Studies in human lactation: milk composition and daily secretion rates of macronutrients in the first year of lactation1 Jonathan
C Allen,
ABSTRACT and
P Keller,
Time-dependent
secretion
from
breast-feeding
trations
Ronald
and
studied
secretion
chloride,
potassium,
glucose,
citrate,
changes
pregnancy
were
Philip
Archer,
in milk
through
rates total
of lipid,
calcium,
inorganic
lactose,
ionized
phosphate,
on day
of exclusive
>
to the
permeability
mammary and ionized potassium,
cells.
and
protein,
sodium,
analyzed
throughout
urea
and
calcium
and
chloride,
between 1 and which persisted
infant
pair. in
between
glucose,
in protein,
concentrations
Our the
potassium,
oflactose, infant
data first
chloride,
ionized
was also
imply
that
month
and
calcium,
individuals, for the con-
of each performance
Am
phos-
Lactation, lactose,
human
minerals,
milk,
pH,
is deter-
of 75 milk
Nutr
>
secretion ionized
rate, calcium
data
with
milk
of individuals sampling
was
cluding
detailed
analysis
and
these
significant
changes
composition and correlated
( 1 -9). However,
volume
analyzed
studies, growth
in none
longitudinally.
carried
out
of the
in milk
at intervals first
composition
gaps we initiated
Further,
2 mo
of
have milk
both
one
feeding
for
are most
rapid.
a comprehensive
macronutrient
partum
analysis
was
divided
into
two
Am J C/in Nutr
and
the period
1991;54:69-80.
ofexclusive Printed
in USA.
taken
from
the day
immediately
showed
elsewhere were
3529
± 337
preTo fill
and
each
breast
male
They
such
and
(1 ± SD)
feed
midfeed on the
sample day
measurements. faithfully
seven
female
3054
1 y. Addi-
(1 3). To disrupt
at a morning
of milk
and
breast-
for
previously
expression
collected three by using an
Caubreast-fed
exclusive
a small
were
for
nonsmoking successfully
as possible,
a sample
volume
as homogeneous
planned
volume
that the
an average
milk
breast-feeding
succeeding that
total
had
described
as little
of a full
samples were when possible
who
partial
were
breast-feeding
infants
represents
from and
of or
We (10)
the
birth
breast. weights
± 3 1 7 g, respectively.
the Six were Milk
times during the antepartum period, electric breast pump (Medela, Inc,
longitudinal from Milk
the anvolume
papers.
In this
we analyze temporal relationships during those intervals milk composition is relatively stable, namely, the anteperiod
volume
dictated
population
1 3 multiparous,
previously.
characteristics
in most
was measured and composition analyzed at frequent intervals during the first 2 mo oflactation, followed by measurements at monthly intervals to 1 y (10). Six subjects were weaned completely during the course of the study, allowing analysis of the effect of weaning on milk composition as well. Because ofthe sheer volume ofdata available from this study, paper when
in
weaning. from this
donated
her
our study
in Denver,
6 mo
woman
measured
were
living infant
composition
infant
and
of resources
(each
to make
Subjects
women
was the
1 mo,
when
study of human-milk composition and secretion teparturn period through the first year oflactation.
the
samples
at least
was
considerations
be restricted
24 d), we chose
normal
composition
during samples
( 12) as were the complete
elsewhere
practical
number
tional
studies of human-milk at stated intervals
changes
5 d postpartum
Subjects
Because
Introduction Many excellent made measurements
first
composition of the milk
are
breast-feeding.
the rapid
the
con-
components
ofexclusive
during
is taking Both
Methods
subject
J Clin
milk
glucose,
infant
(13).
as possible.
junctions,
place
presented
were
milk
(I 1) we analyze
taking
study
casian tight
paper
period
with changes in milk element composition
data
the
food.
of 1 5 major
the entire
composition
mother-
I99 1;54:69-80.
KEY WORDS
rate
compared The trace
and magnesium
postpartum.
secretion
when
of supplementary
sodium,
inorganic
characteristic lactation
pH,
were observed
6 mo. Significant differences among through lactation, were observed
to the
mined
decreases
and calcium
centrations ofsodium, phate. The amount transferred
significant
in lactose,
milk
terminating
kcal/d)
In the companion
magnesium, and
complexes
increases
100
centration
calcium,
and
(>
Concen-
creatinine,
of the junctional
Significant
6 postpartum
4 1 84 kJ/d
women.
pH were analyzed longitudinally from day 6 until weaning cornmenced. The composition of the antepartum secretion was related
C Neville
composition
6 mo
in 13 multiparous
and Margaret
breast-feeding
starting
© 1991 American
Downloaded from https://academic.oup.com/ajcn/article-abstract/54/1/69/4691094 by Washington University in St. Louis user on 09 June 2018
Society
I From the Departments of Physiology and Preventive Medicine and Biometrics, University of Colorado School of Medicine, Denver, and the Department of Food Science, North Carolina State University, Raleigh. 2 Supported by NIH contract HD-2-280 1 and NIH grant HD- 19507 (MCN) and grant RR 69 from the General Clinical Research Centers Program ofthe Division of Research Resources, University of Colorado Health Sciences Center. 3 Address reprint requests to MC Neville, Department of Physiology,
University
Received Accepted for Clinical
of Colorado
School
of Medicine,
April 19, 1990. for publication January Nutrition
Denver,
CO
80262.
