Dietary tomato and grape pomace in rats: effect on lipids in serum and liver, and on antioxidant status

Addition of tomato and grape pomace to the cholesterol (0.3%) diet of male Wistar rats produced a dose-dependent effect. During the eight-week experiment, 5% pomace showed no effect; however, 15% pomace reduced serum cholesterol levels from 4.4 mmol/L to 2.5 mmol/L (tomato) and 2.0 mmol/L (grape). At a concentration of 15%, both tomato and grape pomace induced a redistribution of cholesterol in lipoproteins, resulting in a pronounced anti-atherogenic profile: reduced cholesterol concentration in very-low-density lipoprotein (VDL) (24% [tomato], 50% [grape]) and low-density lipoprotein (LDL) (3-fold, 3.6-fold). In addition, grape pomace increased cholesterol concentration in high-density lipoprotein (HDL) by 26%. Both types of pomace reduced the VLDL and LDL contribution to cholesterol transport in favour of HDL. Grape pomace (15%) produced a significant reduction in cholesterol and triacylglycerols in the liver and serum respectively. Diets containing tomato and grape pomace reduced plasma levels of conjugated dienes by 30-50%, and showed a tendency towards higher superoxide dismutase and glutathione peroxidase activity in the liver.