Olives and olive oil are important ingredients of the Mediterranean diet and have been associated with lower cancer risk. Olives are rich in healthy fatty acids but also contain some specific phytochemicals such as triterpenoids. These phytochemicals are mainly concentrated in the skin and function as insect antifeedants (aversive phytochemicals that inhibit feeding) and antimicrobial agents. Other triterpenoids found in plants and which protect against cancer are betulinic acid and ursolic acid. Previous studies with animals have shown that olive oil protects them against UV induced skin damage and inhibits colon carcinoma.
The aim of this study was to investigate the influence of an extract from olive skins on the proliferation and apoptosis of colon cancer cells. The main phytochemicals of the olive skin extract are triterpenes such as maslinic acid and oleanolic acid. The researchers found a dose-dependant antiproliferative activity of the phytochemicals. The extract also caused apoptosis of the colon cancer cells and activation of caspase-3, which is a key executioner of apoptosis. The cell death was induced by the intrinsic pathway as indicated by the presence in superoxide anions in the mitochondria. The olive extract caused a significant increase in reactive oxygen species levels in the mitochondria of the colon cancer cells. The concentration of maslinic acid and oleanolic acid used in this in-vitro test could also be realized by normal consumption of olive oil. Mediterranean people consume daily 33 g olive oil, which contains 34 mg maslinic acid and 25 mg oleanolic acid.
The study concluded that the phytochemicals maslinic acid and oleanolic acid from olive skin extract inhibited cell proliferation and induced apoptosis of colon cancer cells, without being toxic to normal cells.
Source: Juan ME, Wenzel U, Ruiz-Gutierrez V, Daniel H and Planas JM. Olive Fruit Extracts Inhibit Proliferation and Induce Apoptosis in HT-29 Human Colon Cancer Cells.. Journal of Nutrition. 2006 October;136(10):2553-7