Effect of dietary lactose on the of protein, fat and calcium in the postweaning rat1’2 Joseph
Leichter,3
Ph.D.,
and Arlene
F. Tolensky,4
ABSTRACT
To
assess
fat
in
lactose
and
calcium
the
effect
absorption
B.Sc.
of dietary
intolerance
due
lactose to
on
low
the
levels
intestinal
of
absorption
intestinal
lactase,
of protein, balance
studies
were carried out on postweaning rats (initialweight 164 g) for a period of 10 days. The experimental diets contained either 10% or 30% lactose, while in the control diets the lactose was replaced with equivalent amounts of sucrose. The excretions of fecal and urinary nitrogen, calcium and fat are expressed as percent of intake over the 10-day period. The fecal excretion of nitrogen and fat was significantly higher in the lactose groups (P < 0.05). The fecal calcium excretion, case
of
however, the
between in the
rats
reduce
the
the
intestinal
It is now of adults
well
30%
lactose fed the
lower diet
and 30%
absorption lactase
in the
sucrose lactose of
lactose
(P < 0.00
and
Am.
duals quately such
fat,
that the majority of the world are
(1). Lactose-intolerant indiviare unable to hydrolyze lactose adeand develop gastrointestinal symptoms,
adolescence
as
ingesting that found
stomach
an
gastrointestinal changes in the rapid
passage
cramps
and
diarrhea,
after
of lactose equivalent to cups of milk (2, 3). The
amount in 2-4
symptoms absorption through
the
are likely to of nutrients, small
cause since
intestine
re-
duces the time available for digestion and absorption (4). The prevalence and etiology of lactose intolerance has been studied extensively, but relatively little is known about whether the changes in intestinal motility produced by lactose intolerance have an effect on the absorption of nutrients other than lactose. In some cases it has been shown that lactose intolerance increases excretion of fat, nitrogen, calcium and water in stools (5-7), while in other cases dietary lactose was found to stimulate calcium absorption from the small intestine (8, 9). Kocian et al. (10) reported that, compared to lactose-free milk, the rate of
238
The
American
Journal
the
was
of Clinical
Downloaded from https://academic.oup.com/ajcn/article-abstract/28/3/238/4716317 by University of Glasgow user on 14 August 2018
but
not
J. Clin. Nutr.
lactose intolerant due to a decline of intestinal lactase activity at some time between childhood and
groups,
1). There
difference
being
no difference
Nutrition
of
28:
calcium
calcium,
was
that
in the
excretion
significantly higher dietary lactose may with
low
levels
of
1975.
from
normal
in lactose-intolerant
fecal and affected. In view
only
nitrogen
in individuals
238-241,
absorption
reduced
significant
in urinary
groups, but urinary calcium excretion diet (P < 0.01). These findings suggest
protein
activity.
established populations
in many
was lactose
urinary
milk
patients;
calcium
excretion
was
however, were
not
of the lack of agreement among the various studies, the present investigation was undertaken to determine the effect of different dietary protein,
which
levels
of
lactose
on
the
excretion
of
fat and calcium in the postweaning rat, has a low level of intestinal lactase
activity. Materials
and methods
A total of 24 young male rats of the SpragueDawley strain, each weighing about 164 g, were randomly divided into four groups of 6 rats. In order to conduct balance studies, all animals were placed in individual metabolic cages and each group was allotted one of the four diets shown in Table 1. Feed and water were given ad libitum. The diet intake was measured and urine and feces were collected over a 10-day period for each rat after an adjustment period of 3 days. A small amount of hydrochloric acid was From
the Division
of Human
Nutrition,
School
of
Home Economics, University of British Columbia, Vancouver, B. C., Canada V6T lW5 2 Supported by Grant A6249, National Research Council of Canada. ‘Assistant Professor of Nutrition. Graduate stu-
dent.
28:
MARCH
1975,
pp. 238-241.
