Antioxidants in Olive Oil and Green Tea Have a Short Life

Two articles in the Journal of Food Science bring a warning: if you are relying on virgin olive oil or green tea to provide you with important antioxidants, use them within 6 months of purchase.

The first study comes from the University of Foggia in Italy. The antioxidant activity of extra-virgin olive oils extracted from several Italian varieties were studied at the time of production and during storage. After 3 months the antioxidant activity in the oils was unchanged from that at the time of production. However, after 6 months the antioxidant activity had decreased by approximately 40% in almost all the oils tested. At 12 months, the decrease was reduced even further, with values 15% to 30% of starting levels.

The green tea study, which was done in the USA and Korea, concentrated on the catechin levels commercial tea leaves during storage in warehouse conditions. Analyses at intervals up to 6 months showed progressive degradation. There was a decline in levels after one week, but the decrease was insignificant. By two months, however, the decrease was more marked, and by 6 months there were virtually no catechins measurable in two of the 8 teas sampled.

This information may be useful for consumers of these products, especially if they are buying them for health reasons. Both extra-virgin olive oil and green tea have proven health benefits for some individuals.