J. Nutr. Sci. Vitaminol., 36 (Suppl.), S157-S 164, 1990
Effects of Dietary Proteins on Plasma Lipoprotein Levels in Normal Subjects: Interaction with Dietary Cholesterol
Hans 1
MEINERTZ,1
Karin
NILAUSEN,2
Ole FAERGEMAN1
Department of Medicine B, Rigshospital, Blegdamsvej 9, 2100 Copenhagen, Denmark 2 Department of Anatomy C , Panum Institute, University of Copenhagen, Blegdamsvej 3, 2200 Copenhagen, Denmark
Summary We have compared the effects of dietary soy protein and casein in diets low in cholesterol (less than 100mg/d) and in diets enriched in cholesterol (500mg/d) to examine whether the level of cholesterol intake affects the response of plasma lipoproteins to dietary proteins of plant and animal origin. Normal men and women consumed formula diets containing 20% of calories as soy protein or casein, 27% as fat and 53% as carbohydrate in 2 crossover studies. The dietary periods lasted for 31days and were separated by a month-long interim period on self chosen food. Following an initial reduction of plasma total cholesterol and low-density lipoprotein-cholesterol (LDL-C) levels on all diets, the plasma lipid and lipoprotein concentrations stabilized, On low cholesterol diets the concentration of each of the major lipoprotein classes were similar during the soy and the casein dietary periods. On cholesterol enriched diets, the concentration of LDL-C stabilized at a 16% lower level on soy protein than on the casein diet (p 1.125g/ml fraction, and the
PLASMA
LIPOPROTEINS
plasma
concentration
of
between
the
cholesterol
fraction
and
HDL3-C.
the
5159
of
tion
of
been
the
different
LDL-C
(18)
Statistical by
Cholesterol
assayed
by
for
(17)
com
determina
unpaired
have
and
established
triglycer
procedures.
Statistical or
in
and
concentrations
(14).
paired
cholesterol
fractions
HDL-C
analysis
done
difference
d>1.063g/ml
procedures
and
were
the
the of
lipoprotein
described
ides
as of
Recoveries
ultracentrifugal
parisons
HDL2-C
content
evaluations Student's
were
t-test.
Results Intake
of energy
mean
diets
from and
by
the
each The
and
composition
of
formula
liquid the on
so
and
1.1•}0.81kg
1.4•}0.98
and
kg
on
casein
decreases (mean•}SD)
(casein)
1.1•}0.78kg
(casein)
the
the
dietary and
modest
1.2•}1.03kg
diets,
of consumed
protein
the
the
nutrients
particular
soy
were
namely
protein)
3 shows and
chemical
during
weight,
low-cholesterol and
calories
intake
similar,
body
(soy
the amount
caloric
were
Table
of
individual
period. diets
nutrients
intake
calculated
in
and
daily
on
(soy
the
protein)
cholesterol-enriched
diets. The were
fatty
72%,
the
Table
3.
* Mean•}SD
Vol.
Daily
intake
of average
36, Suppl.
II, 1990
of energy
daily
intakes
and
were
stearic
sterol
virtually
component, was
always
low-cholesterol on
the
about
17%
and
acids
together
with
average
on
the
64%.
than it
Also diets
the The
100mg/d was
saturated 11%.
different
beta-sitosterol,
about
while
the
diets about
the
about of
less
diets,
different
constituting
composition identical
the
acid
constituting
intake
of
oleic
acid
and
plant
composition
similar,
linoleic
palmitic
Fig. 1. Time course of plasma lipid concentrations during the two dietary periods on low-cholesterol diets, separated by a 30day interval on a self chosen diet. Each point and vertical bar represent mean and SD of 5 subjects.
acid
closely
about
cholesterol-enriched
on
11 subjects
on
low-cholesterol
and
cholesterol-enriched
diets.
diets,
the
500mg/d
nutrients.
of 10 and
main
cholesterol
respectively.
The
S160
H. MEINERTZ
Fig.
2.
Time
course
of low-density
point and bar represent the cholesterol-enriched
and mean diets.
high-density and
et al.
lipoprotein-cholesterol
SD; n=10
mean daily cholesterol intake on the casein diets was always about 60mg higher than on the correspond ing soy protein diet due to the presence of small amounts of cholesterol in the casein preparation . Plasma concentrations of lipids and lipoprotein All experimental diets caused an initial fall in plas ma total cholesterol of more than 20%, whereas tri glyceride levels were unaffected (Fig. 1). The re duction in plasma cholesterol was due primarily to a lowering of LDL-C levels, but also HDL-C concentrations decreased (Fig. 2). After about 2 weeks on the formula diets, plasma cholesterol and lipoprotein levels stabilized, and blood samples obtained after 24, 28, and 32days of each dietary period was used to compare the effects of the 2 dietary proteins. During the month-long interval between the 2 dietary periods, when the participants consumed self-chosen food, plasma lipid and lipoprotein levels returned to prestudy values (Fig. 1). During the last part of the experimental dietary periods, when plasma lipid and lipoprotein con centrations had become stable, plasma total cholesterol, triglyceride and VLDL-C levels were similar on the casein and the soy protein diets, regardless of the magnitude of cholesterol intake (Table 4). Correction for the predicted increase in plasma cholesterol on either low-cholesterol or cholesterol-enriched diets, due to the higher daily
for
intake
while
diets
(19),
on
does
response the
of
2
and
the
diets.
