METABOLIC
STUDIES
OF
NORMAL
FULL-TERM
INFANTS
FED PASTEURIZED
HUMAN
MILK
By Samuel J. Fomon, M.D., and Charles D. May, M.D.
Department of Pediatrics, College of Medicine, and University Hospital, State University of Iowa
(Accepted February 21, 1958; submitted January 8.)
These studies were supported by grants from Ross Laboratories, Lever Brothers Company and the
Central Scientific Fund of the College of Medicine, State University of Iowa.
ADDRESS: (S.J.F.) Iowa City, Iowa.
PmIAmIcs, July 1958
101
U
N1’IL satisfactory criteria of optimalnutrition have been established, it
seems reasonable to accept performance of
the normal breast-fed infant as the standard
in infant nutrition and as the basis for
com-parison with performance of infants
ingest-ing milk formulas. Growth of infants fed
cow’s milk formulas has been shown to be
comparable to that of infants ingesting
hu-man milk.1 Data from metabolic balance
studies of infants fed human milk have been
published but, with one exception,2 have
concerned short-term studies.
The primary purpose of the present
re-port is the presentation of data from
nitro-gen balance studies of normal full-term
in-fants fed human milk during the first 6
months of life under conditions similar to
those usually employed in studies of
in-fants receiving milk formulas. Also provided
are data relating gain in weight to
reten-tion of nitrogen, and data regarding growth
and concentrations of hemoglobin in the
blood and of total nitrogen and urea
nitro-gen in the serum.
SUBJECTS AND PLAN OF STUDY
The studies to be reported concern nine
full-term infants fed human milk during the
first 6 months of life. At the time of admission
to the Metabolism Ward, seven of the infants
were between 4 and 5 days of age, one infant
(M.R.) was 15 days of age and one infant
(P.C.) was 20 days of age. General information
about the infants is provided in Tables I and
II.
Six of the infants received human milk as
the sole food during all, or nearly all, of the
period of study. Three infants (P.C., Ja.B., and
R.C.) received human milk for one or more
intervals of 4 to 8 weeks during the first 6
months of life and received “Formula 5,” a
formula prepared from cow’s milk,#{176} during
the remaining periods of the first 6 months
(Table II). Data collected during metabolic
balance periods in which this formula was
employed are to be published together with
data from studies of other infants receiving
the formula.3
From February, 1956, until January 10,
1957, each normal infant admitted to the
Meta-bolism Ward was enrolled in the study.f The
decision regarding the feeding of human milk
to an infant for the entire first 6 months of
life, as opposed to the feeding of human milk
during one or more intervals and Formula S
during other intervals, was made primarily on
the basis of the availability of human milk.
During April, May, and the early part of
June, 1957, a limited supply of fresh human
milk was available and was fed to as many of
the infants as the supply permitted. Four
in-fants (P.C., M.Ev., Jo.B., and Ja.B.) received
fresh human milk by bottle rather than
pas-teurized human milk during one or more
meta-bolic balance periods (Table II). Data collected
during metabolic periods in which fresh human
milk was fed are excluded from the present
0 Similac#{174} Liquid, supplied by Ross
Labora-tories, Columbus, Ohio. This formula supplied 67
calories/100 ml; the concentrations of protein,
lactose and fat were 1.72, 6.61 and 3.35 gm/lO0
ml, respectively.
f A female infant (D.St.), originally enrolled in
the study, developed an infection of the urinary
tract that proved difficult to diagnose and
some-what resistant to therapy. Because the purpose of
the present report is the presentation of data
con-cerning growth and metabolic retention of nitrogen
of normal infants, the data pertaining to infant
D.St. have been excluded from the present analysis
Subject and
Hoap. No.
Sex Race
Birth Wt.
Birth
Date
Father
Height Weight
(cm) (kg)
Mother
Height Wright Additional Information
(cm) (kg)
1-22-56 202 81 173 63 .5 3 older sibs; parents divorced before birth of third child (R.G., subject in
another study).3
7- 1-56 179 87 171 65 1 older sib (G.M., subject in another
study3) ; mother under observation for
possible active tuberculosis in 1955;
diagnosis never established; now
em-ployed as nurses’ aide at tuberculosis
sanatorium.
7-19-56 183 73.5 174 60 Parents not married; 1 older sib; mother
had active tuberculosis 4 years
previ-ously.
102 HUMAN MILK
M.R. Male
56-1710 Negro
3355gm
D.W. Male 3-15-56
56-3711 Negro
3070gm
R.C. Male 6- 5-56
56-6928 White
3825 gm
L.M. Male
56-8831 White
3600 gm
M.Ew. Male
56-9622 White
4105gm
TABLE I
INFORMATION ABOUT FAMILIES OF THE SUBJECTS
63 Mother 18 years of age, unmarried;
father not known; infant in custody of adoption agency.
165 64 1 older sib 5 years of age living and well;
3 other sibs apparently well at birth, died
suddenly and unexpectedly at ages 8-20
days; necropsy done in 2 failed to reveal
cause of death.
P.C. Male
56-14856 Negro
2465 gm
11- 4-56 ?183 107 Mother Negro, unmarried, 15 years of age, I previous child; father said to be
white; infant in custody of adoption
agency.
M.Ev. Male
56-17026 White
3905gm
12-20-56 174 75 165 68 Mother R.N., enrolled in graduate course in psychiatry ; father graduate student
in geography.
