Journal Name:
J Nutr.
Article Title:
Low fat and high monounsaturated fat diets decrease human low density lipoprotein oxidative susceptibility in vitro.
Date Written:
2001
Volume:
131
Number:
6
Page:
1758
Author(s):
Hargrove, R.L.; Etherton, T.D.; Pearson, T.A.; Harrison, E.H.; Kris-Etherton, P.M.
Article:
Oxidative modification of low-density lipoprotein (LDL) is believed to play an important role in the development of atherosclerosis. LDL enriched in monounsaturated fatty acids (MUFA) are less susceptible to oxidation than LDL enriched in polyunsaturated fatty acids (PUFA). Previous studies have shown that LDL isolated from subjects consuming a high carbohydrate diet was more prone to oxidation than LDL isolated from subjects consuming a high MUFA diet. It has also has been demonstrated that a very low fat diet in combination with daily exercise can increase LDL oxidative resistance. Both a Step I diet (29% total fat, 9% SFA) and a low saturated fat diet (25% total fat, 6% SFA) decreased the oxidative susceptibility of LDL, compared with an average American diet (34% total fat, 15% SFA. The present study was designed to evaluate the effects of men and women consuming diets high in MUFA (peanuts plus peanut butter, peanut oil and olive oil) on LDL oxidative susceptibility, and to compare these effects with those of a Step II blood cholesterol-lowering diet.
A randomized, double-blind, five-period crossover design (n=20) was used to study the effects of the following diets on LDL-oxidation: average American [35% fat, 15% saturated fatty acids (SFA)], Step II (25% fat, 7% SFA), olive oil (35% fat, 7% SFA), peanut oil (35% fat, 7% SFA) and peanuts plus peanut butter (35% fat, 8% SFA).
Following the average American diet, the shortest lag time (57 6 6 min) for LDL oxidized ex vivo, was observed, whereas the Step II, olive oil and peanuts plus peanut butter diets resulted in a significantly longer lag time of 66.7min. The slower rate of oxidation [nmol dienes/(min/mg LDL protein)] observed when subjects consumed the olive oil diet (24.2) versus the average American (28.6), peanut oil (28.6) and peanuts plus peanut butter diets (29.6) was associated with a lower LDL PUFA content. Higher-fat diets high in MUFA and low in SFA and cholesterol have been shown to also favorably affect plasma lipids, lipoproteins and LDL oxidative susceptibility.
The faster rate of LDL-oxidation observed after consumption of the average American, peanut oil and peanuts plus peanut butter diets was associated with a greater LDL PUFA content. Rate of oxidation was significantly correlated with LDL linoleic acid (LA) and the ratio of LDL LA to oleic acid. The authors postulated that the increased rate of LDL-oxidation observed after consumption of the average American and peanut diets compared with the olive oil diet was due to an increased amount of substrate (LA) available for oxidation in vitro. Further, it was proposed that an increased consumption of dietary antioxidants might act synergistically with alterations in LDL fatty acid composition to affect LDL oxidative resistance. Antioxidants associated with peanuts, peanut butter, peanut oil and olive oil, could exert individual and combined effects on LDL-oxidative status.
In summary, the results of this study suggest that various blood cholesterol-lowering diets, including both lower-fat and higher-fat (high MUFA) diets, may decrease LDL oxidative susceptibility, and thereby contribute to a decreased risk of CHD. These results can be extrapolated to canola oil as well due to its high MUFA and relatively lower LA contents.
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