Green tea is a good choice for people on a weight-loss program 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 healthful 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.12 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-heme 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.
*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 (To view, roll mouse over the "References" heading; to hide, click on the heading)
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.
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 pharmacist for any health problem and before using any supplements or
before making any changes in prescribed medications. Information expires June 2009.
