Journal Name:
Annals of Nutrition and Metabolism
Article Title:
Replacement of margarine on bread by rapeseed and olive oils: Effects on plasma fatty acid composition and serum cholesterol.
Date Written:
1992
Volume:
37
Number:
4
Page:
161
Author(s):
Steppanen-Laakso, T.; Vanhanen, H.; Laakso, I.; Kohtamaki, H.; Viikari, J.
Article:
Clinical studies prior to that described here have traditionally used vegetable oils and margarines rich in the omega 6 fatty acid linoleic acid (LA) to lower cholesterol. However, reductions in HDL-C have been reported after intake of large amounts of omega 6. Monounsaturated fatty acids (MUFA) are also effective in lowering total cholesterol (TC) levels without decreasing HDL-C. The focus of this European study was zero erucic acid rapeseed oil (canola-type oil) consisting mainly of monoenoic acid (oleic acid, OA, approx. 60%) with a moderate content of essential linolenic (LA, approx. 22%) and -linolenic acids (ALA, approx. 11%).
The aim of this study was to examine the effects of partial rapeseed and olive oil substitution on plasma fatty acid composition and on serum lipids in margarine users. The relationships between plasma fatty acids and serum cholesterol were also studied. Margarine on bread was replaced by these oils, which constituted the only change in the diet. In forty-six subjects, the daily dose of these oils represented 16% of the dietary fat and 7% of the total energy intake, on average. Fatty acid analysis of total plasma indicated a dose-dependent rise in ALA and OA levels during rapeseed and olive oil substitutions, respectively.
An increase in MUFA and the decrease in saturated fatty acids (SFA) were the most abundant changes in the level of plasma phospholipids during the first 3 weeks of rapeseed oil substitution. The latter effect was also expected since the content of SFA in rapeseed oil is about one fifth of that of common margarines. In the present study, ALA represented about 0.7% of the total energy intake during rapeseed oil substitution. An elevation of 0.5%-units in plasma phospholipid EPA concentration during the first 3 weeks was noted and corresponded to a rise of one third compared to the baseline. Such an increase, obtained even with the low degree of substitution, may have a promoting effect on the metabolism of eicosanoids. The increase in EPA is also affected by the decrease in LA supported by their inverse relationship. The results show that ALA is rapidly used for n-3 PUFA metabolism, especially EPA, in plasma phospholipids when margarine is replaced by rapeseed oil. The increase in n-3 PUFA occurs at the expense of n-6 PUFA.
An increase in HDL-C and the slight decrease in TC and LDL-C resulted in a significant rise in the HDL-C/TC ratio during rapeseed oil substitution. The rise in ALA correlated with the decrease in LDL-C and the increase in HDL-C/TC ration. These results indicate that the preference of ALA is not only evident in the competition between phospholipid fatty acids, but also in the relationships with serum lipids.
The results show that the effects of rapeseed oil are primarily attributable to ALA and LA. The results support earlier findings that the changes in the composition of plasma phospholipid fatty acids are closely related to those in serum lipid levels. The associations between the ALA and LDL-C and HDL-C/TC ratios suggest that ALA is of greater importance than MUFA when margarine is replaced by rapeseed oil. In addition to the HDL-C raising effect, rapeseed oil increased the proportion of n-3 PUFA, especially EPA in plasma phospholipids. All these changes can be considered beneficial in respect to the prevention of coronary heart disease.
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