Determinants of energy, protein, lipid, and lactose concentrations in human milk during the first 12 mo of lactation: the DARLING Study13 Laurie

A Nommsen,

ABSTRACT

Factors

ergy-yielding 9, and

Cheryl

associated

nutrients

12 mo

A Lovelady, with

in human

postpartum

search on Lactation, ples were obtained

M Jane concentrations

milk

in the

were

Bo L#{246}nnerdal, and

of en-

examined

DARLING

at 3, 6,

(Davis

Infant Nutrition and by complete expression

over 24 h. Milk energy density was concentration; both were positively

Heinig,

Area

Re-

Growth) Study. Samof alternate breasts

highly related

correlated to maternal

of ideal related

body weight (%IBW) at 6, 9, and 12 mo and negatively to milk volume at 3 mo and to parity at 12 mo. Milk

protein

concentration

was

6 and 9 mo and positively and %IBW at 9 mo. Milk related orrhea protein

related

related lactose

to nursing concentration

16 wk postpartum milk

but

composition

as body

composition,

during

the

first

not

is more diet, few

before.

some

volume

frequency was

at 6 mo positively

and

parity

during

Am

months.

findings

to maternal

at

later

such

lactation

J C/in

Nutr

milk concentrations study was limited

contrast,

data

from

maternal

only become this hypothesis,

poorly

among

well-nourished

and

dietary

factors

breast

milk,

dietary

populations

maternal fat stores milk-sampling pro-

of lactation (Davis Area

women

the effects

on human-milk

prolonged studies

of

composition

breast-feeding. that extend

into

To explore the latter

are necessary. Our data set from the Research on Lactation, Infant Nutrition

than

lipid,

199l;53:

differences

and

energy

thropometric

in the

in milk.

indicators,

These

gitudinal

intake

changes

ofthe

study

measures

will

Subjects

and

data

DARand of 12 to

lactose,

maternal

from

an-

a subgroup

of

variables such as nursing volume. Within-women loncomposition

the interrelationships

be examined

of protein, include

intake

in breast-milk

and

amounts factors

dietary

the participants, and mother-infant frequency, feed duration, and milk Lactation,

nourished

(3, 4). that

evident with longitudinal

interindividual

457-65.

KEY WORDS

of protein, lactose, or to the first 4 mo of lac-

a positive relationship between lipid concentrations when 24-h are used

stages LING

G Dewey

Growth) Study represents the first such effort that we know to collect representative milk samples throughout the first mo oflactation from a relatively large sample of well-nourished women. In this paper we examine factors potentially related

suggest

factors

In

and their

It is possible

to milk

These

sensitive

tation.

cedures

to milk volume at 6 and 9 mo and to continued amenat 9 mo. In a subsample who completed dietary records, intake was positively associated with lipid concentration

after that

negatively

or dietary intake lipid. However, demonstrate and milk

with lipid percent

Kathryn

during

among

in a separate

the

the

12 mo

four

outcome

were

described

publication.

Introduction There

is great

yielding

nutrients

populations amount

(1). of energy

taking

in similar

equate

energy

to identify

many

as maternal

As a result

there

can

and

protein

for growing

ofenergy,

range

in the

by breast-fed the

researchers

have

of ad-

infants,

protein,

lipid,

to milk

attempted

energy,

it is useful and

to relate of these

lactose

varies

both

samples

No significant Am J C/in Nutr

from

et al (2), who

45 well-nourished

relationships l99l;53:457-65.

were

obtained

lactating found

factors One of samples of the

Printed

in USA.

representative in Texas.

maternal ©

1991

fatness

American

overall

Society

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objectives (5).

document

total

Briefly,

data

tinue

infants only

nursing

their

with

I

From

2

Supported

DARLING

intakes

the first

ofNutrition, grant

for Clinical

Nutrition

patterns

86 CRCR

This

who

planned

of 12 mo were

University

to

of breast-

during

40 would

Address reprint requests to K Dewey, University ofCalifornia, Davis, CA 95616. Received November 21, 1989. Accepted for publication June 6, 1990. 3

designed

cohort

mothers that

was

18 mo oflife.

