11 potentially harmful side effects of improper use of green tea:

---

-Stomach Issues-
Green tea may cause stomach irritation when brewed too strongly or consumed on an empty stomach

(1). Green tea contains tannins that can increase the amount of acid in your stomach. Excess acid can lead to digestive issues including constipation, acid reflux, and nausea. Brewing green tea with water that is too hot can exacerbate these side effects. Brew your green tea with water between 160 and 180 F.

Green tea can also cause diarrhea when consumed in large amounts. Caffeine produces a laxative effect as it stimulates the colon muscles to contract and release more frequently. This results in more frequent trips to the bathroom and can cause upset stomach. If you suffer from irritable bowel syndrome, avoid green tea.

To avoid these side effects, do not drink green tea on an empty stomach. Instead, consume green tea after each meal. If you suffer from acid reflux disease, stomach ulcers, avoid green tea since it can increase acidity.

-Headaches-

Green tea can cause headaches in certain individuals since it contains caffeine

(2). People who suffer from migraines can consume green tea occasionally. However, you should avoid drinking green tea every day if you suffer from daily headaches. If you have caffeine sensitivity, avoid drinking green tea.

Green tea contains a compound that is antithetical to sleep: caffeine.

Green tea contains only small amounts of caffeine, but may still cause problems sleeping for people sensitive to caffeine. This is due to the fact that chemical compounds in green tea prevent the release of hormones such as melatonin, which aid in sleep.

Green tea also contains l-theanine, a chemical that helps to induce calm, but also increases alertness and focus—something that may disrupt sleep for some individuals. Some research shows that l-theanine is beneficial for sleep; however, these studies have mainly been conducted on individuals with disorders including ADHD and schizophrenia. Additional research shows that l-theanine may aid sleep by lowering heart rate through the inhibition of glutamate receptors in the brain

(5).These benefits may be outweighed by the presence of caffeine in green tea—particularly in matcha green tea. While research shows l-theanine is beneficial for sleep, there is no agreed upon dosage for it's effectiveness in the medical community. While most people may benefit from a cup of green tea before bed, people with caffeine sensitivity should consume it no later than 5 hours before bed.

-Sleeping Problems-

Green tea contains a compound that is antithetical to sleep: caffeine. 

Green tea contains only small amounts of caffeine, but may still cause problems sleeping for people sensitive to caffeine. This is due to the fact that chemical compounds in green tea prevent the release of hormones such as melatonin, which aid in sleep.

Green tea also contains l-theanine, a chemical that helps to induce calm, but also increases alertness and focus—something that may disrupt sleep for some individuals. Some research shows that l-theanine is beneficial for sleep; however, these studies have mainly been conducted on individuals with disorders including ADHD and schizophrenia. Additional research shows that l-theanine may aid sleep by lowering heart rate through the inhibition of glutamate receptors in the brain.

These benefits may be outweighed by the presence of caffeine in green tea—particularly in matcha green tea. While research shows l-theanine is beneficial for sleep, there is no agreed upon dosage for it's effectiveness in the medical community. While most people may benefit from a cup of green tea before bed, people with caffeine sensitivity should consume it no later than 5 hours before bed.

-Risks of pregnancy and child use-

Tannins, caffeine, and tea catechins have all been linked to increased risks during pregnancy. Experts say that green tea in small amounts — no more than 2 cups per day — is safe during pregnancy and breastfeeding. Caffeine is passed through breast milk to infants so monitor your intake in coordination with your physician. Drinking more than 2 cups per day can lead to miscarriage and birth defects in children. Make sure to keep your caffeine intake below 200 milligrams per day.

-Anemia and Iron Deficiency-

Green tea contains antioxidants that hinder the iron absorption in the human body. A meta-analysis showed that this side effect can be a particularly dangerous for people who suffer from anemia or other disease where iron deficiency is present. One case study found that green tea caused anemia in a 48 year old businessman who consumed 1500 milliliters (6 cups) of green tea every weekday for years.

To avoid this side effect, add lemon to your tea. The vitamin C in lemon promotes iron absorption, counteracting this side effect. Alternatively, you can consume gren tea one hour before or after a meal. This gives your body time to absorb iron without the inhibition caused by tannins. As a precaution, avoid green tea if you have anemia.

-Vomiting-

Excessive amounts of green tea can lead to nausea and vomiting. That's because green tea contains tannins that have been linked to nausea and constipation because of the way proteins bind in the intestines. Avoid consuming more than 4 cups of green tea each day if you are a seasoned tea drinker. If you're just starting out with green tea, start with 1 or 2 cups per day and monitor your reaction. Only increase consumption if you experience no side effects.

-Dizziness and convulsions-

The caffeine in green tea can cause you to feel dizzy or lightheaded when consumed in large amounts. Caffeine decreases blood flow to the brain and central nervous system, resulting in motion sickness. In rare cases, consumption of green tea can lead to convulsions or confusion. In some cases, green tea consumption can also increase tinnitus, known as ringing in the ears. If you suffer from tinnitus, avoid drinking green tea. Always drink green tea in moderate amounts and avoid if you are sensitive to caffeine. Research shows that the maximum tolerated dose in humans is equivalent to 24 cups of the beverage  As mentioned, most of these side effects are rare and occur only when consumed in excessive amounts or in individuals sensitive to green tea ingredients.

-Bleeding Disorders-

In rare cases, green tea can trigger bleeding disorders. Compounds in green tea decrease levels of fibrinogen, a protein that helps clot blood. Green tea also prevents the oxidation of fatty acids, which can lead to thinner blood consistency. If you suffer from a blood clotting disorder, avoid drinking green tea.

-Liver Disease-

Green tea supplements and high consumption of green tea can lead to liver damage and disease.. Experts believe this is due to a build-up of caffeine that can stress the liver. To avoid this side effect, avoid consuming more than 4 to 5 cups of green tea every day.

-Irregular heartbeat & blood pressure-

Some small studies show that green tea may cause irregular heartbeat. This side effect is rare and more research is needed to examine the exact compounds behind the heart rate increase. While research shows that drinking tea can help lower blood pressure, some studies have shown that green tea may still effect blood pressure in certain individuals. One study found that green tea raised blood pressure due to the presence of caffeine.. Another study found that drinking green tea may interfere with certain blood pressure medications including Corgard.  If you suffer from heart disease, seek medical advice from your healthcare professional before consuming green tea.

-Bone Health-

Excess consumption of green tea increases the risk of bone disease such as osteoporosis in sensitive individuals. Compounds in green tea inhibit the absorption of calcium, resulting in a deterioration of bone health.. Limit your intake to 2 to 3 cups of green tea if you are predisposed to bone disease. If you consume more than that, make sure to take a calcium supplement to support bone health.

​