Jo.B. Female 1-10-57
57-512 White
2645gm
JaB. Female
57-513 White
2655gm
1-10-57
Separate-ovum twms; 2 older sibs (ap-proximately 1 yr and 2 yr of age,
respec-176 79 .5 155 48 tively, on 1-10-57); father resident M.l).
in radiology, University Hospitals.
analysis but will be reported with other
meta-bolic studies of infants fed fresh human milk.5
It had been planned that a metabolic
bal-ance study of 3 days’ duration be performed
with each infant every 2 weeks. Certain
devia-tions from this plan occurred. In the concurrent
studies of infants receiving fresh human milk,
some infants living at home were admitted to
the Metabolism Ward for metabolic balance
studies. Available facilities and personnel
per-mitted the performance of metabolic studies
of only five infants at one time so that
occa-sionally some readjustment was necessary in
the scheduling of balance periods of the
in-fants receiving pasteurized human milk.
TABLE II
GENERAL INFORMATION ABOUT THE SUBJEC’rS
Food* and Period
Subject Refusal of PHMf Remarks
When Fed
M.R. PHM age 15-182 days 1 refusal
D.W. PHM age 5-182 days 6 refusals; 1 during balance
period (age 165 days)
R.C. Formula S age 7-73, 135-182 days.
PHM age 74-134 days
5 refusals, age 74-77 days Unexplained poor appetite with failure to gain
weight between 69 and 97 days of age. Volume
of intake decreased to 93 ml/kg at 90 days of age,
then gradually increased (Table IV).
L M. PHM age 4-182 days 1 refusal
M Ew. PHM age 1-182 days 4 refusals Unexplained low gradefever 135-137 and 147 days
of age. Loose stools, poor appetite 146-148 days of
age. Weight 7425 gm at 148 days of age, 7175 gm
at 161 days. Varicella age 158 days.
P.C. Formula S age 2-19, 47-81, 110-146 days.
PHM age 20-46,
82-118, 147-182 days
(exception: FHM age
155-161, 169-175 days)
6 refusals, age 83-148 days Oriental facies; tetany of newborn; concentration
of calcium in serum low during first 50 days of life
but no tetany after 6 days of age.
M.Ev. PHM age 1-182 days
(exception: FHM age 102-108, 116-122, 130-132 days)
4 refusals; 2 during balance
periods (174 days, 179 days)
Varicella at age 21 days.
JoB. PHM age 5-182 days
(exception: FHM age
84-86, 95-97 days)
JaB. Formula S age 5-57,
141-182 days; PHM age 58-140 days (exception: FHM age 81-83, 98-100 days)
30 refusals, all except 2 after
77 days of age; 1 during bal-ance period (age 116 days)
14 refusals, age 72-127 days
* PHM =pasteurized human milk. FilM =fresh human milk. Formula S =Similac#{174} Liquid. t Refusal did not occur during balance periods unless noted.
II) and, with one exception (M.Ew., 151 days
of age), metabolic balance studies were not
performed unless the infants were well.
A portion of the fecal collection from Ja.B.
at 28 days of age was inadvertently discarded
and no analyses were therefore performed on
the specimens collected during that metabolic
balance period.
Two of the infants (P.C. and M.Ev.) served
as subjects in a study of the reproducibility
of the nitrogen balance method.6 For this
pur-pose, two 3-day metabolic balance studies were
performed consecutively on three occasions
with P.C. (beginning at 141, 155, and 169 days
of age) and on two occasions with M.Ev.
(be-ginning on 102 and 116 days of age). Only
the first of each such pair of consecutively
performed balance studies is included in the
data that will be presented here.
104 HUMAN MILK
of milk they would accept readily and
consist-ently; no change in the volume of feeding was
made in the 7 days prior to the onset of, or
during, a metabolic balance period. All of the
infants were given supplementary vitamins A,
C, and D#{176}but no other foods or accessory
food substances.
COLLECTION,
PROCESSING
AND
COMPOSITION OF THE
HUMAN MILK
A facility for the collection of human milk
was established in the Department of
Pedia-trics of the State University of Iowa in
Febru-ary, 1956, and maintained in operation for 14
months. During that time, 1,665 liters of human
milk were collected from a total of 89 donors.
The donors were almost exclusively wives of
students in the University. The mean age of
the donors was 25 years, and the range 18 to
37 years.
Each donor nursed her own infant as well as
supplying milk for investigative purposes. Milk
was generally expressed from the breast
manu-ally, some donors nursing their own infant at
one breast and expressing milk from the other
breast, while other donors expressed milk from
both breasts either before or after nursing their
infants. The particular procedure employed by
a donor may have affected the concentration
of nitrogen.
Daily collections of milk from the individual
donors were pooled, pasteurized, a small
ali-quot taken for bacteriologic analysis and the
remainder of the pool frozen. A quantity of the
frozen milk sufficient to feed the infants under
study for a 24-hour period was allowed to thaw
slowly in a refrigerator. The thawed milk, often
including amounts collected on different days,
was again pooled before being divided into
nursing bottles.
Certain precautions were taken to detect
dilution of the milk (with water or cow’s milk)
by the donors, if this should occur. With rare
exceptions, an aliquot of the milk supplied by
each donor each day was analyzed for effective
osmolarity by determination of depression of
the freezing point. The donors were aware
that these determinations were made. On a
a Tri-Vi-Sol#{174}, 0.3 ml daily, provided 2500 I.U.
vitamin A, 25 mg vitamin C, and 500 lU.
vita-mm D. This preparation was supplied by Mead
Johnson & Company.
few occasions the concentration of nitrogen or
of chloride in the milk of an individual donor
was determined. No instance of dilution was
detected.
The number of donors gradually increased
and the average volume of the individual
dona-tion also increased. Early in the study few of
the donors had been lactating for more than
2 or 3 months, while later in the study a
gradually increasing proportion of the donors
had been lactating for more than 5 months.
It is well known that the composition of
hu-man milk from an individual varies, the
con-centration of nitrogen often becoming
con-siderably less as the duration of lactation
in-creases.ra This may have occurred in the
pres-ent pooled collections of human milk for it
was found that the mean concentration of
nitro-gen in milk collected during the first few
months of the study was 1.9 gm/l, while in the
last few months of the study it was 1.6 gm/l.
