The Green Tea Effect: From Gut Microbes To Weight Loss, New Insights Emerge

In a recent study published in the Foods Journal, a group of researchers investigated the impact of green tea and its functional components on body weight and gut microbiota regulation.

The study was undertaken in mice fed with a high-fat (HF) diet and also identified potential obesity markers via 16Svedberg ribosomal ribonucleic acid (16S rRNA) gene sequencing.

Background

Obesity, affecting over 500 million people globally, leads to multiple metabolic diseases, including high blood pressure and hyperglycemia. The condition is linked with particular gut microflora that favor weight gain.

Green tea, consumed widely, is known to have beneficial effects such as reducing body weight and metabolic syndrome. Its components – polyphenols, caffeine (Caf), and L-theanine (Thea), can decrease calorie uptake and stimulate protein kinase.

The components, primarily residing in the large intestine, interact with and modulate the gut microbiome. Research shows green tea extract reduces harmful gut bacteria and increases beneficial ones, potentially impacting obesity.

About the study

The present study prepared green tea using leaves from the Suchazao tea cultivar, sourced from the Zhongshanling tea garden in Nanjing, China. Various concentrations of tea were brewed with distilled water and tested for total tea polyphenols (TPP), Caf, and Thea content via spectrophotometry and high-performance liquid chromatography.

For animal testing, young male C67BL/6J mice were obtained from Yangzhou University, acclimated for a week, and then divided into groups for different dietary regimens.

Some received a HF diet supplemented with green tea infusions, while others were given an HF diet with major green tea components. Mice’s water intake and weight were monitored daily.

Following dietary treatment, an oral glucose tolerance test was performed, and mice were then sacrificed for tissue preparation and biomarker assessments. Histological liver and small intestine studies were conducted, with serum biomarkers analyzed using commercially available kits.

Gut microbiota was classified using next-generation sequencing (NGS) from fresh fecal samples. Deoxyribonucleic acid (DNA) extraction, amplification, library construction, and sequencing were performed using standardized methods.

Statistical analysis was conducted on data via one-way analysis of variance (ANOVA), with two-way ANOVA used to assess body weight differences. NGS analysis was evaluated using permutational multivariate analysis of variance (PERMANOVA) to identify significant microbial differences.

Study results

The present study examined how green tea affected obesity-related indicators in mice with a HF diet. As anticipated, the mice on this diet gained significant weight and accumulated fat within eight weeks, validating using the HF diet as a model to induce obesity. This contrast in weight gain and fat accumulation was observed against a low-fat (LF) diet group, even though food and water intake had no significant difference for both groups.

However, introducing green tea into the HF diet yielded intriguing results. The study used three different concentrations of green tea in the diet: 1%, 2%, and 4%.

Remarkably, even though the group with the highest concentration of green tea ate more food, they showed the most considerable weight loss and fat reduction, indicating a significant impact of green tea on combating obesity.

Further biochemical tests showed a decline in obesity indicators in green tea mice. Additionally, liver cells from mice on the HF diet plus green tea seemed healthier than those from the pure HF group, providing further evidence of green tea’s anti-obesity properties.

Particularly noteworthy was the reduction of inflammation markers tumor necrosis factor-alpha (TNF-α) and monocyte chemoattractant protein-1 (MCP-1) in the groups treated with green tea.

As revealed through NGS, gut microbiota health was also positively impacted by adding green tea. The group consuming the 4% green tea had significant alterations in the population of their intestinal microflora, indicating a potential shift toward a healthier gut environment.

Delving further into the role of TPP, Thea, and Caf in these effects, researchers found that the groups consuming TPP and Thea significantly reduced weight and fat after eight weeks. Furthermore, their liver inflammation was reduced, with TPP having the strongest impact. These components also enhanced intestinal villi length and surface area, improving gut health.

Regarding gut microbiota composition, TPP substantially increased beneficial bacterial populations while decreasing harmful ones. The gut microbiota clusters for Thea and Caf slightly diverged from the HF group, while the TPP cluster was separate from the HF and similar to the LF group.

TPP showed the greatest impact on operational taxonomic units (OTUs), a measure of microbiome diversity. Out of 32 identified obesity-associated microbial genera, each component significantly influenced ten genera.

Conclusions

The researchers found a unique pattern in gut microbiota clustering in mice fed a HF diet supplemented with a green tea. This infusion, particularly at a 4% concentration, substantially improved the intestinal microflora of obese mice, mitigating the metabolic alterations caused by the HF diet.

The study identified 32 genera, including Akkermansia, Saccharofermentans, Acetatifactor, Bacteroides, Alistipes, Allobaculum, and Falsiporphyromonas, as biomarkers associated with the HF diet.

Of these, TPP notably enhanced the presence of Akkermansia, playing a vital role in re-establishing a healthy bacterial community necessary for countering obesity.

Thus, the research suggests that green tea can be a potent remedy for HF diet-induced complications, primarily by modifying gut microbial communities.

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