Journal Name:
Am. J. Clin. Nutr.
Article Title:
Similar effects of rapeseed oil (canola oil) and olive oil in a lipid-lowering diet for patients with hyperlipoproteinemia.
Date Written:
1994
Volume:
59
Number:
n/a
Page:
356
Author(s):
Miettinen, T.A.; Vanhanen, H.
Article:
Monounsaturated fatty acids from olive oil and canola oil contain 65-75% monoenic (monounsaturated) fatty acids and 9-30% polyunsaturated fatty acids. Serum cholesterol concentrations are actually low in the Mediterranean area, where the consumption of olive oil is very high and where the prevalence of coronary heart disease is also low. Olive oil is, however, rich in squalene a precursor of cholesterol, which is absorbed in humans to some extent enhancing cholesterol synthesis and contributing to serum cholesterol concentrations. Canola oil contains very small amounts of squalene (usually < 0.05 mg/g oil) but it is rich in plant sterols, campesterol, and sitosterol (usually 7 mg/g oil). In part to determine the effects of squalene on blood cholesterol, and because of the low squalene levels in canola oil, variable amounts of squalene in canola oil were fed to hypercholesterolemic subjects for 9- 15 wk. Because squalene was dissolved in canola oil, various aspects of cholesterol metabolism during monoene induced lowering of the serum cholesterol levels were also investigated. The summary of this paper will focus on the lipid lowering effects of the canola oil diet.
A substitution of 50 g dietary fat/d with a corresponding amount of canola oil reduced serum cholesterol concentration by 9% and LDL cholesterol by 10%, and increased cholesterol precursors and plant stenols during a 6-wk baseline period from initial values. The lipoprotein composition was slightly altered. In remnant particles (IDL), mainly core lipids (but also phospholipids) were increased. The reduced number of LDL particles with unchanged ratios of lipid to apo B during canola oil consumption was associated with an increased proportion of core lipids, cholesterol esters, in HDL. The transfer of cholesterol esters from HDL was apparently decreased to VLDL with the increase of the esters in IDLs. The mechanism of LDL cholesterol reduction by canola is not exactly known but may be due to dietary change, mainly to increased monoene fatty acid intake-related activation of hepatic LDL receptors contributed by lowered dietary cholesterol intake. Plant sterols in canola oil may also impair cholesterol absorption, resulting in increased cholesterol synthesis with enhanced precursor sterol values in serum. In this study, canola oil feeding increased daily plant sterol intake by 360 mg/day. Thus, the increase of serum plant sterol values during canola consumption is mainly caused by the enhanced dietary intake of plant sterols, whereas the simultaneous decrease in the serum cholesterol values could be mainly due to a plant sterol-induced decrease in cholesterol absorption.
Addition of 1 g squalene in canola oil for 9 week increased serum cholesterol by 15%, increased significantly the production rate of LDL apo B, and decreased the removal of LDL apo B in subjects with a most marked increase in serum LDL cholesterol concentration. In previous research, low squalene consumption (0.5 g/d) had virtually no effect on serum lipoprotein concentrations. The researchers concluded that long-term use of olive oil products with relatively low squalene content (2-7 mg/g oil) may have relatively little squalene-related harmful effects on serum cholesterol.
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