Wu-long tea (also known as "Oolong tea", "Wulong tea", and "Wu long tea") has been receiving increasing attention lately. Many reports and articles touting the benefits of wulong tea have been brought to light, and it has been talked about on the Oprah Winfrey Show and widely across the Internet.
The Chinese have traditionally believed wulong tea to be effective in controlling and maintaining a healthy body weight. Recent scientific studies have been conducted to determine if wulong is in fact a slimming tea. In one recent study, 102 Chinese women who drank four cups of wulong tea per day lost over a kilogram of body weight over a 6 week period.
There are herbal and nonherbal teas and the Camellia sinensis plant is the source of all nonherbal teas. Leaves from the plant are processed three different ways to produce the three major classes of tea, known as black, green, and wu-long. About 75 percent of the tea produced worldwide is black; about 23 percent is green; and about 2 percent is wu-long.
Wu-long tea differs from other teas in the degree to which it is allowed to ferment after the tea leaf has been picked. The fermentation process is what gives tea its color. Green teas are made from leaves that have been prevented from fermenting through an intial boilng process, while at the other end of the spectrum black teas are made from leaves that have been permitted to fully ferment. Wu-long teas are in between green teas and black teas in that the leaves have been allowed to partially, but not completely, ferment.
In one study conducted by researchers from the Suntory Research Center, University of Tokushima, and the U.S. Department of Agriculture (USDA), drinking wu-long tea was shown to increase the rate of fat oxidation. This is probably why it is gaining a reputation as a fat burning food.
In the study 12 men consumed each of four treatments: plain water, full-strength tea, half-strength tea, and water containing 270 mg caffeine (the same amount of caffeine contained in the full-strength tea).
Each man received each treatment for 3 days. At the end of each three day period their metabolic rates were indirectly measured by observing their energy expenditure in a closed setting.
It was shown that the metabolic rate of the men who had consumed the full-strength tea and the caffeineated water had increased by 2.9% and 3.4% respectively (relative to the plain water treatment), indicating what was already known; that caffeine is effective in increasing metabolic rate.
The more interesting finding however was that the men who had consumed the full-strength tea had experienced a 12.9% increase in fat oxidation (fat burning); an increase that was not shown for the caffeinated water alone.
"Our data suggested that a component of tea other than caffeine might have promoted preferential use of fat as an energy source," said Beverly Clevidence, a study coauthor and head of the Diet and Human Performance Laboratory at the USDA's Agricultural Research Service. "But the information is tentative, and we need more studies to confirm it," she adds.
In yet another study reported in "Diabetes Care" involving subjects with type 2 diabetes, drinking wu-long tea was shown to have a glycemic affect, significantly reducing blood glucose levels.
Researchers from the Suntory Research Center, Providence University, Chorng Kuang Hospital, University of Tokushima, and the U.S. Department of Agriculture (USDA) tested a total of 20 subjects who had type 2 diabetes and took hyperglycemic drugs as prescribed. In the study the subjects each consumed either wu-long tea or water for a 30 day period, after which they were monitored for blood plasma glucose and fructosamine concentrations.
It was found that relative to the control group who only drank water, wu-long tea significantly lowered concentrations of plasma glucose and fructosamine. They concluded that wu-long tea may be an effective adjunct to oral hypoglycemic medications in the treatment of type 2 diabetes.
There still remains much work and research to universally and scientifically validate the nutritional and medical claims of drinking wu-long teas, but the research to date certainly paints the many benefits of wu-long tea in a positive light.
Aside from all the health and weight loss claims, its important not to forget that drinking a nice cup of gourmet tea is a reward in and of itself. So if you're already a coffee or tea drinker, why not give wu-long tea a try the next time you're looking for a nice warm beverage to sit down and relax with?
You may just get slimmer in the process.
William Rumpler, James Seale, Beverly Clevidence, Joseph Judd, Eugene Wiley, Shigeru Yamamoto, Tatsushi Komatsu, Tetsuya Sawaki, Yoshiyuki Ishikura, and Kazuaki Hosoda
Oolong Tea Increases Metabolic Rate and Fat Oxidation in Men
J. Nutr., Nov 2001; 131: 2848 - 2852.
Hosoda, Ming-Fu Wang, Mei-Ling Liao, Chin-Kuang Chuang, Miyuki Iha,
Beverly Clevidence, and Shigeru Yamamoto
Antihyperglycemic Effect of Oolong Tea in Type 2 Diabetes
Diabetes Care, Jun 2003; 26: 1714 - 1718.