The mean value was nearly identical to the
value of 1.76 gm/i (protein, 1.1 gm/100 ml)
reported by Macy8 and most other
investi-gators,aa but less than that reported by
Card-ner and Fox.Sa
Some alteration of the physical properties of
the pooled human milk occurred with the
pasteurization and freezing. After thawing, a
tendency was noted for fat to separate from the
milk so that fat droplets could be seen adhering
to the sides of the nursing bottle after a
feed-ing. The mean amount of fat remaining in 46
such “empty” bottles was 0.3 gm/bottle (range
0.1 to 2.7 gm/bottle, all except one bottle
con-taming less than 1.0 gm of fat). On those
oc-casions when a few milliliters of milk remained
in the bottom of the bottle, the amount of fat
remaining in the bottle after nursing was
greater. However, with the exception of
in-fants Jo.B. and Ja.B., refusal of a portion of
the feeding rarely occurred (Table II). When 4
to 16 ml of milk remained in a bottle, the mean
amount of fat in this residuum was 1.12 gm
(S.D. 0.45 gm) in 16 consecutive
determina-tions. The amount of fat remaining in the bottle
was therefore fairly small and the caloric
con-centration of the milk ingested by the infants
was believed to be similar to that ingested by
the breast-fed infant.
Regurgitation, usually of an amount of milk
estimated as 5 to 15 ml, occurred occasionally.
Subtraction of the estimated amount of the
in-3
2
62
4 A
11W-50
23456
ARTICLES
- MEi
?
:“I
:
-
::;
f:i
-HF;
t__t:7rLr4
GIRLS
,
=
z
.,
r1
EttTh
=
I 23456
AGE (months)
FIG. 1. Growth in length and weight of the nine infants studied. Dotted lines indicate intervals during
which Formula S rather than human milk was fed. (Plotted on Iowa Growth Charts.”)
take resulted in some uncertainty concerning
the true net volume of intake. The minor
dis-crepancy so introduced was considered to be
of little importance except during a balance
period.*
METHODS
The methods of performing the metabolic
balances have been described previously.6 For
analyses of serum, venipuncture was ordinarily
performed 3 to 4 hours after a feeding.
The concentrations of total nitrogen and
urea nitrogen in serum were determined by the
microdiffusion methods of Conway and
O’Mal-ley.1#{176}Ifl the case of total nitrogen in the serum,
microKjeldahl digestion was performed with
an aliquot of serum of 0.2 ml according to the
modffication previously described’ of the
0 The age (in days) when regurgitation occurred
during a balance period and the estimated volume
were as follows: M.R.-65 (days): 5 ml; 79: 30 ml;
95: 15 ml. D.W.-11: 15 ml; 12: 15 ml; 26: 5 ml.
R.C.-92: 5 ml. L.M.-23: 15 ml; 66: 15 ml; 117:
15 ml; 134: 25 ml. M.Ew.-18: 20 ml; 32: 15 ml;
46: iO ml; 47: 100 and 20 ml; 48: 45 ml; 83: 30
ml; 102: 5 ml; 151: 15 ml; 152: 5 ml. P.C.-44:
15 ml; 115: 5 ml. M.Ev.-11: 15 ml; 40: 30 and
10 ml; 75: 15 ml. Jo.B.-67: 15 ml. Ja.B.-67:
15 ml.
method of Van Sbyke and Kugel.1’ The
micro-Kjeldahb digestion tubes were calibrated to a
volume of 15 ml rather than 50 ml.
The concentration of hemoglobin in whole
blood was determined by a modification of
the method of WU.12
The concentration of fat in milk was
deter-mined by a slight modification of the method
of Van de Kamer et aL13
Growth
RESULTS
Growth curves of the nine infants may
be seen in Figure 1.
In the panel on the left, the gains in
weight and increases in length of the five
male infants fed human milk throughout
the first 6 months of life are shown as
con-tinuous heavy lines. Lighter lines indicate
the 16th, 50th and 84th percentiles for
length and weight of normal infants in
Iowa.14 D.W., a Negro infant, was
well-proportioned but small. MEw. was
some-what thin, the weight during the first 4
months of life being at about the 50th
per-centile and the length at about the 84th
TABLE III
CONCENTRATION OF HEMOGLOBIN IN BLOOD AND OF TOTAL AND UREA NITROGEN IN SERUM
106 HUMAN MILK
months of life this infant experienced two
minor illnesses and gained only 250 gm
be-tween 130 and 179 days of age (Table II).
In the central panel of Figure 1, the
growth curves apply to female,
separate-ovum twins. Jo.B. received human milk
(continuous heavy line) throughout the first
6 months of life, and Ja.B. received
For-mula S (dotted line) until 57 days of age,
human milk from 58 to 140 days of age and
Formula S from 140 to 179 days of age.
In the panel on the right in Figure 1 are
the growth curves of two boys (R.C. and
P.C.), who received Formula S during
por-tions of the first 6 months of life and human
milk during other portions (Table II). P.C.,
an infant of a Negro mother, was small at
birth and distinctly smaller than normal
throughout the first 6 months of life. The
father was reported to be tall and white,
but the oriental facies of the infant was
difficult to explain on this basis.
Analyses of Blood
The concentrations of hemoglobin in the
blood and of total nitrogen and urea
nitro-gen in the serum are presented in Table
III. The concentration of hemoglobin
grad-ually decreased with advancing age, as
might be anticipated in infants subjected to
periodic withdrawal of blood and not
re-ceiving iron-containing foods or medicinal
iron. At the time of each venipuncture, 4
or 5 ml of blood (rarely as much as 8 ml)
were withdrawn. Ordinarily blood was
drawn from each infant six to eight times
during the first 6 months of life. Subject
P.C., with tetany of the newborn, and
sub-ject R.C., with a bizarre family history
(
Table I), experienced venipunctures morefrequently than the other infants during the
first few weeks of life. The concentration
of hemoglobin in the blood of P.C. at 37
days of age was 7.5 gm/100 ml but had
in-creased to 10 gm/100 ml by 179 days of age
without administration of iron. With the
exceptions of subjects P.C. and R.C., the
concentrations of hemoglobin between 3
and 5 months of age generally ranged
be-tween 9 and 10 gm/100 ml as compared
TABLE III (Continued)
.
