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The effects of dietary cholesterol upon the hypercholesterolemia of pregnancy
The Effects of Dietary Hypercholesterolemia Martha The hypercholesterolemia factors.
The
controlled
present
P. McMurry,
which accompanies
experiment
metabolic conditions
William
Cholesterol Upon the of Pregnancy*
E. Connor, and Clifford P. Goplerud
the normal human pregnancy
in fourteen
pregnant
women
was
is not known to be influenced
designed
and to study the effect of dietary cholesterol
to document
this
by diet or other
phenomenon
The subjects included twelve normal subjects, one juvenile diabetic, and one type II familial hypercholesterolemic They were fed controlled,
nutritionally
was cholesterol-free
or 600-1000
The cholesterol-free
diet lowered
mg/dl,
a 20% decrease
serum
cholesterol
levels increased
( -47
and triglyceride
triglyceride
responses
serum cholesterol
the mean serum to 223
mg/dl,
similarly
decreased in the familial
of cholesterol
study indicated that the usual hypercholesterolemia by a very low cholesterol,
T
nutritionally
30,
No.
9 ISeptember),
1981
(+36
_t 12) (p
1 wk after
hypercholesterolemic
diets occurred
c 0.001). + 43 (SD.1
parturition.
in women
which
women
from
elevated
234-187 the mean
The mean serum triglyceride mg/dl These
and the diabetic
largely in the low density
homeostasis
of pregnancy adequate
pregnant
subject.
content,
gain of 1.4 kg per mo.
to the diet invariably
of diet. up to 198
strikingly
HE HYPERLIPIDEMIA of human pregnancy was described as early as 1844 by Becquerel and Rodier in France.’ This observation has been periodically reported since that time and has been documented on a worldwide scale, in primitive as well as technically advanced cultures.3m’E There is general agreement that the serum cholesterol concentrations increase progressively throughout the second trimester of pregnancy, reach a peak during the third trimester, and decline after parturition. Increased serum triglyceride concentrations during pregnancy have also been reported.‘6,‘7 Recently detailed studies have characterized the lipoprotein changes and reported increased concentrations of very low density (VLDL), high density (HDL), and low density (LDL) lipoproteins.‘9m22The lipid composition of the lipoproteins was increased proportionally in the VLDL and IDL (intermediate-density lipoprotein) fractions. In contrast, LDL, and HDL showed greater increases in triglyceride than the other lipids, leading to a percentage shift toward enrichment with triglyceride.18 The hypercholesterolemia of pregnancy presumably occurs from metabolic and endocrine influences. Our hypothesis is that diet may be an additional factor. Pregnant American women were advised to consume additional calories during pregnancy to produce a 24 lb average weight gain.23 Eating the usual American diet in increased amounts would mean even greater intakes of cholesterol and saturated fat.24 In addition, an increased intake of animal protein is often recommended for pregnant women25,26 which would further elevate the consumption of dietary cholesterol and saturated fat. Since hypercholesterolemia has been induced with diets containing large amounts of choles-
Metabolism,Vol.
of cholesterol
increase
and lipoprotein
to permit weight
level in the 12 normal
The addition
regardless
levels during the high cholesterol
Despite the inevitable alterations ameliorated
cholesterol
a 19%
pregnancy
concentrations
occurred
except for the cholesterol
mg from egg yolk daily. Calories were adjusted
throughout
cholesterol
diets which were equivalent
+ 37 S.D.) (p < 0.005/.
concentrations steadily
adequate
under
upon this usual increase in serum cholesterol.
at term. serum women.
lipoprotein
which occur in pregnancy, eating the general American
Both serum
cholesterol The
and
increased
(LDL) fraction.
the results of this diet was greatly
diet.
terol under experimental conditions in men,“‘,31 women,32,33 and in animals,34 the diet of pregnant American women may promote the development of hypercholesterolemia. Disorders of cholesterol metabolism are related epidemiologically and clinically to the pregnant state. Of the numerous etiological factors associated with cholesterol gallstones, pregnancy has long been prominent.35’36 In addition, the incidence of atherosclerotic heart disease may be increased in multiparous women3’ although this is equivocal.38 The present study is designed to examine :he hypercholesterolemia found in pregnancy and, further, to determine its nutritional basis. In this study, a cholesterol-free diet known to lower serum cholesterol
*Published
in abstract form
in Clinical
Research
25.521‘4
Abstract.
From the Lipid-Atherosclerosis Laboratory, the Department of Medicine. and the Clinical Research Center, University of Gregon Health Sciences Center, Portland. Oregon and the Clinical Research Center and Departments of Internal Medicine and Obstetrics and Gynecology, University of Iowa College of Medicine. Iowa City, Iowa. Supported in part by U.S. Public Health Service Grants HL19130 and HL-06336 from the National Heart, Lung and Blood Institute and by the General Clinical Research Centers Program (RR-334 and RR-59) of the Division of Research Resources of the National tnstitutes of Health and by the National Heart, Lung and Blood Institute HL-20910 of the National Institutes of Health. Received for publication October IS, 1980. Address Reprint Requests to Dr. William E. Connor, University of Oregon Health Sciences Center. 3181 SW Sam Jackson Park Road, Portland, Oregon, 97201. A 1981 bv Grune & Stratton, Inc. 0026-o495/81/3009-0005$02.00/0
869
MCMURRY, CONNOR, AND GOPLERUD
870
concentration was 180 k 53 mg/dl with a range of 116-297. Six subjects were hyperlipidemic by the standards of the Food and Nutrition Board of the National Academy of Sciences for nonpregnant adults with serum cholesterol concentrations greater than 220 mg/dl.” In addition, two women were studied who had concomitant metabolic diseases. Subject 13 was a 19-yr-old juvenile diabetic diagnosed at age 8. Before her pregnancy, she was reportedly in good diabetic control on 65 units lente insulin daily with negligible glucosuria (negative or 1 plus by Clini-test) and no insulin reactions. During pregnancy, her diabetic control deteriorated and she reported considerable glucosuria and small to moderate ketonuria on spot checks. She was admitted to the research ward in her third trimester of pregnancy and remained there throughout the post partum period. During the metabolic study, she received lente insulin twice daily subcutaneously, 40 units in the morning and 35 units in the evening. Despite great effort, her diabetes was not closely controlled during the study, as evidenced by mean 24 hr urinary glucose excretion before parturition of 55 g (range I-l 17g) and post prandial blood sugars of 15G250 mg/dl. However, her initial ketonuria disappeared and no evidence of acidosis was present. She had both elevated serum cholesterol (314 mg/dl) and triglyceride (286 mg/dl) at admission. Delivery was induced in the 36 wk of pregnancy by intravenous pitocin and artificial rupture of membranes. There were no complications for either the mother or the newborn. The infant weighed 3920 g. After parturition, the mother’s mean glucosuria decreased to 1 I g per 24 hrs with lente insulin doses of 30 units in morning and 12 units in the evening. Subject 14, age 16, had been followed as an outpatient since age 4. She was a member of a large family with well-documented type II hypercholesterolemia, xanthoma, and premature coronary heart disease in at least fourteen family members. Untreated, she had a serum cholesterol of 35&400 mg/dl; with dietary treatment and cholestyramine or PAS-CR, this was reduced to as low as 250 mg/dl. Her fasting serum triglycerides were consistently less than 150 mg/dl. She was classified as a hyperlipidemic type 11-a. Two years before her pregnancy, sterol balance studies had been carried out. At that time, with a mixed food diet of 100 mg of cholesterol per day, 20% fat, and with no medication, her serum cholesterol was 243 mg/dl and triglyceride 77 mg/dl. When admitted in the 6th mo of pregnancy, her serum cholesterol had increased to 346 mg/dl and serum triglycerides to 172 mg/dl.
levels32 was fed to 14 pregnant women. This was alternated with a high cholesterol diet (600-1000 mg cholesterol per day). The study was carried out entirely under metabolic ward conditions in the Clinical Research Center. Subjects were recruited and entered into the study over a IO yr period of time. They were under constant surveillance and consumed the prescribed diet. Serum cholesterol, triglyceride and lipoprotein levels were measured. In addition, sterol balance and bile composition studies were carried out. The latter data are to be reported separately. In one subject, similar measurements were carried out during pregnancy and post partum. MATERIALS AND METHODS
Subjects Twelve normal pregnant women participated in this study. They were admitted to the Clinical Research Center in the second or third trimester where they stayed for the duration of their pregnancy. Prior human research committee approval had been obtained for the project and each subject and a parent, when appropriate, gave informed consent. Subjects were recruited and entered into the study over a ten-year period of time. The subjects (Table 1) had a mean age of 20. They were all primiparous except for one woman who reported one previously aborted pregnancy. Nine of the twelve subjects were within 15Ye of the normal non-pregnant weight for height at the time of admission as compared to non-pregnant college-age women.” The exceptions were Subjects 9, 10, and 11, who were 21%. 57%, and 58% overweight respectively. While most of the subjects were admitted in the sixth month of pregnancy, three began the study in the fourth and fifth months. All women had uneventful full-term deliveries. Subject 7 had twins. All infants appeared normal and healthy at birth, and most of them were put up for adoption. None of the subjects were lactating post partum. There was a wide range of serum lipid concentrations at admission (Table 1). The mean serum cholesterol level was 234 + 40 (S.D.) mg/dl with a range of 187-294; the mean triglyceride Table 1. Description
of Normal Pregnant
Women
on Admission to the Study % of Normal
Subject
Age
Month of
Height
Serum
Serllfll
Weight
Nonpregnant
Cholesterol
Triglyceride
Yr.
Gestation
cm
kg
Weight*
mg/dl
mg/dl
1
20
6
160.5
60.8
110
277
156
2
18
6
160.5
50.4
92
253
134
3
19
5
163.0
59.9
109
233
197
4
18
4
165.5
55.8
96
199
137
5
18
5
165.5
56.3
96
201
180
6
20
6
155.0
57.6
111
288
232
7
20
6
168.0
63.5
109
203
181
8
21
6
163.0
53.6
97
199
143
9
19
6
170.5
74.3
121
187
10
21
6
165.5
91.8
157
294
297
11
21
6
168.0
92.3
158
266
210
12
19
6
160.5
59.9
109
204
116
Mean
20
6
163.8
64.7
114
234
180
1
4.3
14.1
22
40
53
Number
S.D.
