Green Tea – Does It Live Up To The Hype?

Tea is one of the most consumed beverages the world over. Since mediaeval ages, regular consumption of tea has always been associated with health benefits. More recently, however, an unfermented variety of tea – green tea – is being touted as an anti-obesity tool that really works. Flavonols present are mainly responsible for the fat loss and other health benefits of green tea.

Studies have reported an increase in fat oxidation of a whopping 35% after consumption of green tea. However, the best way of using green tea extract may be to combine with caffeine with a sound exercise and diet plan to optimize fat loss.

Tea is one of the most consumed beverages over the world, second probably to only coffee.

Since mediaeval ages, regular consumption of tea has always been associated with health benefits. More recently, however, an unfermented variety of tea – green tea – is being touted as an anti-obesity tool that really works; some consider it a fat-burner ‘par excellence’. Let’s look into the supporting evidence to find out it that indeed is the case.

Composition of Green Tea

If you have a look at the chemical composition of green tea, you’d find that it is nothing less than complex. A plethora of ingredients make up the substance of green tea – proteins, amino acids, carbohydrates like cellulose, pectins, glucose and fructose, minerals like calcium, chromium, iron and vitamins like B,C and E (Chacko, Thambi, Kuttan, & Nishigaki, 2010) Alkaloids (known as methylxanthines) like caffeine, theobromine and theophylline are also present in green tea (Graham, 1992).

Additionally, it contains the bioactive polyphenols which are responsible for most of the amazing health benefits (and fat loss abilities) of green tea. Polyphenols – namely flavanols and flavonols – constitute 30% of the dry weight of green tea leaves (Chacko et al., 2010).

These flavonols present in green tea are also known as catechins and are of 4 types: epicatechin (EC), epigallocatechin (EGC), epicatechin gallate (ECG) and epigallocatechin gallate (EGCG) (Kris-Etherton et al., 2002). EGCG is the one that is mainly responsible for the fat loss and other health benefits of green tea (Moyers & Kumar, 2004; Mandel, Weinreb, Amit, & Youdim, 2004; Higdon & Frei, 2003).

How is Green Tea Different from Other Types of Tea?

Tea is produced from the plant Camellia Sinensis. Commercially it is available in 3 forms: green, oolong and black. Of these, green tea is the least processed during the manufacturing process.

During the production of green tea, fresh tea leaves are steamed to prevent fermentation (Chacko et al., 2010). This steaming destroys enzymes that are responsible for decolourisation of the leaves; thus the green colour of green tea. Additionally, lack of fermentation preserves all the natural polyphenols which is not the case with oolong or black tea. Thus, green tea has more bioactive ingredients and is a healthier option.

Green tea is subsequently fermented to produce oolong and then black tea. As expected, these processes lead to decreased catechin levels.

Green Tea and Fat Loss – Where Is The Evidence?

Human studies investigating green tea extract and its potential to cause fat loss suggest that increased fat oxidation and increased energy expenditure may be mechanism responsible.

A study published in the American Journal of Clinical Nutrition found that fat oxidation increased by a whopping 35% after subjects supplemented with green tea extract (Dulloo et al., 1999). The group of subjects that consumed 150 mg of caffeine along with 270 mg of EGCG had the most increase in fat oxidation compared to the group given a placebo or caffeine alone.

The hypothesis suggested by the authors was that caffeine, by stimulating the sympathetic nervous system, increased energy expenditure. Adding green tea extract to caffeine further bumped up this energy expenditure; thus suggesting that ingredients in green tea extract (EGCG to be precise) had fat burning abilities as well.

A similar study using Oolong tea concluded that fat oxidation increased by 12% when oolong tea (244mg of EGCG) was combined with caffeine (270mg) (Rumpler et al., 2001).

Komatsu and colleagues used caffeine with EGCG from either green tea or oolong tea for their study on Japanese women. They reported an increase in energy expenditure of 111 and 50kJ respectively over the subsequent 2 hours (Komatsu et al., 2003). Furthermore, 24-hour energy expenditure also has been shown to increase after consumption of green tea extract (Bérubé-Parent, Pelletier, Doré, & Tremblay, 2005).

