Numerous studies have shown the health benefits of green tea, but a new study from UCLA found that black tea also offers benefits, including help with weight loss.
Both green and black tea work by changing bacteria in the gut. An animal study showed that tea changes the way energy is metabolized in the liver by changing metabolites in the gut.
The study found that both black and green tea changed the ratio of intestinal bacteria in the animals: The percentage of bacteria associated with obesity decreased, while bacteria associated with lean body mass increased.
Previous studies found that chemicals in green tea called polyphenols are absorbed and alter the energy metabolism in the liver. The new findings show that black tea polyphenols, which are too large to be absorbed in the small intestine, stimulate the growth of gut bacterium and the formation of short-chain fatty acids, a type of bacterial metabolites that has been shown to alter the energy metabolism in the liver.
"It was known that green tea polyphenols are more effective and offer more health benefits than black tea polyphenols since green tea chemicals are absorbed into the blood and tissue," said the study's lead author Susanne Henning
"Our new findings suggest that black tea, through a specific mechanism through the gut microbiome, may also contribute to good health and weight loss in humans.
"The results suggest that both green and black teas are prebiotics, substances that induce the growth of good microorganisms that contribute to a person's well-being," she said.
In the study, four groups of mice received different diets — high-fat, high-sugar; low-fat, high-sugar; high-fat, high-sugar and green tea extract; and high-fat, high-sugar and black tea extract.
After four weeks, the weights of the mice that were given green or black tea extracts dropped to the same levels as those of the mice that received the low-fat diet throughout the study.
When researchers examined bacteria content in the mice's large intestines and livers, those that consumed either type of tea extract contained less of the type of bacteria associated with obesity and more of the bacteria associated with lean body mass.
However, only the mice that consumed black tea extract had an increase in a type of bacteria called Pseudobutyrivibrio, which could help explain the difference between how black tea and green tea change energy metabolism.
Senior author Dr. Zhaoping Li said the study suggests that the health benefits of both green tea and black tea go beyond their antioxidant benefits, and that both teas have a strong impact on the gut microbiome.
"For black tea lovers, there may be a new reason to keep drinking it," she said.
The research is published in the European Journal of Nutrition.
A recent study from Portugal's University of Porto found that drinking tea can drastically cut the risk of cancer. Women whose diets contained the highest amounts of caffeine from tea were 80 percent less likely to develop cancer compared to women who didn't get any caffeine from their tea.
A cup of tea a day can keep dementia away, according to a study from the National University of Singapore, which found that tea can slash the risk of dementia in people aged 55 and older.
Drinking tea cuts the risk of cognitive impairment in older people in half, but the news is even better for those who are genetically at risk of Alzheimer's. In people who carry the APOE e4 gene, tea reduces the risk by as much as 86 percent.
The researchers also discovered that the ability of tea to protect the brain isn't limited to a particular type of tea, as long as the tea is brewed from tea leaves, such as green, black or oolong tea.
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