2, 1991.
69
70
ALLEN
Crystal
Lake,
breasts tions. the
OH)
first
subject
lected from
each
who
infants
had
midmorning
weaned
breast
of 5 mL
expression
in
milk
been
feed
the
nursed
(10).
from
the vial to provide samples
kept
on ice and
24
h, where
into
1 .5-mL
ples
were
from
the
breast
mixed
when
and for that
before could
gave
of their
infants.
ofColorado
be
on Human
cream
cut
the
ion
displaces
ion-
was verified
by potentiometric
( 19). Calcium
and verified
expreswere
diluted
transferred milk
by an
NADH-linked
electric
action
with
by
manual
Protein
participation
was approved
by the
Internal
Review
Subjects.
volume
Infant
intake
was determined
by test weighing,
urease
picric was
acid
after
was
determined
analyzed
method
acid
by the
and
subject and
undertook 14 and
records
a modified
at monthly
ofall
milk
during the assessed.
study
Analytical
methods
schedule,
intervals
pumped,
test weighing.
test
weighing
thereafter.
expressed,
interval
after
so that
total
on days
Mothers
or leaked milk
One
also
from
6
kept
the breast
production
could
be
corrected
in which
Except
were
for citrate,
resentative
ofthe of
samples
two
methods
assays
was
gave
Lipid
was
technician
read
to percent
cream
glucose
and
analyzer
OH).
lactose
(Yellow
The
lactose
obtained
dietary
methods,
described
the
results
samples
using
assays were Springs
days infant
milk
was
analyzed
Folch
performed
analyzed
with
Instrument
assay was verified pressure liquid chromatography and ular-weight carbohydrates. Sodium
initial
pHs (14).
a diet record
for their
infant
for 3 con-
over
3-d period
the
sampling.
supplementary to record
The
day
food
coinciding
following
with
completion
infant
determined
USDA
were
previously
was
handbook
were
by
with
ofnutrient
considered
to be food
been
consumed test weighing
ofthis
record,
who reviewed intake of the
a computer
program
based
composition
offoods
(27). Mothers
in full
exceeded
had
all food
con-
lactation
until
4 1 84 kJ/d
infant
on the intake
of
( 100 kcal/d).
creamatocrit
(1 5). The same the height the
ratio
Statistical
methods
by assaying creamatocrit
The
data
a YSI model
samples:
DATA,
23 Industrial
scriptive
statistics
Yellow
by comparison did not detect and potassium
were
SYSTA STATS,
by using
on whole-milk mc,
measuring
various
Only
developed
Co
calibration
2) The method
fully
converting
fat content by both methods (16).
Hg with
recovery. 105%
(InstrupH was
PCO2 and
was visited in her home by a dietitian in detail with the mother. The caloric
method
curve
with
each month after They were instructed
supplementary
a calibration
were
by the
on the
blood-gas analyzer MA). Measured
by varying
samples
Westlake,
intake
maintained
secutive introduced. and
of milk
an ion-selective
was measured
of 40 mm
empirically
pH in a number
with
America,
Pco2
of
measured specall reagents ex-
the subject the record
SD. and
with
used was not
between
95%
all the creamatocrits,
following
values
method
to determine
the modified
milk samples of varying and the modified Folch The
obtained
The
the intraassay
ways:
here.
milk
against
values
with
between
1) for rep-
in two
difference
used
These
in fresh
the
less than
be summarized
standardized
method.
recoveries
acceptable. will
compared
unless
additions that
sidered (10),
were
and urea,
analytical
acceptable
standard
standardized
creatinine,
at least one other considered
carefully
(14).
