Catechins Anyone?
WHAT EXACTLY ARE TEA CATECHINS?
Catechins, also called flavan-3-ols, are a type of polyphenol found in plants. Catechins are particularly abundant in the young leaves and buds of tea plants, and make up about 70% of a tea leaf’s polyphenol content. To get a bit scientific here, the major catechins present in tea leaves are:
- catechin (C)
- gallocatechin (GC)
- epicatechin (EC)
- epigallocatechin (EGC)
- epicatechin gallate (ECG)
- gallocatechin gallate (GCG)
- epigallocatechin-3-gallate (EGCG).
It is all of the above types of catechins that are the main contributors to the beneficial health effects of tea, particularly the last one - EGCG.
In this article I will give you the low-down on how tea catechins impact the human body, all backed up by science. But before I do that, you need to know about the bioavailability of tea catechins.
BIOAVAILABILITY
The absorption of tea catechins occurs mainly in the small intestine and also in the colon, due to microbiota metabolism (the bacteria in your gut). The uptake rate is low, corresponding to about 1.68% in humans. Diet impacts the bioavailability of catechins. Vitamin C, Omega-3 polyunsaturated fatty acids (found in fish), and Piperine (found in black pepper) have been found to improve the bioavailability of catechins by preventing their oxidation and glucuronidation (the process of metabolising a compound into water-soluble compounds that are eliminated from the body in urine and bile). Catechins are also enhanced in people who are fasting.
The upshot is, if you want the health benefits of tea catechins outlined below, find ways to increase the pathways to bioavailability outlined above.
WHAT ARE THE HEALTH BENEFITS OF CATECHINS?
Anti-Cancer Effects
The therapeutic properties of catechins in the prevention and treatment of cancers are mainly attributed to their antioxidant properties and their ‘chelation’ properties. When cancers are caused by toxic metals, chelation is the process of organic compounds linking to metal ions and excreting them from the body. EGCG in particular has been shown to induce apoptosis (cell death) in some carcinoma cells (Yamauchi et al. 2009), as well as inhibit tumour angiogenesis (the growth of new blood vessels that supply nutrients and oxygen to tumour cells).
Anti-Diabetic Effects
It has been demonstrated that, in diabetes prevention and treatment, catechins can be beneficial in the regulation of ‘insulin’, control of blood glucose levels, inhibition of insulin resistance, and the lowering of inflammation (Granja et al. 2017). Insulin is a hormone made by the pancreas that allows the body to use sugar from foods ingested. In people with type 1 diabetes, the body produces little or no insulin. In people with type 2 diabetes, the body produces insulin but the insulin does not work as well as it should. This is often referred to as insulin resistance.
Anti-Obesity Effects
It has been shown that catechins can inhibit the expression of genes involved in ‘adipogenesis’ and ‘lipogenesis’, which can be highly relevant for weight management (Sanlier et al. 2018). Adipogenesis is the process by which fat-laden cells - called adipocytes - develop and accumulate as fat in various parts of the body. It has also been shown that catechins can have suppressive effects on the enzymes involved in the formation of fatty acids (the building blocks of fat), triacylglycerols and cholesterol (bad fats, which, when in excess in the bloodstream, are linked to obesity), as well as stimulate the enzymes involved in fatty acid mobilisation (fat-burning) (Suzuki et al. 2016).
Anti-Viral Effects
Catechins have been described as anti-viral for several reasons, including their antioxidant effects, their ability to prevent viral attachment and penetration into cells, and the trigger of self-defense mechanisms in cells targeted by viruses. Several studies have demonstrated these effects, particularly in the case of EGCG, including against influenza virus infection in chickens (Lee et al. 2012), the Zika virus (Sharma et al. 2017), HIV-1 (Nance et al. 2009) and hepatitis C (Pastoriza et al. 2017).
Anti-Osteoporosis Effects
Animal studies have shown positive effects of catechins on osteoporosis. EGCG in particular has been found to influence bone cell homeostasis (the healthy balance between osteoblast cells – which build bone substance – and osteoclast cells – which dissolve bone substance) (Dudaric et al. 2015). This protective role of catechins in bone health has been attributed to their antioxidant properties and their anti-inflammatory properties.
Neuroprotective Effects
Due to their antioxidant activities, catechins have been found to have some beneficial effects in neurodegenerative diseases (Rigacci and Stefani 2015). Catechins’ anti-inflammatory properties may also have a neuroprotective role in brain injuries (Hirao et al. 2010).
CATECHINS ARE JUST THE BEGINNING
Of course there are many other health compounds in tea you should know about, and I will be covering those in my next blog posts, so make sure to follow Tea Now on social media to keep informed.
Jaq James has a botany diploma and has studied tea culture and tea science in the birthplace of black tea and oolong tea - Mount Wuyi in China.
REFERENCES
Yamauchi R, Sasaki K and Yoshida K, ‘Identification of epigallocatechin-3-gallate in green tea polyphenols as a potent inducer of p53-dependent apoptosis in the human lung cancer cell line A549,’ Toxicology In Vitro, 2009, vol. 23.
Granja A, Frias I, Rute Neves A, Pinheiro M and Reis S, ‘Therapeutic potential of epigallocatechin gallate nanodelivery systems,’ Biomed Research International, 2017.
Sanlier N, Gokcen BB and Altug M, ‘Tea consumption and disease correlation,’ Trends in Food Science & Technology, 2018, vol. 78.
Suzuki T, Pervin M, Gotoe S, Isemura M and Nakamura Y, ‘Beneficial effects of tea and the green tea catechin epigallocatechin-3-gallate on obesity,’ Molecules, 2016, vol. 21.
Lee HJ, Lee YN, Youn HN, Lee DH, Kwak JHK, Seong BL, Lee JB, Park SY, Choi IS and Song CS, ‘Anti-influenza virus activity of green tea by-products in vitro and efficacy against influenza virus in chickens,’ Poultry Science, 2012, vol. 91.
Sharma N, Murali A, Singh AK and Ranjashi G, ‘Epigallocatechin gallate, an active green tea compound inhibits the Zika virus entry into host cells via binding the envelope protein,’ International Journal of Biological Macromolecules, 2017, vol. 104.
Nance C, Siwak EB and Shearer WT, ‘Preclinical development of the green tea catechin, epigallocatechin gallate, as an HIV-1 therapy,’ Journal of Allergy and Clinical Immunology, 2009, vol. 123.
Pastoriza S, Mesias M, Cabrera C and Rufian-Henares JA, ‘Healthy properties of green and white teas: update,’ Food & Function, 2017, vol. 8.
Dudaric L, Fuzinac-Smojver A, Muhvic D and Giacometti J, ‘The role of polyphenols on bone metabolism in osteoporosis,’ Food Reviews International, 2015, vol. 77.
Rigacci S and Stefani M, ‘Nutraceuticals and amyloid neurodegenerative diseases: a focus on natural phenols,’ Expert Review of Neurotherapeutics, 2015, vol. 15.
Hirao K, Yumoto H, Nakanishi T, Mukai K, Takahashi K, Takegawa D and Matsuo T, ‘Tea catechins reduce inflammatory reactions via mitogen-activated protein kinase pathways in toll-like receptor 2 ligand-stimulated dental pulp cells,’ Life Science, 2010, vol. 86.