Journal Name:
Eur. J. Clin. Nutr.
Article Title:
A diet containing rapeseed oil-based fats does not increase lipid peroxidation in humans when compared to a diet rich in saturated fatty acids.
Date Written:
2001
Volume:
55
Number:
11
Page:
922
Author(s):
Sodergren, E.; Gustafsson, I.B.; Basu, S.; Nourooz-Zadeh, J.; Nalsen, C.; Turpeinen, A.; Berglund, L. .; Vessby, B
Article:
It is well established that a high dietary intake of saturated fatty acids (SFAs) is associated with high levels of total serum cholesterol and with an increased risk of developing coronary heart disease Intervention studies with PUFA-rich diets have shown that the susceptibility of lipoproteins to oxidation was increased and that very high intakes of PUFAs may carry non-favourable effects on the development of atherosclerosis. The oxidizability of fatty acids is considered to be dependent on the degree of unsaturation. An increased consumption of (canola) low-erucic acid rapeseed oil-based fats may lead to an increased dietary intake of MUFAs and PUFAs, especially alpha-linolenic acid (ALA-18:3 n-3). Rapeseed oil contains a high content of oleic acid (18:1) and linoleic acid (18:2 n-6) but also considerable amounts of ALA, which is an easily oxidised fatty acid. It is well established that ALA is partly metabolised in the body into very long-chain n-3 PUFAs, which are also highly susceptible to peroxidation. However, canola/rapeseed oil is rich in both alpha- and gamma-tocopherol. Many factors may influence the evaluation of the propensity of n-3 fatty acids to oxidation such as (a) how they are supplied and the amounts - as supplements or by the diet; (b) their chain length and number of double bounds – ALA or long chain n-3 fatty acids; and (c) how lipid peroxidation assays are performed - in vitro oxidation of LDL or in vivo indices.
The primary aim of this European study was to compare the effects of a rapeseed oil-based diet composed according to present dietary recommendations with a control diet rich in SFAs on biomarkers of lipid peroxidation and antioxidants in plasma and urine. F2-isoprostanes, hydroperoxides and malondialdehyde were measured as biomarkers of lipid peroxidation, and vitamin E and antioxidative capacity were used as biomarkers of antioxidants in the circulation. A secondary aim was to evaluate dietary effects on the serum lipid profile, glucose and insulin concentration and platelet aggregation.
Nineteen healthy moderately hyperlipidemic subjects (six women and 13 men, age 50±8 y and body mass index (BMI) 24.5±2.6 kg=m2) were fed a rapeseed oil-based diet (RO) and a control diet (SAT) rich in saturated fatty acids during two consecutive 4 week periods separated by a 4 week wash-out period.
The results showed no significant differences in plasma or urinary levels of free 8-iso-prostaglandin F2a, plasma total 8-isoprostaglandin F2a plasma hydroperoxides or plasma malondialdehyde were observed between the RO and SAT diets. A higher concentration of serum gamma-tocopherol was detected after the RO diet compared to the SAT diet, whereas the serum alpha-tocopherol concentration and plasma anti-oxidative capacity did not differ between the two test diets. The estimated intake of vitamin E from the dietary records revealed a greater intake of vitamin E expressed as alpha-tocopherol equivalents (alpha-TE) during the RO diet compared to the SAT diet (15.3 and 11.5mg alpha-TE per day). These data corresponds to 13.9 and 11.0 mg alpha-tocopherol and approximately 14.1 and 5.6mg gamma-tocopherol per day during the RO and SAT diets, respectively. Even with the relatively high fat content of the test diets, lower total and LDL cholesterol levels, apo B concentrations, and LDL.HDL ratios and no differences in HDL cholesterol levels were found after the RO diet compared to the SAT diet. *In this study, a rapeseed oil-based diet and a control diet rich in saturated fats produced no differences in the biomarkers of lipid peroxidation and antioxidants, except for increased levels of serum gamma-tocopherol after the RO diet compared to the SAT diet. These findings suggest that there is a balance between the content of antioxidants and PUFA in rapeseed oil-based fats when used in a natural mixed diet and that the amount of antioxidants naturally present is sufficient. The authors conclude that future investigation on other potential beneficial effects of a rapeseed oil-based diet in addition to lipid lowering, such as through effects of high contents of ALA and antioxidants or through effects on endothelial function, should be investigated.
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