Side Effects of Green Tea Supplements

Green tea has long been hailed as a nutritional "superfood" that combats cancer, diabetes, liver disease, and high cholesterol; aids in weight loss; and even cures tooth decay. Scientific evidence supports most of these claims. However, studies also show that the consumption of green tea supplements can cause a wide range of harmful side effects, particularly when too much is taken, when there are interactions with certain medications, or when pre-existing medical conditions exist.

Caffeine

• Green tea is rich in caffeine, which may cause insomnia, irritability, dizziness, heart palpitations, headaches, vomiting, and/or diarrhea, especially when consumed in excessive amounts.

Interactions with Medications

• Green tea contains substances that may interact with medications. Many of these interactions simply inhibit the effectiveness of the medication, i.e. adenosine, benzodiazepines, clozapine, and lithium. Other interactions may be harmful. Medications that have been shown to have harmful interactions with green tea include blood thinners such as aspirin, ephedrine, and monoamine oxidase inhibitors (MOIs).

Other Considerations

• Women who are pregnant should avoid green tea, because it inhibits the action of folate, a vitamin that prevents neural tube defects in unborn babies. Green tea may also exacerbate many pre-existing medical conditions, including ulcers, kidney and heart problems, and psychological issues like depression and anxiety.