Printed
in US.A.
DIETARY TABLE 1 Composition
LACTOSE
EFFECT
10%
30%
10%
30%
Lactose
Lactose
Sucrose
Sucrose
%by Cornstarch”
53.0
weight 33.0
Vitamin-free
20.0
20.0
10.0
30.0
10.0
10.0
10.0
30.0 10.0
5.0 2.0
5.0 2.0
5.0 2.0
5.0 2.0
53.0
33.0
20.0
20.0
Sucrose
Corn oil Salt mixc
10.0
Vitamin
mixC
diets
was
The to
each
urine’
collection
bottle
as a preservative.
samples of urine and feces were collected from rat and frozen until analysis. Fecal dry weights were obtained by grinding and drying the fecal collections to constant weight in vacuum at 60 C. Diets and feces were dry-ashed, dissolved in hydrochloric acid and diluted to appropriate volumes with 1% lanthanum solution for calcium determination by atomicabsorption spectrophotometry (11). Nitrogen was determined by the micro-Kjeldahl method (12), and the fat was measured by continuous ethyl ether extraction
0.05)
each
Weight
food consumption, Initial
#{149}
3).
consistency.
fat
and
higher
as compared The
fecal
nitrogen in
the
excretion
lactose
to the sucrose
calcium,
were (P < (Table
groups
groups
however,
was
lower
in
the lactose groups and the difference was significant (P < 0.001) only in the case of the 30% lactose diet (Table 4). There were no significant
differences
tion between animals, but
in urinary
nitrogen
the experimental the urinary calcium
excre-
and control excretion was
2 gain,
Dietary
of softer
fecal
significantly
Pooled
TABLE
of the
Comparisons of mean values for body weight gain, food consumption and dry fecal weight of rats fed on lactose and sucrose diets over a 10-day period are shown in Table 2. In spite of similar initial body weights, the 30% lactose group had the lowest gain in body weight; this group also had the lowest food intake and food efficiency (grams weight gain per grams food intake). The urine volume in the two lactose groups was appreciably higher than in the sucrose groups (P < 0.001). It was observed that the fecal matter of the rats on the lactose
a Purchased from General Biochemicals, Chagrin Falls, Ohio. b Purchased from Nutritional Biochemicals Corp., Cleveland, Ohio. CRogers, Q. R., and A. E. Harper. J. Nutr. 87: 267, 1965. added
evaluation
Results
caseunb
Lactosea
239
on a Goldfish apparatus. Statistical results was done by Student’s t-test.
of diets
Ingredients
ON ABSORPTION
group
and fecal dry weight
body
weight,
Final
g
10% Lactose
156.6
±
10% Sucrose
162.8
±
30% Lactose
161.8
±
8.9
30% Sucrose
172.2
±
17.0
“Values
refer
to mean
TABLE 3 Excretion of nitrogen
7.1 8.6
Fecal nitrogen 5.02
±
weight
243.8
± ±
9.2 15.5
87.2 86.2
214.9 246.6
±
23.8
±
11.8 bWeight
± 0.55
30% Lactose
6.11
±
a Values
refer
4.22 to mean
± ±
Food
ficiencyt’
ef-
Dry fecal
weight,
174.0
±
8.0
178.7
±
6.6 16.8
0.50 0.48
53.1
±
142.0 173.7
26.6
0.37
3.88
±
0.79
±
18.8 6.7
±
74.4
±
14.4
0.43
4.45
±
0.70
gain,
g/food
as percent
intake,
4.47 3.91
g
4.6
±
1.03
±
0.37
g.
of intake” Urinary
P value
Fecal fat 3.75
±
0.92
0.48 SD for 6 rats.
Downloaded from https://academic.oup.com/ajcn/article-abstract/28/3/238/4716317 by University of Glasgow user on 14 August 2018
P value
0.94
nitrogen
P value
36.97
±
2.51
38.95
±
3.65
36.88
±
6.97
42.06
±
4.18
>0.05
Leichter,3
Ph.D.,
and Arlene
F. Tolensky,4
ABSTRACT
To
assess
fat
in
lactose
and
calcium
the
effect
absorption
B.Sc.
