J Nutr. Sci. Vitaminol.,
The
Effect Serum
of Milk
and
Skim
Lipids
and
Apoproteins
Postmenopausal
Milk
Intake
38, 203-213,
1992
on
in
Females
Chizuko MARUYAMA, Michiko NAKAMURA, Mie ITO, and Ikuko EZAWA Department of Food and Nutrition, Japan Women's University, Bunkyo-ku, Tokyo 112, Japan (Received October 28, 1991)
Summary The effects of milk and skim milk intake on serum lipids, apoprotein levels and fatty acid composition were investigated in post menopausal females. After a 25-day intake of 200ml/day of whole milk, the milk group had increased HDL and LDL cholesterol levels, with a slight decrease in the proportion of 18:0 fatty acids in the phospholipid fraction. The skim milk group, which had consumed 20g/day of skim milk for 25 days, showed no changes. After intake of 400ml/day of whole milk for 29 days, LDL, HDL and total cholesterol concentrations were even more increased and the VLDL-phospholipid concentration was decreased, with significant increases in apoA-I, apoA-II and apoB con centrations. In the skim milk group, consuming 40g of skim milk per day for 29 days, total cholesterol, atherogenic index, HDL-triglyceride con centrations were decreased and HDL-phospholipid, apoA-I and apoA-II concentrations were increased. Daily skim milk consumption, which is effective in preventing osteoporosis, and careful selection of foods should be recommended for Japanese postmenopausal women who consume more than 200ml/day of whole milk. Key Words milk, skim milk, lipoprotein lipids, apoprotein, postmeno pausal women, fatty acids
In postmenopausal women, the secretion of female sex hormones ceases and increased parathyroid hormone sensitivity accelerates the bone resorption which causes osteoporosis. Calcium intake alone, at the recommended dietary require ment of 600mg a day in Japan, is not sufficient (1). Therefore, milk consumption is recommended for prevention and treatment of osteoporosis as milk is an excellent source of calcium. However, ordinary whole milk contains more than 3.5% milk fat and higher levels of saturated fat than plant oil. In previous studies, the consumption of whole milk or dairy products has been suggested to increase serum 203
204
C. MARUYAMA
et al.
cholesterol (2-5), and hypocholesterolemic effects have also been reported (6 , 7). Bearing in mind the atherogenic properties of milk, nutritionists can not recommend consumption of adequate amounts of milk to maintain high serum calcium levels because the volumes required (over 200ml/day; about one large glass of milk) carry the risk of unfavorably elevating serum cholesterol and fatty acid levels. In our previous study, we compared the effects of milk and skim milk intake on serum lipid and apoprotein levels in young adult normolipidemic females, taking into consideration the effects of menstrual cycles. An intake of 400 ml/day of whole milk did not change either total or individual lipoprotein cholesterol levels (8) . In this study, the effects of milk and skim milk intake on serum lipid and apoprotein concentrations and fatty acid composition were investigated in order to find the optimal quantity and type of milk for postmenopausal women. METHODS Subjects years,
consisted
living
explained
to
tionnaires into before
the
start
than
milk
Blood
of
After
analysis
in
a
fatty
was of
Darmstadt,
the into
heat acid
done
fatty
block methyl
at
100•Ž esters
as
acids
within screw-cap for
were
and
.
high
an
(8)
.
period
low
.
density
lipoprotein determined and
by
phospho
method single
25
skim
nutrient
each
density
enzymatic by
the
paper
for
was
milk for
The
Triglyceride
measured
follows: (10).
ether,
Teflon-lined,
II)
(VLDL),
Tokyo). by
and
previous
concentration
were
was
diethyl
milk,
fasting
lipoprotein
skim
milk
(Kokusai
radial
immuno
Tokyo).
et al.
Germany) ether,
overnight
determined
Ltd.,
Folch
after
of
whole
(period a
overnight contained
20g
of
in
divided controlled
which
drank
daily reported
not after
milk
of
been ques
were
was
morning of
400ml
days,
Ltd.,
had
subjects
200ml
2 (HDL2)
Apoproteins Co.,
the
been
Cholesterol Co.,
also
Kagaku
petroleum
scraped
Rebio
the
48-72
period
diet
subjects as
density
lipoprotein (9).
Tokyo).
method
low
in
drank
29
morning
very
density
were
separation
were
The
the
(Merck,
have
(Fuji
Ltd.,
acid
by
for
milk the
the
200ml
group
group
milk
into
high
milk
aged
experiment
The
drawn
calcium
skim in
separated
method
Fatty
the
the
and
drank
milk of
skim
drawn
(Daiichi
serum
of and
skim
ultracentrifugation
Co.,
diffusion
the
obtained
was
volunteers
Preexperimental
consumption.
subjects
content
Then
40g
concentrations
Shiyaku
and same
I).
