Green tea is mostly safe for adults when consumed in moderation. But people with low tolerance to caffeine, stomach problems, iron deficiency, pregnant or nursing women, people with anemia, anxiety disorders, bleeding disorders, heart conditions, diabetic, liver disease and osteoporosis should not consume green tea as it may have side-effects.
It gained quick prominence in the West because of its purported health benefits, weight loss being one of the popular ones. Some of these health benefits are backed by studies while some are not.
Side Effects of Green Tea
Like all teas, green tea also contains caffeine; excessive caffeine intake can lead to or aggravate a variety of problems, including the following:
Iron Deficiency and Anemia
Green tea seems to reduce the absorption of iron from food. Drinking very high doses can actually be fatal. It can also reduce the bioavailability of non-heme iron. Non-heme iron is the primary type of iron in eggs, dairy and plant foods such as beans. A 2001 study reports that green tea extract reduces the absorption of non-heme iron by 25%. However, vitamin C increases non-heme iron absorption, so you can squeeze lemon into your tea or consume other vitamin-C rich foods such as broccoli, with your meal.
Stomach Problems
The tannins present in green tea increase stomach acidity that may cause stomach ache, nausea, or constipation. For this reason, green tea is not consumed on an empty stomach in Japan and China.
It is best to drink green tea after a meal or in-between meals. People with peptic ulcers or acid reflux should not consume green tea excessively. A 1984 study concluded that tea is a potent stimulant of gastric acid, which can be reduced by adding milk and sugar.
Green tea is best brewed with water between 160 and 280°F. Excessively hot water may cause heartburn or an upset stomach.
If you have an iron-deficiency like anemia, then its best if you would consume tea between meals.
Serious Headaches:
According to a research it has been learned that caffeine is a risk factor for chronic daily headache onset.
Sleep Problems, Nervousness and Anxiety
Caffeine exerts obvious effects on anxiety and sleep which may vary according to individual sensitivity to methylxanthine. It blocks sleep-inducing chemicals in the brain and increases adrenaline production.
Vomiting:
Because caffeine affects the movement of food through the food pipe, alternating contraction and relaxation of the food pipe muscles can cause nausea.
Diarrhoea
Caffeine has a laxative effect. It contributes to peristalsis (the movement of food through the digestive system). It stimulates the colon muscles to contract and then relax, which results in an increased need to move your bowels.
Irregular or Accelerated Heartbeat
Caffeine in green tea might cause an irregular heartbeat. It also stimulates the heart muscles to contract when at rest.
Muscle Tremors and Contractions
By regulating calcium ion channels within cells, caffeine forces skeletal muscle contractions.
Dizziness
Caffeine can decrease the flow of blood to the brain, leading to dizziness and motion sickness.
Heartburn
Caffeine increases the release of acid in your stomach. This causes discomfort similar to heartburn.
Diabetes
Caffeine in green tea might interfere with blood sugar control. If you drink green tea and have diabetes, monitor your blood sugar carefully.
High Blood Pressure
The caffeine in green tea might increase blood pressure in people with high blood pressure. However, this does not seem to occur in people who regularly drink green tea or other products that contain caffeine.
