Many commercial bottled tea drinks contain little or no healthful antioxidants, researchers have found.

Home-brewed green or black tea tends to contain more antioxidants than bottled tea, scientists have found. (iStock)

Scientists measured the level of polyphenols - a group of natural antioxidants linked to anti-cancer, anti-inflammatory and anti-diabetic properties - in six brands of tea purchased from supermarkets.

Half contained "virtually no" antioxidants, study author Shiming Li told the national meeting of the American Chemical Society in Boston on Sunday.

The others had small amounts of polyphenols, the researchers found using a laboratory technique called high performance liquid chromatography.

The teas were found to contain 81, 43, 40, 13, four and three milligrams of polyphenols per 16-ounce (473 ml) bottle.

In comparison, an average cup of home-brewed green or black tea contains 50 to 150 milligrams of polyphenols.

Health perception vs. reality

"Consumers spend money on the tea beverages and have a perception it does good to the body. But the reality when they drink tea beverages is that they spent money for nothing related to health, or even worse for health detrimental substances such as lots of sugar and high fructose corn syrup, or chemical sweeteners," the scientists said in a summary of their research.

After water, tea is the world's most widely consumed beverage. Tea sales in the United States have quadrupled since 1990 and now total about $7 billion US a year.