of dietary
intolerance
due
lactose to
on
low
the
levels
intestinal
of
absorption
intestinal
lactase,
of protein, balance
studies
were carried out on postweaning rats (initialweight 164 g) for a period of 10 days. The experimental diets contained either 10% or 30% lactose, while in the control diets the lactose was replaced with equivalent amounts of sucrose. The excretions of fecal and urinary nitrogen, calcium and fat are expressed as percent of intake over the 10-day period. The fecal excretion of nitrogen and fat was significantly higher in the lactose groups (P < 0.05). The fecal calcium excretion, case
of
however, the
between in the
rats
reduce
the
the
intestinal
It is now of adults
well
30%
lactose fed the
lower diet
and 30%
absorption lactase
in the
sucrose lactose of
lactose
(P < 0.00
and
Am.
duals quately such
fat,
that the majority of the world are
(1). Lactose-intolerant indiviare unable to hydrolyze lactose adeand develop gastrointestinal symptoms,
adolescence
as
ingesting that found
stomach
an
gastrointestinal changes in the rapid
passage
cramps
and
diarrhea,
after
of lactose equivalent to cups of milk (2, 3). The
amount in 2-4
symptoms absorption through
the
are likely to of nutrients, small
cause since
intestine
re-
duces the time available for digestion and absorption (4). The prevalence and etiology of lactose intolerance has been studied extensively, but relatively little is known about whether the changes in intestinal motility produced by lactose intolerance have an effect on the absorption of nutrients other than lactose. In some cases it has been shown that lactose intolerance increases excretion of fat, nitrogen, calcium and water in stools (5-7), while in other cases dietary lactose was found to stimulate calcium absorption from the small intestine (8, 9). Kocian et al. (10) reported that, compared to lactose-free milk, the rate of
238
The
American
Journal
the
was
of Clinical
Downloaded from https://academic.oup.com/ajcn/article-abstract/28/3/238/4716317 by University of Glasgow user on 14 August 2018
but
not
J. Clin. Nutr.
lactose intolerant due to a decline of intestinal lactase activity at some time between childhood and
groups,
1). There
difference
being
no difference
Nutrition
of
28:
calcium
calcium,
was
that
in the
excretion
significantly higher dietary lactose may with
low
levels
of
1975.
from
normal
in lactose-intolerant
fecal and affected. In view
only
nitrogen
in individuals
238-241,
absorption
reduced
significant
in urinary
groups, but urinary calcium excretion diet (P < 0.01). These findings suggest
protein
activity.
established populations
in many
was lactose
urinary
milk
patients;
calcium
excretion
was
however, were
not
of the lack of agreement among the various studies, the present investigation was undertaken to determine the effect of different dietary protein,
which
levels
of
lactose
on
the
excretion
of
fat and calcium in the postweaning rat, has a low level of intestinal lactase
activity. Materials
and methods
A total of 24 young male rats of the SpragueDawley strain, each weighing about 164 g, were randomly divided into four groups of 6 rats. In order to conduct balance studies, all animals were placed in individual metabolic cages and each group was allotted one of the four diets shown in Table 1. Feed and water were given ad libitum. The diet intake was measured and urine and feces were collected over a 10-day period for each rat after an adjustment period of 3 days. A small amount of hydrochloric acid was From
the Division
of Human
Nutrition,
School
of
Home Economics, University of British Columbia, Vancouver, B. C., Canada V6T lW5 2 Supported by Grant A6249, National Research Council of Canada. ‘Assistant Professor of Nutrition. Graduate stu-
dent.
28:
MARCH
1975,
pp. 238-241.
Printed
in US.A.
