The effects of adding lyophilized tomato powder to diets for rats on selected biochemical protein and lipid metabolism parameters, as well as on the redox status of livers and blood were determined. For 4 weeks, 2 groups of male Wistar rats (n = 10) were fed isoproteinous diets ad libitum: control (casein) or experimental (10% lyophilized tomato). Inclusion of tomatoes resulted in reduction (P < 0.05) of superoxide dismutase activity in blood. The concentration of 8-oxo-2’-deoxyguanosine, the product of oxidative degradation of liver-cell DNA, was lower (P < 0.01) than in controls, but the activities of serum aspargine and alanine transferases were higher (P < 0.05) in the experimental rats. The influence of the diet on the other selected biochemical parameters of blood did not differ statistically between the groups.