Journal Name:
Am. J. Clin. Nutr.
Article Title:
A diet rich in monounsaturated rapeseed oil reduces the lipoprotein cholesterol concentration and increases the relative content of n-3 fatty acids in serum in hyperlipidemic subjects.
Date Written:
1994
Volume:
59
Number:
3
Page:
667
Author(s):
Gustafsson, I. B.; Vessby, B.; Ohrvall, M.; Nydahl, M.
Article:
The substitution of n-6 polyunsaturated fatty acids (PUFA) for saturated fatty acids (SFA) in the diet lowers the serum cholesterol and triglyceride concentrations by reducing the concentrations of low-density and very-low density lipoproteins. Monounsaturated fatty acids (MUFA) have usually been regarded as neutral in this respect. In most studies diets rich in MUFA olive oil were used. The most common high MUFA oil in Scandinavia is a low erucic acid rapeseed oil, which in the United States and Canada is called canola oil. The principal aim of this study was to compare the effects of a diet rich in MUFA rapeseed oil with those of a diet rich in PUFA sunflower oil in subjects with moderate hyperlipoproteinemia. The effects on the lipoprotein and glucose metabolism and on the fatty acid composition in the serum were analyzed. The plasma tocopherol concentrations were also evaluated.
Ninety-five subjects were randomly as signed to one of the two well-controlled diets prepared in a hospital kitchen. Total serum, low-density- and high-density-lipoprotein cholesterol concentrations decreased significantly by 15%, 16%, and 11%, respectively, on the rapeseed oil diet and significantly by 16%, 14%, and 13% on the sunflower oil diet. Serum triglycerides decreased significantly by 29% on the sunflower oil and by 14% on the rapeseed oil diet. HDL cholesterol was decreased compared with the baseline value on both diets. This might be an effect of a lower fat content the test diets (27 E%) than in the baseline diet (37 E%). The apo B concentration was lowered to the same degree on both diets whereas apo A-I decreased more on the sunflower oil than on the rapeseed oil diet. The ratio of apo A-1/apo B did not change significantly on either diet. The change in the fatty acid composition of the serum phospholipids was in accordance with the composition of the diets, with an increase in oleic acid on the rapeseed oil diet and a decrease on the sunflower oil diet, and opposite changes in linoleic acid on the two diets. The n-3 long chain PUFA (20:5 and 22:5) in serum phospholipids increased significantly on the rapeseed oil diet but decreased on the sunflower oil diet. There was no change in ALA (18:3n-3). These results indicate that ALA from rapeseed oil might provide a source of long chain n-3 fatty acids. Fasting blood glucose was reduced after both diets, with no significant difference between the diets. An increase was noted in alpha-tocopherol concentration on both diets. Epidemiological studies have suggested that low plasma concentration of vitamin E is correlated with increased mortality from ischemic heat disease.
In conclusion, MUFA (rapeseed oil) or PUFA (sunflower oil) in lipid-lowering diets effectively lower the serum cholesterol and LDL-cholesterol concentrations. The serum triglyceride concentration was decreased more effectively by the sunflower oil diet than by rapeseed oil. A significant increase in n-3 fatty acids (20:5, 22:5) after rapeseed oil supports the assumption that ALA is elongated and desaturated to these fatty acids in vivo. The data provide further support for the inclusion of canola (here reported as rapeseed) oil in heart-healthy lipid-lowering diets.
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