DIETARY TABLE 1 Composition
LACTOSE
EFFECT
10%
30%
10%
30%
Lactose
Lactose
Sucrose
Sucrose
%by Cornstarch”
53.0
weight 33.0
Vitamin-free
20.0
20.0
10.0
30.0
10.0
10.0
10.0
30.0 10.0
5.0 2.0
5.0 2.0
5.0 2.0
5.0 2.0
53.0
33.0
20.0
20.0
Sucrose
Corn oil Salt mixc
10.0
Vitamin
mixC
diets
was
The to
each
urine’
collection
bottle
as a preservative.
samples of urine and feces were collected from rat and frozen until analysis. Fecal dry weights were obtained by grinding and drying the fecal collections to constant weight in vacuum at 60 C. Diets and feces were dry-ashed, dissolved in hydrochloric acid and diluted to appropriate volumes with 1% lanthanum solution for calcium determination by atomicabsorption spectrophotometry (11). Nitrogen was determined by the micro-Kjeldahl method (12), and the fat was measured by continuous ethyl ether extraction
0.05)
each
Weight
food consumption, Initial
#{149}
3).
consistency.
fat
and
higher
as compared The
fecal
nitrogen in
the
excretion
lactose
to the sucrose
calcium,
were (P < (Table
groups
groups
however,
was
lower
in
the lactose groups and the difference was significant (P < 0.001) only in the case of the 30% lactose diet (Table 4). There were no significant
differences
tion between animals, but
in urinary
nitrogen
the experimental the urinary calcium
excre-
and control excretion was
2 gain,
Dietary
of softer
fecal
significantly
Pooled
TABLE
of the
Comparisons of mean values for body weight gain, food consumption and dry fecal weight of rats fed on lactose and sucrose diets over a 10-day period are shown in Table 2. In spite of similar initial body weights, the 30% lactose group had the lowest gain in body weight; this group also had the lowest food intake and food efficiency (grams weight gain per grams food intake). The urine volume in the two lactose groups was appreciably higher than in the sucrose groups (P < 0.001). It was observed that the fecal matter of the rats on the lactose
a Purchased from General Biochemicals, Chagrin Falls, Ohio. b Purchased from Nutritional Biochemicals Corp., Cleveland, Ohio. CRogers, Q. R., and A. E. Harper. J. Nutr. 87: 267, 1965. added
evaluation
Results
caseunb
Lactosea
239
on a Goldfish apparatus. Statistical results was done by Student’s t-test.
of diets
Ingredients
ON ABSORPTION
group
and fecal dry weight
body
weight,
Final
g
10% Lactose
156.6
±
10% Sucrose
162.8
±
30% Lactose
161.8
±
8.9
30% Sucrose
172.2
±
17.0
“Values
refer
to mean
TABLE 3 Excretion of nitrogen
7.1 8.6
Fecal nitrogen 5.02
±
weight
243.8
± ±
9.2 15.5
87.2 86.2
214.9 246.6
±
23.8
±
11.8 bWeight
± 0.55
30% Lactose
6.11
±
a Values
refer
4.22 to mean
± ±
Food
ficiencyt’
ef-
Dry fecal
weight,
174.0
±
8.0
178.7
±
6.6 16.8
0.50 0.48
53.1
±
142.0 173.7
26.6
0.37
3.88
±
0.79
±
18.8 6.7
±
74.4
±
14.4
0.43
4.45
±
0.70
gain,
g/food
as percent
intake,
4.47 3.91
g
4.6
±
1.03
±
0.37
g.
of intake” Urinary
P value
Fecal fat 3.75
±
0.92
0.48 SD for 6 rats.
Downloaded from https://academic.oup.com/ajcn/article-abstract/28/3/238/4716317 by University of Glasgow user on 14 August 2018
P value
0.94
nitrogen
P value
36.97
±
2.51
38.95
±
3.65
36.88
±
6.97
42.06
±
4.18
>0.05
