01.Shelf time reduces tea's health benefits
Just six months in the pantry could be enough to destroy nearly 90% of antioxidants in some tea, according to a recent US study.
The finding follows growing evidence that antioxidants in tea – particularly a class of compounds called catechins – have health benefits.
The study, Stability of Green Tea Catechins in Commercial Tea Leaves During Storage for Six Months, published in the Journal of Food Science, looked at levels of catechins in green tea samples bought from stores in the US, Japan and Korea.
Researchers found that all samples lost catechins after six months of storage in a dark place at 20ºC – similar to conditions in a cupboard or pantry. Loss ranged from 14% to 88%, with an average loss of 32%.
Antioxidants are naturally occurring compounds in food that neutralise free radicals – unstable molecules that may damage body cells if their levels are not controlled. According to the Dietitians Association of Australia, a diet rich in antioxidants can help prevent free radicals damaging the body.
Tea is high in a class of antioxidants called flavonoids, to which catechins belong. These flavonoids are potent antioxidants, thought to be the healthy “active ingredient” in tea, says nutritionist Dr Tim Crowe.
While tea is promoted as being beneficial for the heart, cognitive performance and protection against certain cancers, Crowe says a lack of research involving humans prevents making a definitive conclusion.
He is also not surprised about this latest research. “With storage, all foods will lose nutrients over time,” he says.
“Buying tea from wholefood stores could be better for consumers, as their distribution network may be a bit quicker than supermarkets.”