Another study that investigated the role of pure EGCG rather than green tea or oolong tea extracts concluded that ‘EGCG supplementation has the potential to increase fat oxidation in men, an action that may contribute to the apparent anti-obesity effects of green tea’ (Boschmann & Thielecke, 2007).

Reduction of body weight using green tea extract has other potential benefits as well; by reducing body weight and blood glucose levels, green tea extract may help protect against the development of heart disease (Tsuneki et al., 2004).

Other Health Benefits of Green Tea Extract

Health benefits of green tea extract are due to its polyphenol content (Khan & Mukhtar, 2007).

Green tea extract helps prevent or fight the following diseases or conditions:

  • Cancer; regular consumption of green tea has been shown to protect against many types of cancer: mouth, lungs, oesophagus, stomach, small intestine, colon, pancreas and mammary glands (Kavanagh et al., 2001; Koo & Cho, 2004).
  • Cardiovascular diseases (Sueoka et al., 2001; Sartippour et al., 2002)
  • Arthritis (Haqqi et al., 1999)
  • Has antioxidant property; helps fight stress and chronic diseases (Osada et al., 2001; Zaveri, 2006)
  • Antibacterial and antiviral properties as well (Sudano, Blanco, Giuliano, Rusciano, & Enea, 2004; Weber, Ruzindana-Umunyana, Imbeault, & Sircar, 2003)

Verdict on Green Tea Extract

Notwithstanding the scientific evidence for green tea extract to boost energy expenditure, not much research has been done to define the exact mechanisms induced by green tea that are responsible for causing fat loss.

Having said that, however, there is no denying that green tea does seem to cause increased energy expenditure – both immediately post-consumption and for 24-hours thereafter. This energy expenditure is significant – as much as 35% above your normal energy expenditure – and would in all probability contribute significantly to causing weight loss.

As stated above, for optimum fat loss, green tea extract seems to work best in conjunction with caffeine. Thus, picking up a fat loss supplement that contains caffeine in addition to green tea extract would make more sense than drinking green tea alone.

To conclude, a combination of an exercise plan to burn calories, a diet plan that restricts calorie intake, along with a supplement containing green tea extract and caffeine seems to be the best option to lose fat.

Useful References:

  • Bérubé-Parent, S., Pelletier, C., Doré, J., & Tremblay, A. (2005). Effects of encapsulated green tea and Guarana extracts containing a mixture of epigallocatechin-3-gallate and caffeine on 24 h energy expenditure and fat oxidation in men. Br J Nutr, 94, 432-436. Online Reference
  • Chacko, S. M., Thambi, P. T., Kuttan, R., & Nishigaki, I. (2010). Beneficial effects of green tea: a literature review. Chin Med, 5, 13. Online Reference
  • Dulloo, A. G., Duret, C., Rohrer, D., Girardier, L., Mensi, N., Fathi, M. et al. (1999). Efficacy of a green tea extract rich in catechin polyphenols and caffeine in increasing 24-h energy expenditure and fat oxidation in humans. Am J Clin Nutr, 70, 1040-1045. Online Reference
  • Graham, H. N. (1992). Green tea composition, consumption, and polyphenol chemistry. Prev.Med, 21, 334-350. Online Reference
  • Haqqi, T. M., Anthony, D. D., Gupta, S., Ahmad, N., Lee, M. S., Kumar, G. K. et al. (1999). Prevention of collagen-induced arthritis in mice by a polyphenolic fraction from green tea. Proc.Natl.Acad.Sci.U.S.A, 96, 4524-4529. Online Reference
  • Higdon, J. V. & Frei, B. (2003). Tea catechins and polyphenols: health effects, metabolism, and antioxidant functions. Crit Rev Food Sci.Nutr., 43, 89-143. Online Reference
  • Kavanagh, K. T., Hafer, L. J., Kim, D. W., Mann, K. K., Sherr, D. H., Rogers, A. E. et al. (2001). Green tea extracts decrease carcinogen-induced mammary tumor burden in rats and rate of breast cancer cell proliferation in culture. J Cell Biochem., 82, 387-398. Online Reference
  • Khan, N. & Mukhtar, H. (2007). Tea polyphenols for health promotion. Life Sci., 81, 519-533. Online Reference
  • Komatsu, T., Nakamori, M., Komatsu, K., Hosoda, K., Okamura, M., Toyama, K. et al. (2003). Oolong tea increases energy metabolism in Japanese females. J Med Invest, 50, 170-175. Online Reference
  • Koo, M. W. & Cho, C. H. (2004). Pharmacological effects of green tea on the gastrointestinal system. Eur J Pharmacol., 500, 177-185. Online Reference
  • Kris-Etherton, P. M., Hecker, K. D., Bonanome, A., Coval, S. M., Binkoski, A. E., Hilpert, K. F. et al. (2002). Bioactive compounds in foods: their role in the prevention of cardiovascular disease and cancer. Am J Med, 113 Suppl 9B, 71S-88S. Online Reference
  • Mandel, S., Weinreb, O., Amit, T., & Youdim, M. B. (2004). Cell signaling pathways in the neuroprotective actions of the green tea polyphenol (-)-epigallocatechin-3-gallate: implications for neurodegenerative diseases. J Neurochem., 88, 1555-1569. Online Reference
  • Moyers, S. B. & Kumar, N. B. (2004). Green tea polyphenols and cancer chemoprevention: multiple mechanisms and endpoints for phase II trials. Nutr.Rev, 62, 204-211. Online Reference
  • Osada, K., Takahashi, M., Hoshina, S., Nakamura, M., Nakamura, S., & Sugano, M. (2001). Tea catechins inhibit cholesterol oxidation accompanying oxidation of low density lipoprotein in vitro. Comp Biochem.Physiol C.Toxicol.Pharmacol., 128, 153-164. Online Reference
  • Rumpler, W., Seale, J., Clevidence, B., Judd, J., Wiley, E., Yamamoto, S. et al. (2001). Oolong tea increases metabolic rate and fat oxidation in men. J Nutr, 131, 2848-2852. Online Reference
  • Sartippour, M. R., Shao, Z. M., Heber, D., Beatty, P., Zhang, L., Liu, C. et al. (2002). Green tea inhibits vascular endothelial growth factor (VEGF) induction in human breast cancer cells. J Nutr., 132, 2307-2311. Online Reference
  • Sudano, R. A., Blanco, A. R., Giuliano, F., Rusciano, D., & Enea, V. (2004). Epigallocatechin-gallate enhances the activity of tetracycline in staphylococci by inhibiting its efflux from bacterial cells. Antimicrob.Agents Chemother., 48, 1968-1973. Online Reference
  • Sueoka, N., Suganuma, M., Sueoka, E., Okabe, S., Matsuyama, S., Imai, K. et al. (2001). A new function of green tea: prevention of lifestyle-related diseases. Ann N Y.Acad.Sci., 928, 274-280. Online Reference
  • Tsuneki, H., Ishizuka, M., Terasawa, M., Wu, J. B., Sasaoka, T., & Kimura, I. (2004). Effect of green tea on blood glucose levels and serum proteomic patterns in diabetic (db/db) mice and on glucose metabolism in healthy humans. BMC Pharmacol., 4, 18. Online Reference
  • Weber, J. M., Ruzindana-Umunyana, A., Imbeault, L., & Sircar, S. (2003). Inhibition of adenovirus infection and adenain by green tea catechins. Antiviral Res., 58, 167-173. Online Reference
  • Zaveri, N. T. (2006). Green tea and its polyphenolic catechins: medicinal uses in cancer and noncancer applications. Life Sci., 78, 2073-2080. Online Reference

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