(LDL), by
enzymatic
lipid
fat,
milk
was
3 (HDL3)
gas
milk
were
Serum
blood
and group
milk
the
samples
milk
of
obtained.
were
skim
female
purpose
was
habits
and
The
the
lipoprotein
milk
The
consent
experiment,
drank of
Tokyo. their
of
(period
group
contents
postmenopausal
N).
3.5%
daily
seventeen
eating
i. e.,
approximately
days,
gel
and
(period
with
use
Bunkyo-ku,
groups,
fasting
an
in them
concerning
two
more
of
30min extracted
Lipids
were
Thin-layer used
to
and
acetic
the
separate
the
acid
triglyceride glass
by
using with
extracted
from
chromatography
and
tubes
and
3.5% petroleum
fatty
acid
(84.15:15
1ml
with fractions
.0:0.85,
sulfuric ether
fractions under
acid and
J. Nutr.
by v/v/v).
phospholipid methylated
of
Silica
in
argon
methanol.
separated
Sci.
by
Vitaminol.
EFFECT
gas-liquid Japan)
OF
MILK
chromatography using
succinate
a
on
60-80
Japan).
Injector
Nitrogen
was
Diet
in
The
MILK
as
were
kept
period,
and
significance
of
the
column
W
for
3
nutrient data
205
230•Ž
Works and
Tokyo,
diethyleneglycol
200•Ž,
Ltd.,
Tokyo,
respectively.
gas. days
before
intakes
was
LIPIDS
chromatograph,
Chromato
were
carrier
SERUM
containing
(Nihon
temperatures the
ON
gas-liquid
packing
Chromosorb.
column
INTAKE
GC-12A
glass
mesh and
each
SKIM
(Shimadzu
3mm•~2.1m
employed
records
obtained
AND
analyzed
the were by
day
the
blood
samples
were
calculated. paired
t-test.
RESULTS
The age, age at menopause, height, weight, body mass index, and systolic and diastolic blood pressure of each of the subjects are shown in Table 1. There were no significant differences between the two groups. In the skim milk group, systolic blood pressure decreased in period II as compared to period N (p
The
Effect Serum
of Milk
and
Skim
Lipids
and
Apoproteins
Postmenopausal
Milk
Intake
38, 203-213,
1992
on
in
Females
Chizuko MARUYAMA, Michiko NAKAMURA, Mie ITO, and Ikuko EZAWA Department of Food and Nutrition, Japan Women's University, Bunkyo-ku, Tokyo 112, Japan (Received October 28, 1991)
Summary The effects of milk and skim milk intake on serum lipids, apoprotein levels and fatty acid composition were investigated in post menopausal females. After a 25-day intake of 200ml/day of whole milk, the milk group had increased HDL and LDL cholesterol levels, with a slight decrease in the proportion of 18:0 fatty acids in the phospholipid fraction. The skim milk group, which had consumed 20g/day of skim milk for 25 days, showed no changes. After intake of 400ml/day of whole milk for 29 days, LDL, HDL and total cholesterol concentrations were even more increased and the VLDL-phospholipid concentration was decreased, with significant increases in apoA-I, apoA-II and apoB con centrations. In the skim milk group, consuming 40g of skim milk per day for 29 days, total cholesterol, atherogenic index, HDL-triglyceride con centrations were decreased and HDL-phospholipid, apoA-I and apoA-II concentrations were increased. Daily skim milk consumption, which is effective in preventing osteoporosis, and careful selection of foods should be recommended for Japanese postmenopausal women who consume more than 200ml/day of whole milk. Key Words milk, skim milk, lipoprotein lipids, apoprotein, postmeno pausal women, fatty acids
In postmenopausal women, the secretion of female sex hormones ceases and increased parathyroid hormone sensitivity accelerates the bone resorption which causes osteoporosis. Calcium intake alone, at the recommended dietary require ment of 600mg a day in Japan, is not sufficient (1). Therefore, milk consumption is recommended for prevention and treatment of osteoporosis as milk is an excellent source of calcium. However, ordinary whole milk contains more than 3.5% milk fat and higher levels of saturated fat than plant oil. In previous studies, the consumption of whole milk or dairy products has been suggested to increase serum 203
204
C. MARUYAMA
et al.