by
casein
or
soy
however,
while
higher
the
HDL-C
LDL-C
on
1•}1.0mg/100ml diets
ol-enriched ificantly
and
diets,
For
HDL-C
and
8•}6/mg/100ml,
were
significantly
the
these
in
mainly
HDL3-C
were
on
concentrations
unaffected
diets
by
HDL
the
kind
. 2•}4
likewise
and
in
HDL2-C protein
casein
similar of
that
the
observed
soy
levels
they
revealed
were
plasma
were
and
protein
the
sign
.025).
concentrations
differences
higher
cholesterol
were
(p1.125g/ml
for
each
significant
concentrations
minus the
concentrations
determined
determined
periods.
* 3 LDL-cholesterol
heparin-MnCl2, were
were
each
diets.
respectively;
*4 HDL-cholesterol
with
concentrations
of
fraction,
(16).
precipitation
concentrations
32
fractions,
Ref.
32 of the dietary
diets,
protein
d1.063g/ml
according
2) plasma
PLASMA
and
3) d1.006minus
fraction, of
on
values
precipitation,
d>1.063g/ml
d>1.125g/ml
Table 5.
as
from LDL
cholesterol,
11
lipoprotein-cholesterol
between
determined after
and
and
calculated
from
the
d>1.006g/ml
concentrations were
of
determined
d>1.006g/ml
fraction
d>1.063minus
the
fraction.
Plasma lipoprotein-cholesterol concentrations in female and male subjects, taking cholesterol-enriched diets, on days 24, 28, and 32 of each dietary period.*l
* 1 Mean•}SD LDL-C (method a,b Cholesterol
Vol.
10
difference
fraction total
of
was
(p>0.05)
lipid
PROTEINS
36, Suppl.
. *2 No
significant
(p>0.05)
1), HDL-C intake by men
(method significantly
II, 1990
difference 1) and HDL2-C greater than
between
the
dietary
periods.
see Table 4, footnotes. that by women (p
Effects of Dietary Proteins on Plasma Lipoprotein Levels in Normal Subjects: Interaction with Dietary Cholesterol
Hans 1
MEINERTZ,1
Karin
NILAUSEN,2
Ole FAERGEMAN1
Department of Medicine B, Rigshospital, Blegdamsvej 9, 2100 Copenhagen, Denmark 2 Department of Anatomy C , Panum Institute, University of Copenhagen, Blegdamsvej 3, 2200 Copenhagen, Denmark
Summary We have compared the effects of dietary soy protein and casein in diets low in cholesterol (less than 100mg/d) and in diets enriched in cholesterol (500mg/d) to examine whether the level of cholesterol intake affects the response of plasma lipoproteins to dietary proteins of plant and animal origin. Normal men and women consumed formula diets containing 20% of calories as soy protein or casein, 27% as fat and 53% as carbohydrate in 2 crossover studies. The dietary periods lasted for 31days and were separated by a month-long interim period on self chosen food. Following an initial reduction of plasma total cholesterol and low-density lipoprotein-cholesterol (LDL-C) levels on all diets, the plasma lipid and lipoprotein concentrations stabilized, On low cholesterol diets the concentration of each of the major lipoprotein classes were similar during the soy and the casein dietary periods. On cholesterol enriched diets, the concentration of LDL-C stabilized at a 16% lower level on soy protein than on the casein diet (p 1.125g/ml fraction, and the
PLASMA
LIPOPROTEINS
plasma
concentration
of
between
the
cholesterol
fraction
and
HDL3-C.
the
5159
of
tion
of
been
the
different
LDL-C
(18)
Statistical by
Cholesterol
assayed
by
for
(17)
com
determina
unpaired
have
and
established
triglycer
procedures.
Statistical or
in
and
concentrations
(14).
paired
cholesterol
fractions
HDL-C
analysis
done
difference
d>1.063g/ml
procedures
and
were
the
the of
lipoprotein
described
ides
as of
Recoveries
ultracentrifugal
parisons
HDL2-C
content
evaluations Student's
were
t-test.
