4 possible green tea side effects

4 possible green tea side effects

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Green tea side effects are rare for the average adult drinking in moderation. I regularly drink green tea and I feel great.

I live in Japan where most everyone has 2 or 3 cups a day. Negative effects of green tea isn’t really a common topic. It’s usually the other way around.

But that’s not to say that there aren’t any possible side effects. If you have concerns, it would be best to speak to your doctor before starting to drink green tea.

The following are some possible side effects of green tea.

1. Stomach upset and constipation

In Japan and China, it is common knowledge that you shouldn’t drink green tea on an empty stomach. The green tea tannins increase stomach acid. So, if you drink green tea before eating, it may give you a stomachache, a nauseous feeling, or cause constipation.

It is best to drink green tea after a meal or in-between meals. People with peptic ulcers or acid reflux should be especially careful. You can try adding milk if it continuously causes stomachaches.

2. Sensitivity to caffeine

Green tea has less caffeine than coffee or black tea, but it still contains caffeine. So, how much is too much green tea? WebMD says more than five cups. Drinking too much green tea can cause caffeine intolerance and minerals overdose.

A moderate amount of caffeine is less than 200 mg a day. Too much caffeine can cause the following side effects.

  • Headache
  • Nervousness
  • Sleep problems
  • Vomiting
  • Diarrhea
  • Irritability
  • Irregular heartbeat
  • Tremor
  • Heartburn
  • Dizziness
  • Ringing in the ears
  • Convulsions
  • Confusion

Caffeine may also interact with some medications. If you’re worried about the caffeine in green tea, you can try Houji-cha or Bancha, which contains lower levels of caffeine.

Green Tea Side Effects: Low Caffeine BanchaHouji Bancha at a Green Tea Shop in Uji, Japan

3. Decreased intake of iron

Green tea catechins can cause a decrease in the absorption of iron from food.

If you have iron-deficiency anemia, the National Cancer Institute recommends consuming tea between meals. If you like to drink green tea with your meal, then studies show you should eat foods that enhance iron absorption. Foods high in iron include meats such as red meat and foods high in Vitamin C, such as lemons.

4. Drug interactions

If you are taking prescription drugs, you should check to make sure there are not any drug interactions with green tea. The University of Maryland website shows a list of possible interactions.

Final thoughts

Side effects from drinking green tea are rare. Now, if you are taking a green tea extract, that is a different story. Read more

Are you interested in buying green tea?

All the green teas that I drink in Japan can now be delivered to your front door. Visit my shop at Daily Matcha to discover real Japanese green tea!

This article contains links to DailyMatcha.com. Daily Matcha is our store where we sell green tea directly from Japan. Your purchases support our effort to raise awareness about green tea. Thank you!


Cabrera, C., Artacho, R., & Giménez, R. (2006). Beneficial effects of green tea – A review. Journal of the American College of Nutrition, 25(2), 79-99.

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