cholesterol (2-5), and hypocholesterolemic effects have also been reported (6 , 7). Bearing in mind the atherogenic properties of milk, nutritionists can not recommend consumption of adequate amounts of milk to maintain high serum calcium levels because the volumes required (over 200ml/day; about one large glass of milk) carry the risk of unfavorably elevating serum cholesterol and fatty acid levels. In our previous study, we compared the effects of milk and skim milk intake on serum lipid and apoprotein levels in young adult normolipidemic females, taking into consideration the effects of menstrual cycles. An intake of 400 ml/day of whole milk did not change either total or individual lipoprotein cholesterol levels (8) . In this study, the effects of milk and skim milk intake on serum lipid and apoprotein concentrations and fatty acid composition were investigated in order to find the optimal quantity and type of milk for postmenopausal women. METHODS Subjects years,
consisted
living
explained
to
tionnaires into before
the
start
than
milk
Blood
of
After
analysis
in
a
fatty
was of
Darmstadt,
the into
heat acid
done
fatty
block methyl
at
100•Ž esters
as
acids
within screw-cap for
were
and
.
high
an
(8)
.
period
low
.
density
lipoprotein determined and
by
phospho
method single
25
skim
nutrient
each
density
enzymatic by
the
paper
for
was
milk for
The
Triglyceride
measured
follows: (10).
ether,
Teflon-lined,
II)
(VLDL),
Tokyo). by
and
previous
concentration
were
was
diethyl
milk,
fasting
lipoprotein
skim
milk
(Kokusai
radial
immuno
Tokyo).
et al.
Germany) ether,
overnight
determined
Ltd.,
Folch
after
of
whole
(period a
overnight contained
20g
of
in
divided controlled
which
drank
daily reported
not after
milk
of
been ques
were
was
morning of
400ml
days,
Ltd.,
had
subjects
200ml
2 (HDL2)
Apoproteins Co.,
the
been
Cholesterol Co.,
also
Kagaku
petroleum
scraped
Rebio
the
48-72
period
diet
subjects as
density
lipoprotein (9).
Tokyo).
method
low
in
drank
29
morning
very
density
were
separation
were
The
the
(Merck,
have
(Fuji
Ltd.,
acid
by
for
milk the
the
200ml
group
group
milk
into
high
milk
aged
experiment
The
drawn
calcium
skim in
separated
method
Fatty
the
the
and
drank
milk of
skim
drawn
(Daiichi
serum
of and
skim
ultracentrifugation
Co.,
diffusion
the
obtained
was
volunteers
Preexperimental
consumption.
subjects
content
Then
40g
concentrations
Shiyaku
and same
I).
(LDL), by
enzymatic
lipid
fat,
milk
was
3 (HDL3)
gas
milk
were
Serum
blood
and group
milk
the
samples
milk
of
obtained.
were
skim
female
purpose
was
habits
and
The
the
lipoprotein
milk
The
consent
experiment,
drank of
Tokyo. their
of
(period
group
contents
postmenopausal
N).
3.5%
daily
seventeen
eating
i. e.,
approximately
days,
gel
and
(period
with
use
Bunkyo-ku,
groups,
fasting
an
in them
concerning
two
more
of
30min extracted
Lipids
were
Thin-layer used
to
and
acetic
the
separate
the
acid
triglyceride glass
by
using with
extracted
from
chromatography
and
tubes
and
3.5% petroleum
fatty
acid
(84.15:15
1ml
with fractions
.0:0.85,
sulfuric ether
fractions under
acid and
J. Nutr.
by v/v/v).
phospholipid methylated
of
Silica
in
argon
methanol.
separated
Sci.
by
Vitaminol.
EFFECT
gas-liquid Japan)
OF
MILK
chromatography using
succinate
a
on
60-80
Japan).
Injector
Nitrogen
was
Diet
in
The
MILK
as
were
kept
period,
and
significance
of
the
column
W
for
3
nutrient data
205
230•Ž
Works and
Tokyo,
diethyleneglycol
200•Ž,
Ltd.,
Tokyo,
respectively.
gas. days
before
intakes
was
LIPIDS
chromatograph,
Chromato
were
carrier
SERUM
containing
(Nihon
temperatures the
ON
gas-liquid
packing
Chromosorb.
column
INTAKE
GC-12A
glass
mesh and
each
SKIM
(Shimadzu
3mm•~2.1m
employed
records
obtained
AND
analyzed
the were by
day
the
blood
samples
were
calculated. paired
t-test.
RESULTS
The age, age at menopause, height, weight, body mass index, and systolic and diastolic blood pressure of each of the subjects are shown in Table 1. There were no significant differences between the two groups. In the skim milk group, systolic blood pressure decreased in period II as compared to period N (p
