Green tea reduces the effectiveness of blood pressure medication.

A study published in the journal Clinical Pharmacology & Therapeutics (USA) on January 13, 2014, showed that drinking green tea may reduce the effects of the blood pressure medication nadolol (Corgard).

These results were obtained after researchers monitored 10 volunteers with high blood pressure, who were given a 30mg dose of nadolol per day for 14 days. The participants were divided into two groups, one group drank water and the other group drank three cups of green tea each day.

The researchers then tested the nadolol levels in their blood and found that those who drank green tea had 76% lower nadolol levels than those who drank water.

According to the American Heart Association, nadolol is a blood pressure-lowering medication, called a beta-blocker, used to treat both high blood pressure and angina, chest pain associated with heart disease.

Beta-blockers, in general, work by reducing heart rate and the workload of the heart, as well as decreasing blood output, thus helping to lower blood pressure.

The U.S. Food and Drug Administration (FDA) states that nadolol is not the only medication that interacts with food or drinks. For example, grapefruit juice and grapefruit can also interact with and reduce the effectiveness of cholesterol-lowering medications and some blood pressure medications.

According to researchers, components in green tea are believed to affect the absorption of nadolol into the intestines.

Dr. Gregg Fonarow, a professor of cardiology at the University of California, Los Angeles (USA), advises: "People who drink green tea while taking nadolol to treat high blood pressure need to be aware of the interaction and should discuss it with their doctor."

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