Written by Tommy Li and Jerry Lau
Tea was and still is one of the most highly sought after commodities in the world. From its origins in a small province in ancient China, to its massive rise as a huge motivator in world conflicts, tea has been anything but a drink. But why tea? Tea has been used around the world for its perceived medicinal qualities, its rich taste, its ability to bring people together, etc. Here we will focus on tea’s perceived medicinal qualities and weigh out how the health claims on tea hold out versus the scientific community.
Teas’ health claims range from the relatively benign claim of improving blood pressure and circulation to eye-raising claims of being able to fight various forms of cancer (3). However most studies state that these health benefits come from drinking tea over long periods of time and do not paint tea as a “miracle substance” that many from the tea industry characterize it to be. How does tea have these benefits? There are substances in tea called polyphenols, more specifically catechins and epicatechins. Lab and animal studies find that these molecules have anti-inflammatory and antioxidant properties (1). This is corroborated by multiple studies in the field; one such study stating that patients with elevated blood pressure or hypertension would benefit from regular tea intake which was shown to have positive effects on the patients’ blood pressure (2).
There are many different types of tea available to purchase; some popular ones being black tea, green tea, oolong tea, and Kombucha. Although all teas contain polyphenols, not all teas are made equal. For example, Kombucha, a probiotic-rich fermented drink made with tea (green or black), sugar, bacteria, and yeast, is very interesting. Kombucha has a yeast component that usually includes Saccharomyces and other species; the bacterial component almost always includes Gluconacetobacter xylinus. It can be a fermented slightly effervescent, sweetened (slightly sour) drink used as a functional beverage to provide health benefits (0.5-3% alcohol). Microbes break sugars down to alcohol and CO2. Then bacteria converts alcohol to acids (e.g. acetic). It has been traditionally used primarily in Manchuria, Russia, eastern Europe and Japan. Kombucha claims to have benefits to asthma, cataracts, diabetes, diarrhea, gout, herpes, insomnia and rheumatism; to shrink the prostate, raise the libido, reverse grey hair, remove wrinkles, relieve hemorrhoids, lower hypertension, prevent cancer, to promote general well-being, help to lose weight, treat constipation, and to stimulate the immune system (4). But because of its microbial sourcing and possible non-sterile packaging, it is not recommended for people with poor immune function (HIV), women who are pregnant or nursing, and children under 4 years old. Furthermore, matcha, a type of green tea, is very effective in reducing stress. Beside caffeine, it also contains theanine, a major amino acid in green tea that exhibits a stress-reducing effect in mice and humans (5).
The potentials of tea have been analyzed in many experiments. Further research will be needed to investigate more benefits and side effects. Given the tremendous amount of time in history, people have learned to appreciate tea - a taste of age.
Zhang Z, Feng X, Wang Y, et al. Advances in research on functional genes of tea plants. Gene. 2019;711:143940.
Mahdavi-Roshan M, Salari A, Ghorbani Z, Ashouri A. The effects of regular consumption of green or black tea beverages on blood pressure in those with elevated blood pressure or hypertension: A systematic review and meta-analysis. Complement Ther Med. 2020;51:102430.
“The Hidden Health Benefits of Tea”. Health and Wellness. PennMedicine. https://www.pennmedicine.org/updates/blogs/health-and-wellness/2019/december/health-benefits-of-tea. Accessed 2021 Aug 26.
Beaufort, S, Bouajila, J, Taillandier, P. “Understanding Kombucha Tea Fermentation: A Review”. https://pubmed-ncbi-nlm-nih-gov.jerome.stjohns.edu/29508944/ 2018 Mar;83(3):580-588.
Unno K, Furushima D, Hamamoto S, Iguchi K, Yamada H, Morita A, et al. . Stress-reducing function of matcha green tea in animal experiments and clinical trials. Nutrients. (2018) 10:1468. 10.3390/nu10101468