Green tea may sabotage blood pressure medication

Green tea chemicals linked to reducing the risk of cancer and cardiovascular disease may also thwart a blood pressure medication by preventing it from getting into the bloodstream.

In a preliminary study, researchers gave 10 healthy adults the blood pressure medication nadolol after the volunteers drank about two glasses of green tea a day for two weeks and again after they stopped drinking tea for two weeks. Compared with taking the medication after they avoided drinking tea, the volunteers had just 24 percent as much nadolol in their blood after consuming tea, the researchers found. What’s more, after drinking tea, the drug was less effective at lowering blood pressure.

In lab-dish studies, the team, led by Shingen Misaka of Fukushima Medical University in Japan, found that antioxidants in green tea called catechins shut down the cellular machinery that pumps nadolol into cells.

The findings, appearing January 13 in Clinical Pharmacology & Therapeutics, suggest that green tea catechins may block uptake of nadolol in the intestines, where the drug gains access to the blood stream.