1
*Compared to non-pregnant college-aged womerxa6
871
DIETARY CHOLESTEROL UPON PREGNANCY
Dietary Periods All subjects received a general hospital diet for 1 wk after admission, followed by the series of metabolic balance diets which continued until one or two weeks post partum. Two diets were used: a cholesterol-free diet and a diet in which was incorporated 6001000 mg cholesterol. Each dietary period was 4-9 wk in duration. The series of dietary periods usually began with the high cholesterol diet which was alternated with the cholesterol-free diet until delivery. However, five of the subjects (IO, 11, 12, 13, and 14) began the study with the cholesterol-free diet. Since the time of delivery was variable, the entire series of diets was not always completed for each subject. Five subjects delivered during Period III, eight during Period IV, and one during an additional high cholesterol dietary period. After delivery, the subjects continued their pre-delivery metabolic diet minus 200 calories for 1 or 2 wk and were then given a general diet until discharge from the hospital. The diets were comprised of either formulas or mixed foods and contained sufficient calories to permit a moderate weight gain. The composition of the diets was planned to simulate the usual American diet in terms of carbohydrate, protein, and fat composition with
modification of the cholesterol content (Table 2). acid composition of the study diets was 11% of the saturated, 19 percent monounsaturated, and 9% (iodine number 80, P/S value of 0.8). However, received a slightly more saturated fat diet (iodine
The usual fatty total calories as polyunsaturated some subjects number 60, P/S
value of 0.3). Both diets were within the range of fatty acid compositions normally consumed by Americans. For most of the subjects, the fatty acid composition remained constant throughout their diet sequence. For Subjects 2 and 4, the cholesterol-free and high cholesterol diet sequence was given once with a dietary fat of iodine number 60 and again with a dietary fat of iodine number 80. Dietary cholesterol was provided by egg yolk. During the cholesterol-free diets, appropriate adjustments were made, so that the total protein and fat and the fatty acid composition remained the same for the cholesterol-free and high cholesterol diets. The high cholesterol diets contained 600 mg cholesterol except for Subject 12 who received 750 mg and Subjects 1I and 14 who received 1000 mg per day for the high cholesterol diets. These amounts of dietary cholesterol are within the range consumed in the United States. Examples of the mixed food and the formula diets are shown in Table 2. The type of diet given to each subject varied depending on
Table 2. The Composition of Diets For the Different Dietary Periods HighCholesterol Diet Sequence
I and
III
Cholesterol-Free II and IV
600 mg
0
15%
15%
Carbohydrate’
45
45
Fat*$
40
40
Saturated Fatty Acids*
11
11
Monounsaturated Fatty Acids*
19
19
Polyunsaturated Fatty Acids*
9
9
P/S9
0.8
Cholesterol mg/dayt Protein*
Iodine Number Formula Diet lngredientsll
80
Skim milk powder Frozen egg yolk mix
205 g
0.8 60 225 g
59
0
Sweet chocolate(
42
48
Peanut oilll
66
79
Dextrimaltose
63
63
Cornstarch
40
40
16
7
Sugar Mixed Food Diet Ingredients11 Egg yolk
59
0
Egg white
48
56
Sktm milk powder
90
90
Fat-free cottage cheese
34
58
Peanut buttery
30
30
Margarinen Sweet chocolate1
67 10
41
6
6
3 6
6
8
7
Oilll Vegetable exchanges* Bread exchanges**
l
Frurt exchanges**
72
3
‘Percent of total calories. tSubject 12 received 750 mg; subjects 13 and 14. 1000 mg. $Some subjects received a dietary fat somewhat more saturated, with 19% monounsaturates, 5% polyunsaturates and 16% saturates, P/S 0.3 and Iodine number 60. §Ratio of polyunsaturated fabsaturated fat. /IExamples for 2000 calories diets. ISpecific brands of known fattY acid composition were used. **Using
established diabetic exchange lists, using weighed amounts of food.
872
MCMURRY, CONNOR. AND GOPLERUD
individual tolerance and preference. Mixed food and formula diets were interchangeable in calories, cholesterol, amount of protein, carbohydrate, fat, and type of fat. The diets were fed in six feedings, 3 meals and 3 snacks. During the high cholesterol periods, the egg yolk was given at each of the six feedings for the formula diets; in the mixed food diets, the egg yolk was given in three equal portions at mealtimes. The mixed food diets were from a variety of foods which gave a diet adequate in nutrients. Vitamin and mineral supplements were added to meet the National Research Council recommendations for pregnant women4’ To be emphasized was the nutritional adequacy of the diet during the cholesterol-free periods. The protein intake at 15% of total calories averaged 87 g/day, thus meeting the recommended intakes for pregnant women. Of the total protein intake, 100% was from high quality animal proteins, mostly from milk, during the formula diets. In the mixed food diets, 60% of the protein was from animal sources (milk products and eggs) and 40% was from vegetable sources (peanut butter, cereals and vegetables). Thus the protein intake was more than adequate for both the cholesterol-free and high cholesterol diets.
RESULTS
Laboratory
Serum Cholesterol
Studies
Blood was obtained for lipid measurements twice weekly after an overnight (12 hr) fast. The serum was analyzed for cholesterol by the method of Block, Jarrett and Levine4* as the samples were obtained. The serum for triglyceride determinations were frozen and analyzed at the end of the study (the Kessler and Lederer method).43 The average of all values from the third to the last week for each subject during each dietary period (final mean value) was used in the data analysis since the mean serum cholesterol had stabilized by that time. The final mean value included from 1-12 points, but usually was the mean of 4 values. Sera from Subjects 1 I and 14 were analyzed for lipoprotein cholesterol. The separation of lipoproteins was done by ultracentrifugation.“’ Group t tests were used to compare the data for each individual. In groups, with each subject acting as her own control, statistical comparisons were made by utilizing the student’s paired t analysis. A P value < 0.05 was considered to be a significant difference.4s
Table 3. The Mean Serum Cholesterol Concentration
Dietary cholesterol had a pronounced effect upon the serum cholesterol concentrations in all 12 normal pregnant women, The key serum cholesterol changes occurred with the removal and addition of cholesterol in the diet. Mean serum cholesterol concentrations for each individual subject and serum cholesterol changes (mg/dl) are shown in Table 3. Each subject served as her own control. Of the 27 individual dietary exchanges of high cholesterol and cholesterol-free diets, 25 exchanges produced increases or decreases of serum cholesterol levels dependent upon the presence or absence of cholesterol in the diet. The only exceptions were in subject 7, the only woman to have twins. She did not show a decrease in serum cholesterol during cholesterol-free diets II and IV but did have the usual hypercholesterolemic effect of the high cholesterol dietary period III. As a group, the mean serum cholesterol concentrations responded to the dietary cholesterol intakes (Table 4). Compared to admission values, the 12 normal women showed a marked decrease in serum cholesterol concentration after consuming a cholesterol-free diet, from 234-187 mg/dl, a 20% decrease (p < 0.001). Reintroducing cholesterol into the diet in Period I11 produced a similar change, increasing the serum cholesterol to 223 mg/dl, a 19% increase (p < 0.001). The fourth dietary period, Period IV cholesterol-free, completed by six subjects before delivery, decreased the plasma cholesterol level from 238-2 18 mg/dl (p < 0.05). For Each Pregnant Woman During Each Dietary Period
(mg/dl)*
II Cholesterol-Free
Subjects
Mean ? SD.
11
1
251
t
2
214
? 5
III High Cholesterol
Mean + S.D.
% Change
P VellE
IV Cholesterol-Free §
§
I High Cholesterol
Concentrations
Mean + SD.
$ Change
P V&E
225 * 6
-26
254 r 12
+29
<0.005
201 t 1
-13
258
+ 9
f57
4 Mean + S.D.
210 ? 8
$ Change
-44
P Value
<0.005
3
189 + 5
170 + 3
-19
216 + 7
+46
194 + 8
-22
<0.005
4
237 + 10
218 + 9
-19
<0.005
253 ? 17
+35
242 ? 11
-11
>0.2
217 177 + 20
+2 -10
II >0.4
269 + 16
-33
<0.05
5
165 + 5
145 t 8
-20
188 i
11
+43
6
246 i
186 t 3
-60
206 + 12
+20
7 8
171 + 16 197 +- 11
174 ? 15 165 + 6
+3 -32
>0.5 <0.005
215 5 5 187 * 10
f41 +22
9
-30
10
189 ? 8
159 + 5
184 + 16
+25
<0.005
10
t
253 * 13
302 + 18
+49
to.05
11
t
197 +4
237 + 11
f40
12
t
150 + 6
171 i 18
f21
to.005
*Mean of all values after and including wk 3. tBegan study with Period II cholesterol-free. fChange compared to previous dietary period. $T test compared to previous period. 11Not
enough
values
for statistical
comparison.
DIETARY
CHOLESTEROL
UPON
873
PREGNANCY
Table 4. Group Mean Serum Cholesterol Changes During Each Dietary Comparison Serum Cholesterol Number Subiects Admission
I High
Diet to
Cholesterol
I High Diet
Cholesterol
Diet
III High
Cholesterol
t SD.
to
f
%
9
227
207
-20
27
9
207
183
-24
? 17
P Value
-9
>0.05
-- 12
<0.005
12
234
187
-47
+ 37
-20
<0.005
Cholesterol
12
187
223
f36
+ 12
t19
io.001
to IV Cholesterol-free
6
238
218
-20
k
to II Cholesterol-free
II Cholesterol-free
horn
Mean mg/dl
to II Cholesterol-free
Diet Admission
Change
mg/dl
of
to Ill High
Length of‘ Gestation
Subjects responded similarly to changes in dietary cholesterol regardless of the trimester of pregnancy. The subjects began the study at various months of gestation, some in the second and some in the third trimester. The five subjects (1, 3, 4, 7 and 8) who were admitted relatively early in pregnancy were able to complete all four dietary periods in sequence: I, high cholesterol; 11, cholesterol-free; III, high cholesterol: and IV, cholesterol-free. The high cholesterol diets produced increased serum cholesterol levels, 209 * 34 (S.D.) mg/dl and 225 + 29 mg/dl respectively, while the cholesterol-free diets led to much lower values, 190 t 29 and 208 k 24, respectively. These changes, whether in the second or third trimesters of pregnancy, were similar. There appeared to be an increased serum cholesterol concentration during the latter months of gestation (dietary periods 111 and IV) compared to earlier comparisons (I and II). The mean increase of 17 + 20 mg/dl of III and IV combined compared to 1 and 11 combined correspond roughly to the increase in plasma cholesterol from the second to the third trimester. Subjects admitted in or near the third trimester failed to show this gradual increase in serum cholesterol: they had already attained maximal values. However, there did not appear to be any augmentation of the hypercholesterolemic effect of dietary cholesterol later in pregnancy. Early dietary comparisons (usually in the second trimester) were the same as those seen in late pregnancy (third trimester) (mean changes + 3 I 4 25 and + 31 + 15 mg/dl respectively). Serum cholesterol concentrations were especially stable in Subject 12. who was given the cholesterolfree diet for a period of 9 wk (Fig. 1). Her serum cholesterol remained low at approximately 152 k 6 mg/dl for the entire nine week period, most of which was during her third trimester. The introduction of 750 mg cholesterol into the diet during the 34th week
17
-8
co.05
of pregnancy resulted in a rise in the serum cholesterol level to 17 1 f 18 mg/dl. Serum
Triglyceride
Concentrations
After the baseline diet, the mean serum triglyceride concentration increased progressively with the duration of pregnancy regardless of diet (Table 5). At baseline, the mean serum triglyceride level of all subjects was 169 f 33 mg/dl. During Period I, the mean declined slightly to 161 i 44 mg/dl (nine subjects), then increased in 14 subjects to 186 + 66 mg/dl in Period 11 and to 212 f 59 mg/dl in Period III. The mean triglyceride concentration during Period III (high cholesterol) prior to delivery was significantly increased (p < 0.025) compared to Admission in all 12 subjects and compared to Period I (high cholesterol) with nine subjects (p < 0.001) (paired t tests). Post Partum
Changes
in Serum
Lipids
Serum lipid concentrations in most subjects, all of whom were not breast feeding the infants. decreased Subject # 12 750 mg Cholesterol Diet
17 Dellvery
1
Week of Pregnancy
38
I
‘
40 1
Fig. 1. The serum cholesterol concentrations during the study for subject 12. a normal subject.
