Background: Cardiovascular disease (CVD) is the leading global cause of death. CVD risk
factors are considered intermediaries for the association between dietary fatty acids and CVD.
Raised plasma total cholesterol, low density lipoprotein (LDL) cholesterol, raised triglycerides
and decreased levels of high density lipoprotein (HDL) cholesterol, as well as reduced
fibrinolytic potential (measured as increased clot lysis time) are known risk factors for CVD.
Plasminogen activator inhibitor-1 (PAI-1) is a major inhibitor of the fibrinolytic process and an
elevated PAI-1 level is therefore considered to be a potential risk factor for CVD. The growing
number of controversies around the role that fat intake (more specifically the type of dietary fat)
plays in CVD risk, is making it increasingly difficult for consumers and practitioners alike to form
conclusions, and make recommendations and decisions regarding fat intake. Knowledge of the
intake of individual fatty acids, fatty acid status (as opposed to subgroups of fat such as
polyunsaturated fatty acids) and their associations with blood lipids, PAI-1act and fibrinolytic
potential is lacking in black South Africans and other populations. Therefore we aimed to
investigate dietary fatty acid intake, as well as plasma phospholipid fatty acid status and their
associations with blood lipids, PAI-1act and clot lysis time, as a marker for fibrinolytic potential.
Methods: Cross-sectional data analysis within the Prospective Rural Urban Epidemiology
(PURE) baseline study of apparently healthy black South African men and women (n=1950, 35–
70 years) from rural and urban areas in the North West Province, from whom dietary data were
collected. Blood lipid analyses, as well as laboratory analyses of fibrinolysis markers such as
PAI-1act and clot lysis time were also performed. Plasma phospholipid fatty acid extraction and
isolation were performed on a random subsample (n = 716).
Results: The intake of individual fatty acids was significantly higher in urban than rural dwellers.
However, the intake of omega-3 polyunsaturated fatty acids was below recommendations in all
groups (rural and urban males, and rural and urban females). Total cholesterol and LDL
cholesterol were higher in females than in males, with no rural‒urban differences. Intake of
alpha-linolenic acid was positively associated with total cholesterol (β=0.143) and triglycerides
(β=0.256) in males. The risk of having elevated LDL cholesterol also increased with increased
intake of alpha-linolenic acid (OR 1.49, 95% CI 1.04, 2.14). In females, dietary arachidonic acid
and eicosapentaenoic acid (EPA) were positively associated with total cholesterol and LDL
cholesterol, whereas docosahexaenoic acid (DHA) was negatively associated with total
cholesterol and LDL cholesterol. Dietary alpha-linolenic acid was positively correlated with
plasma EPA (males r = 0.19, p = 0.002, females r = 0.25, p < 0.001) and DHA (males r = 0.33, p
< 0.001, females r = 0.30, p < 0.001). Plasma DHA was positively associated with triglycerides
in males (β = 0.410, p< 0.001) and in females (β = 0.379, p< 0.001). PAI-1act was positively
associated with clot lysis time, and plasma myristic acid and DHA were positively associated
with PAI-1act in females. However, these fatty acids were not associated with clot lysis time.
Different types of plasma fatty acids were associated with PAI-1act than with clot lysis time.
Plasma alpha-linolenic acid (β = 0.123, P = 0.037), mead acid (β = 0.176, P = 0.019),
arachidonic acid (β = 0.253, 0.025) and omega-3 docosapentaenoic acid (omega-3 DPA) (β =
0.224, P = 0.002) were positively associated with clot lysis time, while both myristic acid (β = -
0.130, P = 0.016) and EPA (β = -0.131, P = 0.021) were negatively associated with clot lysis
time in male subjects. Plasma oleic acid (C18:1n9) (β = -0.411, P = 0.001) and omega-6 DPA
(C22:5n6) (β = -0.285, P = 0.001) were negatively associated with clot lysis time, while dihomogamma-
liolenic acid (DGLA) (C20:3n6) were positively associated (β = 0.178, P = 0.001) with
clot lysis time in females.
Conclusions: These results suggest that specific individual dietary fatty acids might be
associated with blood lipids in males differently than in females, irrespective of rural or urban
dwelling. It is not known however, if associations would still be present under conditions of
greater intake of alpha-linolenic acid. Our results further suggest that a higher percentage of
alpha-linolenic acid might be converted to DHA in this population with low intake of essential
and long-chain polyunsaturated fatty acids compared to populations with a high intake of these
fatty acids. These results suggest that plasma phospholipid fatty acids should not be used in
isolation as biomarkers for intake of fat, without taking dietary intake data into consideration
also. Associations between fatty acids and clot lysis time might be independent from PAI-1act.
The association between mead acid and clot lysis time indicates that clot lysis time might
increase with an essential fatty acid deficiency. This may be of particular concern in this
population with a documented lower fat intake. Because the study design of this study is crosssectional,
it is not able to determine cause-and-effect, and results should therefore be verified
with a randomised controlled trial. / PhD (Nutrition), North-West University, Potchefstroom Campus, 2015
| Identifer | oai:union.ndltd.org:netd.ac.za/oai:union.ndltd.org:nwu/oai:dspace.nwu.ac.za:10394/15523 |
| Date | January 2014 |
| Creators | Richter, Marilize |
| Source Sets | South African National ETD Portal |
| Language | English |
| Detected Language | English |
| Type | Thesis |
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