Dietary Flavonoids Reduce Lipid Peroxidation in Rats Fed Polyunsaturated or Monounsaturated Fat Diets

Manuscript received 11 February 1998. Initial reviews completed 11 March 1998. Revision accepted 6 May 1998.

Laboratoire de Nutrition et Sécurité Alimentaire, INRA-CRJ, 78352 Jouy-en-Josas, Cedex, France

We investigated the influence of dietary flavonoids on -tocopherol status and LDL peroxidation in rats fed diets enriched in either polyunsaturated fatty acids (PUFA) or monounsaturated fatty acids (MUFA). Diets equalized for -tocopherol concentrations were or were not supplemented with 8 g/kg diet of flavonoids (quercetin + catechin, 2:1). After 4 wk of feeding, plasma lipid concentrations were lower in rats fed PUFA than in those fed MUFA with a significant correlation between plasma -tocopherol and cholesterol concentrations, r = 0.94, P < 0.0001). Dietary lipids influenced the fatty acid composition of VLDL + LDL more than that of HDL or microsomes. The resistance of VLDL + LDL to copper-induced oxidation was higher in rats fed MUFA than in those fed PUFA as assessed by the lower production of conjugated dienes and thiobarbituric acid reactive substances (TBARS) and by the >100% longer lag time for dienes production. (P < 0.0001). Dietary flavonoids significantly reduced by 22% the amounts of dienes produced during 12 h of oxidation in rats fed diets rich in PUFA and lengthened lag time 43% in those fed MUFA. Microsomes of rats fed MUFA produced ~50% less TBARS than those of rats fed PUFA (P < 0.0001) and they contained more -tocopherol in rats fed MUFA than in those fed PUFA with higher values (P < 0.0001) in both groups supplemented with flavonoids (P < 0.0001). Our findings suggest that the intake of dietary flavonoids is beneficial not only when diets are rich in PUFA but also when they are rich in MUFA. It seems likely that these substances contribute to the antioxidant defense and reduce the consumption of -tocopherol in both lipoproteins and membranes.

The Journal of Nutrition Vol. 128 No. 9 September 1998, pp. 1495-1502
Copyright ©1998 by the American Society for Nutritional Sciences

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