The Effects of Green Tea Overdose

A lot has been written about the benefits of green tea, but everyone who drinks it needs to be aware of the effects of green tea overdose too. If you are the kind of person who tends to think that if a little is good, more will be even better, please read on.

Green tea is good for you because it is rich in antioxidants. Antioxidants prevent the formation of free radicals in the bloodstream. Free radicals are involved in a chain reaction that results in damage to the cells of the body. Antioxidants may be beneficial in preventing certain diseases like cancer and heart disease. People who want to get plenty of antioxidants may tend to drink too much green tea.

Moderation is the key with green tea consumption, just like with anything else. One average cup of green tea contains only about half (20mg) the caffeine of that contained in an average cup of black tea (40mg). However, it is still a good idea to be aware of the amount of caffeine you are getting. Too much caffeine can cause sleepless nights, nervousness, tummy upset, nausea, diarrhea, and a lot of trips to the bathroom to urinate.

The World Health Organization has stated that a very large percentage of the world's population might be iron deficient and that about 30% are so deficient that they have anemia. Because of that, it is important to be aware that a green tea overdose can interfere with iron absorption from plant sources. The very antioxidants that are sought after for health reasons, along with the tannins in the tea, can cause decreased iron absorption. This seems to be dose dependent and should not be a problem with a few cups a day. However, it is best to enjoy your green tea between meals so that the iron you get at mealtime will be absorbed properly. Poor iron absorption from green tea can be offset somewhat by making sure the diet contains plenty of vitamin C. Vitamin C increases the absorption of the iron.

If you are taking anticoagulant (blood thinner) medications such as warfarin, you also need to know that green tea is a rich source of vitamin K. Your doctor and pharmacist should have told you to avoid changes in the amount of vitamin K you get. Because it can offset the effects of the warfarin, too much vitamin K increases the risk of clot formation. Also, if your intake of vitamin K fluctuates over a wide range, going up and down, your dose of warfarin will need to be frequently adjusted and you may run into trouble before the need for an adjustment is noticed. People on this type medication are at the biggest risk for green tea overdose.

According to the 19th century English poet, Martin Farquhar Tupper, "...the choicest pleasures of life lie within the ring of moderation." This applies to anything we do for our health, including green tea--drink it, enjoy it, but avoid a green tea overdose!

Sources:

"Dietary Supplement Fact Sheet: Iron." Office of Dietary Supplements, National Institutes of Health.

"Herbs at a Glance. Green Tea." National Center for Complementary and Alternative Medicine.

Cathy Wong. "Does Herbal Tea Interfere with Iron Absorption?" About.com Alternative Medicine.

Samir Samman, Brittmarie Sandström, Maja Bjørndal Toft, Klaus Bukhave, Mikael Jensen, Sven S Sørensen, and Marianne Hansen."Green tea or rosemary extract added to foods reduces nonheme-iron absorption." Am J Clin Nutr 2001;73:607-12.