. . #{149}#{149}.
#{149}...:.. .
? .. #{149}.% 0’ E w z IL 0 0 > 300 250 200 I50 I00 50 - 0-#{149}#{149} . #{149}. . . .. .#{149} . . #{149}. . .
#{149}1 C
20 60 00 40
(days)
180
2 3 4 5 6
sUk;ect Age (days) Hemo-giobin (gm/100 ml) Total . Urea Nitrogen (mg/100 ml) M.Ev. 21 84 112 133 168 13.6 9.5 10.0 10.8 10.5 7.2 6.3 5.2 7.6 9.0 5.0 6.6 5.6 Jo.B. 7 63 91 112 143 15.2 10.2 10.0 9.8 10.1 7.4 9.4 7.6 8.6 10.6 6.5 7.5 6.4 JaB. 63 91 112 9.0 10.8 10.4 6.8 8.5 7.4 5.8 5.8 6.3
with normal values of 12.2 ± 2 gm/100 ml
for infants in this age group.15
The concentrations of total nitrogen in
the serum did not systematically increase
nor decrease with advancing age. The mean
concentration was 8.4 gm/l and the
standard deviation ± 1.2 gm/I.
Assum-ing that 1 gm of nitrogen in the serum is
equivalent to 6.25 gm of protein, this mean
concentration of nitrogen is equivalent to
5.25 gm of protein/100 ml of serum. The
mean concentration of urea nitrogen in the
serum was 6.3 mg/100 ml and the standard
deviation ± 1.5 mg/100 ml.
Metabolic Studies
Data pertaining to 74 metabolic balance
studies performed with the nine infants
fed pasteurized milk are presented in Table
IV.
VOLUME OF INTAKE: Table IV and Figure
2 indicate the volume of milk ingested with
respect to body weight during the first 6
months of life. Each point on the graph
indicates the mean daily volume of intake
of one infant during the 3 days of a
meta-bolic balance period. Mean volume of
in-take in relation to body weight gradually
decreased during the first 6 months of life,
being 218 mb/kg/day (S.D. ± 22) in the
first 45 days and 140 mI/kg/day (S.D. ± 10)
during the last 45 days (age 137 to 182
days) of the first 6 months.
NITROGEN BALANCE: The intake of
nitro-gen expressed in relation to body weight
is depicted graphically in Figure 3. The
in-fants ingested sufficient human milk to
re-sult in a mean intake of nitrogen of 38.3
AGE (months)
Fic. 2. Volume of intake in relation to body weight of infants fed pasteurized
Subject
Age Weight Length Volume
of Intake
IntakeofNitrogen Excretion of Nitrogen
-Retention of Nitrogen
Urine Feces Total (% of
(days) (gm) (cm) (mi/kg) (mg) (mg/kg) (mg) (mg) (mg) (mg) (mg/kg)
in-take)
M.R. 30 3750 52.2 224.0 1332 355 365 209 574 758 202 57
(male) 44 4470 53.8 234.9 1819 406 585 189 774 1045 233 57
58 4930 55.8 182.6 1650 334 808 206 1014 636 129 38
65 5160 56.7 174.0 1853 359 712 243 955 898 174 48
79 5575 58.8 159.6 1684 302 771 229 1000 684 123 41
93 6025 60.3 148.5 1769 294 861 159 1020 749 125 42
107 6525 61.9 147.1 1859 284 720 323 1043 816 125 44
135 7000 63.1 137.1 1769 252 707 329 1036 733 104 41
149 7450 65.4 136.9 2066 277 988 436 1424 642 86 31
163 7760 66.5 135.3 2103 271 1122 293 1415 688 89 34
177 8300 66.7 137.3 2214 266 1279 356 1635 579 70 30
D.W. 11 2960 49.6 209.5 1279 432 379 209 588 691 234 54
(male) 24 3325 50.8 215.6 1856 407 470 243 713 643 193 47
38 3840 53.2 218.8 1660 432 586 289 875 785 205 47
52 4300 54.4 191.9 1598 371 793 805 187 51
81 4800 56.7 175.0 1548 322 393 273 666 882 184 57
95 5260 57.5 158.7 1691 321 567 306 873 818 156 49
109 5500 58.9 152.7 1682 305 645 209 854 828 150 49
123 5985 59.8 160.4 1865 311 1100 765 128 41
137 6250 61.4 153.6 1862 297 808 329 1137 725 116 39
151 6650 61.8 144.4 1830 275 776 296 1072 758 114 41
165 6890 63.0 137.9 1741 252 1115 229 1344 397 57 23
179 6930 63.8 129.9 1632 235 1085 226 1311 321 46 20
R.C. 90 6355 62.0 106.1 1234 194 664 186 850 384 61 31
(male) 104 6575 63.8 136.9 1608 244 624 189 813 795 121 50
118 6890 64.8 139.3 1670 242 899 166 1065 605 88 36
132 7140 65.6 140.1 1736 243 949 169 1118 618 87 36
L.M. 8 3655 53.3 213.4 1304 356 459 219 678 626 171 48
(male) 22 4255 55.2 233.8 1936 454 743 273 1016 920 216 47
36 4760 57.1 210.1 1930 405 834 179 1013 917 193 47
50 5290 58.7 189.0 1776 335 886 209 109.5 681 129 39
64 5675 59.4 177.5 1970 347 821 442 1263 707 125 33
78 6225 62.0 173.5 1929 309 962 316 1278 651 104 35
92 6500 62.9 166.1 1878 288 1135 246 1381 497 76 26
106 6840 63.9 157.9 1875 274 1001 163 1164 711 104 38
120 7120 64.7 151.7 1896 266 1113 223 1336 560 79 30
