Fiona Macrae Science Correspondent Published: January 13, 2014 11: 44 EDT | update: January 13, 2014 15: 22 EDT, a health option for many people with high blood pressure.
But green tea can actually stop their pills from working properly.
A study found that the effect of lowering drug nadolol after drinking green tea was poor.
The researchers recommend that people taking nartolol not drink green tea and warn that this popular drink may also dilute the effects of some other drugs.
This warning is particularly relevant for people with blood pressure, as some may switch to green tea to reduce caffeine intake.
In addition, some studies suggest that green tea can lower blood pressure.
Japanese researchers measured blood pressure in 10 healthy men and women after taking nadolol.
They took the drug twice, once after drinking two cups of green tea a day for two consecutive weeks, and once after drinking water.
Drinking green tea can reduce the amount of drugs entering the blood by 3-quarters.
This also means that the drug is less effective in lowering blood pressure, which is also used to treat coronary heart disease and irregular heartbeat and prevent migraine.
It is believed that the plant chemicals in green tea prevent nadolol from entering the blood from the intestines, in which it can start to lower blood pressure.
They wrote in the journal Clinical Pharmacology and Therapeutics: "Patients with nadolol should avoid taking green tea.
Researchers from Fukushima Medical University only tested nadolol.
However, they speculate that green tea may have a far-reaching effect on the pollen fever drug, non-Sofina.
Sotiris alimiou, a member of the Royal Pharmaceutical Association, said blood pressure drug celiprolol could also be weakened.
It and nadolol are part of the Beta
The blocking Family of Blood pressure drugs.
Mr. Antonio, a consultant pharmacist, said: "The patient knows that there are other beta-
Inhibitors such as bisool and attiol are considered not to be affected by this effect.
If patients have any concerns and drink a lot of green tea, they should discuss it with the community pharmacist.
Green tea is far from the first food or drink to interfere with the drug, and orange, apple, and grapefruit juices can prevent some of the tabletting, hay fever pills and antibiotics from working properly.
Blood-diluted warfarin is particularly sensitive, with dozens of drugs and foods including broccoli, brussels sprouts and cranberry juice at risk.