Exploring the anti-cancer potential of dark tea

By Vijay Kumar MalesuSep 11 2023Reviewed by Sophia Coveney

In a recent review published in Nutrients, researchers reviewed the potential of dark tea in cancer prevention and management, highlighting its mechanisms and future prospects.

Background 

The rise in cancer cases and related deaths is alarming, with cancer now a primary cause of mortality globally. World Health Organization (WHO) data from 2020 recorded 19.3 million new cases and 10 million deaths, with lung, breast, bowel, and prostate cancers being the most prevalent.

By 2040, global new cancer cases could reach 27.5 million annually, influenced by many factors including lifestyle and genetics. Some studies suggest that tea, especially dark tea, may offer protective benefits against cancer.

Dark teas, like Yunnan Pu’er tea (Pu’er) tea, and Hunan Fubrick (Fu brick) tea, have unique properties and active ingredients beneficial for health. Further research is needed to comprehensively understand the precise anti-cancer mechanisms and potential limitations of dark tea.

Bioactive compounds of dark tea

Dark tea boasts an array of bioactive compounds: catechins, phenolic acids, flavonols, and alkaloids, to name a few. The unique flavors and health benefits stem from microbial fermentation, distinguishing it from other teas like green and oolong.

Key compounds include polyphenols (with roles in anti-oxidation and anti-inflammation) and amino acids like theanine that enhance immunity and memory. Additionally, alkaloids such as caffeine promote cardiovascular health, while polysaccharides regulate immunity and gut health. A standout compound is theabrownin, known for its anti-oxidative and anti-cancer properties.

Anti-cancer potency of dark tea

Research confirms that dark tea components, such as the polysaccharides in dark brick tea, have anti-cancer properties that hinder lung and liver cancer cell growth. Theabrownin suppresses lung cancer cell proliferation, while a derivative from Anhua dark tea boosts apoptosis in lung cancer cells.

Furthermore, dark tea extracts inhibit the growth of pancreatic, colon, and tongue cancer cells, and notably, theophylline present in dark tea also curtails the growth of breast and cervical cancer cells.

Dark tea: mechanisms against cancer

The anti-cancer effects of dark tea are evident, with inflammation playing a pivotal role. Chronic inflammation often leads to cancer, with the Nuclear factor-kappa B (NF-κB) pathway influencing oncogene transcription. Dark tea exhibits anti-inflammatory properties, specifically inhibiting the NF-κB pathway.

In experiments, Pu’er tea extract reduced inflammatory proteins and factors, suggesting its efficacy in curbing intestinal inflammation. In cases of fat-induced inflammation, dark tea reduced pro-inflammatory factors, suggesting its potential role in cancer prevention, and future studies should further explore the anti-inflammatory effects of dark tea on other organs.

Antioxidative properties of dark tea

Oxidative stress and its implications

Oxidative stress arises when there is an imbalance in the production and removal of oxygen-free radicals in the body. This stress is linked to various diseases, especially in promoting cancer cell transformation and proliferation.

Dark tea's antioxidant activity

Dark tea exhibits antioxidant properties, which potentially reduce the risk of cancer by counteracting oxidative stress. Extensive research using various experiments, like 2,2'-Azino-bis(3-ethylbenzothiazoline-6-sulfonic acid) (ABTS), ferric reducing antioxidant power (FRAP), and 2,2-diphenyl-1-picrylhydrazyl (DPPH), has confirmed the antioxidative nature of dark tea.

Active components such as polyphenols, flavonoids, and tea polysaccharides significantly contribute to this antioxidative action.

In vitro and in vivo antioxidant studies

Various studies have shown that dark tea extracts, especially from Pu’er tea, diminish oxidative stress markers in cells. In vivo experiments have confirmed dark tea's ability to reduce reactive oxygen species (ROS) levels, enhancing the survival rate in certain adverse conditions.

Mechanisms behind antioxidant effects

Dark tea's antioxidant properties are largely attributed to polyphenols, flavonoids, and tea polysaccharides. Although many studies have addressed its antioxidative effects, deeper insights into the pathways and mechanisms of these antioxidants are needed.

Dark tea's role in cancer management

Inhibition of cancer cell proliferation

Dark tea blocks cancer cell growth, especially by halting the cell cycle at various phases. The first gap (G1) phase blockage in certain cells, for instance, Hepatocellular Carcinoma Cell Line (HepG2) cells, by Pu’er tea has been attributed to the activation of specific pathways.

Promotion of cancer cell apoptosis 

Components of dark tea, especially after microbial fermentation, can induce apoptosis in various cancer cells. Mechanisms include inducing reduction-oxidation (REDOX) imbalance in cells or activation of specific signaling pathways like Mitogen-Activated Protein Kinase/c-Jun N-terminal Kinase (MAPK/JNK).  

Dark tea holds promise in preventing and treating cancer by suppressing cell proliferation, metastasis, and promoting apoptosis. While cellular and animal studies dominate current research, more human population-based studies are required.

Obesity and its relationship with cancer

Obesity is rapidly becoming a major health concern due to factors like diet, metabolic abnormalities, and genetics. Its prevalence has surged recently, and links between obesity and certain cancers have been established. Significantly, a study showed that patients who underwent bariatric surgery experienced a notable reduction in cancer incidence compared to those who did not. Furthermore, severe obesity is linked to a higher risk of cancers like colon and breast cancer, with tumorigenesis often fueled by inflammatory responses.

Beneficial properties of dark tea

Dark tea has demonstrated potential in combating obesity and, indirectly, cancer. Studies on Fu Brick Tea and Pu’er Tea revealed their ability to reduce serum lipid levels, which can assist in treating and preventing cancer.

Numerous research efforts, spanning from examining lipid reduction in Pu’er tea to Liupao tea’s effects on obese mice, underscore the lipid-lowering properties of these teas. Dark tea’s impact extends to human studies, too.

Regular intake of Pu’er tea extract has been shown to significantly reduce body weight and improve blood lipid status among hyperlipidemic individuals. Moreover, daily tea consumption, particularly dark varieties, has been linked to a lower risk of diabetes among various demographics.

Dark tea's impact on intestinal flora

Imbalances in intestinal flora can result in many health issues, including cancer. However, dark tea, particularly its polyphenols, has been shown to modulate gut microbiota. This tea increases the diversity of gut microbiota, benefiting obese and diabetic conditions by enhancing the presence of beneficial bacteria. For instance, Pu’er tea can adjust the gut microbes in colitis mice, enhancing the abundance of beneficial bacteria, which, in turn, might reduce the chances of colon cancer. 

However, individual variations in gut flora modulation and the exact mechanisms through which dark tea extracts influence the intestinal flora need further research.