Although rare, allergic reactions to green tea may occur. Stop taking green tea and seek emergency medical attention if you experience symptoms of a serious allergic reaction including difficulty breathing; closing of your throat; swelling of your lips, tongue, or face; or hives.
Interactions between green tea and other prescription or over-the-counter medicines or herbal/ health supplements may also occur. Talk to your doctor, pharmacist, or health care professional before taking green tea if you are taking any other medicines or supplements.
Overconsumption may cause irritability, insomnia, nervousness, and tachycardia. Because studies on its possible teratogenic effect are inconclusive, caffeine consumption is contraindicated during pregnancy. Lactating women should also limit caffeine intake to avoid sleep disorders in infants.
One cup of tea typically contains 2 to 3 grams of leaves. Some people can brew as much as 15 grams in an 8-ounce (or 225 millimetres) cup. If you have a weak stomach, that is not a good idea.High strength tea contains concentrated caffeine and polyphenols. Caffeine can cause insomnia. Polyphenols can over-stimulate the production of gastric acids and cause stomach upset.
One of the most commonly recognized green tea side effects is insomnia. Since green tea contains caffeine, it stimulates the central nervous system and causes sleeplessness. Aside from this, caffeine also acts as a diuretic and can aggravate urge incontinence, increases the production of stomach acid, causes constipation due to the tannin component in tea, increases heart rate and blood pressure, and increases blood sugar levels.
Green tea does have some side effects but most come from the caffeine. One 6 oz. cup of green tea contains approximately 30 mg. of caffeine. People who are caffeine sensitive should take green tea supplements instead of brewing their own tea. More than 6 cups of green tea daily can cause sleeplessness, irregular heart beat, diarrhea, vomiting, dizziness, headaches, and loss of appetite.People with heart conditions, anxiety, panic attacks, kidney disease and sensitive stomachs should be cautioned about ingesting green tea.
While caffeine leads to a temporary increase in blood pressure, there is no evidence that ingesting it can lead to heart disease or hypertension.
There is evidence to suggest that tea inhibits absorption of iron. For most people, this is not a problematic. For anyone with an iron deficiency, however, this means that you might need to limit your intake.
The problem of green tea during pregnancy is that the EGCG molecules are structurally similar to a compound called methotrexate. Methotrexate is able to kill cancer cells by chemically bonding with an enzyme in the body called enzyme dihydrofolate reductase (DHFR). Healthy people have this enzyme also - it is part of what is called the folate pathway, which is the pathway, or steps, the body takes to transform nutrients like folate into something that can be used to support its normal functions.
Stomach upset, diarrhea and constipation may occur. If any of these effects persist or worsen, contact your doctor promptly. Unlikely but report promptly: fast or irregular pulse, trouble sleeping, restlessness, tremors, mental/mood changes. If you notice other effects not listed above, contact your doctor or pharmacist.
If you drink more than 5 to 6 cups of green tea daily you may experience sleeplessness, irregular heart beat, dizziness, diarrhea, vomiting, headache, loss of appetite or other caffeine-related side effects.
