Shiming Li, Ph.D. who reported on research carried out by Professor Chi-Tang Ho, explained:
Consumers understand very well the concept of the health benefits from drinking tea or consuming other tea products. However, 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.
Bottled tea is not only poor in levels of health-improving ingredients for which tea is famous, but it often contains high quantities of sugar and some other substances - substances the health-conscious consumer may be trying to avoid, Li pointed out.
Li and team measured polyphenol levels in six brands of tea bought from supermarkets. Half of them contained "virtually no antioxidants" while the rest had small quantities of polyphenols which would most likely carry little health benefit, especially when the high sugar content was taken into consideration.
What are polyphenols? A chemical which is known to protect against some health problems, as well as some of the effects of aging. A polyphenol, a type of antioxidant, protect cells and chemicals in our bodies from the damage caused by free radicals. Polyphenols can block the actions of some enzymes that help cancer growth. All brewed tea contain polyphenols. Put simply, polyphenols may protect against cancer, anti-inflammatory conditions and diabetes.
Someone would have to drink bottle after bottle of these teas in some cases to receive health benefits," he said. "I was surprised at the low polyphenol content. I didn't expect it to be at such a low level.
The six teas contained:
- 81, 43, 40, 4 and 3 milligrams of polyphenols per 16-ounce bottle Compared to
- 50 to 150 milligrams found in 1 average cup of home-brewed black or green tea, and costs only a few cents
Although bottled-tea makers do list polyphenol content on their labels, the amounts may not be right because there are no industry or government standards/guidelines for measuring or listing the polyphenolic compounds in a given product.
A regular tea bag may contain up to 175 milligrams of polyphenols, says Li. However, the polyphenol content drops when the bag is immersed into hot water. As manufacturers of bottled-tea change their processes, polyphenol levels may also vary.
"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. The simplest way is to add less tea, which makes the tea polyphenol content low, but tastes smoother and sweeter.
Li used high-performance liquid chromatography (HPLC) to make the first measurements of polyphenols in bottled tea beverages. He hopes this study will encourage similar use of HPLC by bottled-tea makers and others to provide consumers with better nutritional information.
Source: The American Chemical Society