874
MCMURRY,
CONNOR, AND GOPLERUD
Table 5. The Serum Triolvceride Concentrations (ma/dlj During the Fourth Week of Each Diet I
Ill
II
High
Cholesterol-
IV
High
Cholesterol-
Cholesterol
Free
1
156
159
312
2
123
113
135
166
3
166
137
133
166
159
4
137
151
136
196
218
Subjects
Admission
Cholesterol
Free
204
252
5
175
129
131
182
6
232
263
300
337
7
176
155
186
250
8
158
194
190
213
151
182
223
9 10
195
248
306
11
208
146
163
12
135
130
142
169 + 33.
186 + 66
212 + 59.
189 f 70
215 f 53t
207 + 88
218 f 61
247
Mean + S.D. of Subjects l-2 Mean + SD. of Subjects l-9
165*32
161 + 44t
Mean ? S.D.of Subjects 1, 3, 4, and 10
164 + 24
Significantly different by paired T test: l<0.025;
219 * 43
tiO.OO1.
serum cholesterol of 246 mg/dl during pregnancy compared to 193 mgfdl after pregnancy, a 22% difference. Although the increases in serum cholesterol concentration from dietary cholesterol feeding were similar during and after pregnancy, the serum cholesterol concentrations under both dietary conditions were higher during the pregnant state. The serum triglyceride concentrations were likewise increased during pregnancy. The increased LDL cholesterol made up the bulk of the cholesterol elevations induced by dietary cholesterol, LDL cholesterol increasing 38 and 24 mg/dl, pregnant and post partum respectively. While HDL cholesterol also increased, the LDL to HDL ratio actually became greater, so that the relative increase of HDL was less than that of LDL.
after delivery. By l-2 wk post partum, the mean serum cholesterol concentration had decreased from 213 + 12 (S.E.M.) to 200 f 7 (S.E.M.) mg/dl, a 6% reduction (not significant). The serum triglyceride level dropped in all subjects from mean 198 f 13 (S.E.M.) to 132 f 8 mg/dl, a 33% decrease (p < 0.001). Changes were not related to the diet consumed at parturition (whether cholesterol-free or high cholesterol) and the changes occurred rapidly, in only l-2 wk. Comparison of the Responses to Dietary Cholesterol in the Same Subject: Pregnant Versus Non-Pregnant Subject 11 repeated the same dietary sequence 4 wk after delivery (Table 6), thus receiving both the high cholesterol and cholesterol-free diets before and after delivery. The high cholesterol diet produced similar percentage elevations in the serum cholesterol concentrations during and after pregnancy. During pregnancy with the cholesterol free diet, the serum cholesterol was 199 mg/dl. After pregnancy, the same diet led to a serum cholesterol concentration of 164 mg/dl, 18% lower. The high cholesterol diet resulted in a
The Serum Lipid Changes in the Pregnant Diabetic Patient
Juvenile
Subject 13, with severe juvenile diabetes, had responses in serum cholesterol levels similar to the other pregnant subjects. She entered the study in the
Table 6. The Effects of Dietary Cholesterol Upon the Serum Lipoproteins in a Normal Subject* During Pregnancy and Post Partum Cholesterol mgldl LDL to
Triglycerides
Pregnancy
Total
VLDL
LDL
HDL
HDL Ratio
mgldl
Cholestarol-free
30
199
14
127
58
2.19
146
High Cholesterol
40
246
19
165
62
2.66
163
Week of Diet
Post Parturn Cholesterol-free High Cholesterol ‘Subject No. 11
7
164
13
113
38
2.97
98
10
193
14
137
42
3.26
125
875
DIETARY CHOLESTEROL UPON PREGNANCY
H TotalCholesterol c----o LOL cholesktol
Subject # 14
Week of Pregnancy Fig. 2. trations
Total
serum
in the familial
cholesterol
and
LDL
hypercholesterolemic
cholesterol subject
concen-
14.
middle of the third trimester of pregnancy. Diabetic control was imperfect despite hospitalization and intensive effort, as illustrated in her case report (see Materials and Methods). On admission, she was hyperlipidemic with both serum cholesterol and triglyceride concentrations near 300 mg/dl. During the cholesterol-free diet, her serum cholesterol decreased to 226 + 6 mg/dl (wk 3 and 4). After the 600 mg cholesterol diet, her serum cholesterol level increased to 242 mg/dl in the third week of the diet, before delivery was induced. The serum triglycerides also increased to 334 mg/dl just before delivery. Although she received the same high cholesterol diet (less 200 calories) after delivery, her serum cholesterol concentration dramatically decreased to 194 mg/dl and triglycerides from 334-59 mg/dl. Concurrently, her insulin requirements lessened and diabetic control improved greatly.
EfSects of the Types of Diets Both mixed food and formula diets were used in this study, as well as dietary fatty acid compositions of I#60 (P/S 0.3) and 80 (P/S 0.8). The changes in serum cholesterol concentration were similar irrespective of whether the diet was composed of mixed foods or formula. On formula diets, 16 separate exchanges of high cholesterol to cholesterol-free in 12 subjects produced a mean decrease of 31 + 19 (S.D.) mg/dl serum cholesterol; five similar comparisons in 4 subjects on mixed foods produced a decrease of 30 + 17 mg/dl. The slight difference in fatty acid composition produced no consistent differences in response between the two subjects receiving both diets (Subjects 2 and 4) or in the group as a whole. Weight Changes Our pregnant subjects gained an average of 10.9 kg from their reported pre-pregnancy weight of 58.6 t 12.3 to 69.5 f 12.5 kg at parturition. This is within the recommended weight gain from the Committee on Maternal Nutrition of 9-l 1.4 kg. The mean weight
The Serum Lipid Changes in the Familial Hypercholesterolemic Patient The subject with type II-a familial hypercholesterolemia (Subject 14) had an initial total serum __~
Table
7. Effect of Dietary
Cholesterol
Upon
Plasma
Lipids
cholesterol concentration of 346 mg/dl with LDL cholesterol of 294 mg/dl (Fig. 2 and Table 7). Her serum cholesterol and LDL cholesterol levels were most responsive to changes in dietary cholesterol intake. During the cholesterol-free diet, her serum cholesterol decreased to 260 mg/dl. With an intake of 1000 mg cholesterol/day, there was an increase to 360 mg/dl. With a subsequent cholesterol-free diet, the serum cholesterol decreased again to 291 mg/dl. One week post partum, her serum cholesterol level fell further while she was still consuming the same cholesterol-free diet. The LDL cholesterol paralleled the total cholesterol changes (Fig. 2). The cholesterol-free diet decreased the LDL cholesterol concentration from the admission value of 294 to 218 mg/dl; the 1000 mg cholesterol diet increased LDL cholesterol to 303 mg/dl. Dietary cholesterol increased HDL cholesterol somewhat also, but the LDLf HDL cholesterol ratio increased at the same time.
end Lipoproteins
in a Subject
With
Familial
Hypercholesterolemia
Cholesterol mgldl week
Tnglycerides
Of
Pregnancy
DIH
Tots1
VLDL
LDL
HDL
LDL/HDL
mg/dl
Admission
25
346
15
294
37
7.95
172
Cholesterol-free
29
262
6
218
39
5.59
103
High
34
348
1
303
44
6.89
129
38
291
10
245
36
6.81
140
2
261
5
225
31
7.26
74
12
296
2
254
40
6.35
62
Cholesterol
Cholesterol-free Post Cholesterol-free Home
diet,
controlled
Partum
poorly
876
MCMURRY.
gain during the 2-5 mo study was 1.4 +. 0.7 kg per mo. By 1 wk post partum, the mean decrease in weight was 7.0 f 1.8 kg. The mean newborn weight was 3.32 f .42 kg (excluding the twins of 2.53 and 2.35 kg). This is within the fiftieth percentiles of newborn boys (3.44) and girls (3.30) in the U.S.46 No significant correlation occurred between total weight gain or weight gain during the study and the weight of the newborn infant. The initial serum triglyceride concentrations were, however, positively correlated with the admission weight (r = 0.57, p < 0.05). The amount of weight gain did not correlate with the changes in serum triglyceride concentration during the study. Cord Blood Cholesterol
Levels
In 12 infants, the cord blood cholesterol concentration ranged from 64-114 mg/dl (Table 8). Five infants, (including the twins) the children of the two obese pregnant women, and the infant of the subject with type 11-a hypercholesterolemia, all had cholesterol levels of over 100 mg/dl, definitely elevated. There was a positive correlation (+0.587) between the maternal serum cholesterol level just before delivery and the cord blood cholesterol concentration (p < 0.05). DISCUSSION
The hypercholesterolemia of human pregnancy is not only the most common cause of hypercholesterolemia in premenopausal women but also represents an example of a primary metabolic state which might be modified by dietary influences. The results of our study in 14 pregnant women document that the hypercholesterolemia of pregnancy can be greatly ameliorated by the removal of cholesterol from the diet. Table 8. Serum Cholesterol
Concentration
of Maternal
and Cord
Blood MatWlal* Subject
lmg/dl)
Cwd Blood (mg/dl)
1
200
79
2
235
90
3
198
64
5
190
74
6
239
77
7
217
101
8
188
9
203
87
10
274
105
12
219
113
14
291
113
Mean f S.D.
223 + 34
90 + 16
114 82
CONNOR, AND GOPLERUD
Some 31 separate dietary periods under controlled metabolic conditions of either high cholesterol or cholesterol-free diets provided the proof for this conclusion. Dietary effects upon the plasma cholesterol and lipoproteins have not been shown previously in pregnant women. Our results are in contrast to two previous studies reporting unsuccessful attempts to modify the hypercholesterolemia of pregnancy using very different approaches. Green concluded that the use of a fat-modified diet, decreased in saturated fat and increased in polyunsaturated fat, failed to prevent the rise of serum cholesterol in seven outpatient pregnant women.’ Moses et al. could not produce an exaggerated hypercholesterolemia by adding 2 g crystalline cholesterol to the usual diet of pregnant women4’ In contrast, our study shows dietary cholesterol in a range of intake commonly consumed by pregnant American women can affect the plasma cholesterol concentration. Dietary cholesterol has been shown repeatedly to affect the plasma cholesterol levels in normolipidemic and hyperlipidemic men and non-pregnant women27-33 and in diabetic patients.48 The pregnant women reported in the present study, though exhibiting the usual hypercholesterolemia of pregnancy, were not different than non-pregnant adults in their response to dietary cholesterol. Their 20% increase in plasma cholesterol concentration from high cholesterol feeding compared to a cholesterol-free diet is similar to those changes previously reported.* The hypercholesterolemic effect of dietary cholesterol was similar in all the pregnant women studied, including the normals and the obese, diabetic and hypercholesterolemic patients. The serum cholesterol changes were most pronounced in the patient with familial hypercholesterolemia. This finding is similar to previous observations of the enhanced sensitivity of these patients generally to dietary cholesterol intake” and confirms recent reports showing amelioration of the hypercholesterolemia of pregnancy in patients with familial hypercholesterolemia with the use of a modified diet.“,‘* The only woman in our study who delivered twins, subject number 7, seemed the least sensitive to the dietary cholesterol changes, showing no decrease in serum cholesterol concentration during the cholesterol-free diets but exhibiting the typical rise in serum cholesterol following high cholesterol feeding. The diabetic patient exhibited the characteristic lipid responses to dietary changes despite the enhanced tendency in patients with diabetes mellitus toward hyperlipidemia and atherosclerosis.2’.48.53.s4
The correlation ccx&cient of maternal and cord blood cholesterol was +0.587.
p < 0.05.
