Extra-virgin¹ olive oil（初榨橄榄油） can protect the liver from oxidative（氧化的） stress. Researchers writing in BioMed Central's open access journal Nutrition and Metabolism² exposed rats to a moderately toxic³ herbicide known to deplete⁴ antioxidants（抗氧化剂） and cause oxidative stress, finding that those rats fed on a diet containing the olive oil were partially⁵ protected from the resulting liver damage. Mohamed Hammami from the University of Monastir, Tunisia and King Saud University, Riyadh, Saudi Arabia, worked with a team of researchers to carry out the experiments in a group of 80 rats. He said, "Olive oil is an integral ingredient in the Mediterranean⁶ diet. There is growing evidence that it may have great health benefits including the reduction in coronary heart disease（冠心病） risk, the prevention of some cancers and the modification⁷ of immune and inflammatory（炎症的） responses. Here, we've shown that extra virgin olive oil and its extracts protect against oxidative damage of hepatic（肝的） tissue".

The researchers separated the rats into a control group, an olive oil group, and 6 groups that were exposed to the herbicide '2,4-Dichlorophenoxyacetic acid' with or without either whole olive oil, or one of two oil extracts – the hydrophilic（亲水的） fraction or the lipophilic（亲油的） fraction. All rats given the herbicide showed signs of significant liver damage. However, extra virgin olive oil and hydrophilic fraction intake⁸ induced a significant increase in antioxidant enzyme⁹ activity and a decrease in markers of liver damage.

Speaking about the results, Hammami said, "The hydrophilic fraction of olive oil seems to be the effective one in reducing toxin-induced oxidative stress, indicating that hydrophilic extract may exert a direct antioxidant effect on hepatic cells. However, more detailed¹⁰ studies about the effect of antioxidant compounds separately and/or their interactions are necessary to substantiate¹¹ these observations".