A new study has discovered that if olive oil has been sitting on the shelf for six months, it can lose up to 40 percent of its health benefits.
The research was carried out an analysis on several varieties of extra-virgin olive oil produced from groves in the Italian countryside at production and during storage.
It was discovered that after three months of storage, the antioxidant activity in the oils remained unchanged, but antioxidants decreased by about 40 percent for almost all of the oils after six months.
"The protective role of virgin olive oil is the result of its specific composition including phenolic compounds known to act as antioxidants," says lead researcher Antonella Baiano of the University of Foggia in Italy.
The health benefits of extra-virgin olive oil may include preventing conditions related to coronary disease, stroke and certain types of cancers.
Researchers recommend consumers store extra virgin olive oil in small glass bottles (one liter maximum because the oxygen contained in the headspace determines its oxidation), in a dark location, at a temperature lower than 68-770F (20-250C).
The study has been presented in the March Journal of Food Science, published by the Institute of Food Technologists.