Guide to green tea extract

For thousands of years, green tea’s potent health-boosting properties have been celebrated in China and Japan. The good news is many of these benefits have stood up to the scrutiny of modern scientific studies.

Green tea contains antioxidants, called polyphenols, which may protect the body against damage from free radicals – these are unstable oxygen molecules which contribute to disease.

Studies have suggested green tea may protect against heart disease, although experts say more studies are needed.

Dr Sarah Brewer says: ‘Some people who are interested in green tea’s potential health benefits but don’t like the taste, prefer to take a green tea supplement.

Green tea supplements are a rich source of epigallocatechin-3-gallate (EGCG), a strong antioxidant which studies suggest may protect against premature ageing.’

What does green tea extract do?

The antioxidant effects of polyphenols in green tea may protect cells in the body from damage by free radicals, including those in the heart and arteries. The caffeine content in green tea may also benefit memory and concentration.

Metabolic syndrome and heart disease

Metabolic syndrome is the medical term for a combination of cardiovascular disease risk factors including: diabetes and pre-diabetes; high blood pressure; raised cholesterol; and abdominal obesity (a big waist measurement). People with metabolic syndrome are twice as likely to die from, and three times as likely to have a heart attack or stroke compared with people without it.

Some studies suggest green tea may help reduce some of these risk factors including obesity, blood pressure, high blood sugar and raised cholesterol.

Weight control

A review of studies on the effects of drinking green tea on body weight, concluded drinking green tea had a small positive effect on weight loss and management.

Getting green tea from your diet

Green tea can be enjoyed as a hot drink made with leaves; several cups a day may be beneficial, but be aware it also contains caffeine so may keep you awake if you drink it too close to bedtime.


There are no recommended set upper daily limits for green tea consumption; it is regarded as safe, and a couple of cups a day are usually suggested by tea manufacturers. However, as stated above, drinking too much caffeine could result in sleep problems and irritability.

There have been some isolated case reports of liver toxicity in people who took supplements at doses of 700mg to 2,000mg a day.

Correct dosage

There is no official guidance on the correct dosage of green tea extract; most supplements are in the 240 to 340mg range as a rough guide. Look for a supplement with a high polyphenol content. One to two 340mg tablets a day is a suggested dose. One 340mg tablet of green tea extract with 95 per cent polyphenols has the same benefits as several cups of green tea.

Nothing beats a healthy, balanced diet to provide all the nutrients we need. But when this isn't possible, supplements can help. This article isn't intended to replace medical advice. Please consult your healthcare professional before trying supplements or herbal medicines.

Green tea supplements are a rich source of epigallocatechin-3-gallate (EGCG), a strong antioxidant which studies suggest may protect against premature ageing.

Dr Sarah Brewer


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