134 7400 66.3 147.6 1812 244 988 279 1267 545 73 30
148 7610 66.5 144.6 1756 230 1052 296 1348 408 53 23
162 7885 67.7 139.5 1749 221 1085 263 1348 401 51 23
M.Ew. 18 4300 57.8 221.7 1839 427 561 309 870 969 225 53
(male) 32 4880 58.7 195.7 1696 347 630 329 959 737 151 44
46 5250 59.9 171.9 1651 314 621 333 954 697 133 40
60 5575 60.4 172.2 1714 307 729 382 1111 603 108 35
81 6125 63.2 155.1 1615 263 803 303 1106 509 83 31
102 6500 65.6 153.5 1753 269 836 256 1092 661 101 38
116 6850 66.9 160.6 1826 266 1340 486 71 27
130 7150 68.0 153.8 1756 245 867 286 1153 603 84 34
151 7175 69.5 138.4 1513 210 817 369 1186 327 45 21
179 7400 71.5 148.6 163 227 937 356 1293 390 53 23
- 108 HUMAN MILK
TABLE IV
TABLE IV (Continued)
Subject
Age Weight Length Volume
of Intake
IntalceofNitrogen Excretio n of Nitrogen Reteni on of Nitrogen
(% of
Urine Feces Total
(days) (gm) (cm) (mi/kg) (mg) (mg/kg) (mg) (mg) (mg) (mg) (mg/kg)
in-take)
P.C. 29 2850 47.4 210.5 968 339 385 163 548 420 147 43
(male) 43 3325 49.8 239.1 1211 364 437 166 605 608 183 50
99 4075 .53.8 220.9 1347 330 556 219 775 572 140 42
113 4525 .55.5 198.5 1392 307 640 169 809 503 129 42
182 6175 61.3 161.9 1450 234 764 269 1033 417 67 29
M.Ev. 11 3875 52.2 179.4 1104 284 283 163 446 658 169 60
(male) 39 4840 55.7 170.9 1438 297 515 316 831 607 126 49
60 5240 58.0 160.3 1408 268 486 106 .599 816 156 58
74 .5650 .59.4 158.4 1342 237 613 129 752 590 104 44
88 6010 60.4 149.8 1260 909 630 183 813 447 74 35
144 7460 65.2 134.0 1753 234 816 306 1122 631 84 36
158 7650 65.7 130.7 1550 t02 998 316 1314 236 31 15
172 7800 67.1 127.9 1700 217 987 199 1186 514 65 30
179 7900 67.6 126.2 1622 905 964 943 1207 415 53 26
Jo.B. 11 2580 48.3 232.6 1030 399 753 277 108 27
(female) 2.5 3125 49.6 256.0 1309 418 700 609 194 46
39 3485 50.9 243.9 1424 408 833 591 169 41
53 3925 .52.6 216.6 1275 394 767 508 129 40
67 4315 54.0 194.7 1182 273 687 495 114 42
116 5340 58.0 157.8 1922 228 860 362 67 99
131 5550 59.1 153.9 1391 250 967 424 76 30
144 5900 60.0 152.5 1386 234 913 473 80 34
JaB. 67 4035 54.3 203.2 1147 284 700 447 111 39
(female) 123 542.5 60.0 152.4 1447 266 947 500 99 35
137 5775 60.0 147.1 1317 228 840 477 83 36
630
‘; :i500
.3
-E E #{149}#{149} .
. ;400 #{149} I
Lii #{149}C
z
w- c #{149} #{149}
#{149} C #{149}#{149}
2 300 #{149} CC C #{149}#{149}#{149} #{149}
U. #{149}$ #{149} #{149}S
LI. U #{149} #{149} #{149} *s
0 0 C #{149}*#{149} #{149}
#{149} #{149}. #{149}
LU W20#{176} S
“a’
I-
I-100 20 60 00 140 180
(days)
0 1 1 1 I
I 2 3 4 5 6
AGE (mcvi//,s)
Fic. 3. Intake of nitrogen in relation to body weight of infants fed pasteurized
. S
S
. . S
S S
300
a’
.
- 250
z 200
0
I-z $50
LL
0
$00
a: 50
o
S
S S
55
#{149}#{149}
S #{149}SSS 5
S
#{149}a..
S
#{149}#{149} S
S S
555 5
S 5
S
S S
S
S S
20 60 00 40 80
(days)
S
2 3
AGE (months)
4 5 6
Fic. 4. Retention of nitrogen in relation to body weight of infants fed pasteurized
human milk during the first 6 months of life. The calculated regression line is
included.
110 HUMAN MILK
mg/kg/day (S.D. ± 45) in balance studies
performed during the first 45 days of life,
and 240
mg/kg/day
(S.D. ± 27) in thestud-ies performed during the last 45 days of the
first 6 months of life. Because ofthe gradual
decrease in the concentration of nitrogen in
the pooled human milk during the course
of the study
(
see p. 104) the intakes ofni-trogen of subjects M.R. and D.W. (studied
between February and September, 1956)
tended to be slightly greater at comparable
ages than the intakes of M.Ev., Jo.B., and
Ja.B. (studied between December, 1956,
and June, 1957).
The retention of nitrogen at various ages
and the retention of nitrogen plotted against
intake of nitrogen are presented graphically
in relation to body weight in Figures 4 and
5.
The regression of retention of nitrogenon age has a slope of -0.81 and a standard
error of the estimate of the regression
equa-lion16 of ± 29.6 mg/kg/day. The regression
of retention of nitrogen on intake of nitrogen
has a slope of + 0.67 and a standard error of
the estimate of the regression equation of
± 22.3 mg/kg/day.
