Natural health enthusiasts for years have hailed the benefits of drinking an assortment of teas for weight loss but now scientific research not only supports that claim, it explains exactly how that can happen.
A study  published in the European Journal of Nutrition has discovered that both black and green tea influenced the ratio of gut bacteria in animals. Specifically, the percentage of intestinal bacteria associated with obesity decreased, while bacteria associated with lean body mass increased.
Previous research showed that the polyphenols in green tea improved energy, but this new study reveals that black tea polyphenols stimulate the growth of certain gut bacteria and the formation of short-chain fatty acids, a type of bacterial metabolite known to influence energy metabolism in the liver which can lead to weight loss.
Susanne Henning, the study’s lead author and adjunct professor at the UCLA Center for Human Nutrition said, “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.”
The study was conducted on four different groups of mice, all of which were given a high-sugar diet. One group was also given a low-fat diet, a second a high-fat diet, a third high-fat and green tea extract and the fourth group was given a high-fat diet and a black tea extract. After four weeks the mice were weighed and the ones given either green or black tea had weight that dropped to the same levels as those given just a low-fat diet, high-sugar.
After collecting samples from the mice’s large intestines (to measure bacteria content) and liver tissues (to measure fat deposits) researchers found that the mice that consumed either type of tea extract had 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 showed that the weight loss benefits were different than for green tea. Green tea is easily absorbed in the stomach and small intestine and can more directly influence the liver. Black tea molecules are too large to be absorbed in this way and instead remain in the intestine where they appear to boost the growth of “friendly” gut bacteria (probiotics) and help form metabolites that control liver energy metabolism.
Although the research has only been conducted so far on rodents, this is exciting news for proponents of natural health alternatives for human weight loss, and also shows that both green and black tea have far more than just antioxidant benefits.