: SM, DC, JK: planned the study and
wrote study protocol; SM: collected the data; DC: analyzed the data; JK:
laboratory measurements were supervised; DC,SJ. data was interpreted;
SM: wrote first draft of the manuscript. All authors approved the final
draft.
Funding: None; Competing interest:
None stated.
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What This Study Adds?
• Preterm breastmilk shows marked temporal
and inter-individual variation in protein and energy content and
is not able to meet nutritional requirements of preterm
neonates.
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