Green Tea Aficionado – Ingredients and Safe Dosages

Green tea leaves contain various quantities of polyphenols (mainly catechins), caffeine, theanine, theobromine, theophylline, and phenolic acids. The primary polyphenol of green tea is epigallocatechin gallusan (EGCG). A single cup of 250 ml holds between 50 and 100 mg EGCG. The caffeine content ranges between 22 and 40 mg per cup. While the infusion of the leaves is safe for healthy adults in moderate amounts, green tea extract supplements should be taken with caution. It is best to consume only one supplement containing the respective constituent. Consuming various supplements containing the same constituent can lead to unwanted side effects caused by overdosing.

Iron deficiency can be caused by disruptions in iron absorption in the digestive tract, chronic bleeding, or insufficient intake in the diet. Some components of green tea can make it difficult to absorb this element in the intestines. It happens that regularly drinking green tea in large quantities can lead to anemia, as in the case described in 2016 in the journal "Clinical Case Reports". A 48-year-old businessman with high blood pressure and type 2 diabetes was diagnosed with anemia due to iron deficiency. The cause was the long-term consumption of more than 1,5 liters of green tea per day during work. The patient was given iron supplementation, but after some time, a low level of hemoglobin in the blood was observed again. It turned out that the man had returned to drinking green tea during business meetings. Green tea contains phenolic compounds that can interfere with the growth of iron hemoglobin in the intestine, both hematic and non-hematic (S. Samman and colleagues, 2001). A balanced diet and moderate consumption of green tea do not put you at risk of iron deficiency. However, people diagnosed with iron deficiency who orally supplement this nutrient should be careful when using green tea. It is important to maintain an appropriate distance between taking the supplement and drinking tea (about 1.5-2 hours). In a study of 3200 school-age children in India, a high percentage of them had anemia, especially those who did not eat meat and did not take iron and folic acid supplements. A correlation was found between the occurrence of anemia and the habit of drinking tea with meals (P. S. Rakesh and colleagues, 2015).

There is evidence to suggest that green tea may reduce the bioavailability of folic acid (N. C. Alemdaroglu et al. 2008). Consuming 0.4 mg of folic acid with 250 ml of green tea reduced the maximum folic acid concentration in the blood by almost 40% compared to taking the same amount with water. This information is particularly important for pregnant women who are supplementing with folate. During pregnancy, folic acid and in many cases iron supplementation is necessary. Their absorption may be disrupted by drinking green tea or taking supplements with its extract. Additionally, due to its caffeine content, consumption of green tea should be limited during pregnancy. The maximum daily dose of caffeine for pregnant women should not exceed 300 mg.

If we consume green tea and supplements containing its active ingredients, it is important to consider the potential interactions that green tea may have with medications taken. Animal studies have shown that catechins in green tea can have a significant effect on the action of enzymes involved in drug metabolism. They may inhibit or enhance their action (C. S. Yang et al., 2012). Interactions of green tea with drugs may lead to increased or decreased blood levels, leading to a risk of an increased concentration of the drug or a weakened antidote. There is a high risk of interactions occurring with the following medications. If someone is taking one of them, they should consult with their doctor before taking green tea extracts at the same time. - Adenosine - Medications used to treat asthma - Medications used to treat depression and mental disorders - Medications affecting blood clotting, such as Aspirin, clopidogrel, diclofenac, naproxen, heparin - Medications used to treat cancer - Estrogen and contraceptive pills - Antibiotics and antifungal medications.

According to a systematic review, for an adult with a healthy liver, the secure daily dosage of EGCG is at least 300 mg (equivalent to 3-6 cups of tea). In the European Union, the average daily consumption of green tea steamed EGCG is 90-300 mg (J. Hu et al., 2018). In line with EFSA's opinion on the safety of consumption, studies indicate that regular intake of a daily dose equal to or greater than 800 mg EGCG in the form of a dietary supplement may result in an increase in serum concentration of transaminases (liver enzymes), leading to liver disorders. An illustration of such a case is a middle-aged man who, after several weeks of regular intake of green tea extract, suffered irreversible liver damage requiring organ transplantation (BBC News, 2020). Over 80 cases of liver damage due to the consumption of green tea supplements have been reported worldwide (BBC News, 2020). Despite this number being relatively small in comparison to millions of people using these supplements, it still serves as evidence of the existence of a risk. Any supplementation should be discussed with a doctor or a nutritionist.