Citrate
the reduction
ofNADH, containing
Radiometer
described
determined
Mothers used
ICA1,
to the pH at a Pco2
curves
Infant Methods
(model
before
used. modification
Gruber(26)
same samples with a carbon dioxide mentation Laboratories, Lexington,
the day
by re-
analysis
Boehringer-Mannheim
ples
ofor
creatinine
were
electrode
on the day
and
on col-
method (21) was measured
by Kjeldahl
to the oxidation A separate blank
as previously
measured
Urea
precipitation
test weighed for 24 h plus two feeds at weekly intervals through 2 mo postpartum and at monthly intervals thereafter. Milk samtaken
was
(23)
cept citrate lyase was run for each sample. pH and ionized calcium were analyzed OH),
and
measured by colorimetric spectrophotometry
phosphate
measured
ofMoellering
system
(18)
of Cotlove
by the bicinchoninic acid method (25) (Rockford, IL). Human milk standards
trichloroacetic
ofcitrate is coupled trophotometrically.
as described
Chloride
the chloride
(24).
with reagents from Pierce whose protein had been and
milk.
thiocyanate
earlier (1 3). Twelve subjects test weighed their infants before and after all feeds for 9 ofthe first 14 d after birth. They then
were
whole
the
All assays
by the method
magnesium were by atomic-absorption
were
containing (10).
in which
mercury
mL)
polyethylene
layer
with
titration
Inorganic
on skim-
(0.5
blade
procedure from
(20).
samples
an
techniques
thiocyanate
samples
upper
a razor
E2A
by flame-
performed samples
orimetrically by the phosphomolybdate-complex verified by the Fiske-Subbarrow method (22).
#{176}C. Sam-
with
other
milk
in a 0.5-ml
the
with
by a colorimetric
procedures
within
and
tube
lipid
and
,
by using
the method Milk
frozen,
verified
at -70
Center
x g for 10 mm
from
a Beckman for
were Milk
at 9000 tube, then
analyzed
for total
assays
centrifuged microfuge was
using
verified
as follows:
were
for their
Sciences
prepared
was
obtained
consent
samples
im-
Some
The protocol
Health
for Research
not
informed
milk
by
was
emission photometry. The following colorimetric
at a
All samples
obtained
technique
mm
for analysis
analysis. were
milk
Subjects
University
once
electrodes
This
filled
by manual
stored
ion-selective (17).
2-3
inversion,
and
manual
vial after
Pco2
(14).
by gentle tubes,
2 d postpartum
pump
expression.
Board
were only
first
time
tubes
col-
with
analyzer
were
sample of pH,
to the laboratory
microcentrifuge
thawed
a mixed
capillary
transported
they
for tubes
at the same
Natelson
by
plastic
breast
for analysis
were collected into
homes
creamatocrit
Additional
directly
each
were
AL
sured
secredaily for
Samples
subjects’
on
Three
mediately
ized calcium
at 8 mo.
into an acid-washed
analysis. sion
of both
other day to 14 d, weekly to 8 for 1 y postpartum with the cx-
thereafter
of one
contents
to 7 d, every
monthly
ception
of the entire
Not all subjects produced antepartum milk samples were obtained twice
3 d, daily
wk, and
the
for collection
(3-25 mL). Postpartum
ET
Spnngs,
with highhigh-molecwere mea-
Downloaded from https://academic.oup.com/ajcn/article-abstract/54/1/69/4691094 by Washington University in St. Louis user on 09 June 2018
was found
initially
subjected
to cross-sectional
analysis
T on a Macintosh SE microcomputer using CORR, and MGLH modules to obtain (28).
No significant
difference
between
the
de-
breasts
and
lactose
milk component except during episodes of and chloride concentrations were elevated decreased. Samples from these mastitis episodes,
five
for the
entire
mastitis
for any
when
sodium
study,
were
excluded
from
further
analysis.
TIME
DEPENDENCE
OF
HUMAN
MILK
71
COMPOSITION
For other samples, the data from the left and right breasts were averaged at each time point before further analysis. For detailed analysis oftime dependence, lactation was broken down into six periods defined as follows: 1) antepartum: samples were taken at various intervals beginning at 3 rno antepartum and continuing until birth; 2) lactogenesis: measurements of volume and composition from birth to day 5 were analyzed to determine the time course of lactogenesis; 3) month 1 : measurement of volume and composition from days 6 to 35; 4) month 2: measurement of volume and composition from days 36 to 60; 5) full lactation: measurement of volume and cornposition
from
day
61 until
>
4 1 84 kJ/d
(>
100 kcal/d)
supple-
was taken in, between 6 and 8 mo for all subjects; and 6) late lactation and weaning: measurement of volume and composition from day 180 until termination of the study at mentary
:
food
1 y. Lactogenesis
changes
and
and
late
lactation
represent
are dealt
with
separately
of the
four
other
(1 1). In each
periods
of nonlinear
in the accompanying periods
we
had
paper
at least
three
measures, often many more, over time for each mdividual. We analyzed the time dependence ofthe data from each individual before pooling, using regression analysis (29). A wide repeated
variety
of models
fit than
linear
points,
namely
dividuals.
tiplying centration
derived between
but
none
and
intercepts
for milk
individuals.
of that
more
secretion
consistent
at specified
derived
composition The
component.
gave
180 d, were
for these days was derived her time-corrected volume
were rate
determined of each
for each individual by the time-corrected
Mean
time
for all in-
secretion
corn-
by mulcon-
rate
was
then
by pooling across individuals. Significance of difference times was determined by Tukey’s multiple-comparison (28).
