Nutrition Notes

A Tea Party for the Microbiome

The importance of obtaining and maintaining optimal gastrointestinal (GI) health is still headline-worthy news. Even as dietary trends shift, each one inevitably focuses on its ability to improve GI health, recognizing that the GI tract is the foundation of all health. But sometimes, full dietary changes are not so easy to start. Instead, dietary “nuggets” can offer positive changes because they are manageable and don’t require massive shifts in lifestyle and schedules. One “nugget” that can improve GI health is drinking more tea.

One of the primary health benefits of tea is found in the polyphenol content, which exerts significant antioxidant and anti-inflammatory activity. Green, white, and black tea are rich sources of polyphenols. Water temperature and infusion times can certainly change the polyphenol content of the beverage, but in general, a 5-minute infusion will deliver a high quantity of polyphenols.  A study published in 2017 compared the total phenolic content (TPC), total flavonoid content (TFC), ferric reducing antioxidant power (FRAP), DPPH radical scavenging capacity, and caffeine content of teas (black, green, white, chamomile, and mixed berry/hibiscus) over a range of infusion times (0.5–10 mins) at 90°C. The highest total phenolic content was found in green tea at 557.58 ± 74.98; followed by black 499.19 ± 46.56; white 190.24 ± 7.73; berry 98.86 ± 14.72; and chamomile 75.31± 3.65 μg GAE/g tea. Results were similar for the TFC, FRAP, and DPPH radical scavenging capacity, with green tea coming in first place, followed by black tea. White tea possessed these same properties, but in much lower quantities, comparatively speaking.

Better Microbiome Diversity

Green tea contains the polyphenols epicatechin, epigallocatechin, epicatechin gallate, and epigallocatechin gallate, which positively modulate the microbiome of the GI tract; especially in the colon where the conjugates of green tea polyphenols are most often detected. These compounds provide substrates for various bacterial classes including Clostridia and Erysipelotrichia, as well as genera, Allobaculum and Lachnoclostridium, which increase the diversity of the microbiome. Additionally, the microbial communities metabolize the compounds of green tea into various bioactive components which subsequently improves the health of the GI tract through prebiotic effects and antimicrobial activities against pathogenic bacteria in the gut. The greater health benefits may be observed as protection against gastrointestinal disorders and pathogens, nutrient processing, reduction of serum cholesterol, reinforcement of intestinal epithelial cell-tight junctions and increased mucus secretion and modulation of the intestinal immune response through cytokine stimulus.

Better Satiety

Green tea may also have positive effects on satiety, thereby reducing hunger and helping manage obesity. In an in vitro study, the secretion of satiety hormones cholecystokinin (CCK) and glucagon-like peptide-1 (GLP-1)) was measured in response to green tea using a simulated digestion process. Green tea resulted in increased secretion of GLP-1, compared to controls (proteins and short chain fatty acids).

Better Colon Protection

Tea may also exert healthful benefits on the gut through the antioxidant capacity of the polyphenols. The polyphenols of tea are minimally available in the small intestine, but upon reaching the colon, the microbes metabolize the polyphenols which increases their bioavailability as well as their antioxidant and anti-inflammatory activities. The favorable yeast, S. cerevisiae, has been shown, in in vitro studies, to notably increase the bioaccessibility and antioxidant capacity of polyphenols,which have a unique affinity for binding to the cell wall components of yeast. This relationship is most prominent among black tea polyphenols. Therefore, some of the greatest gut health benefits of tea are imparted upon the colon, offering protection against many common colon-related inflammatory conditions. For example, a review of the anti-inflammatory effects of tea flavonoids indicated epigallocathechin gallate and apigenin from tea inhibit cytokines and chemokines, and activated immune cells in vivo and in vitro and may be useful in managing Crohn's disease, ulcerative colitis and irritable bowel syndrome. Since cytokine suppression helps to inhibit carcinogenesis, the polyphenols from tea may also aid in the prevention of intestinal neoplasia.

Regularly drinking a hot cup of tea can offer health benefits for the gut that reach far beyond what may appear in a simple mug of this tasty, comforting beverage. Black, green, and white tea present the gift of polyphenols to the gut microbiome, supporting its growth and diversity, and in return, the microbes metabolize the polyphenols into rich antioxidant and anti-inflammatory compounds that will help ensure a healthy environment in the colon.