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updated 8/22/2010 2:38:39 PM ET 2010-08-22T18:38:39

Labels on bottled tea beverages are typically plastered with declarations of their rich antioxidant content. But a new study suggests, if you're looking for high doses of healthful antioxidants, you might be better off brewing your tea at home.

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Many of the popular beverages included in the study contain fewer antioxidants than a single cup of home-brewed green or black tea, the researchers say. Some store-bought teas contain such small amounts that consumers would have to drink 20 bottles to get the antioxidants, also called polyphenols, present in one cup of tea.

"There is a huge gap between the perception that tea consumption is healthy and the actual amount of the healthful nutrients — polyphenols — found in bottled tea beverages. Our analysis of tea beverages found that the polyphenol content is extremely low," said study researcher Shiming Li, an analytical and natural product chemist at WellGen, Inc., a biotechnology company in North Brunswick, N.J., that develops medical foods for patients with diseases, including a proprietary black tea product that will be marketed for its anti-inflammatory benefits.

In addition, bottled beverages often contain large amounts of sugar that health-conscious consumers may be trying to avoid, Li said.

The study was presented Aug. 22 at the 240th National Meeting of the American Chemical Society (ACS) in Boston.

Bottled vs. brewed
Antioxidants are substances that protect cells against damage from unstable molecules called free radicals. They may play a role in preventing a host of diseases, including cancer, cardiovascular disease and Alzheimer's.

Li and colleagues measured the level of polyphenols of six brands of tea purchased from supermarkets. Half of them contained what Li characterized as "virtually no" antioxidants. The rest had small amounts of polyphenols that Li said probably would carry little health benefit, especially when considering the high sugar intake from tea beverages.

The six teas Li analyzed contained 81, 43, 40, 13, 4, and 3 milligrams of polyphenols per 16-ounce bottle. One average cup of home-brewed green or black tea, which costs only a few cents, contains 50-150 milligrams of polyphenols.

Less tea, more water
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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 annually.

Some manufacturers do list polyphenol content on the bottle label, Li said. But the amounts may be incorrect, because there are no industry or government standards or guidelines for measuring and listing the polyphenolic compounds in a given product. A regular tea bag, for example, weighs about 2.2 grams and could contain as much as 175 mg of polyphenols, Li said. But polyphenols degrade and disappear as the tea bag is steeped in hot water. The polyphenol content also may vary as manufacturers change their processes, including the quantity and quality of tea used to prepare a batch and the tea brewing time.

"Polyphenols are bitter and astringent, but to target as many consumers as they can, manufacturers want to keep the bitterness and astringency at a minimum," Li explained. "The simplest way is to add less tea, which makes the tea polyphenol content low but tastes smoother and sweeter."

Li used a standard laboratory technique, termed high-performance liquid chromatography (HPLC), to make what he described as the first measurements of polyphenols in bottled tea beverages. He hopes the research will encourage similar use of HPLC by manufacturers and others to provide consumers with better nutritional information.

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