According to researchers from the University of California, a study on mice showed that black tea alters energy metabolism in the liver by changing the gut metabolites.
The study found that both black and green tea changed the ratio of intestinal bacteria in animals: The percentage of bacteria associated with obesity decreased, while bacteria associated with lean body mass increased.
The new findings showed 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.
Lead author Susanne Henning said that 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.
Henning added that black tea, through a specific mechanism of the gut microbiome, may also contribute to good health and weight loss in humans.
The results suggested that both green and black teas are prebiotics, substances that induce the growth of good micro-organisms that contribute to a person’s well-being.
In the study, four groups of mice received different diets – two of which were supplemented with green tea or black tea extracts: Low-fat, high-sugar; High-fat, high-sugar; High-fat, high-sugar and green tea extract; 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. The researchers also collected samples from the mice’s large intestines (to measure bacteria content) and liver tissues (to measure fat deposits).
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.
The research is published in the European Journal of Nutrition.