RELATION OF GAIN IN WEIGHT TO RETEN
flON OF NITROGEN: In Figure 6 the mean
daily gain in weight from 1 week prior to
the onset of a metabolic balance period
until 1 week after the onset of the balance
period is plotted against the daily
reten-tion of nitrogen during the balance period.
The regression of gain in weight on
reten-tion of nitrogen has a slope of +31.9 and
a standard error of the estimate of the
re-gression equation of ± 6.7 gm/day.
The ratio of gain in weight to
reten-tion of nitrogen remained quite constant
throughout the first 6 months of life, having
a mean of 42.1 and a standard deviation of
± 11.5. Calculations from the data of Jeans
et al.17 indicate that this ratio for infants less
than 6 months of age fed cow’s milk and
ad-ditional carbohydrate has a mean value of
approximately 27.
DISCUSSION
The objectives in the field of infant
flu-trition are as yet vaguely conceived. The
attainment of greatest possible size or
. .
.
.
I, - 250
-a’ E z200 Lii
0
:: ISO
z IL
0
z 100
0
I-z w
I-w
a:
a
-INTAKE
OF NITROGEN
(mg/kg)
Fic. 5. Relation of retention of nitrogen to intake of nitrogen, both expressed in
terms of body weight. The calculated regression line is included. .
200 300 400 500
>,
0
.v
E
a’
I-Li
2
2
LI,
S
S S
S S
S
55
S
S S
$5
S S
.4 .5 .6 .7 .8 .9 1.0
goals of animal husbandry, are clearly of
little consequence per se. Small differences
in longevity, general vitality and
suscepti-bility to disease might well result from
clinically inapparent differences in
nutri-tional state and would seem of more
pro-found importance than mere attainment of
size. However, except in states of gross
malnutrition, such criteria have thus far
proved exceedingly difficult to correlate
with nutritional state.
In the present phase of development of
infant nutrition, the immediate goals must
be thought of as descriptive. It seems
es-sential to ascertain the result, in terms of
growth, metabolic performance or body
RETENTION OF NITROGEN (gm/day)
Fic. 6. Relation of daily gain in weight to retention of nitrogen. The calculated
112 HUMAN MILK
composition, of various feeding regimens.
Only then can a satisfactory attempt be
made to interpret the differences, if any,
by correlation with differences in physical,
motor or mental behavior.
It has been shown in the study by Paiva1
that in a relatively homogeneous racial and
socio-economic group, the growth of
breast-fed infants during the first 3 months of life
does not differ significantly from that of
in-fants fed cow’s milk formulas. Because both
groups of infants received solid foods
be-tween 3 and 7 months of age, the similarity
of rates of growth during that period
can-not be interpreted. The growth in length
and weight of the nine infants in the
present study proceeded parallel with
standard growth curves. Three of the
in-fants (P.C., Jo.B., and Ja.B.) were small at
birth and continued to be small during the
first 6 months of life. One other infant
(R.C.) received human milk for only 2 of
the first 6 months of life.
The somewhat greater concentrations of
total protein in serum of normal infants
studied by other workers (mean value 6
gm/100 ml)1SL than in serum of the
sub-jects of the present investigations (mean
value 5.25 gm/i#{174} ml) may be related to
the ingestion of greater amounts of
pro-tein by the majority of infants included in
those studies. The mean concentration
of protein in the serum of 15 breast-fed
infants studied by Natelson et al.19 was
5.15 gm/100 ml (S.D. ± 0.21) at 32 days
of age.
The mean concentration of urea nitrogen
in the serum in the present study was 6.3
mg/100 ml, a value slightly less than the 8
mg/100 ml (S.D. ± 2) reported by
Natel-son et al. for 15 breast-fed infants at 32
days of age. The mean concentration of 12
mg/100 ml reported in studies of other
normal infantslSb almost surely is the
re-suit of a greater intake of protein.
Assuming a mean concentration of 67
calories/100 ml of pooled human milk, the
mean daily volume of intake of 218 mb/kg
provided 147 cal/kg in balance studies
per-formed during the first 45 days of life, and
the daily intake of 140 ml/kg in similar
stud-ies during the last 45 days of the first 6
months of life provided 94 cal/kg. Assuming
that 1 gm of nitrogen in human milk is
equivalent to 6.25 gm of protein,Sb the
quan-tity of nitrogen ingested by the infants fed
pasteurized human milk ad libitum by bottle
was equivalent to an intake of protein of 2.4
gm/kg/day during the first 1% months of
life and to 1.5 gm/kg/day between 4% and
6 months of age (Fig. 3). The mean retention
of nitrogen at 1 month of age (calculated
from the regression equation) was 180 mgI
kg/day, gradually decreasing to 47 mg/kg/
day by 6 months of age (Fig. 4).
These retentions of nitrogen are less than
those reported for infants receiving the
greater intakes of protein ordinarily
sup-plied by formulas of cow’s 21 The
regression of nitrogen retention on age,
calculated from the data of Jeans et al.17
pertaining to the first 6 months of life,
dem-onstrates a mean retention of 174 mg/kg/
day at 7 weeks of age (no data available
for younger infants) and 125 mg/kg/day at
6 months of age. The mean retention of
ni-trogen of the infants fed pasteurized human
milk was only slightly less at 7 weeks of age,
155 mg/kg/day, but by 6 months of age
had decreased to 47 mg/kg/day.
Because it was conceivable that the
proc-essing of the pooled human milk
(consist-ing of pasteurization, freezing, storing and
eventual thawing) could result in some
al-teration of the nutritional adequacy of the
protein, 29 metabolic balance studies were
performed with seven infants receiving
fresh human milk either directly from the
breast or by bottle.5 It was found that
re-tentions of nitrogen attained by infants fed
fresh human milk are the same as those
at-tamed by infants fed processed human milk.
