• 21 May 2024

  • Tips from the herbalist

Plants as medicine: Green Tea

We were inspired to write this article having heard Michael Mosley's 'Just One Thing' programme on the BBC earlier this year. Our thanks go to Michael for his relentless curiosity and commitment to helping people lead healthier lives.

The origins of tea trace back to China, thousands of years ago. 

From there, the use of tea spread to Japan, where it was taken as a medicinal drink.1 Rich and now ancient tea traditions, intersecting art, medicine and ceremony developed across Asia — including the Japanese practice chado, ‘the way of tea’, a mindful ritual that embodies harmony between people and nature and exemplifies the sacred culture that surrounds the tea leaf.1,2  From Asia, tea use expanded west, being adopted by the British in the 17th century.2  Today, tea is copiously cultivated and consumed around the world, and green tea in particular is receiving increased recognition for its positive influence on human health.

Tea is produced from the leaf of the tea bush, Camellia sinensis. Compared to black and white teas, the processing of green tea involves a shorter drying time which minimises oxidation and retains the green colour of the leaves. as well as the medicinal properties. How exactly the leaves are processed, as well as how and where the tea bushes are grown, varies greatly between regions and cultures, resulting in an abundant diversity of green tea flavours and characteristics.

Not only is green tea a pleasant, uplifting drink, it’s a medicinal herbal infusion.

Green tea has boasted many claims for its health-promoting properties — protecting against cardiovascular, metabolic and neurodegenerative disease.3,4 There are several constituents that green tea contains that are understood to contribute to its positive effects — theanine, caffeine and, the most acclaimed of green tea’s constituents, the antioxidant catechin epigallocatechin gallage (EGCG).5,6  These constituents are also responsible for green tea’s flavour profile, with EGCG giving it a bitter quality, and theanine giving it its savoury, umami taste.

Brain health

Acetylcholine is a neurotransmitter that facilitates signalling throughout the nervous system, essential for a myriad of functions, including learning, memory and attention. EGCG increases acetylcholine levels, so improves cognitive function and protects against age-related cognitive decline. EGCG has also demonstrated the ability to inhibit the formation of amyloid plaques in the brain, a pathological feature of Alzheimer’s disease.5,7 These properties give green tea a neuroprotective quality, promoting brain health and protecting against neurodegenerative diseases.8  The presence of caffeine in green tea also promotes alertness, combats fatigue and enhances mood.3,4,6

Metabolic health

Green tea has shown to improve fat and carbohydrate metabolism and reduce insulin resistance.3,9,10  Studies have shown that consuming green tea prior to exercise leads to increased visceral fat burning, which in turn lowers risk for heart disease.11,12  Green tea increases the number of mitochondria, structures in cells that generate energy, so with more mitochondria, more energy stores (fat) are burnt, therefore facilitating weight loss.5

Insulin resistance is associated with type II diabetes and cardiovascular disease, so as EGCG alleviates insulin resistance, green tea reduces risk of these conditions.10  Drinking green tea daily has also shown to decrease mortality in diabetic populations.13

Cardiovascular health

Green tea has also demonstrated an ability to improve the integrity of the inner lining of blood vessels, the endothelium.3  Endothelial disruption is a process that precedes the development of cardiovascular disease, such as atherosclerosis, heart attack and stroke.14  Green tea, therefore, has potential to reduce the risk of these conditions.

Consequently, research suggests that green tea may have a lot to offer us in the way of protection against cardiovascular, neurodegenerative and metabolic disorders.3,5  So, when you next sit down to a cup of green tea, you are taking care yourself in more ways than one.

TOP TIP! Unlike black tea, which brews best at 95–98°C, brewing green teas with water between 75 and 80° C brings out the best flavours.

 

References

  1. Japanese tea ceremony, the way of tea. Zen Wonders Tea. (n.d.).  https://zenwondersmatcha.com.au/pages/4-principles-of-chado
  2. History of tea. UK Tea & Infusions Association. (n.d.). https://www.tea.co.uk/history-of-tea
  3. Green tea. Herbal Reality. (2024, May 14). https://www.herbalreality.com/herb/green-tea/
  4. Kurosaka, C., Tagata, C., Nakagawa, S., Kobayashi, M., & Miyake, S. (2024). Effects of green tea and roasted green tea on human responses. Scientific Reports, 14(1), 8588. https://doi.org/10.1038/s41598-024-59383-y
  5. Drink Green Tea. (2024). Just One Thing. episode. Retrieved 2024, from https://www.bbc.co.uk/sounds/play/m001vmbm.
  6. Mancini, E., Beglinger, C., Drewe, J., Zanchi, D., Lang, U. E., & Borgwardt, S. (2017). Green tea effects on cognition, mood and human brain function: A systematic review. Phytomedicine, 34, 26–37. https://doi.org/10.1016/j.phymed.2017.07.008
  7. Özduran, G., Becer, E., & Vatansever, H. S. (2023). The Role and Mechanisms of Action of Catechins in Neurodegenerative Diseases. Journal of the American Nutrition Association, 42(1), 67–74. https://doi.org/10.1080/07315724.2021.1981487
  8. Robinson, R. (2001). Green tea extract may have neuroprotective effects in Parkinson’s disease. The Lancet, 358(9279), 391. https://doi.org/10.1016/S0140-6736(01)05594-5
  9. Luo, M., Kannar, K., Wahlqvist, M., & O’Brien, R. (1997). Inhibition of LDL oxidation by green tea extract. The Lancet, 349(9048), 360–361. https://doi.org/10.1016/S0140-6736(05)62864-4
  10. Liu, C.-Y., Huang, C.-J., Huang, L.-H., Chen, I.-J., Chiu, J.-P., & Hsu, C.-H. (2014). Effects of Green Tea Extract on Insulin Resistance and Glucagon-Like Peptide 1 in Patients with Type 2 Diabetes and Lipid Abnormalities: A Randomized, Double-Blinded, and Placebo-Controlled Trial. PLoS ONE, 9(3), e91163. https://doi.org/10.1371/journal.pone.0091163
  11. Maki, K. C., Reeves, M. S., Farmer, M., Yasunaga, K., Matsuo, N., Katsuragi, Y., Komikado, M., Tokimitsu, I., Wilder, D., Jones, F., Blumberg, J. B., & Cartwright, Y. (2009). Green tea catechin consumption enhances exercise-induced abdominal fat loss in overweight and obese adults. The Journal of nutrition, 139(2), 264–270. https://doi.org/10.3945/jn.108.098293
  12. Nagao, T., Hase, T., & Tokimitsu, I. (2007). A green tea extract high in catechins reduces body fat and cardiovascular risks in humans. Obesity (Silver Spring, Md.), 15(6), 1473–1483. https://doi.org/10.1038/oby.2007.176
  13. Komorita, Y., Iwase, M., Fujii, H., Ohkuma, T., Ide, H., Jodai-Kitamura, T., Yoshinari, M., Oku, Y., Higashi, T., Nakamura, U., & Kitazono, T. (2020). Additive effects of green tea and coffee on all-cause mortality in patients with type 2 diabetes mellitus: The Fukuoka Diabetes Registry. BMJ Open Diabetes Research & Care, 8(1), e001252. https://doi.org/10.1136/bmjdrc-2020-001252
  14. Wang, Z. M., Chen, B., Zhou, B., Zhao, D., & Wang, L. S. (2023). Green tea consumption and the risk of stroke: A systematic review and meta-analysis of cohort studies. Nutrition (Burbank, Los Angeles County, Calif.), 107, 111936. https://doi.org/10.1016/j.nut.2022.111936

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