The concentration for each individual tionships
Slopes
values
across
procedure
using
examined
21, 45, 90, and
Mean
by pooling
ponent
was
regression.
the
data derived were subjected
Pearson
product-moment
between
concentration
sistency of milk volume mother-infant pair during by lag correlation
for the various to correlation method and
secretion
time points analysis by
to examine
rela-
variables.
Con-
and secretion rate for an individual exclusive breast-feeding was analyzed
(30).
Results
Figures 1-3 show the detailed time course ofmilk composition and secretion rate for all variables, averaged across women for each time point examined. Analysis of the time dependence of the composition of mammary secretion during the antepartum period showed no significant trends when averaged across women for any of the milk components analyzed. The greatest source of variation was between individuals, followed by breast and time (NS). For this reason, mean values for the composition of the antepartum secretion were obtained by first averaging the data for each woman and then averaging across subjects. The means are given in Table 1 along with their CVs. For all components except citrate and urea, the interindividual CV was substantially larger than the intraindividual CV, consistent with the conclusion that during the antepartum period the mammary secretion of each woman has a characteristic composition. The mean slopes and variation for changes in milk composition
for the
three
subdivisions
of full
lactation
are
presented
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100
200
300
DAYS POSTPARTUM FIG 1. Milk volumes and concentrations (A) and secretion rates (0) ofprotein, lipid, lactose, glucose, and pH in milk and antepartum mammary secretions. i ± SD of all subjects studied at the indicated time. Data from 3 to 13 subjects are averaged at each point. Antepartum concentrations are values from 4 to 6 women. Thirteen subjects remained in the study from 1 to 180 d, 10 subjects for 360 d. Means for days 390, 420, 450, and 480 represent 4, 5, 4, and 3 subjects, respectively. Secretion rates are given for exclusively breast-feeding subjects only, which represented all 13 subjects through 150 d and 10, 6, 4, and 4 women at 180, 2 10, 240, and 270 d, respectively.
in Table 2. Linear trends were calculated for each individual during each time period before pooling across women. These slopes and the appropriate zero-time intercepts were used to calculate the extrapolated milk composition for each woman on
72
ALLEN
ET
AL
increasing
%#7 mL/d
sodium,
potassium,
tein by 0.0l%/d
and
lactose
by 0.7 mmol
and
chloride
all declined
and the others
month 2 the only significant in sodium and potassium As lactation
continued
(between
7 and
9 mo
increase
in volume,
decreases
in protein,
by ‘-0.1
changes at a rate
from in most amounting sodium,
L
-
-
d’.
mmol
L
.
3 to the
onset
there
was
subjects), to
1 mL/d,
potassium,
and
chloride,
pro-
d.
-
were a continued of --0.04 mmol
month
Protein,
significantly,
During -
L’
decline - d’.
of weaning a significant significant magnesium,
a .5
0
E E (5
a)
0
E E C C (5 C.)
.5 0
E E 0
0.
w
LI-
a .5 0
E
B a) 100
200
DAYS
CS
300
I-
POSTPARTUM
C-)
FIG 2. Concentrations (A) and secretion rates (0) of calcium, magnesium, potassium, sodium, and chloride (top to bottom) in milk and antepartum mammary secretions. i ± SD of all subjects studied at the indicated time. See Figure 1 legend.
a .5 0
days
21, 45, 90, and
3. The
extrapolated
180. These concentrations
responding extrapolated the secretion rate
tam
Pooled
represent intakes,
secretion-rate
total and
pooled
include
were
are shown
multiplied
volumes, again of each component data
milk
data
by the
for each woman, for these same
rates
pumped
and
to obdays.
(5
C.)
in Table 4. These values by the women, not infant
leaked
milk.
Infant
and glucose month
increases
during
DAYS POSTPARTUM
intakes
centrations
significant
cor-
are presented
secretion
tended to be -5% lower (13). Table 2 shows that volume as well as lactose showed
E E
in Table
free
con-
1 , volume
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FIG 3. Concentrations (inorganic) phosphate,
in milk
and
studied
at the indicated
antepartum
and secretion rates (0) of urea, creatinine, citrate, and ionized calcium (top to bottom)
(A)
mammary
time.
secretions.
See Figure
i
1 legend.
