Recent studies provided evidence that genetic variabil- ity at apolipoprotein gene loci may contribute to the
variation in lipid and lipoprotein response to dietary manipulations [27 – 36].
The present study examined the association between genotypes at the apo B, apo E, LPL and CETP loci
with the response of plasma lipids and lipoproteins to dietary manipulation. This was carried out in 214 indi-
viduals who participated in dietary experiments in which fatty acid composition and cholesterol intake
were modified while total energy intake remained constant.
2. Material and methods
The study was performed on healthy members of two large kibbutz settlements. Before the beginning of the
study, all eligible subjects were assembled and the pur- pose of the study, its performance and requirements, on
the part of the participants, were explained by the investigators. Signed consent was obtained from all
subjects agreeing to participate.
Each subject underwent a medical examination and a routine biochemical screening. Subjects with endocrine
or metabolic disturbances, such as diabetes mellitus, hypothyroidism, or those who reported any other cause
of secondary dyslipoproteinemia were excluded. Also excluded were subjects who were found to consume
more than 20 of their energy intake outside the kibbutz. Prior to the intervention, subjects were asked
to record their entire food intake for several days. This enabled the investigators to calculate the energy re-
quirements of each participant and to plan hisher diet accordingly.
Two different diets were administered in a crossover design. The first diet was characterized by a high con-
tent of saturated fatty acid and cholesterol HSC while the second diet consisted of low saturated fatty acid
and low cholesterol content LSC. The two diets were administered to the randomly allocated groups for a
4-week period period 1 followed by a wash-out period of 4 weeks consisting of the participants’ regular home
diet. Thereafter, subjects were given the other of the two diets for a second 4-week period period 2. During
the last week of each dietary period the participants were asked again to keep a record for several days a
record of all foods eaten. The food records were coded by dieticians. Quantities of food were coded by fre-
quencies, with one frequency representing the weight or volume of a standard serving or part of it. For several
composite dishes, such as cakes or fillings, standard recipes were used to estimate their composition. A set
of coding rules was used to estimate the amount of fat absorbed during cooking or frying and factors were
calculated for converting raw materials to cooked and baked foods. The nutrient content of the codes was
derived from several sources including local food pro- ducers and retailers, and local laboratory analyses for
some items. For more general items, local food tables were applied [37]. These records were analyzed and the
results are presented in Table 1. Total caloric intake was not significantly different between the two diets,
but the SFA content and the amount of cholesterol intake did differ.
At the beginning and at the end of each period, fasting blood was drawn twice within 2 – 3 days for
determination of lipids and lipoproteins. Participants’ weights were measured at several occasions throughout
the study and an attempt was made to immediately identify all subjects who showed weight change. Such
subjects where then advised by the dieticians how to adjust their energy intake so as to control the weight.
Table 1 Composition of the diets during the two periods
Energy Total fat
Cholesterol Total fat
SFA
a
SFA
a
kcal¯day gr
g of total kcal
of total kcal mgday
1926 9 572 75.9 9 28.0
35.1 9 6.3 Baseline
20.4 9 8.1 117 9 122
9.4 9 2.0 LSC
b
1714 9 483 63.6 9 23.6
33.4 9 8.8 Period 1
14.9 9 6.1 7.8 9 2.2
107 9 103 1595 9 553
58.7 9 26.1 32.6 9 7.6
Period 2 12.6 9 6.3
7.0 9 2.1 75 9 76
1652 9 521 61.0 9 25.0
33.0 9 8.2 Total
13.7 9 6.3 7.4 9 2.2
90 9 92 HSC
b
1865 9 682 Period 1
78.6 9 33.3 37.5 9 7.5
25.7 9 12.6 12.1 9 3.3
210 9 164 81.5 9 33.9
38.4 9 8.7 27.7 9 12.0
Period 2 13.1 9 3.8
1883 9 596 264 9 222
Total 80.1 9 33.6
238 9 199 12.6 9 3.6
26.8 9 12.3 1874 9 637
38.0 9 8.2
a
SFA, saturated fatty acids.
b
LSC, low SFAcholesterol diet; HSC, high SFAcholesterol diet.
3. Laboratory methods
