Green Tea for Weight Control

Common name: Epigallocatechin Gallate (EGCG)

Botanical name: Camellia sinensis

Why do dieters use it?*

Some dieters say that green tea

promotes weight loss.

What do the advocates say?*

Green tea is a good choice for people on a weight-loss programme because it can help them to lead a healthier lifestyle. For example, substituting green tea for coffee with cream and sugar not only saves calories but also supplies a lot of healthy substances, such as polyphenols and flavonoids, that can help improve one’s overall health.

Green tea contains a small amount of caffeine, so it serves as a mild appetite suppressant as well.

How much is usually taken by dieters?

Test tube studies suggest that green tea extracts high in catechins may inhibit fat digestion and a preliminary human study found a green tea extract increased calorie burning.¹ ² A preliminary human study found that people taking a green tea extract containing 375 mg per day of total catechins (of which 270 mg per day was epigallocatechin gallate) for three months lost an average of 4.6% of their body weight without dieting.³ Double-blind trials are needed to confirm this effect.

Are there any side effects or interactions?

Green tea is generally free of side effects. The most common adverse effects reported from consuming large amounts (several cups per day) of green tea are insomnia, anxiety, and other symptoms caused by the caffeine content in the herb.

An extract of green tea taken by healthy women with a meal inhibited the absorption of non-haem iron (e.g., the form of iron in plant foods) by 26%.⁴ Frequent use of green tea could, in theory, promote the development of iron deficiency in susceptible individuals.

There are several case reports of people developing liver damage while consuming weight-loss products that contained concentrated extracts of green tea.⁵ A cause–effect relationship was not proven, and most of the products contained other ingredients in addition to green tea extract. Nevertheless, researchers have cautioned against the use of large amounts, or concentrated extracts, of green tea.

Are there any drug interactions?
Certain medicines may interact with green tea. Refer to drug interactions for a list of those medicines.

Parts used and where grown

All teas (green, black, and oolong) are derived from the same plant, Camellia sinensis. The difference is in how the plucked leaves are prepared. Green tea, unlike black and oolong tea, is not fermented, so the active constituents remain unaltered in the herb. The leaves of the tea plant are used both as a social and a medicinal beverage.

Resources

See a list of books, periodicals, and other resources for this and related topics.

*Dieters and weight-management advocates may claim benefits for green tea based on their personal or professional experience. These are individual opinions and testimonials that may or may not be supported by controlled clinical studies or published scientific articles on green tea. For more complete and detailed information, including references and safety information, see Green Tea as an herbal remedy.

References
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1. Juhel C, Armand M, Pafumi Y, et al. Green tea extract (AR25) inhibits lipolysis of triglycerides in gastric and duodenal medium in vitro. J Nutr Biochem 2000;11:45–51.

2. Dulloo AG, Duret C, Rohrer D, et al. 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 1999;70:1040–5.

3. Chantre P, Lairon D. Recent findings of green tea extract AR25 (Exolise) and its activity for the treatment of obesity. Phytomedicine 2002;9:3–8.

4. Samman S, Sandstrom B, Toft MB, et al. Green tea or rosemary extract added to foods reduces nonheme-iron absorption. Am J Clin Nutr 2001;73:607–12.

5. Bonkovsky HL. Hepatotoxicity associated with supplements containing Chinese green tea (Camellia sinensis). Ann Intern Med 2006;144:68–71.

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The information presented in Healthnotes is for informational purposes only. It is based on scientific studies (human, animal, or in vitro), clinical experience, or traditional usage as cited in each article. The results reported may not necessarily occur in all individuals. For many of the conditions discussed, treatment with prescription or over the counter medication is also available. Consult your doctor, practitioner, and/or chemist for any health problem and before using any supplements or before making any changes in prescribed medications. Information expires March 2007.