Although green tea consumption has been associated with a number of health benefits, but green tea can cause side effects for some people, especially if taken in large amounts.
The green tea’s health benefits are mostly due to its high flavonoids content known as polyphenols, which have antioxidant properties. The major group of polyphenols in green tea are called catechins.
Some studies indicate that green tea catechins can potentially have positive effects on weight management, cancer prevention and overall health. However, drinking too much of it is considered to be harmful. The reason for this is because green tea contains caffeine, even though it is lower than in coffee.
How Much Green Tea Is Safe To Drink Per Day?
This can be a tricky question to answer because some research shows that drinking more than 4 to 5 cups per day may have some health benefits, while some research indicates it could have negative side effects.
For example, a research conducted by Dr. Zuo-Feng Zhang, a professor of cancer epidemiology at UCLA, suggests drinking 4 to 5 cups of green tea per day may lower risk of stomach cancer. However, drinking more than 2 to 3 cups recommendation per day may significantly decrease the absorption of iron and folic acid.
In general, 2 to 3 cups per day shows to be a healthy recommendation, with possibly beneficial effects on health. Pregnant women, children or adults with heart issues should seek medical guidance before drinking green tea, as it may be harmful in some instances.
Side Effects of Green Tea
The side effects of green tea are due to the caffeine and tannins present in it, which can cause serious problems when taken in large doses.
1. Iron-deficiency anemia
Green tea contains tannins which can block the absorption of iron. If you are suffering from anemia or having problems getting enough iron in the diet, avoid drinking green tea at meal times.
These tannins can also block the absorption of folic acid, which is critical during pregnancy. For this reason, health professionals recommend limiting green tea consumption during pregnancy. In addition, drinking tea between meals seems to have little effect on iron absorption, according to the National Cancer Institute.
2. Stomach upset
The tannins present in green tea increase stomach acidity. So, if you drink green tea on an empty stomach, it may upset your stomach. In particular, people who already suffer from acid reflux are at higher risk. They might feel heartburn and irritation. So, it is best to drink green tea after a meal or between meals.
Green tea is a natural diuretic that can help flush waste materials out of your system through your urine. But, if you drink too much of green tea, it can also flush away minerals like calcium, which can lead to osteoporosis.
This usually occurs when a person consumes more than 400 mg of caffeine (about 4 to 5 cups of green tea) per day and this side effect can be reduced by taking calcium supplements or eating a diet rich in calcium.
4. Heart palpitations
Since green tea contains caffeine, excess consumption of green tea can cause heart palpitations, increased heart rate and elevated blood pressure. People with caffeine sensitivity are more susceptible to these side effects.
To mitigate these potential side effects, you can reduce the consumption of green tea or choose a low-caffeine green tea.
5. Sleep problems
Due to the caffeine contained in green tea, drinking too much green tea may lead to sleep problems such as insomnia. It may also contribute to restlessness and anxiety. To prevent these problems, you should avoid or limit green tea consumption before bedtime.
6. Drug interactions
The polyphenols present in green tea are known for their health-promoting properties. However, this substance is found to block the beneficial effect of certain drugs such as birth control pills, blood-thinning medications, and certain anti-cancer drugs.
If you are taking prescription drugs, you should check with your doctor to make sure there are no any drug interactions with green tea.