A new study, carried out by researchers at the University of California, Los Angeles (UCLA), in the United States, has shown, for the first time, that black tea can help us lose weight and that it also has other benefits for our health by promoting a change in the bacteria that inhabit our intestines. The results have been published in the European Journal of Nutrition .
The research, which was carried out with mice, concluded that both black and green tea alter the proportion of intestinal bacteria in animals. In this way, while the percentage of bacteria that are associated with obesity decreased in them, that of those linked to a lower body mass increased.
In previous studies they had already discovered that the polyphenols – antioxidants with many properties and benefits for human health – inherent in green tea were absorbed and altered the energy metabolism of the liver. Now, in this new North American study, they have detected that the polyphenols in black tea, which are too large to be absorbed by the small intestine, fulfill the mission of stimulating the growth of intestinal bacteria and the formation of short-chain fatty acids.
“It was already known that the polyphenols in green tea are more effective and offer more benefits to our health than the polyphenols in black tea,” explained Susanne Henning, one of the study’s lead authors and an associate professor at the Center for Human Nutrition in the United States UCLA. However, “the new findings we have made suggest that black tea, through a specific mechanism, via the gut microbiome, may also contribute to good health and weight loss in humans, ” he continues.
“The results suggest that green and black teas are prebiotics , substances that induce the growth of microorganisms that contribute to the well-being of a person,” says Susanne Henning.
Like a low-fat diet
To carry out this study, they divided the mice into four different groups with the aim of providing them with different diets ; and two of them were supplemented with extracts of green tea or black tea.
After four weeks, the weight of the mice that had received tea extract (either green or black) fell to the same levels as that group of rodents that had received a low-fat diet throughout the study. And, when the researchers collected samples from the large intestines of the mice in order to measure their intestinal microbiota – a group of microorganisms that coexist in symbiosis with ours – and from liver tissue, to measure fat deposits, they saw that in the Mice that had consumed tea had fewer bacteria associated with obesity and more than those associated with lean body mass.
However, only mice that consumed black tea extract experienced an increase in a type of bacteria called Pseudobutrivibrio , which could help explain the difference between how black and green tea change energy metabolism.