for a minimum

the expectation

by USDA

growth

breast-feeding

breast-feeding

the Department

study

and

during

infants

Study

longitudinal

for the

Ninety-two

recruited

ofthe this

nutrient

formula-fed

12 mo.

diurnally

women

between

The

presents

feedings. Very few researchers have used a sampling that accounts for this variability. One exception to by Butte

design

previously and

nutrients

have been found. is obtaining milk the concentration lipid,

Study

infants

importance

to concentrations

associations investigations intake, because

methods

well-nourished

be a wide

Given

intakes

of energy-

within

milk.

nutrition

contributor

concentrations

consumed

of milk.

protein

consistent in such of 24-h

this was in a study milk

even

in human

in milk, few the difficulties representative major

milk,

the determinants

Although

and within procedure

in the

in human

volumes and

concentrations such

variability

continue

paper the

first

to coninitially through

ofCalifornia

at Davis.

1-1968. Department

of Nutrition,

457

458

NOMMSEN

the first year. Selection criteria for the breast-fed group were mother and infant both be healthy with no chronic illnesses that

the

ofage

mother

plan

or to feed

the first Human

12 mo. Subjects

fomnia,

not

to introduce

120 mL/d

>

solid

ofother

milk

The protocol for this Review Committee

before

or formula

4 mo

throughout

the

92

50, and 46 respectively.

breast-feeding provided Of those

so because

they

data who

were

be inconvenient.

subjects

by the of Cali-

initially

73,

too

chronic

or found

the

to

upper

middle Average

medication,

the study

infants

had

weaned developed

3 subjects

procedures

either

to

been

given

majority

prepregnant

of subjects

incomes,

pregnancy

weight

percent

Mean maternal were primiparous.

ideal

age

was

Milk

sample

were

and

were

white

gain

was

14.8

body 30.4

weight ± 4.6

cup

at each

The remaining Test-weighing

nonHispanic.

(%IBW)

kg and was

36%

101 ± 14%.

of the

mothers

Home several height the

visits infant while

nearest

were

made

and maternal subjects were 0.5

cm

by use

monthly

from

indices (5). At the first visit, maternal not wearing shoes was measured to

was

performed total

of a steel

tape

measure

and

90#{176} angle against a wall. At each monthly visit maternal was measured on a Norelco digital scale (Stamford, CT)

wooden weight accurate

(in g) was added

during

sampled Total

pump,

period,

it carefully

be fed back infant intake

the

same

24-h and

Milk

test

(7).

intake

At 3, 6, 9, and weighing the

12 mo, breast-milk infant before and

by use of an electronic curate to the nearest

balance 1 g and

secutive

older

weights.

from below Subjects their were 24-h

For

the balance were asked

(Sartorius, programmed

infants

a swing

daily schedule for the test-weigh rescheduled ifthe infant showed milk intake was calculated by

on the

last day,

3) multiplying Because there insensible water

and

milk

intake

ment

factor

determined

by the

IWL

was was

typical

time

for each

by measuring

interval

feed of the after that (in hours),

test weighing we corrected

infant. IWL

First, directly

both summer and winter months in a subsample ofinfants. a total of 342 measurements of 37 infants, an average 0.05

g - kg

.

min’

was calculated,

of

which

was relatively

due to breastan adjust-

proportional for analysis.

Lowry

amount

pour

offa

10-

freeze the sample.

to the infant as desired. from the opposite breast period

to assess the

each

sub-

proportion

pumped as described

and the above.