± SD
of all subjects
TIME TABLE
DEPENDENCE
OF
HUMAN
MILK
73
COMPOSITION
1
Composition
of antepartum
milk samples1
Variable
i
SD
±
Range
Interindividual
Intraindividual
CV
CV
% Lipid (gIL) [1 1] Lactose (mmol/L) [9] Protein (g/L) [8] Sodium (mmol/L) [10] Potassium (mmol/L) [10] Chloride (mmol/L) [10] Calcium (mmol/L) [10] Magnesium (mmol/L) [10] Citrate (mmol/L) [8]
20.7 79.8 54.3 61.3 18.3 62.2 6.3 2.32 0.40
±
[P0;]
0.75
± ±
(mmol/L)
[9)
± ± ± ± ± ± ±
Glucose (mmol/L) [8] Urea (mmol/L) [9] Creatinine (mmol/L) [9]
0.34 2.48 0.13
pH (corrected) [6] [Ca] (mmol/L) [6]
6.82 2.24
All values
I
computed
from
means
9.8
8.6-43.5
17.0 25.8 5.6 17.4 0.2 0.50 0.17
27.5-86.0 36.5-107.3 9.5-29.0 43.8-90.3 3.3-10.6 1.1-3.3 0.18-0.67
47.2 27.2 31.4 42.2 31.0 28.0 33.5 25.5 42.7
0.23 0. 15 0.04 0.03 0. 18 0.84
0.31-1.04 0. 1 1-0.59 1.88-3.10 0.06-0.16 6.68-7. 1 1 2.44-4.71
30.4 44.6 16.2 23.8 7.6 25.9
± 21.7
± ± ± ±
of two to eight
calcium, free phosphate, and citrate. There crease in fat content over this period.
37.7-109.7
values
for each woman,
was a significant
in-
averaged
rates
before
pooling
across
of magnesium,
consistent
ionized
through
1 80 were even volume, shown
which
even in the face of changes The concentrations ofthe
there
are significant
and lipid increased sodium, potassium, Because creases
decreases
in volume,
nutrients
6 were
by fully
data
significantly chloride,
in the literature.
in concentration
changes
were
in the
breast-feeding
Note
that
during lactation whereas and calcium decreased. daily
compensated
by in-
between
of many months
2 and
small
(Table 4). However, significant and fairly large increases in lipid, lactose, glucose, and creatinine secretion rates and decreases in sodium and citrate secretion rates are apparent when the data for days 21 and 180 are compared. It is of considerable interest to know whether the milk composition and/or the secretion rate of any milk component is characteristic
of a mother-infant
pair
and
maintained
urea
for concentration
of these
substances
were higher than their correlations for secretion rate. For these substances we conclude that each woman has a characteristic milk composition that is maintained at least through the first 6 mo oflactation. The secretion rates ofthese components showed less correlation than did milk volume itself. Group 2 contained three nutrients: lactose, magnesium, and ionized calcium, whose concentrations were not very consistent through lactation as shown by the low correlation coefficients, particularly
between
days
21 and
180.
However,
somewhat
higher
in Group
3 showed
correlation
in secretion
For protein individuals
were
through
3 and
4 (Table
lactation
although
than the rest. However, those good correlation in secretion
rate
and glucose,
for these nutrients each secretion rate, maintained
volume. in Groups
correlation
for milk This ob-
comrate
for these milk components there secretion rate. There was little for
the
differences
components
in Group
in concentration
4.
between
small.
Discussion
through
period of exclusive breast-feeding. We used the method of lag correlation to examine this question (3 1). On days 45, 90, and 180, the milk composition ofeach individual was compared with her milk composition on day 21. For all components analyzed, correlation coefficients between the two times were calculated for the group. The results are given in Table 5 where data are presented in four groups. The concentrations of those milk components in Group 1 , namely sodium, potassium, phosphate, and chloride, showed significant correlations from days correlations
poor
that
in milk nutrients
through day 90, suggesting that is also a tendency for a consistent
We demonstrated
the
2 1 to 180. The
showed
was
ponents
lactose were quite coefficients at day
higher than the correlation coefficient at the top of the table for comparison.
servation leads to the conclusion mother-infant pair has a characteristic
5) generally
production
mothers
lactose
protein,
24.2 51.2 16.5 13.4 0.9 7.5 n in brackets.
calcium, and The correlation
lactation.
To compare the data from this study with data from other, cross-sectional studies, the mean (heavy line) and ranges (lighter lines) of the extrapolated milk-composition data from Table 3 are plotted in Figure 4 for all milk components for generally
subjects.
28.1 12.3 23.9 1 1.7 13.1 11.4 10.5 17.0 57.5
the
secretion
Downloaded from https://academic.oup.com/ajcn/article-abstract/54/1/69/4691094 by Washington University in St. Louis user on 09 June 2018
slow but continuous
with protein, sodium, potassium, and citrate, all of which 25% between months 1 and 6 of lactation. Lactose, calcium, and glucose increase 10% and chloride de-
creases by a similar amount. to be always in transition. milk,
often
applied
only
For
These
changes
com-
marked ionized
oflactation.
in milk
with
decrease
duration
changes
position
are particularly
Milk composition can this reason the term
to milk
produced
from
thus
be said
transitional days
5 to
10
postpartum, should be dropped from the scientific vocabulary. There is a need for standard values for milk composition to be used in evaluating clinical problems of apparently insufficient lactation and as a basis for establishing the nutrient requirements of
infants.
