Tea is an ancient drink that is made by steeping the leaves of the Camellia sinensis plant in boiling water. The resulting drink contains active ingredients such as caffeine, flavonoids and fluoride. Many health benefits have been linked to regular tea consumption, including one observational study that noted an 11 percent decrease in heart attack risk for subjects drinking three or more cups of tea per day. However, excessive consumption can lead to some adverse side effects.
According to Brown University, black and green teas both average 40 mg of caffeine per cup. While the average American consumes around 200 mg of caffeine per day and the caffeine in tea is only about half that of a single cup of coffee, consuming too much caffeine still can lead to negative side effects. If you drink a lot of tea per day, you may develop a caffeine dependency, find it difficult to concentrate or feel jittery, restless or experience disruptions in your sleeping pattern.
Increasing your daily tea consumption can have significant health benefits. The Linus Pauling Institute reports that compared with drinking one cup of tea or less per day, drinking five cups or more of green tea per day is associated with a 26 percent reduction in mortality from cardiovascular disease. Regularly drinking green or black tea also has been strongly related to reduced cancer risk in animals, but as of 2011 human trials have proven inconclusive.
Tea can affect how well some medications work, and it may be advisable if you are on medication to avoid drinking large amounts of tea without first seeking permission from your doctor. The University of Maryland Medical Center reports that drinking tea may increase the effectiveness of some antibiotics and blood-thinning medications. It may also lead to adverse side effects or reduced medication effectiveness in combinations with monoamine oxidase inhibitors (MAOIs), some chemotherapy drugs, clozapine and oral contraceptives.
Lowered Iron Absorption
Tea contains tannins, a chemical structure that is known to interfere with the body's ability to absorb iron. Colorado State University reports that tea may reduce your ability to absorb iron by 60 percent. For vegetarians or other individuals who consume a limited amount of iron in their diets, drinking a lot of tea per day could exacerbate the already existing risk of iron deficiency.
- Linus Pauling Institute; Tea; Jane Higdon, Ph.D.; January 2005
- University of Maryland Medical Center; Green Tea; David Zieve, M.D., M.H.A. et al.; September 2010
- Brown University: Caffeine
- Columbia University; Herbal Teas Tame the Munchies, but Are They a Healthy Substitute?; December 2004
- Colorado State University Extension; Iron--An Essential Nutrient; J. Anderson and C. Fitzgerald; June 2010