The retentions are also comparable to those
reported in the older German literature for
normal infants fed fresh human millc7b, 22
and to those of the infant studied by
Swan-son.2 The data from both the present groups
may be interpreted as being comparable to
those expected from normal infants fed
ARTICLES
CONCLUSIONS
It seems reasonable to consider as
stand-ards of reference the growth and metabolic
retentions of nitrogen of normal infants fed
at the breast. The requirement of infants
for protein from whatever source may
be stated to be the amount producing
growth equivalent to that of the normal
breast-fed infant and permitting similar
re-tentions of nitrogen. The rates of growth
of normal infants fed human milk cannot be
established from the present study in which
only six infants received human milk as the
sole food. However, in the study by Paiva1
of a larger number of infants, growth was
similar during the first 3 months of life in
infants receiving human milk and milk
for-mulas. The rates of growth between 3 and 7
months of age were also similar but both
groups received solid foods during that
pe-nod. Mean retentions of nitrogen in the
present study were 180 mg/kg/day at
1 month of age, gradually decreasing to
47 mg/kg/day by 6 months of age. These
retentions were attained with mean intakes
of protein of approximately 2.4 and 1.5
gm/kg/day, respectively.
The greater mean retentions of nitrogen
by infants receiving greater intakes of
pro-tein from cow’s milk formulas are not
asso-ciated with greater rates of growth than
those of normal breast-fed infants. Greater
retention of nitrogen without a
correspond-ingly greater rate of growth suggests an
alteration in body composition, with the
artificially-fed infant having accumulated
proportionately more nitrogen in the body
than the breast-fed infant. The significance
of this alteration in body composition is not
known.
Although it may be possible to achieve
greater rates of growth, and it is certainly
possible to achieve greater retentions of
nitrogen than those resulting from the ad
libitum ingestion of human milk, it is by no
means evident that such results are
bene-ficial or even harmless. It would seem
reas-onable that until more satisfactory criteria
are available, the evaluation of substitutes
for human milk should be based on rates of
growth and retentions of nitrogen at least
equivalent to, but not necessarily greater
than, those observed in infants fed human
milk.
SUMMARY
Six normal full-term infants were fed
human milk during all of the first 6 months
of life and three normal full-term infants
were fed human milk during portions of
that period. Data are presented concerning
growth in length and weight. The mean
con-centration of total protein in the serum was
5.2 gm/100 ml and that of urea nitrogen
was 6.3 mg/i00 ml. Data from 74 nitrogen
balance studies of the nine infants are
pre-sented.
The mean volume of intake of
pasteur-ized human milk during the balance periods
performed in the first 1% months of life was
218 mb/kg/day, decreasing to 140 ml/kg/
day between 4% and 6 months of age.
As-suming a mean concentration of 67 cal/100
ml of the pooled human milk, the mean
caloric intake of the infants during the first
lx months of life was 147 cal/kg/day,
de-creasing to a mean intake of 94 cal/kg/day
between 4% and 6 months of age. The mean
intake of protein during the first 13 months
of life was 2.4 gm/kg/day, decreasing to
1.5 gm/kg/day between 4% and 6 months of
age.
The mean retention of nitrogen at 1
month of age (calculated from the
regres-sion equation) was 180 mg/kg/day,
gradu-ally decreasing to 47 mg/kg/day by 6
months of age. These retentions are
con-siderably less than those reported for
in-fants receiving the higher intakes of
pro-tein (generally more than 3.5 gm/kg/day)
provided by many formulas of cow’s milk.
The mean gain in weight for each gram
of nitrogen retained by the infants was 42.1
gm.
ACKNOWLEDGMENT
The results reported here represent the
combined efforts of many individuals. The
authors take pride in acknowledging,
114 HUMAN MILK
Le concentration medie de proteina in le
Thomas, R.N., the nurse in charge of the
Metabolism Ward, and Robert L. Jensen,
A.B., the chemist primarily responsible for
the accuracy of the laboratory
determina-tions.
REFERENCES
1. Paiva, S. L. : Pattern of growth of selected
groups of breast-fed infants in Iowa
City. PTmcs, 11:38, 1953.
2. Swanson, W. W. : The composition of
growth. II. The full-term infant. Am.
J.
Dis. Child., 43:10, 1932.3. Fomon, S.
J.,
and May, C. D. : Metabolicstudies of normal full-term infants fed
a prepared formula proyiding
intermedi-ate amounts of protein. PEDIATRICS, to
be published.
4. Fomon, S.
J.,
and May, C. D. : Metabolicstudies of an infant prior to and during
an indolent infection of the urinary
tract. In preparation.
5. Fomon, S.
J.,
Thomas, L. N., and May,C. D. : Equivalence of pasteurized and
fresh human milk in promoting nitrogen
retention by normal full-term infants.
PEDIATRICS, to be published.
6. Fomon, S.
J.,
Thomas, L. N., Jensen, R. L.,and May, C. D. : Determination of
mtro-gen balance of infants less than 6 months
of age. PEDIATRICS, 22:94, 1958.
7. Czerny, A., and Keller, A. : Des Kindes
Ernahrung, Ernahrungsstrorungen und
Ernahrungstherapie. Ein Handbuch f#{252}r
Arzte, Vol. I. Leipzig, Deuticke, 1925,
(a) pp. 117-120; (b) p. 691.
8. Macy, I. C. : Composition of human
cobs-trum and milk. Am.
J.
Dis. Child., 78:589, 1949.
9. Macy, I. C., Kelly, H.
J.,
and Sloan, R. E.:The Composition of Milks. A
Compila-tion of the Comparative Composition
and Properties of Human, Cow and Goat
Milk, Cobostrum, and Transitional Milk.