In
developing
such
values,
one
must
determine
whether data from one population group are comparable with those from another. For this reason we compared our data with data obtained in 27 other studies from both affluent and impoverished populations (Fig 4). Most values for total calcium fall within the range observed in the present study. Where sufficient data are available, the
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1
c).-L)
0 .
.5:
TIME TABLE
milk volume
and composition
Variable Volume
(mL/d)
4.7
±
1.9
±
1.5 3.03 0.203
±
6.7 2.6
±
(mol/L) SE, range
I
to Table 2. Mean differ, P < 0.05.
temporal
75
COMPOSITION
(37-39,
Pakistan
(47)
of ionized
is the
standardized
samples,
possibly
In this study, through
developed
TABLE
± 0.2
(6.8_8.5)a
(1.5-1.8)
0.1 (1.3-2.4) 0.06 (l.l_1.9)a
± 0.1 1 (2.25-3.56)
exception.
Many
No
The
other
were
(35)
showed studies
and
40,
41,
1.8 ± 0.1
(#{216}9_l8)ab
± 0.15
(2.2-4.0)
±
0.006
developing
values
countries
show
for the magnesium
(0.159-0.230)
(1.3_2.l)a
± 0.20
0.186
(1.98-3.90)
± 0.006
(2.7_2.8)c
1.8 ± 0.1
(1.2-2.6)
1.8 ± 0.1
(1322)b
2.90
± 0.20
0.186
(0.168-0.230)
(6.576.85)’
6.8
± 0.02
(6#{149}7_69)b
6.9
± 0.02
2.9
± 0.09
(2.5-3.50)’
3.0
± 0.01
(2.6_3.5)b
3.0
±
from the slopes for each
variable.
de-
lower
from
within
ours,
the one
obtained
on
centration
milk
should
the values
American differences
milk
from
described
being
the magnesium
by why
from
40, 42, generally
consistent
ions are
Butte
the magnesium
43,
5 1) fall mainly
decline
concentration
within
through milk
species,
lactation.
are lower
totaling
only
than
the
in milk
concentrations and chloride
ranges
The those
that
after
the
of the (4, 37, 39,
observed
in many
(40)
of other
here
concentrations
-‘.-25 mmol/L
et con-
or Texas
women (37, 4 1 , 5 1), and therefore conclude may arise from the methods employed.
in human
rodent
from
letter
atomic-absorption
Colorado
The limited data available for the monovalent cations sodium, potassium,
display
in the legend
superscript
the data
samples
of women
(0.159-0.230) (6.87.0)’
0.1 (2.53.9)’
a common
We see no reason
in the differ
regressions
exception
dry-ashed
spectrophotometry.
were
ofmilk
of the linear
a row not sharing
than
al (40)
study
and intercepts Values
(2.10-4.01)
± 0.007
± 0.02
obtained
(1.4-2.0)
± 0.1
6.8
48)
no
content
(1.1-2.3)
1.7 ± 0.07 2.88
an increase in magnesium during the first 2 followed by a leveling offor decrease. Values and
(43_74)b
(1.3-2.3)
± 0.07
in concentration 47,
± 0.2
± 0.1
(1.4-1.9)
(50).
little change (4, 37,
6.3
1.8 1.5
on fresh from
(l0.0-l8.5)’
(6.3_9.0)a
1.6 ± 0.05
we obtained
Chan
± 0.7
2.3
A study
performed
± 0.4
13.9
12_173)b
(2.3_3.3)c
systematic
values
(1#{216}4_154)L
12.4
(7.0_l7.8)a (1.5-2.3)
in both
(48).
(4.39.ly
1.8 ± 0.05
individuals
noted
for the differences
Jenness
Other
been
countries
± 0.4
2.6 ± 0.08
for each individual
has
± 0.2
(0.7-1.2)
6.0
(25_4#{149}1)b
0.194
across
1.0 ± 0.03
(0.8_l.2)c
± 0.1
2.96
0.004 (0.168-0.212) 0.04 (6.57.0)* 0.06 (2.4_3.0)a
7.5
(3.8_8.2)b
191. ± 4 (l592l4)’
3.1
1.6 ± 0.04
(2.74.4)*
for pH and
a tendency toward or 3 mo postpartum differences.
7.5
calcium
magnesium
lactation.