+Last serum cholesterol concentration before parturition.
*Summarized
in a review of the literature
human metabolic studies.49
(Table
6) of the ten
877
DIETARY CHOLESTEROL UPON PREGNANCY
We would stress the universality of the plasma cholesterol increase occurring in human pregnancy. The hypercholesterolemia of pregnancy has occurred in all cultures surveyed including those whose habitual diets are high in cholesterol: United States,2’5.7.‘4”5”6 Scotland,3.4 African Masai” and South African white$ and in those who typically consume a diet low in cholesterol: Guatemala,” India,’ Mexican Tarahumara, Thailand” and Nigeria.13 However, the customary dietary cholesterol and fat intakes of the various populations would appear to determine the baseline serum cholesterol concentration from which the increase in pregnancy occurs. For example, at the time of admission (usually the second trimester) in our group of subjects, the mean serum cholesterol level of 235 mg/dl already constituted an increase of 3 1% over the usual serum cholesterol concentration of 178 mg/dl in 18-yr-old non-pregnant women from the general population.“j Changing to a cholesterol-free diet decreased the serum cholesterol to 187 mg/dl, a level similar to that seen in pregnant Tarahumara women5’ and those from other cultures consuming a low cholesterol, low fat diet. Reintroducing cholesterol into the diet of our subjects increased the serum cholesterol level to 223 mg/dl. This increase was probably less than the maximum level they would have reached if they had consumed their usual home diet throughout their pregnancy. In fact, the usual home diet of our subjects appeared to be more hypercholesterolemic than the “high cholesterol” dietary periods used in our study. The mean serum cholesterol at admission decreased from 2277207 mg/dl (p < 0.05) during the high cholesterol diet given initially to the first 9 subjects. Perhaps the home diets were less limited than the high cholesterol diet used in the study. a diet moderate in cholesterol (usually 600 mg) and saturated fat (1 I%-16% of calories) content and controlled in calories. The usual dietary suggestions for pregnant women include special recommendations to consume particularly high cholesterol foods, to wit: on a daily basis, 2 servings of meat, frequent liver, l-2 eggs, 2 servings of cheese and 1 quart of milk.*’ These foods could easily result in a typical daily cholesterol intake of greater than 1000 mg. The increased plasma lipid levels during pregnancy were reflected in changes in the amounts of lipoprotein cholesterol and triglyceride. In the normal subject of our study, pregnancy was associated with increased LDL and HDL cholesterol levels. In the type II hypercholesterolemic patient, the LDL concentration was increased even more over the elevated nonpregnant levels. The gradual, independent increase in serum triglyceride concentration which occurred in
our subjects despite the serum cholesterol changes induced by diet supports the concept of triglyceride enrichment of lipoproteins, particularly LDL, and VLDL, during pregnancy.*’ In contrast to the hypercholesterolemia of human pregnancy, many animals have hyporcholesterolemia during pregnancy: rabbits, guinea pigs, and subhuman primates-monkeys and baboons.57”2 Some animals, however, mimic humans in having hypercholesterolemia during pregnancy: the dog and rat.63”5 The reasons for these species difference are completely unknown and warrant further investigation. This study documents the amelioration of the usual hypercholesterolemia of pregnancy by the restriction of cholesterol in the diet. The risks and benefits of a general recommendation to restrict the dietary cholesterol intake in pregnant women are not known. The fifteen infants born during this study were normal and healthy but were not followed further. However, there is little reason to suspect health risk. Cholesterol is not an essential nutrient for humans. The fetus is able to synthesize cholesterol66 and the newborn infant invariably has much lower plasma cholesterol concentration than the mother, usually about 70 mg/d1.67 Worldwide, normal infants are born to mothers who vary widely in plasma cholesterol concentrations because there are wide ranges in the cholesterol and fat contents of diet from different cultures. This being said, we should add that there may be several benefits of recommending a diet low in cholesterol and reduced in fat content during pregnancy. A low cholesterol diet may reduce the high incidence of gallstones in multiparous women since diet is known to influence the cholesterol to bile acid ratio in bile and thus may affect stone formation.6x Women with previously diagnosed hyperlipidemia who become pregnant could reduce their even more pronounced hyperlipidemia of pregnancy by consuming a diet low in cholesterol content and controlled in other dietary constituents. A diet low in cholesterol ( 100 mg) and fat (20% of calories) and composed of foods widely available in our culture could be adequate in protein, vitamins and minerals for the pregnant woman.“9*70 In addition, this diet could have increased fiber, be high in nutrient density and be consistent with current recommendations for dietary prevention of atherosclerosis and other chronic diseases common in the United States.‘4,7’ ACKNOWLEDGMENT The authors wish to acknowledge
the cooperation of many social
service agencies which referred subjects to us for study, and to thank Dr. Donald Wiebe and Dr. S. N. Jagannathan
for the separation of
the serum lipoproteins and Linda Sears. Meg Larson, and Joanne Skirving for the typing and preparation
of the manuscript.
MCMURRY,
878
CONNOR, AND GOPLEAUD
REFERENCES 1. Becquerel A, Rodier A: La composition du sang. Gazette Medicale 20-I 27, 1844 2. Boyd EM: The lipemia of pregnancy. J Clin Invest 13:347363,1934 3. Oliver MF, Boyd GS: Plasma lipid and serum lipoprotein patterns during pregnancy and puerperium. Clin Sci 1415-23, 1955 4. Watson WC: Serum lipids in pregnancy and the puerperium. Clin Sci 16:475480, 1957 5. deAlvarez RR, Gaiser DF, Simkins DM, et al: Serial studies of serum lipids in normal human pregnancy. Am J Obstet Gynecol 77:743-757,1959 6. vonstudnitz W: Studies on serum lipids and lipoproteins in pregnancy. Stand J Clin Lab Invest 7:329-335, 1955 7. Green JG: Serum cholesterol changes in pregnancy. Am J Obstet Gynec 95~387-393, I966 8. Bersohn 1, Wayburne S: Serum cholesterol concentration in newborn African and European infants and their mothers. Am J Clin Nutr 4: 117-l 23, 1956 9. Mullick S, Bagga OP. DuMullick V: Serum lipid studies in pregnancy. Am J Obstet Gynecol 89:766-770, 1964 IO. Mendez J, Scrimshaw NS. Abrams MD, et al: Serum lipids and proteinbound iodine levels of Guatemalan pregnant women from two different socioeconomic groups. Am J Obstet Gynecol 80:11&l 18, 1960 Il. Visethkul D, Chiamudom U, Chuprasert S: The lipid patterns in normal pregnant Thai women and the effect of lactation. J Med Assoc Thai 58:491-494, 1975 12. Biss K, Taylor CB, Lewis LA, et al: Atherosclerosis and lipid metabolism in the Masai of East Africa. Afr J Med Sci 2:249-257, 1971 13. Taylor GO, Akande EO: Serum lipids in pregnancy and socioeconomic status. Brit J Obstet Gynecol 82:297-302, 1975 14. Smith EK, deAlvarez RR, Forsander J: Serum protein, lipid and lipoprotein fractions in normal human pregnancy. Am J Obstet Gynecol77:326-334, 1959 15. Gupta AN, Sarkar AK, Chakravarti RN: Lipid-protein interrelationship in pregnancy. Am J Med Sci 253:469-472, 1967 16. Peters JP, Heinemann M, Man EB: The lipids of serum in pregnancy. J Clin lnvest 30:388-394, 195 1 17. Cramer K, Aurell M, Pherson S: Serum lipids and lipoproteins during pregnancy. Clin Chim Acta 10:470-472, 1964 18. Knopp RH, Montes A, Warth MA: Carbohydrateyand lipid metabolism, in National Academy of Sciences: Laboratory Indices of Nutritional Status in Pregnancy. Washington, DC, 1978, pp 35-88 19. Hillman L, Schonfeld G, Miller JP, et al: Apolipoproteins human pregnancy. Metabolism 24:943-952, 1975
in
20. Warth MR. Arky RA, Knopp RH: Lipid metabolism in pregnancy. III. Altered lipid composition in intermediate, very low, low and high density lipoprotein fractions. J Clin Endocrinol Metab 41:649655, 1975 21. Warth MR. Knopp RH: Lipid metabolism in pregnancy. V. Interactions of diabetes, body weight, age and high carbohydrate diet. Diabetes 26:1056-1062, 1977 22. Mantes A, Knopp RH: Lipid metabolism in pregnancy. IV. C apoprotein changes in very low and intermediate density lipoproteins. J Clin Endocrinol Metab 45:106(rlO63, 1977 23. Maternal Nutrition and the Course of Pregnancy. ton, DC, National Academy of Science, 1970, p 190
Washing-
24. Connor WE, Connor SL: The key role of nutritional factors in the prevention of coronary heart disease. Prev Med l:49-83, 1972