Results Intake
of energy
mean
diets
from and
by
the
each The
and
composition
of
formula
liquid the on
so
and
1.1•}0.81kg
1.4•}0.98
and
kg
on
casein
decreases (mean•}SD)
(casein)
1.1•}0.78kg
(casein)
the
the
dietary and
modest
1.2•}1.03kg
diets,
of consumed
protein
the
the
nutrients
particular
soy
were
namely
protein)
3 shows and
chemical
during
weight,
low-cholesterol and
calories
intake
similar,
body
(soy
the amount
caloric
were
Table
of
individual
period. diets
nutrients
intake
calculated
in
and
daily
on
(soy
the
protein)
cholesterol-enriched
diets. The were
fatty
72%,
the
Table
3.
* Mean•}SD
Vol.
Daily
intake
of average
36, Suppl.
II, 1990
of energy
daily
intakes
and
were
stearic
sterol
virtually
component, was
always
low-cholesterol on
the
about
17%
and
acids
together
with
average
on
the
64%.
than it
Also diets
the The
100mg/d was
saturated 11%.
different
beta-sitosterol,
about
while
the
diets about
the
about of
less
diets,
different
constituting
composition identical
the
acid
constituting
intake
of
oleic
acid
and
plant
composition
similar,
linoleic
palmitic
Fig. 1. Time course of plasma lipid concentrations during the two dietary periods on low-cholesterol diets, separated by a 30day interval on a self chosen diet. Each point and vertical bar represent mean and SD of 5 subjects.
acid
closely
about
cholesterol-enriched
on
11 subjects
on
low-cholesterol
and
cholesterol-enriched
diets.
diets,
the
500mg/d
nutrients.
of 10 and
main
cholesterol
respectively.
The
S160
H. MEINERTZ
Fig.
2.
Time
course
of low-density
point and bar represent the cholesterol-enriched
and mean diets.
high-density and
et al.
lipoprotein-cholesterol
SD; n=10
mean daily cholesterol intake on the casein diets was always about 60mg higher than on the correspond ing soy protein diet due to the presence of small amounts of cholesterol in the casein preparation . Plasma concentrations of lipids and lipoprotein All experimental diets caused an initial fall in plas ma total cholesterol of more than 20%, whereas tri glyceride levels were unaffected (Fig. 1). The re duction in plasma cholesterol was due primarily to a lowering of LDL-C levels, but also HDL-C concentrations decreased (Fig. 2). After about 2 weeks on the formula diets, plasma cholesterol and lipoprotein levels stabilized, and blood samples obtained after 24, 28, and 32days of each dietary period was used to compare the effects of the 2 dietary proteins. During the month-long interval between the 2 dietary periods, when the participants consumed self-chosen food, plasma lipid and lipoprotein levels returned to prestudy values (Fig. 1). During the last part of the experimental dietary periods, when plasma lipid and lipoprotein con centrations had become stable, plasma total cholesterol, triglyceride and VLDL-C levels were similar on the casein and the soy protein diets, regardless of the magnitude of cholesterol intake (Table 4). Correction for the predicted increase in plasma cholesterol on either low-cholesterol or cholesterol-enriched diets, due to the higher daily
for
intake
while
diets
(19),
on
does
response the
of
2
and
the
diets.
by
casein
or
soy
however,
while
higher
the
HDL-C
LDL-C
on
1•}1.0mg/100ml diets
ol-enriched ificantly
and
diets,
For
HDL-C
and
8•}6/mg/100ml,
were
significantly
the
these
in
mainly
HDL3-C
were
on
concentrations
unaffected
diets
by
HDL
the
kind
. 2•}4
likewise
and
in
HDL2-C protein
casein
similar of
that
the
observed
soy
levels
they
revealed
were
plasma
were
and
protein
the
sign
.025).
concentrations
differences
higher
cholesterol
were
(p1.125g/ml
for
each
significant
concentrations
minus the
concentrations
determined
determined
periods.
* 3 LDL-cholesterol
heparin-MnCl2, were
were
each
diets.
respectively;
*4 HDL-cholesterol
with
concentrations
of
fraction,
(16).
precipitation
concentrations
32
fractions,
Ref.
32 of the dietary
diets,
protein
d1.063g/ml
according
2) plasma
PLASMA
and
3) d1.006minus
fraction, of
on
values
precipitation,
d>1.063g/ml
d>1.125g/ml
Table 5.
as
from LDL
cholesterol,
11
lipoprotein-cholesterol
between
determined after
and
and
calculated
from
the
d>1.006g/ml
concentrations were
of
determined
d>1.006g/ml
fraction
d>1.063minus
the
fraction.
Plasma lipoprotein-cholesterol concentrations in female and male subjects, taking cholesterol-enriched diets, on days 24, 28, and 32 of each dietary period.*l
* 1 Mean•}SD LDL-C (method a,b Cholesterol
Vol.
10
difference
fraction total
of
was
(p>0.05)
lipid
PROTEINS
36, Suppl.
. *2 No
significant
(p>0.05)
1), HDL-C intake by men
(method significantly
II, 1990
difference 1) and HDL2-C greater than
between
the
dietary
periods.
see Table 4, footnotes. that by women (p
