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Green Tea

Posting Date: 08/26/2002

People with ulcers, heart rhythm problems, and clinical anxiety disorders should minimize their intake of caffeine.

Adverse Effects

People who drink excessive amounts of green tea may get too much caffeine. High concentrations of caffeine (hard to achieve with moderate green tea intake) can result in rapid heart rate or altered heart rhythm (PVC), excess fluid elimination, jitteriness, and insomnia.

Chronic use of caffeine can lead to symptoms of headache, sluggishness, and irritability upon withdrawal. Withdrawal has been reported in people who stop drinking as little as two or three cups of coffee daily and therefore might be anticipated in people who suddenly stop drinking many cups of green tea (five or six daily).

Possible Interactions

The tannins in tea can interfere with the absorption of non-heme iron (iron supplements, for example) taken at the same time. Milk added to black tea can reduce the binding capacity of tannins. (Milk is rarely if ever added to green tea.)

Caffeine (65 mg) can increase the analgesic effects of aspirin or acetaminophen.

Antibiotics such as Cipro, Noroxin, or Penetrex, and the ulcer drug Tagamet (cimetidine) can increase the stimulant effects of caffeine. Combining tea with a medication containing theophylline or caffeine could result in too much caffeine and resulting nervousness or insomnia.