**Abstract**

Oxidative stress is caused by the imbalance between the amount of reactive oxygen species (ROS) and antioxidant capacity in the body. A balanced diet involving the daily intake of antioxidant-rich foods makes improvements in the total antioxidant capacity of individuals and would therefore reduce the incidence of oxidation-related diseases. It may also regulate the degree of oxidative stress. In fact, dietary micronutrients are either direct antioxidants or components of antioxidant enzymes, which may contribute positively to certain indicators of hepatic function. Liver plays an important role in the regulation of various processes such as metabolism, secretion, storage, and the clearance of endogenous and exogenous substances. Once liver is damaged by pursuing a wrong diet and inflammation takes place, most of these physiological functions get altered. Apart from drugs that used to treat the ailments, it is also necessary to determine the pharmaceutical alternatives for the drugs that are used in the treatment of liver diseases. Therefore, this chapter aims to summarize all known information on the effects of dietary nutrients on oxidative stress in experimental liver models.

**Keywords:** dietary antioxidant, free radicals, oxidative stress, liver

## **1. Introduction**

The liver is the major organ metabolizing xenobiotics and endogenous molecules in order to maintain metabolic homeostasis in the organism, which is why it is a target of many toxic substances that cause dysregulated hepatic homeostasis. One of the mostly found clinical liver diseases is nonalcoholic fatty liver disease (NAFLD) (**Figure 1**) [2, 3]. In NAFLD, hepatocytes get filled up with triglycerides, liver expands and its normal functions may get altered. Although it is a disease, the triglyceride accumulation can still be reversed and normal functions may be restored by proper nutrition and exercise. If these lifestyle changes are not pursued, the damage goes on and results in inflammation followed with fibrosis which is unfortunately irreversible.

The liver is made up of hepatocytes, Kupffer cells, liver sinusoidal endothelial cells, pit cells, and hepatic stellate cells (HSC) [4]. Activation of stellate cells by injury caused by many etiological factors would lead to cirrhosis, and it would mark the end stage of progressive fibrosis [5]. Oxidative stress has a vital part in establishing

fibrosis and consequently cirrhosis [6]. For this reason, using molecules with antioxidant properties has been proposed as a treatment for not only fibrosis but also oxidative stress-related cirrhosis. Liver diseases are considered a major medical problem worldwide. There are known to be a large number of liver diseases caused by different insults. Furthermore, the disease type depends on lifestyle factors. For example, the main causes of liver diseases are reported to be viral and parasitic infections in regions like Africa and Asia. For Europe and America, alcohol consumption is thought to be the most important cause of this disease. However, viral hepatitis has showed an increase in recent times in most of the countries [7]. Lifestyle and unhealthy diet is the leading cause of liver diseases in almost all western countries. Until today, no medication is approved for the treatment of this disease; however, improving diet habits and physical exercise works if the disease is not accompanied by inflammation. On the other hand, biologically active food compounds that regulate gene expressions in lipogenesis, fibrosis, and inflammation serve as good therapeutic means to ameliorate these pathological states observed in liver [1] (**Figure 1**).