Washington, D.C., National Academy of
Sciences-National Research Council,
Publication 254, 1953, (a) p. 37; (b) p. 4.
10. Conway, E.
J.,
and O’Malley, E. :Micro-diffusion methods. Ammonia and urea
using buffered absorbents (revised
meth-ods for ranges greater than 10 g N).
Biochem.
J.,
36:655, 1942.1 1. Van Slyke, D. D.4 and Kugel, V. H. :
Im-provements in manometric
micro-Kjel-dahl and blood urea methods.
J.
Biol.Chem., 102:489, 1933.
12. Wu, H. : Studies on hemoglobin. I. The
advantage of alkaline solutions for
color-imetric methods for the determination
of hemoglobin.
J.
Biochemistry (Japan),2:173, 1922.
13. Van de Kamer,
J.
H., Huinink, H. B., andWeyers, H. A. : Rapid method for the
determination of fat in feces.
J.
Biol.Chem., 177:347, 1949.
14. Jackson, R. L., and Kelly, H. C. : Growth
charts for use in pediatric practice.
J.
Pediat., 27:215, 1945.
15. Wintrobe, M. M. : Clinical Hematology,
3rd Ed., Philadelphia, Lea, 1951, p. 95.
16. Wilks, S. S. : Elementary Statistical
Analy-sis. Princeton, N.J., Princeton, 1949, p.
236 ff.
17. Jeans, P. C., Stearns, C., McKinley,
J.
B.,Goff, E. A., and Stinger, D. : Factors
possibly influencing the retention of
calcium, phosphorus and nitrogen by
infants given whole milk feedings. I.
The curding agent.
J.
Pediat., 8:403,1936.
18. Brock,
J.
: Biologische Daten f#{252}r denKinderarzt, Vol. II. Berlin,
Springer-Verlag, 1954, (a) p. 317; (b) p. 319.
19. Natelson, S., Penniall, R., Crawford, W. L.,
and Munsey, F. A. : Noncasein protein
to casein ratio of feeding formulas.
Ef-fect on blood component levels in
nor-mal infants. Am.
J.
Dis. Child., 89:656,1955.
20. Nelson, M. V. K. : The growth and
nitro-gen metabolism of infants receiving
un-diluted milk. Am.
J.
Dis. Child., 39:701,1930.
21. Jeans, P. C., and Stearns, G. : Growth and
retentions of calcium, phosphorus and
nitrogen of infants fed evaporated milk.
Am.
J.
Dis. Child., 46:69, 1933.22. Rominger, E., and Meyer, H. :
Untersuch-ungen des Stickstoffumsatzes beim
ges-unden Saugling. Ztschr. Kinderh., 50:
509, 1931.
SUMMARIO IN INTERLINGUA
Studios Metabolic In Normal Infantes
Nascite A Termino, Alimentate Con
Lacte Human Pasteurisate
Sex normal infantes esseva alimentate con
lacte human durante le integre periodo del
prime 6 menses de br vitas. Tres alteres esseva
alimentate con lacte human durante discrete
portiones de ille periodo. Le crescentia de
sero esseva 5,25 g per 100 ml; le concentration
medie de nitrogeno de urea esseva 6,3 mg per
100 ml. Ambe iste valores es un pauco inferior
al correspondente valores reportate pro infantes
normal qui recipeva plus grande quantitates de
proteina in br alimentation artificial.
Es presentate datos ab 74 studios del
balan-cia de nitrogeno in omne be 9 infantes. Le
volumine medie del ingestion de pasteurisate
lacte human durante le periodos de balancia
studiate durante be prime medie mense del
vita esseva 218 ml/kg/die, sequite per un
re-duction usque a 140 ml/kg/die a etates de
inter 43 e 6 menses. Si nos accepta un
con-centration medie de 67 calorias per 100 ml del
lacte human (que esseva obtenite per collection
heterogenee), le ingestion caloric medie del
in-fantes durante be prime 13 menses del vita
esseva 147 cal/kg/die, sequite per un
reduc-tion usque a 94 cal/kg/die a etates de inter
43 e 6 menses. Le ingestion medie de proteina
durante le prime 1 menses del vita esseva
2,4 g/kg/die, sequite per un reduction usque
a 1,5 g/kg/die a etates de inter 4X e 6 menses.
Le retention medie de nitrogeno al etate de
1 mense (calculate per medio del equation de
regression) esseva 180 mg/kg/die, sequite per
un reduction gradual usque a 47 mg/kg/die
al etate de 6 menses. Iste valores es
considera-bilemente inferior a! valores del retention de
nitrogeno reportate pro infantes recipiente be
plus alte quantitates de
proteina-general-mente plus que 3,5 g/kg/die-que es providite
per multe formulas a lacte de vacca.
Le augmento medie de peso per gramma de
nitrogeno retenite esseva 42,1 g.
Usque plus satisfacente criterios deveni
dis-ponibile, il es recommendate que be
evaluta-tion de substitutos pro lacte human debe esser
basate super be desiderato de un crescentia e
de un retention de nitrogeno que es al minus
equal, ben que non necessarimente superior,
a ilbos observate in infantes qui es alimentate
con lacte human.
GROWTH OF CHILDREN OF THE SAME RACE UNDER DIFFERENT ENVIRONMENTAL
CoN-DITIONS, W. W. Greulich. (Science, 127:515, March 7, 1958.)
The growth and development of American-born Japanese children in California
was compared with that of children of the same sex and age in Japan using
obser-vations of the stature, weight, sitting height and skeletal age. The findings
demon-strated a striking superiority in growth and development in many respects for the
California-born Japanese children compared with corresponding measurements in
children in Japan. On the basis of their observations the authors caution against
ascribing differences in the rate of physical growth and development of children of
different racial groups entirely to hereditary factors. It is suggested that the inferior
growth of children in Japan results from a less adequate diet and other
