43 / 64
CARDIOVASCULAR JOURNAL OF AFRICA • Volume 30, No 4, July/August 2019
AFRICA
229
By contrast with this, however, a study that investigated dietary
intake of carbohydrate and SFAs in 18 countries undergoing
rapid nutritional transition documented that SFA intake was
associated with lower risk of mortality.
12
Studies investigating circulating FAs have also reported some
conflicting results. A recent study examined the relationship
between body mass index (BMI) and plasma phospholipid FA
composition in men aged between 48 and 65 years and reported
higher plasma phospholipid levels of palmitic (C16:0) and
stearic acid (C18:0) in obese individuals.
13
Furthermore, plasma
concentrations of C16:0 were positively associated with risk for
total mortality in men and women in a prospective study in the
USA.
14
SFAs, myristic acid (C14:0), C16:0 and C18:0 in plasma
were positively associated with the MetS, while longer-chain
SFAs, and arachidic (C20:0), behenic (C22:0) and lignoceric
acid (C24:0) were inversely associated in men and women
from Taiwan.
15
Another study also reported lower levels of
plasma C22:0 and C24:0 in the MetS participants.
16
Palmitoleic
acid (C16:1n-7) level in plasma phospholipids was positively
associated with BMI in men and women,
13,17
and higher levels of
plasma C16:1n-7 were associated with multiple metabolic risk
factors in men and women.
18,19
In different populations, total n-3 FAs in plasma were
associated with lower BMI, waist circumference (WC) and hip
circumference
20
and inversely associated with the MetS,
21
while
omega-6 PUFA have been associated with obesity and the MetS.
Pickens and associates reported higher plasma phospholipid
levels of dihomo-
γ
-linolenic acid (C20:3n-6) in overweight and
obese individuals.
13
Positive associations of serum phospholipid
C20:3n-6 with BMI, as well as total n-6 PUFAs with waist:hip
ratio were also documented in a study of Mexican women.
17
Some studies also report positive associations of specific plasma
phospholipids n-6 PUFAs with metabolic risk,
18,22
while other
studies report inverse associations of total n-6 PUFAs in
erythrocytes and serum, respectively, with the MetS.
23,24
Due to
inconsistent results in different studies relating to circulating n-6
PUFAs, further research to understand their role in association
with obesity and the MetS is highly recommended.
25
Since people consume food rather than individual nutrients,
it is difficult to isolate the individual nutrients in the diet and
link them to disease and health.
26
Therefore, the analysis of
food intakes into patterns derived from various combinations
of nutrients or foods has developed as a preferred alternative
to investigating associations between nutrients and diseases.
27
Several studies have applied factor and cluster analysis to derive
patterns from food and tissues in investigating the association of
these patterns with health and diseases.
28
FA patterns from adipose tissue and plasma have been
employed to describe associations of FAs with obesity
29
and the
MetS.
22,30
Despite the extensive use of plasma FAs in research,
there is limited epidemiological research on the use of both
dietary and circulating FA patterns in association with obesity
and the MetS in black populations in Africa. To address the
key gaps in the current knowledge, the aim of this study was to
investigate the associations of dietary and plasma phospholipid
FA patterns with adiposity measures [BMI, waist circumference
(WC) and waist-to-height ratio (WHtR)] and the MetS in a
selected group of black South African adults. This study was
based on a random sub-sample of 711 participants selected
from the South African site (North West Province) of the multi-
country Prospective Urban and Rural Epidemiological (PURE)
study. This study made use of cross-sectional data collected at
baseline during the months of August to November 2005.
Methods
A sub-sample of 711 black South African participants were
randomly selected from 2 010 adults recruited at baseline (in
2005) from urban (1 004) and rural (1 006) households in the
North West Province to assess dietary FA intake and plasma
phospholipid FA status. Those included were apparently healthy
subjects older than 30 years at baseline, with no reported diseases
of lifestyle, tuberculosis or HIV, and used chronic medication for
diabetes and hypertension only.
Ethical approval for the South African PURE study was
obtained from the Ethics Committee of North-West University
(Ethics number 04M10). Participants provided written informed
consent and participation was voluntarily.
Transportation was provided for the study subjects to reach
the data-collection centres in both rural and urban areas.
During face-to-face interviews by trained fieldworkers, each
participant completed questionnaires in his or her preferred
language (Afrikaans, Setswana or English). The questionnaires
included demographic,
31
physical activity
32
and quantitative
food-frequency questions (QFFQ),
33,34
and made use of, among
others, validated food photo-books to estimate portion sizes.
35
Reproducibility
33
and details of dietary assessments have been
published elsewhere.
10
Dietary macronutrients and FAs were calculated using the
South African Medical Research Council food composition
tables.
36
Twenty-eight dietary FAs were included initially, but
FAs that had a daily median intake of less than 0.10 mg were
excluded. A total of 11 dietary FAs were used to derive FA
patterns for investigation in this study.
Anthropometric measurements were performed by
trained research assistants according to standards prescribed
by the International Society for the Advancement of
Kinanthropometry.
37
A portable electronic scale (Precision
Health Scale, A&DCompany, Tokyo, Japan) was used tomeasure
weight. Height was measured using a calibrated stadiometer
(Seca, Hamburg, Germany). Waist and hip circumferences were
recorded using steel tapes (Lufkin, Apex, NC, USA). BMI and
WHtR were calculated using weight (kg)/height (m
2
) and waist
(cm)/height (cm) formulas, respectively. Blood pressure (mmHg)
was measured in duplicate (five minutes apart) on the right upper
arm. Appropriately sized cuffs were used for obese subjects.
Fasting blood samples were collected from the antecubital
vein with a sterile winged infusion set with minimal stasis. The
samples were collected and plasma and serum were prepared and
aliquoted by a registered nurse and then stored at –80°C in the
urban areas. In rural areas, the samples were stored at –18°C for
up to five days, where after it was transported to the laboratory
facility and stored at –80°C until analysed.
Fasting plasma glucose concentration was determined by
the hexokinase method using the Synchron
®
system (Beckman
Coulter Co, Fullerton, CA, USA). The sequential multiple
analyser computer (SMAC) using the Konelab™ auto-analyser
(Thermo Fisher Scientific Oy, Vantaa, Finland) performed
quantitative determinations of high-density lipoprotein
cholesterol (HDL-C), triglycerides and total cholesterol (TC).