## 4 Discussion
In our study, the activity of GPx in the blood serum of animals receiving the hypercholesterolic diet modified with the addition of dried leaves of the plant from Polish cultivation showed a tendency to increase in comparison to animals fed the hypercholesterolic diet and the hypercholesterolic diet with the addition of steviol glycosides. A significant increase in the concentration of GPx in the blood serum of healthy rats receiving a diet with 4% addition of dried leaves of _Stevia rebuudiana_ [PERSON]. compared to the control diet was found in the study by [PERSON] et al. [43]. On the other hand, a significant decrease in the value of the examined parameter was observed in the blood of rats with induced diabetes, fed with the above-mentioned addition of dried leaves of the tested plant in relation to the control group of diabetic animals. In our own study, various concentrations of MDA were found in the blood serum and liver of the experimental animals. An increase (\(\approx\)50%) in the concentration of MDA in the blood serum of animals receiving the hypercholesterolic diet as compared to the animals fed the AIN-93G diet was observed, but these differences were not significant. In rats fed the diet with the addition of steviol glycosides, but not in rats fed a diet with the addition of Stevia leaves (\(p>0.05\)), a significant decrease in MDA concentration was found in relation to rats fed the hypercholesterolic diet (\(p\leq 0.05\)). In the liver of rats fed the hypercholesterolic diet with the addition of steviol glycosides, there was a significant decrease in the value of the examined parameter compared to rats fed the hypercholesterolic diet. [PERSON] et al. [44] found a tendency that the concentration of MDA increased in the blood and liver of experimental animals fed a diet with the addition of water extract of _Stevia rebuudiana_. At the same time, it was shown that the addition of the extract to the diet of diabatic rats caused a significant reduction in MDA, both in the blood and in the liver, compared to the control group. There are no data in the available literature on histological evaluation of rats' liver fed with steviol glycosides or Stevia leaves. Histological evaluation of the liver of rats fed the diet with the addition of dried leaves of _Stevia rebuudiana_ [PERSON], originating from domestic cultivation, showed the formation of fine- and coarse-grained steatosis of the examined organ and various degrees of damage to hepatocytes. In addition, small foci of necrosis and numerous inflammatory infiltrates were also found in comparison to rats fed the hypercholesterolic diet and the hypercholesterolic diet with the addition of steviol glycosides. The addition of 17% and 18% of dried leaves of the plant cultivated in Brazil and Paraguay to the diet of animals resulted in smaller inflammatory foci compared to animals receiving a hypercholesterolemia diet with the addition of dried leaves of _Stevia rebaudiana_ [PERSON] from Polish cultivation. To summarize, it is extremely difficult to conclude why the addition of whole Stevia leaves to the diet caused changes mainly in the blood lipid profile while the addition of steviol glycosides alone did not alter these parameters. As mentioned above, a plant is a carrier of many nutritional and non-nutritive ingredients that interfere and can trigger different, sometimes unexpected, biological effects. In order to precisely explain the obtained results, different combinations of the individual ingredients would have to be used both together and separately in similar studies, which is not easy, as long-term studies involving experimental animals must be compliant with the 3R principle.