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Nutrition and daily life

Green tea: a cup yes, capsules with caution

Green tea is often promoted as a health drink. A cup of green tea is a pleasant drink, but its extract and capsules need serious care during treatment. This section explains the difference.

Last updated: ~1 min read
A cup of green tea is a pleasant drink
Figure 1.A cup of green tea is a pleasant drink.

01Short answer

Green tea is tea leaves heated without oxidation and rich in catechins (EGCG). In ordinary amounts it is generally safe. But green tea extract capsules can harm the liver and may weaken medicines such as bortezomib. With some medicines you may need to limit the tea itself; ask your doctor. Green tea does not treat leukemia.

02Simple explanation

Green tea is an unoxidised leaf.

Catechins are its main compounds.

A cup is usually safe; capsules are not.

Possible interactions with medicines.

03Scientific explanation

NCCIH: green tea extract has rarely been linked to liver injury.

MSK: EGCG reduced the effect of bortezomib in lab studies; patients on this drug are advised to avoid green tea products.

NCI: it has not been shown in people that tea prevents or treats cancer.

MedlinePlus: about 400 mg of caffeine a day is generally considered safe for adults; during treatment watch your sleep and heart rate.

04What happens in the body?

Cup versus capsule

A cup of tea has few catechins; a capsule has many times more and loads the liver.

Hot green tea in front, a capsule bottle in shadow behind.
Figure 2.A cup yes, capsules with caution.

Brewing

Brew green tea with boiled water that has cooled a little, so it does not turn bitter.

Green tea leaves unfurling in a glass teapot.
Figure 3.Leaves unfurl in hot water.

Safe brewing

Freshly boiled water, a clean teapot and a fresh brew. During neutropenia avoid cold tea that has stood for hours.

Iron and medicines

Drink tea about an hour after meals; do not take extract capsules without your doctor.

05Brewing: four steps

Sealed pack, fresh brew, right temperature, drink hot.

Sealed pack — Dry place.1Sealed packDry place.
Fresh brew — Not old cold tea.2Fresh brewNot old cold tea.
Right water — Boiled.3Right waterBoiled.
Drink soon — Do not keep.4Drink soonDo not keep.
FlavourTradition.
FluidsA warm drink.
SafetyBoiled water.

06Key points at a glance

TopicIn brief
Cup versus capsuleA cup of tea has few catechins; a capsule has many times more and loads the liver.
BrewingBrew green tea with boiled water that has cooled a little, so it does not turn bitter.
Safe brewingFreshly boiled water, a clean teapot and a fresh brew. During neutropenia avoid cold tea that has stood for hours.
Iron and medicinesDrink tea about an hour after meals; do not take extract capsules without your doctor.

07Key terms

EGCG
The main green tea catechin.
Bortezomib
A medicine used for blood cancers.
Caffeine
A stimulant.
Polyphenols
Antioxidant plant compounds.
Neutropenia
Low neutrophils.

08Key points

  • A cup is usually safe.
  • Extract capsules are a risk.
  • Check your medicines with your doctor.
  • Brew with boiled water.
  • Capsules only with your doctor.

09Frequently asked questions

Does green tea boost immunity?

No benefit in leukemia has been shown.

Can I drink it during chemotherapy?

It depends on your medicine; ask your oncologist or pharmacist.

Does this tea treat leukemia?

No. Tea is a pleasant drink, not a treatment.

10Questions for your doctor

Take these questions to your appointment. The ones you save are collected on the “My questions” page and stay on this device only.

  1. Does green tea boost immunity?

  2. Can I drink it during chemotherapy?

  3. Does this tea treat leukemia?

My questions

12Sources

  1. National Center for Complementary and Integrative Health (NIH). Green Tea
  2. Memorial Sloan Kettering Cancer Center — About Herbs. Green Tea
  3. MedlinePlus. Caffeine
  4. Leukemia & Lymphoma Society. Diet Guidelines for Immunosuppressed Patients
  5. National Cancer Institute. Diet and Cancer Risk
  6. Harvard T.H. Chan School of Public Health — The Nutrition Source. Added Sugar
  7. British Dietetic Association. Wholegrains: Food Fact Sheet
  8. U.S. Food and Drug Administration (FDA). Added Sugars on the Nutrition Facts Label
  9. MedlinePlus (U.S. National Library of Medicine). Dietary Fats
  10. NHS. Fat: the facts
Medical disclaimerThis information is for educational purposes only and does not replace medical advice.
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