Green tea is a well-know natural health resource, which can deliver powerful antioxidant polyphenols that help protect the body from a host of chronic conditions, such as diabetes or heart disease.

However, a recent study has found that not all green teas are created equal. It appears that the benefits of the drink vary, depending on whether it is consumed from a bottle or freshly brewed.

Speaking at the 240th National Meeting of the American Chemical Society in Boston on August 22, scientists involved in the research said that many commercial beverages – whose sales may be as high as $1 billion a year in the U.S. – have fewer polyphenols than a cup of home-brewed green or black tea.

“There is a huge gap between the perception that tea consumption is healthy and the actual amount of the healthful nutrients found in bottled tea beverages,” said researcher Shiming Li, who presented the findings.

“Our analysis of tea beverages found that the polyphenol content is extremely low,” he added.

In fact, the scientists estimate that in order to reap full health benefits of a single cup of tea, individuals would have to drink about 20 bottles of commercial beverages.