You're likely familiar with the fact that green tea has been linked with weight loss, but new research out of the University of California Los Angeles (UCLA) shows that black tea can also blast blubber by working through a different mechanism.
According to the researchers, compounds in green tea called polyphenols are smaller than those found black tea, so they can be absorbed through the body's tissues and can impact energy metabolism in the liver. But black tea polyphenols are too big to pass through the small intestine into the rest of the body, so it was unclear whether or not they could have a beneficial weight-loss effect.
"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 Susanne Henning, the study's lead author and an adjunct professor at the UCLA Center for Human Nutrition. "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."
That specific mechanism seems to be that it changes the ratio of bacteria in the intestine by increasing the microbes associated with lean body mass and decreasing those associated with obesity. While both green and black teas act as prebiotics in this way, it seems that black tea might have a leg up over its green partner.
The study fed four groups of mice different diets. One group ate low-fat, high-sugar foods,while another had high-fat, high-sugar meals. The other two were both on a high-fat, high-sugar diet but one got green tea extract, while the other received black tea extract.
At the end of four weeks, both groups that got the tea extracts had weights that were in line with those on the low-fat diets. And in both of those groups, intestinal samples showed lower obesity-related bacteria and high lean-related bacteria. But only the mice that were given the black tea extract showed increased levels of a bacteria called Pseudobutyrivibrio, which, the researchers suspect, is the secret to the extract's success.
These mice also demonstrated an increased level of short-chain fatty acids in their guts, compounds that have previously been linked to a beneficial effect on energy metabolism.
Because black tea seems to work in the gut, while green tea works in the liver as well as the gut, a combination of both drinks might be most helpful, especially since both beverages have been linked to multiple health benefits beyond weight loss.
"For black tea lovers, there may be a new reason to keep drinking it," said Dr. Zhaoping Li, director of the UCLA Center for Human Nutrition, chief of the UCLA Division of Clinical Nutrition and the study's senior author.
The research has been published in the European Journal of Nutrition.