(% was

infant’s

assay

to the volume pumped Protein was determined

(8), with

bovine

serum

at each by use

albumin

(BSA)

result

in slightly

values

cause

of the

elevated

instability

for total

of human-milk

protein. protein

in longitudinal by a modified

to

However,

be-

standards,

they

studies at the Folch extraction procedure was calculated

present (9, 10)

described by by summing

the values for protein, lactose, and lipid multiplying them by 5.65, 3.95, and 9.25 (12). A subset of samples was also analyzed

concentrations and kcal/g, respectively directly for energy

by the bomb-calorimetry The two methods where (13).

by Garza et al (12). as reported else-

Maternal

dietary

A subsample

Park,

yielded

of mothers

during

one

were

provided

NJ)

method described similar results,

intake

balance

volunteered

of the

to record

test-weigh

periods

a small

electronic

with

accurate

to 2 g and

a tape

their

dietary

at 3, 6, or 9 mo. (Ohaus, recorder

Florham that

they

used to document their food intake over a 3

or required

from weight mined

60,

busy

Another

recruited,

AL

product

study was approved of the University

Davis.

Of

(5).

foods

that and

ET

were

analysis package and food-composition tables the sample size for analysis of relationships intake

and

subjects with

an earlier cross-sectional milk composition were

milk

who data

from

composition,

completed 17 subjects

data

dietary

from

records

participating

study in which dietary intake assessed by the same methods

and breastas outlined

(n in

HUMAN-MILK above

(1 5). Characteristics

drawn

from

identical

the

to those

though

half

lactation,

of the

in the

subjects;

were

were

DARLING

exercised was

who

area,

nearly

study.

strenuously

not

different

therefore,

Al-

we included

of

analysis

was

carried

correlation

relationships

out

coefficients

between

dependent

maternal

variables

concentrations

12 mo

all of them

at each

postpartum.

the

were

used

or infant

of milk

to examine

protein,

four

Independent

package

characteristics

lipid,

of the

SPSSx

with

lactose,

time

points:

variables

the

maternal h, and

weight,

nursing

volume

produced in maternal

on

1 1 - 12 mo

resent

total

three

TSF

dummy returned

used

in the

four

dependent

fat,

and

from

data

for all subjects

not

available

degree

the following

fatness: weight,

prepregnancy %IBW, and

able

“%IBW

regressions was most also

because consistently

collection

4 d of test

use

in multiple

elsewhere.

and

on

the per-

carbohydrate,

in ad-

above (except changes return because these among

(r

this

0.78)

>

were

was

subgroup). was

indicative

selected

between

day

and

mean

for

exhibited of maternal

use

and

infant

the

infant

Stepwise

breast-milk

in multiple

intake

with

will

the

selected

the

during

selected

between

was then

and was on

intake was

relationships

regression

associations

volume

volume

breast-milk

multiple

fatness There

breast-milk

Breast-milk

regressions;

simultaneously

12-mo

regressed

it best reflected current maternal related to milk composition.

weighing.

concentrations

or

dietary-intake

intakes

listed menses

which

of visit”

relationship

the

the

8-9, to rep-

maternal weight and %IBW, and maternal TSF at time of visit. The independent van-

at time

a strong

sample

variables,

5-6,

9-,

were

and

of multicolinearity

among

For

carbohydrate

variables TSF and

In addition,

6-,

variables fat,

and

constructed

analysis.

protein,

intake/

2-3,

by the

dition to the independent in maternal weight and were

day.

between

variables

were

of calories

A high

for

nutrient

Results

of Pearson’s

nursing

However,

correlations

frequency because

had these

two

effects

tively correlated with each other, composition tended to be obscured included

in the

volume

and

regression variables were

was on

found

regression.

% pumped. used

milk the

This Thus,

to examine composition.

variables

were

that

van-

although

the

variable

volume

composition.

variables

were

situation forced the

also combined

When

significant

added

to the

itself

existed

with

forward-entry

posi-

was

only

milk

multiple effect

of these

relationships model

maternal mo

actual

(r

parity

and

milk

variable

their

infants

when

was

maternal

P