(1
1 1.6 ± 0.8
is available.
and
± 0.4
13.9
± 0.1
accounting
by Holt
(4.l_9.4)c
(lO.9_l9.l)a
developing
one
± 0.4
(l3.2_17.3)a
by averaging
calcium
± 0.03
180
± 22.0 (732966)”
5.6 ± 0.4
(173_2#{216}1)b
6.3
± 0.6
(5.6-8.8)’
801
(2.2_7.3)a
0.9
± 0.4
Value
in total
(4.99.8/’
13.0
obtained
49) and
188. ± 2
(#{216}.9_1.3)ab
± 0.4
Day
38 (583_920)a
± 0.4
15.1
± 0.02
±
± 0.03
±
(l3.8_19.9)a
± 0.2
±
4.2
0.8 (9.6_20.8)a
± 0.45 ±
700
(3.2-7.6)
182. ± 1 (l72_190.)ab
1.1 7.2
in parentheses.
carefully published
5.3 ± 0.6
0.04 (l.0-l.6) 0.4 (7.l_l6.l)a
±
Day 90
713 ± 31 (532_965)a
(2.6_6.5)a
values
decline
veloped
± 0.3
1.2 9.2 16.2 15.4 7.7 1.6 3.6
[POfl (mmol/L)
and
of these ruminant
3 mo
and
lactation.
4
Extrapolated
secretion
rate of milk
Variable Lipid (g/d) Lactose (mmol/d) Protein (g/d) Sodium (mmol/d) Potassium (mmol/d) Chloride (mmol/d) Calcium (mmol/d) Magnesium (mmol/d) Citrate (mmol/d) EPOZI (mmol/d) Glucose (mmol/d) Urea (mmol/d) Creatinine (mmol/d)
I
MILK
Day 45
176. ± 2 (165-189)’
Glucose (mmol/L) Urea (mmol/L) Creatinine (mmol/L)
[Cai
HUMAN
days postpartum1
717 ± 37 (538-l023r
(%/d)
pH [Ca]
on selected
Day 2 1
Lactose (mmol/L) Protein (%/d) Sodium (mmol/L) Potassium (mmol/L) Chloride (mmol/L) Calcium (mmol/L) Magnesium (mmol/L) Citrate (mmol/L)
from
OF
3
Extrapolated
Lipid
DEPENDENCE
(mmol/d)
components1
Day 21 postpartum 33.8 127 8.8 6.5 I 1.6 10.9 5.6 1.2 2.6
Day 45 postpartum
±
3.2 (l8.3_54.5)a
40.1
± 3.5 (2l.769.2)’
±
8 (93_195)a 0.4 (6.1-1 1.8) 0.4 (4.4_8.9)a 0.6 (8.8-16.3) 0.6 (6.0-13.7)
138 8.3 5.4 1 1.4 10.5
±
± ± ± ±
± 0.4
(3.7-8.9)
0.1 (0.9-1.8)
5.8
± 0.4 ± ±
± 3.2
(12.6_57.2)a
(107_181)ab
144
± 6.8
(100_183)b
(5.1-1
7.6
± 0.4
(5.5-1
4.7
± 0.3
(3.l6.3)’
10.6
± 0.4
10.6 5.7
± 0.5
(6.7-13.6)
5.7
± 0.3
(4.0-8.1)
1.2
±
(l.64.3)a
2.3
± 0.1 (l.8-3.4)’
1.4 1.0 2.13 0.133
± 0.1
(0.8-1.9)
1.4 ± 0.1
± 0.1
(0.7_1.6)*
1.8
± 0.1
SE, range in parentheses.
± ±
0.10 (1.42-2.90) 0.009 (0.106-0.194)” (l.4_2.4)*
2.1
Values were derived by multiplying
for each individual. The mean, SEM, and maximum a common superscript letter differ, P < 0.05.
and minimum
Downloaded from https://academic.oup.com/ajcn/article-abstract/54/1/69/4691094 by Washington University in St. Louis user on 09 June 2018
46.7
180 postpartum
± 3.0 (28.6_65.2)b
159
±
7.8
± 0.4
(6.3-11.8)
5.0
± 0.3
(3.67.6)’
(8.6-12.9)
10.4
± 0.4
(7.6-12.7)
± 0.5 ± 0.2
(7.6-14.6) (4.7-7.2)
9.7 5.3
± 0.7 ± 0.3
(5.1-14.8) (3.2-7.1)
1.3
± 0.0
(1.1-1.6)
1.4 ± 0.1
(1.1-1.7)
2.0
± 0.1
(1.3-2.5)”
1.9 ± 0.1
(l.32.3)’
1.8)
5 (132.0200.4y
1.5 ± 0.1
(0.64-1.96)
1.4 ± 0.1
(0.93-2.16)
(0.6_l.5)a
1.3 ± 0.1
(0.73l.85)’
1.5 ± 0.1
(l.06l.99)’
(1.45-2.95)
0.016
± 0.1
Day
(0.9-2.2)
± 0.15 ±
1.3)
0.1 (0.9-1.7)
± 0.1
2.21 0.124
32.6
0.3 (3.86.9)’ 0.5 (8.2-15.2)
± 0.2
±
Day 90 postpartum
(0.00.l77)a
(l.82.8)’
the milk output values
2.08
0.134 2.2
± 0.20 ±
0.009
± 0.1
(0.102-0.162)”
2.36 0.149
(l.82.7)’
for the relevant
were then calculated
(1.32-3.36)
2.5
± 0.17 ± 0.007 ±
0.1
time period by the corresponding
across
individuals.