25. Hellman LM, Pritchard JA: Williams Obstetrics. New York, Meredith Corp. 197 1, p 338 26. Worthington BS, Vermeersch J. Williams SR: Nutrition in Pregnancy and Lactation. St. Louis, CV Mosby Co, 1977, p 88 27. Connor WE, Hodges RE, Bleiler RE: The effect of dietary cholesterol upon the serum lipid levels in man. J Lab Clin Med 57:331-342, 1961 28. Connor WE. Hodges RE, Bleiler RE: The serum lipids in men receiving high cholesterol and cholesterol-free diets. J Clin Invest 40:894901, I96 1 29. Connor WE, Stone DB, Hodges RE: The interrelated effect of dietary cholesterol and fat upon human serum lipid levels. J Clin Invest 43:1691-1695, 1964 30. Hegsted DM, McGandy RB, Myers ML, et al: Quantitative effects of dietary fat on serum cholesterol in man. Am J Clin Nutr 17:281-295,1965 3 1. Mattson FH, Erickson BA, Kligman AM: Effects of dietary cholesterol on serum cholesterol in man. Am J Clin Nutr 25:589594, 1972 32. Raymond TL, Connor WE, Lin DS, et al: The interaction of dietary fibers and cholesterol upon the plasma lipids and lipoproteins, sterol balance. and bowel function in human subjects. J Clin Invest 60:1429-1437, 1977 33. Okey R, Stewart D: Diet and blood cholesterol in normal women. J Biol Chem 99:717-727, 1933 34. Armstrong ML, Warner ED, Connor WE: Regression of coronary atheromatosis in rhesus monkeys. Circ Res 27:59-67, 1970 35. Friedman GD, Kannel WB, Dawber TR: The epidemiology of gallbladder disease: Observations in the Framingham study. J Chron Dis 19:273-292, 1966 36. Richardson JD, Scutchfield FD, Proudfoot WH, et al: Epidemiology of gallbladder disease in an Appalachian community. Health Serv Rep 88:241-246, 1973 37. Bengtsson C, Rybo G, Westerberg H: Number of pregnancies, use of oral contraceptives and menopausal age in women with ischaemic heart disease, compared to a population sample of women. Acta Med Stand Supp 549:75-g I, 1973 38. Parrish HM, Carr CA, Silberg SL, et al: Relationship of pregnancy to coronary atherosclerosis. Am J Obstet Gynecol 97:1087-1091, 1967 39. Hathaway ML, Foard ED: Heights and weights of adults in the US. USDA Home Econ Res Rept IO, US Government Printing Of, Washington, DC, 1960 40. Food and Nutrition Board, National Academy of Sciences: National Research Council and Council on Foods and Nutrition, American Medical Assoc, Diet and Coronary Heart Disease: A joint statement. Prev Med 1:559-561, 1972 41. Recommended Dietary Allowances. Washington, DC, National Academy of Sciences, 1974 42. Block WD, Jarrett KJ, Levine JB: Use of a single color reagent to improve the automated determination of serum total cholesterol, in Skeggs LT, Jr (ed): Technicon Symposia. New York, Median, 1966, p 345 43. Kessler G, Lederer H: Fluorometric measurement of triglycerides, in Skeggs LT, Jr (ed): Technicon Symposia. New York, Median. 1966, p 34 1 44. Have1 RJ, Eder HA, Bragdon HG: The distribution and chemical composition of ultracentrifugally separated lipoproteins in human serum. J Clin Invest 34: 1345-l 353, 1955 45. Snedecor GW, Cochran WG: Statistical Methods (ed 6). Ames, Iowa, Iowa State University Press, 1967, pp 91-95 46. Fomon SJ: Infant Nutrition. Philadelphia, W. B. Saunders co, 1974, p 40
DIETARY CHOLESTEROL UPON PREGNANCY
47. Moses C, Rhodes GL, Leatham E, George RS: Effect of cholesterol feeding during pregnancy on blood cholesterol levels and placental vascular lesions. Circ 6:103-105, 1952 48. Stone DB, Connor WE: The prolonged effects of a low cholesterol, high carbohydrate diet upon the serum lipids in diabetic patients. Diabetes 12:127-l 32. 1963 49. Roberts SL, McMurry MP, Connor WE: Does egg feeding (i.e. dietary cholesterol) affect plasma cholesterol levels in humans? The results of a double-blind study. Am J Clin Nutr (in press) SO. Lin DS, Connor WE: The long-term effects of dietary cbolesterol upon the plasma lipids, lipoproteins, cholesterol absorption and the sterol balance in man: the demonstration of feedback inhibition of cholesterol biosynthesis and increased bile acid excretion. J Lipid Res 21:1042-1052, 1980 5 I Glueck CJ, Tsang RC, Mellies MJ: Cholesterol-free diet and the physiologic hyperlipidemia of pregnancy in familial hypercholesterolemia. Metabolism 29:949-955, 1980 52. Tsang RC, Glueck CJ, McClain C, et al: Pregnancy, parturition, and lactation in familial homozygous hypercholesterolemia. Metabolism 27:823-829, 1978 53. Vernet A, Smith EB: Lipoprotein pattern in diabetes and the changes occurring during pregnancy. Diabetes 10:345-350, 1961 54. Knopp RH, Warth MR, Carrol CJ: Lipid metabolism in pregnancy. 1. Changes in lipoprotein triglyceride and cholesterol in normal pregnancy and the effects of diabetes mellitus. J Reprod Med 10:95-101, 1973 55. Connor WE, Cerqueira MT, Connor RW, et al: The plasma lipids, lipoproteins and diet of the Tarahumara Indians of Mexico. Am .I Clin Nutr 31:1131-l 142, 1978 56. Lauer RM, Connor WE, Leaverton PE, et al: Coronary heart disease risk factors in school children: The Muscatine study. J Pediatr 86:697-706, 1975 57. Pitkin RM, Connor WE, Lin DS: Cholesterol metabolism and placental transfer in the pregnant rhesus monkey. J Clin Invest 51:2584-2592, 1972 58. Martin DE, Wolf RC, Meyer RK: Plasma lipid levels during
879
pregnancy in the rhesus monkey. Proc Sot Exp Biol Med 138:638641, 1971 59. Wolf RC, Temte L, Meyer RK: Plasma cholesterol in pregnant rhesus monkeys. Proc Sot Exp Biol Med 125: 123&l 23 1,1967 60. Van Zyl A: Serum protein-bound iodine and serum lipid changes in the baboon (Papio ursinus). II. During pregnancy, lactation and abortion. J Endocrinol 14:317-324, 1957 61. Popjak G, Beckmans M: Synthesis of cholesterol and fatty acid in fetuses and in mammary glands of pregnant rabbits. Biochem J 46:547-56 1, 1950 62. Connor WE, Lin DS: Placental transfer of cholesterol-4-C? into rabbit and guinea pig fetus. J Lipid Res 8:558-564, 1967 63. Fillios LC, Kaplan R, Martin RS, et al: Some aspects of the gonadal regulation of cholesterol metabolism. Am J Physiol 193:4751.1958 64. Knobil E, Hagney MC, Lampcrt NR: Lipemia of pregnancy in the rat. Abst. Fed Proc 16:74, 1957 65. Tietz WJ, Jr, Benjamin MM. Angleton GM: Anemia and cholesterolemia during estrus and pregnancy in the Beagle. Am J Physiol 2121693-697, 1967 66. Lin DS, Pitkin RM. Connor WE: Placentral transfer of cholesterol into the human fetus. Am J Obstet Gynecol 128:735139.1977 67. Barnes K, Nestel PJ, Pyrke ES. et al: Neonatal plasma lipids. Med J Aust 2: 1002-l 005, 1972 68. Den Besten L, Connor WE, Bell S: The effect of dietary cholesterol on the composition of human bile. Surgery 73:266-273, 1973 69. Connor WE, Connor WL, Fry MM, Warner SL: The Alternative Diet Book, Iowa City, University of Iowa Press, 1976 70. Connor WE, Connor SL: Dietary treatment of hyperlipidemia, in Rifkind BM, Levy RI (eds): Hyperlipidemia: Diagnosis and Therapy. New York, Grune and Stratton, 1977, pp 281-518 71. Symposium: Report of the task force on the evidence relating six dietary factors to the nation’s health. Am J Clin Nutr 32:26212748, 1979
The
controlled
present
P. McMurry,
which accompanies
experiment
metabolic conditions
William
Cholesterol Upon the of Pregnancy*
E. Connor, and Clifford P. Goplerud
the normal human pregnancy
in fourteen
pregnant
women
was
is not known to be influenced
designed
and to study the effect of dietary cholesterol
to document
this
by diet or other
phenomenon
The subjects included twelve normal subjects, one juvenile diabetic, and one type II familial hypercholesterolemic They were fed controlled,
nutritionally
was cholesterol-free
or 600-1000
The cholesterol-free
diet lowered
mg/dl,
a 20% decrease
serum
cholesterol
levels increased
( -47
and triglyceride
triglyceride
responses
serum cholesterol
the mean serum to 223
mg/dl,
similarly
decreased in the familial
of cholesterol
study indicated that the usual hypercholesterolemia by a very low cholesterol,
T
nutritionally
30,
No.
9 ISeptember),
1981
(+36
_t 12) (p
1 wk after
hypercholesterolemic
diets occurred
c 0.001). + 43 (SD.1
parturition.
in women
which
women
from
elevated
234-187 the mean
The mean serum triglyceride mg/dl These
and the diabetic
largely in the low density
homeostasis
of pregnancy adequate
pregnant
subject.
content,
gain of 1.4 kg per mo.
to the diet invariably
of diet. up to 198
strikingly
HE HYPERLIPIDEMIA of human pregnancy was described as early as 1844 by Becquerel and Rodier in France.’ This observation has been periodically reported since that time and has been documented on a worldwide scale, in primitive as well as technically advanced cultures.3m’E There is general agreement that the serum cholesterol concentrations increase progressively throughout the second trimester of pregnancy, reach a peak during the third trimester, and decline after parturition. Increased serum triglyceride concentrations during pregnancy have also been reported.‘6,‘7 Recently detailed studies have characterized the lipoprotein changes and reported increased concentrations of very low density (VLDL), high density (HDL), and low density (LDL) lipoproteins.‘9m22The lipid composition of the lipoproteins was increased proportionally in the VLDL and IDL (intermediate-density lipoprotein) fractions. In contrast, LDL, and HDL showed greater increases in triglyceride than the other lipids, leading to a percentage shift toward enrichment with triglyceride.18 The hypercholesterolemia of pregnancy presumably occurs from metabolic and endocrine influences. Our hypothesis is that diet may be an additional factor. Pregnant American women were advised to consume additional calories during pregnancy to produce a 24 lb average weight gain.23 Eating the usual American diet in increased amounts would mean even greater intakes of cholesterol and saturated fat.24 In addition, an increased intake of animal protein is often recommended for pregnant women25,26 which would further elevate the consumption of dietary cholesterol and saturated fat. Since hypercholesterolemia has been induced with diets containing large amounts of choles-
Metabolism,Vol.
of cholesterol
increase
and lipoprotein
to permit weight
level in the 12 normal
The addition
regardless
levels during the high cholesterol
Despite the inevitable alterations ameliorated
cholesterol
a 19%
pregnancy
concentrations
occurred
except for the cholesterol
mg from egg yolk daily. Calories were adjusted
throughout
cholesterol
diets which were equivalent
+ 37 S.D.) (p < 0.005/.
concentrations steadily
adequate
under
upon this usual increase in serum cholesterol.
at term. serum women.
lipoprotein
which occur in pregnancy, eating the general American
Both serum
cholesterol The
and
increased
(LDL) fraction.
the results of this diet was greatly
diet.
terol under experimental conditions in men,“‘,31 women,32,33 and in animals,34 the diet of pregnant American women may promote the development of hypercholesterolemia. Disorders of cholesterol metabolism are related epidemiologically and clinically to the pregnant state. Of the numerous etiological factors associated with cholesterol gallstones, pregnancy has long been prominent.35’36 In addition, the incidence of atherosclerotic heart disease may be increased in multiparous women3’ although this is equivocal.38 The present study is designed to examine :he hypercholesterolemia found in pregnancy and, further, to determine its nutritional basis. In this study, a cholesterol-free diet known to lower serum cholesterol
*Published
in abstract form
in Clinical
Research
25.521‘4
Abstract.
