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-

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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

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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

(

Studies in human lactation: milk composition and daily secretion rates of macronutrients in the first year of lactation.

Time-dependent changes in milk composition and secretion from pregnancy through greater than or equal to 6 mo of exclusive breast-feeding were studied...
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