Values
within
(1.65-3.20) (0.1
16_0.l85)c
(l.8_3.2)c
concentration a row not sharing
76
ALLEN
AL
2.5
Calcium(mmol/L)
10ITotol
ET
Magnesium
(mmol/L)
2.0 4n:n:YAeA
4r
Va
mm 25
20P,tassjum
17Protein
[
(mmol/L)
20
;::::::::
i4
Chloride
(mmol/L)
‘ (mmol/L)
Sodium
(%)
15 t
b’
3
9
.
I;
KZJH
Li
2 50
-
Lactose(mmol/L)
T
e j
6200
I
T
Tj
H
OHC
4bZVV’
3AGBBJ m b
I
.
_0
40
I
80 Days
120
160
40
2000
80
Postpartum
Days
120
160
200
Postpartum
FIG 4. Summary of concentration data for total calcium, potassium, protein, lipid, magnesium, chloride, sodium, and lactose as a function of days postpartum. The heavy curve represents the mean values for days 2 1, 45, 90, and 180 from Table 3 with ranges indicated by lighter lines. Mean values from other studies are indicated by lower-case letters representing values from reportedly well-nourished individuals: (country symbol and reference number) Australia, f(3 1); Canada, x (32); Egypt, h (33); Sweden, c (34); Thailand, u (7); United Kingdom, b(l), r(35), m (36); and United States, p (4), q (5), v (8), a (37), d (38), e (39), w (40), n (41), s (42), z (43). Upper-case letters represent values from undernourished individuals: Bangladesh, T (6); Ethiopia, K (44); The Gambia, J (3), B (9); India, 0 (45); Ivory Coast, I (46); USA, A (47); USA (Navajo), G (2); United States and Egypt, Y (48).
In cow
milk
centration
sodium and potassium The sum ofsodium,
cow
milk
is -82
mmol/L
(53),
and
in mouse
milk
75
milk
mmol/L
ofthese
to speculate may decrease water, thereby
water loss. Milk
46) not
protein in most
showed be little
and
(54).
species
that
In
(53),
the
and
contrast,
content
baby
renal greater
make
up
concentration
milk.
of
It is interesting
of human
excretion latitude
milk
of ions and for the use of
by sweating
and
insensible
water
to decline
with
duration
of lac-
tended
(1, 3, 8, 34, 37, 43, 46, 47, 5 1) and generally
values within the range reported systematic difference between
developed
alone
lactose
concentration for
control
milk
in human
low ionic
twice this conand chloride in 100 mmol/L
potassium
the
than
the requirement allowing the
studies
in goat
sodium
is lower
in temperature
tation
are about potassium,
(52).
countries.
Higher
here. values
protein
tended to be associated with colorimetric been standardized against human milk
The lipid content of human because of the large within-feed
There from
contents
appears developing
to
(3 1, 36, 37,
assays that proteins (55).
had
milk is very difficult to measure variation (I, 10). It is therefore
Downloaded from https://academic.oup.com/ajcn/article-abstract/54/1/69/4691094 by Washington University in St. Louis user on 09 June 2018
of considerable
interest
that
similar
values
were
obtained
in
studies from several laboratories in developed countries, including 1) Dewey and Lonnerdal (37) (Davis, CA; entire pumped contents of one breast at the second feed of the day), 2) Butte et al (40) (Houston; complete 24-h expression of milk from alternate breasts), 3) Clark et al (5) (Connecticut; complete expression 24-h
of one
expression
midfeed
samples).
breast),
ofboth Very
4)
Hytten
breasts),
(1)
(Scotland;
and 5) present
different
analytical
study methods
complete
(Colorado; were
used
Nevertheless the mean fat concentrations from these five studies were 4.3 ± 0.2% (SE) at 30 d and 4.6 ± 0.2% at 90 d postpartum. Milk samples from mothers in developing countries were also obtained by a variety of methods by 1) Butte and Calloway (2) (USA, Navajo; small afternoon sample), 2) Prentice et al (9) (The Gambia, unsupplemented subjects; pooled fore- and hindmilk samples from both breasts), 3) Nagra (47) (Pakistan; foreand hindmilk from a morning feed), and 4) Brown et al (6) (Bangladesh; complete 24-h expression from both breasts). The in these
mean
studies.
fat contents
from
these
studies
at 30 and
90 d postpartum
TIME TABLE
DEPENDENCE
OF
HUMAN
MILK
COMPOSITION
77
5
Lag correlation
between
day 2 1 and successive
lactation
intervals1
Concentration Day 45 Milk volume Group 1 Sodium Potassium Phosphate Chloride Group 2 Magnesium
Day 90
-
0.87 0.79 0.75 0.82
(