From the Lipid-Atherosclerosis Laboratory, the Department of Medicine. and the Clinical Research Center, University of Gregon Health Sciences Center, Portland. Oregon and the Clinical Research Center and Departments of Internal Medicine and Obstetrics and Gynecology, University of Iowa College of Medicine. Iowa City, Iowa. Supported in part by U.S. Public Health Service Grants HL19130 and HL-06336 from the National Heart, Lung and Blood Institute and by the General Clinical Research Centers Program (RR-334 and RR-59) of the Division of Research Resources of the National tnstitutes of Health and by the National Heart, Lung and Blood Institute HL-20910 of the National Institutes of Health. Received for publication October IS, 1980. Address Reprint Requests to Dr. William E. Connor, University of Oregon Health Sciences Center. 3181 SW Sam Jackson Park Road, Portland, Oregon, 97201. A 1981 bv Grune & Stratton, Inc. 0026-o495/81/3009-0005$02.00/0
869
MCMURRY, CONNOR, AND GOPLERUD
870
concentration was 180 k 53 mg/dl with a range of 116-297. Six subjects were hyperlipidemic by the standards of the Food and Nutrition Board of the National Academy of Sciences for nonpregnant adults with serum cholesterol concentrations greater than 220 mg/dl.” In addition, two women were studied who had concomitant metabolic diseases. Subject 13 was a 19-yr-old juvenile diabetic diagnosed at age 8. Before her pregnancy, she was reportedly in good diabetic control on 65 units lente insulin daily with negligible glucosuria (negative or 1 plus by Clini-test) and no insulin reactions. During pregnancy, her diabetic control deteriorated and she reported considerable glucosuria and small to moderate ketonuria on spot checks. She was admitted to the research ward in her third trimester of pregnancy and remained there throughout the post partum period. During the metabolic study, she received lente insulin twice daily subcutaneously, 40 units in the morning and 35 units in the evening. Despite great effort, her diabetes was not closely controlled during the study, as evidenced by mean 24 hr urinary glucose excretion before parturition of 55 g (range I-l 17g) and post prandial blood sugars of 15G250 mg/dl. However, her initial ketonuria disappeared and no evidence of acidosis was present. She had both elevated serum cholesterol (314 mg/dl) and triglyceride (286 mg/dl) at admission. Delivery was induced in the 36 wk of pregnancy by intravenous pitocin and artificial rupture of membranes. There were no complications for either the mother or the newborn. The infant weighed 3920 g. After parturition, the mother’s mean glucosuria decreased to 1 I g per 24 hrs with lente insulin doses of 30 units in morning and 12 units in the evening. Subject 14, age 16, had been followed as an outpatient since age 4. She was a member of a large family with well-documented type II hypercholesterolemia, xanthoma, and premature coronary heart disease in at least fourteen family members. Untreated, she had a serum cholesterol of 35&400 mg/dl; with dietary treatment and cholestyramine or PAS-CR, this was reduced to as low as 250 mg/dl. Her fasting serum triglycerides were consistently less than 150 mg/dl. She was classified as a hyperlipidemic type 11-a. Two years before her pregnancy, sterol balance studies had been carried out. At that time, with a mixed food diet of 100 mg of cholesterol per day, 20% fat, and with no medication, her serum cholesterol was 243 mg/dl and triglyceride 77 mg/dl. When admitted in the 6th mo of pregnancy, her serum cholesterol had increased to 346 mg/dl and serum triglycerides to 172 mg/dl.
levels32 was fed to 14 pregnant women. This was alternated with a high cholesterol diet (600-1000 mg cholesterol per day). The study was carried out entirely under metabolic ward conditions in the Clinical Research Center. Subjects were recruited and entered into the study over a IO yr period of time. They were under constant surveillance and consumed the prescribed diet. Serum cholesterol, triglyceride and lipoprotein levels were measured. In addition, sterol balance and bile composition studies were carried out. The latter data are to be reported separately. In one subject, similar measurements were carried out during pregnancy and post partum. MATERIALS AND METHODS
Subjects Twelve normal pregnant women participated in this study. They were admitted to the Clinical Research Center in the second or third trimester where they stayed for the duration of their pregnancy. Prior human research committee approval had been obtained for the project and each subject and a parent, when appropriate, gave informed consent. Subjects were recruited and entered into the study over a ten-year period of time. The subjects (Table 1) had a mean age of 20. They were all primiparous except for one woman who reported one previously aborted pregnancy. Nine of the twelve subjects were within 15Ye of the normal non-pregnant weight for height at the time of admission as compared to non-pregnant college-age women.” The exceptions were Subjects 9, 10, and 11, who were 21%. 57%, and 58% overweight respectively. While most of the subjects were admitted in the sixth month of pregnancy, three began the study in the fourth and fifth months. All women had uneventful full-term deliveries. Subject 7 had twins. All infants appeared normal and healthy at birth, and most of them were put up for adoption. None of the subjects were lactating post partum. There was a wide range of serum lipid concentrations at admission (Table 1). The mean serum cholesterol level was 234 + 40 (S.D.) mg/dl with a range of 187-294; the mean triglyceride Table 1. Description
of Normal Pregnant
Women
on Admission to the Study % of Normal
Subject
Age
Month of
Height
Serum
Serllfll
Weight
Nonpregnant
Cholesterol
Triglyceride
Yr.
Gestation
cm
kg
Weight*
mg/dl
mg/dl
1
20
6
160.5
60.8
110
277
156
2
18
6
160.5
50.4
92
253
134
3
19
5
163.0
59.9
109
233
197
4
18
4
165.5
55.8
96
199
137
5
18
5
165.5
56.3
96
201
180
6
20
6
155.0
57.6
111
288
232
7
20
6
168.0
63.5
109
203
181
8
21
6
163.0
53.6
97
199
143
9
19
6
170.5
74.3
121
187
10
21
6
165.5
91.8
157
294
297
11
21
6
168.0
92.3
158
266
210
12
19
6
160.5
59.9
109
204
116
Mean
20
6
163.8
64.7
114
234
180
1
4.3
14.1
22
40
53
Number
S.D.
1
*Compared to non-pregnant college-aged womerxa6
871
DIETARY CHOLESTEROL UPON PREGNANCY
Dietary Periods All subjects received a general hospital diet for 1 wk after admission, followed by the series of metabolic balance diets which continued until one or two weeks post partum. Two diets were used: a cholesterol-free diet and a diet in which was incorporated 6001000 mg cholesterol. Each dietary period was 4-9 wk in duration. The series of dietary periods usually began with the high cholesterol diet which was alternated with the cholesterol-free diet until delivery. However, five of the subjects (IO, 11, 12, 13, and 14) began the study with the cholesterol-free diet. Since the time of delivery was variable, the entire series of diets was not always completed for each subject. Five subjects delivered during Period III, eight during Period IV, and one during an additional high cholesterol dietary period. After delivery, the subjects continued their pre-delivery metabolic diet minus 200 calories for 1 or 2 wk and were then given a general diet until discharge from the hospital. The diets were comprised of either formulas or mixed foods and contained sufficient calories to permit a moderate weight gain. The composition of the diets was planned to simulate the usual American diet in terms of carbohydrate, protein, and fat composition with
modification of the cholesterol content (Table 2). acid composition of the study diets was 11% of the saturated, 19 percent monounsaturated, and 9% (iodine number 80, P/S value of 0.8). However, received a slightly more saturated fat diet (iodine
The usual fatty total calories as polyunsaturated some subjects number 60, P/S
value of 0.3). Both diets were within the range of fatty acid compositions normally consumed by Americans. For most of the subjects, the fatty acid composition remained constant throughout their diet sequence. For Subjects 2 and 4, the cholesterol-free and high cholesterol diet sequence was given once with a dietary fat of iodine number 60 and again with a dietary fat of iodine number 80. Dietary cholesterol was provided by egg yolk. During the cholesterol-free diets, appropriate adjustments were made, so that the total protein and fat and the fatty acid composition remained the same for the cholesterol-free and high cholesterol diets. The high cholesterol diets contained 600 mg cholesterol except for Subject 12 who received 750 mg and Subjects 1I and 14 who received 1000 mg per day for the high cholesterol diets. These amounts of dietary cholesterol are within the range consumed in the United States. Examples of the mixed food and the formula diets are shown in Table 2. The type of diet given to each subject varied depending on
Table 2. The Composition of Diets For the Different Dietary Periods HighCholesterol Diet Sequence
I and
III
Cholesterol-Free II and IV
600 mg
0
15%
15%
Carbohydrate’
45
45
Fat*$
40
40
Saturated Fatty Acids*
11
11
Monounsaturated Fatty Acids*
19
19
Polyunsaturated Fatty Acids*
9
9
P/S9
0.8
Cholesterol mg/dayt Protein*
Iodine Number Formula Diet lngredientsll
80
Skim milk powder Frozen egg yolk mix
205 g
0.8 60 225 g
59
0
Sweet chocolate(
42
48
Peanut oilll
66
79
Dextrimaltose
63
63
Cornstarch
40
40
16
7
Sugar Mixed Food Diet Ingredients11 Egg yolk
59
0
Egg white
48
56
Sktm milk powder
90
90
Fat-free cottage cheese
34
58
Peanut buttery
30
30
Margarinen Sweet chocolate1
67 10
41
6
6
3 6
6
8
7
Oilll Vegetable exchanges* Bread exchanges**
l
Frurt exchanges**
72
3
‘Percent of total calories. tSubject 12 received 750 mg; subjects 13 and 14. 1000 mg. $Some subjects received a dietary fat somewhat more saturated, with 19% monounsaturates, 5% polyunsaturates and 16% saturates, P/S 0.3 and Iodine number 60. §Ratio of polyunsaturated fabsaturated fat. /IExamples for 2000 calories diets. ISpecific brands of known fattY acid composition were used. **Using
established diabetic exchange lists, using weighed amounts of food.
872
MCMURRY, CONNOR. AND GOPLERUD
individual tolerance and preference. Mixed food and formula diets were interchangeable in calories, cholesterol, amount of protein, carbohydrate, fat, and type of fat. The diets were fed in six feedings, 3 meals and 3 snacks. During the high cholesterol periods, the egg yolk was given at each of the six feedings for the formula diets; in the mixed food diets, the egg yolk was given in three equal portions at mealtimes. The mixed food diets were from a variety of foods which gave a diet adequate in nutrients. Vitamin and mineral supplements were added to meet the National Research Council recommendations for pregnant women4’ To be emphasized was the nutritional adequacy of the diet during the cholesterol-free periods. The protein intake at 15% of total calories averaged 87 g/day, thus meeting the recommended intakes for pregnant women. Of the total protein intake, 100% was from high quality animal proteins, mostly from milk, during the formula diets. In the mixed food diets, 60% of the protein was from animal sources (milk products and eggs) and 40% was from vegetable sources (peanut butter, cereals and vegetables). Thus the protein intake was more than adequate for both the cholesterol-free and high cholesterol diets.
RESULTS
Laboratory
Serum Cholesterol
Studies
Blood was obtained for lipid measurements twice weekly after an overnight (12 hr) fast. The serum was analyzed for cholesterol by the method of Block, Jarrett and Levine4* as the samples were obtained. The serum for triglyceride determinations were frozen and analyzed at the end of the study (the Kessler and Lederer method).43 The average of all values from the third to the last week for each subject during each dietary period (final mean value) was used in the data analysis since the mean serum cholesterol had stabilized by that time. The final mean value included from 1-12 points, but usually was the mean of 4 values. Sera from Subjects 1 I and 14 were analyzed for lipoprotein cholesterol. The separation of lipoproteins was done by ultracentrifugation.“’ Group t tests were used to compare the data for each individual. In groups, with each subject acting as her own control, statistical comparisons were made by utilizing the student’s paired t analysis. A P value < 0.05 was considered to be a significant difference.4s
Table 3. The Mean Serum Cholesterol Concentration
Dietary cholesterol had a pronounced effect upon the serum cholesterol concentrations in all 12 normal pregnant women, The key serum cholesterol changes occurred with the removal and addition of cholesterol in the diet. Mean serum cholesterol concentrations for each individual subject and serum cholesterol changes (mg/dl) are shown in Table 3. Each subject served as her own control. Of the 27 individual dietary exchanges of high cholesterol and cholesterol-free diets, 25 exchanges produced increases or decreases of serum cholesterol levels dependent upon the presence or absence of cholesterol in the diet. The only exceptions were in subject 7, the only woman to have twins. She did not show a decrease in serum cholesterol during cholesterol-free diets II and IV but did have the usual hypercholesterolemic effect of the high cholesterol dietary period III. As a group, the mean serum cholesterol concentrations responded to the dietary cholesterol intakes (Table 4). Compared to admission values, the 12 normal women showed a marked decrease in serum cholesterol concentration after consuming a cholesterol-free diet, from 234-187 mg/dl, a 20% decrease (p < 0.001). Reintroducing cholesterol into the diet in Period I11 produced a similar change, increasing the serum cholesterol to 223 mg/dl, a 19% increase (p < 0.001). The fourth dietary period, Period IV cholesterol-free, completed by six subjects before delivery, decreased the plasma cholesterol level from 238-2 18 mg/dl (p < 0.05). For Each Pregnant Woman During Each Dietary Period
(mg/dl)*
II Cholesterol-Free
Subjects
Mean ? SD.
