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Contraindications of green tea

Health & FitnessContraindications of green tea

Green tea as an infusion has been drunk for centuries in many Asian countries. Today it is – together with coffee – one of the most consumed beverages in the world. Some choose it for its taste and others for its properties.

In any case, it is important to know that there are also contraindications in the consumption of green tea.

Therefore, it is advisable to avoid or moderate its consumption, as its excessive use could have negative effects. Do you want to know more about it? Below, we tell you in which cases it is better to avoid its intake and how to consume it safely.

Green tea: an ancient and beneficial beverage

In many Western countries, green tea can be considered a novelty drink. However, in the East, its use and cultivation dates back centuries. Today, the main producing countries are China and India, followed by Sri Lanka, Kenya and Indonesia.

Green tea (like black or oolong) comes from the Camellia sinensis plant. In this case, it is an unfermented tea, so it keeps some of its active ingredients intact. Its leaves are picked fresh and then rolled and dried.

In China, it has always been considered a medicinal infusion. In particular, it is noted for its content of vitamins, minerals, caffeine, polyphenols, as well as catechins with antioxidant capacity.

Human studies suggest that it may contribute to reduce the risk of some diseases, such as cardiovascular diseases and some types of cancer. It also promotes oral health, is neuroprotective and helps increase bone mineral density.

This places it within the group of functional foods and beverages. Research is promising, but more evidence is needed to understand its contributions to health and thus to formulate advice on its consumption.

Moreover, as we have mentioned, their consumption is not always adequate and in excess could have some harmful effects. Which ones? In the following space we detail them.

Main contraindications of green tea

Although green tea contains nutrients that contribute to well-being, in certain cases it is better to avoid its consumption.

Iron deficiency anemia

As with coffee, green tea interferes with the absorption of iron. This happens both in the case of non-heme iron (which comes from vegetables) and heme iron (provided by animal sources).

For this reason, its excessive intake could cause iron deficiency anemia due to absorption problems. In this sense, it is advisable to avoid it or to consume it far from meals in case of having anemia or tendency to suffer it.

Problems in falling asleep

Drinks containing caffeine are not the most suitable for people who have difficulty sleeping. This is what the experts of the Sleep Foundation point out, based on data from scientific studies.

Adenosine is a chemical substance produced in the brain that promotes sleep. Caffeine has the capacity to block it and, when this happens, people remain alert and vigilant for a longer period of time.

It has also been discovered that caffeine interferes with the circadian rhythms of melatonin. Therefore, if tea or other caffeinated beverages are consumed close to bedtime, sleep onset is delayed.

Anxiety symptoms

Apart from insomnia problems, excessive caffeine intake is also related to anxiety and the nervous system. Moreover, the American Psychiatric Association notes the existence of four caffeine-related disorders:

  • Caffeine intoxication.
  • Caffeine withdrawal.
  • Some non-specific disorders.
  • Caffeine-induced problems, such as anxiety and sleep disorder.

When caffeine amounts are very high, the effects due to adenosine blockade are multiplied. And then anxiety symptoms may appear. People with panic disorder or social anxiety disorder may be especially sensitive.

Key warning signs include the following:

Sleeping difficulties.
Gastrointestinal problems.
Increased heart rate.

Negative effects on the liver

One of the most abundant active ingredients in tea are catechins. Among them, epigallocatechin-3-gallate (EGCG) stands out, excessive intake of which has been linked to possible liver damage.

Indeed, as concluded by a special panel of the European Food Safety Authority (EFSA), there is scientific evidence of these. To be more precise, an increase in transaminases is observed in some people after ingestion of doses higher than 800 milligrams of EGCG.

However, it should be noted that this same group of experts considers that the intake of infusions prepared in the traditional way and reconstituted beverages are safe, since they provide levels of EGCG that are not ingested in the traditional way.

Other contraindications of green tea

Often, contraindications about green tea consumption refer to large doses or improper use of supplements. In general, the intake of infusions is considered safe for most healthy adults. However, there are some groups of people in whom its consumption is discouraged.

People with caffeine sensitivity

Susceptibility to this component may vary among people. For those who are to a high degree it is best to avoid consumption of green tea and other types of caffeinated beverages.

Taking medication

The active ingredients in green tea may interact with some drugs or other supplements. Some examples are ephedrine or theophylline. So in case of following a medication regimen, it is preferable to consult a doctor to avoid possible harm.

Pregnancy and lactation

For pregnant women, the American Medicines Agency considers it safe to drink less than 6 cups of green tea a day. However, the same organization cites studies showing that pregnant women who consume it have lower blood folate levels.

Folic acid is considered a critical nutrient because of its ability to reduce the risk of neural tube defects. For this reason, it may be prudent to avoid green tea during pregnancy. In addition, during lactation, it is advisable to consult with a physician to ensure adequate intake.

Children and adolescents

The American Academy of Child and Adolescent Psychiatry notes that there is no dose of caffeine considered safe for minors. In general, pediatricians advise against its consumption in children under 12 years of age. They also propose limiting the maximum amount to 100 milligrams per day for 12 to 18 year olds.


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