Green tea is known as a drink rich in antioxidants, helping to reduce the risk of heart disease, support weight control and improve brain health. However, if consumed excessively, this benefit can turn into a health risk.
According to Dr. Kelli McGrane, a nutritionist in the US, Most of the benefits of green tea come from drinking 2-3 cups a day. Exceeding this figure, especially over 56 cups, high caffeine and tannin levels can cause unwanted side effects.
One of the most common side effects is anxiety, insomnia and headaches. The amount of caffeine in green tea stimulates the central nervous system, making sensitive people susceptible to anxiety, heartbeat or difficulty sleeping. According to the Mayo Clinic, high doses of caffeine can also cause shaking, stress, and reduce sleep quality.
In addition, digestive problems are also common. Theannin in green tea increases the amount of acid in the stomach, causing nausea or indigestion, especially when drunk on an empty stomach. Research from the National Institutes of Health (NIH) also shows that tannins can bind to iron in food, reducing the ability to absorb this mineral, leading to the risk of iron deficiency anemia, especially in pregnant women or people with low-irone diets.
Some studies have also recorded cases of liver damage when using high doses of green tea extract. Dr. Herbert Bonkovsky from Wake Forest Medical Center (USA) warns: "Catechins, especially EGCG, when accumulated in excess, can cause hepatitis or liver damage in some sensitive people". Although these cases are rare, they show the importance of taking them in moderation.
For people with heart disease or high blood pressure, consuming too much green tea also has potential risks. Caffeine can increase your heart rate, cause sessioniness, or cause sudden changes in blood pressure. According to Johns Hopkins Medicine, those who are taking anticoagulants or cardiovascular drugs should be cautious, as some compounds in green tea can interact with drugs, reducing treatment effectiveness or increasing the risk of bleeding.
To limit side effects, experts recommend drinking green tea in moderation, about 23 cups per day and avoiding drinking it in the evening so as not to affect sleep. People with liver problems, anemia or pregnant women should consult a doctor before increasing their intake.
Green vegetables are a great part of a healthy diet, but the benefits will only be maximized when we drink them in moderation, Dr McGrane emphasizes. Too much, even if it is a good thing, can still become a problem".