11
1
251
t
2
214
? 5
III High Cholesterol
Mean + S.D.
% Change
P VellE
IV Cholesterol-Free §
§
I High Cholesterol
Concentrations
Mean + SD.
$ Change
P V&E
225 * 6
-26
254 r 12
+29
<0.005
201 t 1
-13
258
+ 9
f57
4 Mean + S.D.
210 ? 8
$ Change
-44
P Value
<0.005
3
189 + 5
170 + 3
-19
216 + 7
+46
194 + 8
-22
<0.005
4
237 + 10
218 + 9
-19
<0.005
253 ? 17
+35
242 ? 11
-11
>0.2
217 177 + 20
+2 -10
II >0.4
269 + 16
-33
<0.05
5
165 + 5
145 t 8
-20
188 i
11
+43
6
246 i
186 t 3
-60
206 + 12
+20
7 8
171 + 16 197 +- 11
174 ? 15 165 + 6
+3 -32
>0.5 <0.005
215 5 5 187 * 10
f41 +22
9
-30
10
189 ? 8
159 + 5
184 + 16
+25
<0.005
10
t
253 * 13
302 + 18
+49
to.05
11
t
197 +4
237 + 11
f40
12
t
150 + 6
171 i 18
f21
to.005
*Mean of all values after and including wk 3. tBegan study with Period II cholesterol-free. fChange compared to previous dietary period. $T test compared to previous period. 11Not
enough
values
for statistical
comparison.
DIETARY
CHOLESTEROL
UPON
873
PREGNANCY
Table 4. Group Mean Serum Cholesterol Changes During Each Dietary Comparison Serum Cholesterol Number Subiects Admission
I High
Diet to
Cholesterol
I High Diet
Cholesterol
Diet
III High
Cholesterol
t SD.
to
f
%
9
227
207
-20
27
9
207
183
-24
? 17
P Value
-9
>0.05
-- 12
<0.005
12
234
187
-47
+ 37
-20
<0.005
Cholesterol
12
187
223
f36
+ 12
t19
io.001
to IV Cholesterol-free
6
238
218
-20
k
to II Cholesterol-free
II Cholesterol-free
horn
Mean mg/dl
to II Cholesterol-free
Diet Admission
Change
mg/dl
of
to Ill High
Length of‘ Gestation
Subjects responded similarly to changes in dietary cholesterol regardless of the trimester of pregnancy. The subjects began the study at various months of gestation, some in the second and some in the third trimester. The five subjects (1, 3, 4, 7 and 8) who were admitted relatively early in pregnancy were able to complete all four dietary periods in sequence: I, high cholesterol; 11, cholesterol-free; III, high cholesterol: and IV, cholesterol-free. The high cholesterol diets produced increased serum cholesterol levels, 209 * 34 (S.D.) mg/dl and 225 + 29 mg/dl respectively, while the cholesterol-free diets led to much lower values, 190 t 29 and 208 k 24, respectively. These changes, whether in the second or third trimesters of pregnancy, were similar. There appeared to be an increased serum cholesterol concentration during the latter months of gestation (dietary periods 111 and IV) compared to earlier comparisons (I and II). The mean increase of 17 + 20 mg/dl of III and IV combined compared to 1 and 11 combined correspond roughly to the increase in plasma cholesterol from the second to the third trimester. Subjects admitted in or near the third trimester failed to show this gradual increase in serum cholesterol: they had already attained maximal values. However, there did not appear to be any augmentation of the hypercholesterolemic effect of dietary cholesterol later in pregnancy. Early dietary comparisons (usually in the second trimester) were the same as those seen in late pregnancy (third trimester) (mean changes + 3 I 4 25 and + 31 + 15 mg/dl respectively). Serum cholesterol concentrations were especially stable in Subject 12. who was given the cholesterolfree diet for a period of 9 wk (Fig. 1). Her serum cholesterol remained low at approximately 152 k 6 mg/dl for the entire nine week period, most of which was during her third trimester. The introduction of 750 mg cholesterol into the diet during the 34th week
17
-8
co.05
of pregnancy resulted in a rise in the serum cholesterol level to 17 1 f 18 mg/dl. Serum
Triglyceride
Concentrations
After the baseline diet, the mean serum triglyceride concentration increased progressively with the duration of pregnancy regardless of diet (Table 5). At baseline, the mean serum triglyceride level of all subjects was 169 f 33 mg/dl. During Period I, the mean declined slightly to 161 i 44 mg/dl (nine subjects), then increased in 14 subjects to 186 + 66 mg/dl in Period 11 and to 212 f 59 mg/dl in Period III. The mean triglyceride concentration during Period III (high cholesterol) prior to delivery was significantly increased (p < 0.025) compared to Admission in all 12 subjects and compared to Period I (high cholesterol) with nine subjects (p < 0.001) (paired t tests). Post Partum
Changes
in Serum
Lipids
Serum lipid concentrations in most subjects, all of whom were not breast feeding the infants. decreased Subject # 12 750 mg Cholesterol Diet
17 Dellvery
1
Week of Pregnancy
38
I
‘
40 1
Fig. 1. The serum cholesterol concentrations during the study for subject 12. a normal subject.
874
MCMURRY,
CONNOR, AND GOPLERUD
Table 5. The Serum Triolvceride Concentrations (ma/dlj During the Fourth Week of Each Diet I
Ill
II
High
Cholesterol-
IV
High
Cholesterol-
Cholesterol
Free
1
156
159
312
2
123
113
135
166
3
166
137
133
166
159
4
137
151
136
196
218
Subjects
Admission
Cholesterol
Free
204
252
5
175
129
131
182
6
232
263
300
337
7
176
155
186
250
8
158
194
190
213
151
182
223
9 10
195
248
306
11
208
146
163
12
135
130
142
169 + 33.
186 + 66
212 + 59.
189 f 70
215 f 53t
207 + 88
218 f 61
247
Mean + S.D. of Subjects l-2 Mean + SD. of Subjects l-9
165*32
161 + 44t
Mean ? S.D.of Subjects 1, 3, 4, and 10
164 + 24
Significantly different by paired T test: l<0.025;
219 * 43
tiO.OO1.
serum cholesterol of 246 mg/dl during pregnancy compared to 193 mgfdl after pregnancy, a 22% difference. Although the increases in serum cholesterol concentration from dietary cholesterol feeding were similar during and after pregnancy, the serum cholesterol concentrations under both dietary conditions were higher during the pregnant state. The serum triglyceride concentrations were likewise increased during pregnancy. The increased LDL cholesterol made up the bulk of the cholesterol elevations induced by dietary cholesterol, LDL cholesterol increasing 38 and 24 mg/dl, pregnant and post partum respectively. While HDL cholesterol also increased, the LDL to HDL ratio actually became greater, so that the relative increase of HDL was less than that of LDL.
after delivery. By l-2 wk post partum, the mean serum cholesterol concentration had decreased from 213 + 12 (S.E.M.) to 200 f 7 (S.E.M.) mg/dl, a 6% reduction (not significant). The serum triglyceride level dropped in all subjects from mean 198 f 13 (S.E.M.) to 132 f 8 mg/dl, a 33% decrease (p < 0.001). Changes were not related to the diet consumed at parturition (whether cholesterol-free or high cholesterol) and the changes occurred rapidly, in only l-2 wk. Comparison of the Responses to Dietary Cholesterol in the Same Subject: Pregnant Versus Non-Pregnant Subject 11 repeated the same dietary sequence 4 wk after delivery (Table 6), thus receiving both the high cholesterol and cholesterol-free diets before and after delivery. The high cholesterol diet produced similar percentage elevations in the serum cholesterol concentrations during and after pregnancy. During pregnancy with the cholesterol free diet, the serum cholesterol was 199 mg/dl. After pregnancy, the same diet led to a serum cholesterol concentration of 164 mg/dl, 18% lower. The high cholesterol diet resulted in a
The Serum Lipid Changes in the Pregnant Diabetic Patient
Juvenile
Subject 13, with severe juvenile diabetes, had responses in serum cholesterol levels similar to the other pregnant subjects. She entered the study in the
Table 6. The Effects of Dietary Cholesterol Upon the Serum Lipoproteins in a Normal Subject* During Pregnancy and Post Partum Cholesterol mgldl LDL to
Triglycerides
Pregnancy
Total
VLDL
LDL
HDL
HDL Ratio
mgldl
Cholestarol-free
30
199
14
127
58
2.19
146
High Cholesterol
40
246
19
165
62
2.66
163
Week of Diet
Post Parturn Cholesterol-free High Cholesterol ‘Subject No. 11
7
164
13
113
38
2.97
98
10
193
14
137
42
3.26
125
875
DIETARY CHOLESTEROL UPON PREGNANCY
H TotalCholesterol c----o LOL cholesktol
Subject # 14
Week of Pregnancy Fig. 2. trations
Total
serum
in the familial
cholesterol
and
LDL
hypercholesterolemic
cholesterol subject
concen-
14.
middle of the third trimester of pregnancy. Diabetic control was imperfect despite hospitalization and intensive effort, as illustrated in her case report (see Materials and Methods). On admission, she was hyperlipidemic with both serum cholesterol and triglyceride concentrations near 300 mg/dl. During the cholesterol-free diet, her serum cholesterol decreased to 226 + 6 mg/dl (wk 3 and 4). After the 600 mg cholesterol diet, her serum cholesterol level increased to 242 mg/dl in the third week of the diet, before delivery was induced. The serum triglycerides also increased to 334 mg/dl just before delivery. Although she received the same high cholesterol diet (less 200 calories) after delivery, her serum cholesterol concentration dramatically decreased to 194 mg/dl and triglycerides from 334-59 mg/dl. Concurrently, her insulin requirements lessened and diabetic control improved greatly.
EfSects of the Types of Diets Both mixed food and formula diets were used in this study, as well as dietary fatty acid compositions of I#60 (P/S 0.3) and 80 (P/S 0.8). The changes in serum cholesterol concentration were similar irrespective of whether the diet was composed of mixed foods or formula. On formula diets, 16 separate exchanges of high cholesterol to cholesterol-free in 12 subjects produced a mean decrease of 31 + 19 (S.D.) mg/dl serum cholesterol; five similar comparisons in 4 subjects on mixed foods produced a decrease of 30 + 17 mg/dl. The slight difference in fatty acid composition produced no consistent differences in response between the two subjects receiving both diets (Subjects 2 and 4) or in the group as a whole. Weight Changes Our pregnant subjects gained an average of 10.9 kg from their reported pre-pregnancy weight of 58.6 t 12.3 to 69.5 f 12.5 kg at parturition. This is within the recommended weight gain from the Committee on Maternal Nutrition of 9-l 1.4 kg. The mean weight
The Serum Lipid Changes in the Familial Hypercholesterolemic Patient The subject with type II-a familial hypercholesterolemia (Subject 14) had an initial total serum __~
Table
7. Effect of Dietary
Cholesterol
Upon
Plasma
Lipids
cholesterol concentration of 346 mg/dl with LDL cholesterol of 294 mg/dl (Fig. 2 and Table 7). Her serum cholesterol and LDL cholesterol levels were most responsive to changes in dietary cholesterol intake. During the cholesterol-free diet, her serum cholesterol decreased to 260 mg/dl. With an intake of 1000 mg cholesterol/day, there was an increase to 360 mg/dl. With a subsequent cholesterol-free diet, the serum cholesterol decreased again to 291 mg/dl. One week post partum, her serum cholesterol level fell further while she was still consuming the same cholesterol-free diet. The LDL cholesterol paralleled the total cholesterol changes (Fig. 2). The cholesterol-free diet decreased the LDL cholesterol concentration from the admission value of 294 to 218 mg/dl; the 1000 mg cholesterol diet increased LDL cholesterol to 303 mg/dl. Dietary cholesterol increased HDL cholesterol somewhat also, but the LDLf HDL cholesterol ratio increased at the same time.
end Lipoproteins
in a Subject
With
Familial
Hypercholesterolemia
Cholesterol mgldl week
Tnglycerides
Of
Pregnancy
DIH
Tots1
VLDL
LDL
HDL
LDL/HDL
mg/dl
Admission
25
346
15
294
37
7.95
172
Cholesterol-free
29
262
6
218
39
5.59
103
High
34
348
1
303
44
6.89
129
38
291
10
245
36
6.81
140
2
261
5
225
31
7.26
74
12
296
2
254
40
6.35
62
Cholesterol
Cholesterol-free Post Cholesterol-free Home
diet,
controlled
Partum
poorly
876
MCMURRY.
gain during the 2-5 mo study was 1.4 +. 0.7 kg per mo. By 1 wk post partum, the mean decrease in weight was 7.0 f 1.8 kg. The mean newborn weight was 3.32 f .42 kg (excluding the twins of 2.53 and 2.35 kg). This is within the fiftieth percentiles of newborn boys (3.44) and girls (3.30) in the U.S.46 No significant correlation occurred between total weight gain or weight gain during the study and the weight of the newborn infant. The initial serum triglyceride concentrations were, however, positively correlated with the admission weight (r = 0.57, p < 0.05). The amount of weight gain did not correlate with the changes in serum triglyceride concentration during the study. Cord Blood Cholesterol
Levels
In 12 infants, the cord blood cholesterol concentration ranged from 64-114 mg/dl (Table 8). Five infants, (including the twins) the children of the two obese pregnant women, and the infant of the subject with type 11-a hypercholesterolemia, all had cholesterol levels of over 100 mg/dl, definitely elevated. There was a positive correlation (+0.587) between the maternal serum cholesterol level just before delivery and the cord blood cholesterol concentration (p < 0.05). DISCUSSION
The hypercholesterolemia of human pregnancy is not only the most common cause of hypercholesterolemia in premenopausal women but also represents an example of a primary metabolic state which might be modified by dietary influences. The results of our study in 14 pregnant women document that the hypercholesterolemia of pregnancy can be greatly ameliorated by the removal of cholesterol from the diet. Table 8. Serum Cholesterol
Concentration
of Maternal
and Cord
Blood MatWlal* Subject
lmg/dl)
Cwd Blood (mg/dl)
1
200
79
2
235
90
3
198
64
5
190
74
6
239
77
7
217
101
8
188
9
203
87
10
274
105
12
219
113
14
291
113
Mean f S.D.
223 + 34
90 + 16
114 82
CONNOR, AND GOPLERUD
Some 31 separate dietary periods under controlled metabolic conditions of either high cholesterol or cholesterol-free diets provided the proof for this conclusion. Dietary effects upon the plasma cholesterol and lipoproteins have not been shown previously in pregnant women. Our results are in contrast to two previous studies reporting unsuccessful attempts to modify the hypercholesterolemia of pregnancy using very different approaches. Green concluded that the use of a fat-modified diet, decreased in saturated fat and increased in polyunsaturated fat, failed to prevent the rise of serum cholesterol in seven outpatient pregnant women.’ Moses et al. could not produce an exaggerated hypercholesterolemia by adding 2 g crystalline cholesterol to the usual diet of pregnant women4’ In contrast, our study shows dietary cholesterol in a range of intake commonly consumed by pregnant American women can affect the plasma cholesterol concentration. Dietary cholesterol has been shown repeatedly to affect the plasma cholesterol levels in normolipidemic and hyperlipidemic men and non-pregnant women27-33 and in diabetic patients.48 The pregnant women reported in the present study, though exhibiting the usual hypercholesterolemia of pregnancy, were not different than non-pregnant adults in their response to dietary cholesterol. Their 20% increase in plasma cholesterol concentration from high cholesterol feeding compared to a cholesterol-free diet is similar to those changes previously reported.* The hypercholesterolemic effect of dietary cholesterol was similar in all the pregnant women studied, including the normals and the obese, diabetic and hypercholesterolemic patients. The serum cholesterol changes were most pronounced in the patient with familial hypercholesterolemia. This finding is similar to previous observations of the enhanced sensitivity of these patients generally to dietary cholesterol intake” and confirms recent reports showing amelioration of the hypercholesterolemia of pregnancy in patients with familial hypercholesterolemia with the use of a modified diet.“,‘* The only woman in our study who delivered twins, subject number 7, seemed the least sensitive to the dietary cholesterol changes, showing no decrease in serum cholesterol concentration during the cholesterol-free diets but exhibiting the typical rise in serum cholesterol following high cholesterol feeding. The diabetic patient exhibited the characteristic lipid responses to dietary changes despite the enhanced tendency in patients with diabetes mellitus toward hyperlipidemia and atherosclerosis.2’.48.53.s4
The correlation ccx&cient of maternal and cord blood cholesterol was +0.587.
p < 0.05.
+Last serum cholesterol concentration before parturition.
*Summarized
in a review of the literature
human metabolic studies.49
(Table
6) of the ten
877
DIETARY CHOLESTEROL UPON PREGNANCY
We would stress the universality of the plasma cholesterol increase occurring in human pregnancy. The hypercholesterolemia of pregnancy has occurred in all cultures surveyed including those whose habitual diets are high in cholesterol: United States,2’5.7.‘4”5”6 Scotland,3.4 African Masai” and South African white$ and in those who typically consume a diet low in cholesterol: Guatemala,” India,’ Mexican Tarahumara, Thailand” and Nigeria.13 However, the customary dietary cholesterol and fat intakes of the various populations would appear to determine the baseline serum cholesterol concentration from which the increase in pregnancy occurs. For example, at the time of admission (usually the second trimester) in our group of subjects, the mean serum cholesterol level of 235 mg/dl already constituted an increase of 3 1% over the usual serum cholesterol concentration of 178 mg/dl in 18-yr-old non-pregnant women from the general population.“j Changing to a cholesterol-free diet decreased the serum cholesterol to 187 mg/dl, a level similar to that seen in pregnant Tarahumara women5’ and those from other cultures consuming a low cholesterol, low fat diet. Reintroducing cholesterol into the diet of our subjects increased the serum cholesterol level to 223 mg/dl. This increase was probably less than the maximum level they would have reached if they had consumed their usual home diet throughout their pregnancy. In fact, the usual home diet of our subjects appeared to be more hypercholesterolemic than the “high cholesterol” dietary periods used in our study. The mean serum cholesterol at admission decreased from 2277207 mg/dl (p < 0.05) during the high cholesterol diet given initially to the first 9 subjects. Perhaps the home diets were less limited than the high cholesterol diet used in the study. a diet moderate in cholesterol (usually 600 mg) and saturated fat (1 I%-16% of calories) content and controlled in calories. The usual dietary suggestions for pregnant women include special recommendations to consume particularly high cholesterol foods, to wit: on a daily basis, 2 servings of meat, frequent liver, l-2 eggs, 2 servings of cheese and 1 quart of milk.*’ These foods could easily result in a typical daily cholesterol intake of greater than 1000 mg. The increased plasma lipid levels during pregnancy were reflected in changes in the amounts of lipoprotein cholesterol and triglyceride. In the normal subject of our study, pregnancy was associated with increased LDL and HDL cholesterol levels. In the type II hypercholesterolemic patient, the LDL concentration was increased even more over the elevated nonpregnant levels. The gradual, independent increase in serum triglyceride concentration which occurred in
our subjects despite the serum cholesterol changes induced by diet supports the concept of triglyceride enrichment of lipoproteins, particularly LDL, and VLDL, during pregnancy.*’ In contrast to the hypercholesterolemia of human pregnancy, many animals have hyporcholesterolemia during pregnancy: rabbits, guinea pigs, and subhuman primates-monkeys and baboons.57”2 Some animals, however, mimic humans in having hypercholesterolemia during pregnancy: the dog and rat.63”5 The reasons for these species difference are completely unknown and warrant further investigation. This study documents the amelioration of the usual hypercholesterolemia of pregnancy by the restriction of cholesterol in the diet. The risks and benefits of a general recommendation to restrict the dietary cholesterol intake in pregnant women are not known. The fifteen infants born during this study were normal and healthy but were not followed further. However, there is little reason to suspect health risk. Cholesterol is not an essential nutrient for humans. The fetus is able to synthesize cholesterol66 and the newborn infant invariably has much lower plasma cholesterol concentration than the mother, usually about 70 mg/d1.67 Worldwide, normal infants are born to mothers who vary widely in plasma cholesterol concentrations because there are wide ranges in the cholesterol and fat contents of diet from different cultures. This being said, we should add that there may be several benefits of recommending a diet low in cholesterol and reduced in fat content during pregnancy. A low cholesterol diet may reduce the high incidence of gallstones in multiparous women since diet is known to influence the cholesterol to bile acid ratio in bile and thus may affect stone formation.6x Women with previously diagnosed hyperlipidemia who become pregnant could reduce their even more pronounced hyperlipidemia of pregnancy by consuming a diet low in cholesterol content and controlled in other dietary constituents. A diet low in cholesterol ( 100 mg) and fat (20% of calories) and composed of foods widely available in our culture could be adequate in protein, vitamins and minerals for the pregnant woman.“9*70 In addition, this diet could have increased fiber, be high in nutrient density and be consistent with current recommendations for dietary prevention of atherosclerosis and other chronic diseases common in the United States.‘4,7’ ACKNOWLEDGMENT The authors wish to acknowledge
the cooperation of many social
service agencies which referred subjects to us for study, and to thank Dr. Donald Wiebe and Dr. S. N. Jagannathan
for the separation of
the serum lipoproteins and Linda Sears. Meg Larson, and Joanne Skirving for the typing and preparation
of the manuscript.
MCMURRY,
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CONNOR, AND GOPLEAUD
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