Tea is, other than water itself, the oldest beverage on the planet. Its health effects are always the focus of medical studies and, in the past few years, it has been green tea’s protective effects against cancer under the microscope. But here, we look at the strange but true effects of tea on blood pressure.
The immediate and long-term effects of drinking tea on blood pressure are quite different.
Effects of Drinking Tea on Blood Pressure
The acute, or relatively immediate, effects of drinking green tea and black tea at a dose equivalent to four standard cups were tested in 20 men with normal blood pressure. Both green and black tea raised systolic and diastolic blood pressure 30 and 60 minutes later:
- Green tea: Systolic blood pressure rose 5.5 mmHg (as much as 12.4 mmHg); diastolic blood pressure rose 3.1 mmHg (as much as 6.3 mmHg).
- Black tea: Systolic blood pressure rose 10.7 mmHg (as much as 17.4 mmHg); diastolic blood pressure rose 5.1 mmHg (as much as 8.4 mmHg).
However, 24-hour blood pressure measurements did not show any significant increase, so it seems that tea’s immediate effect is to raise blood pressure, but only temporarily.
The effects of long-term tea consumption on blood pressure using a biomarker of exposure to tea-derived chemical polyphenols were studied in 218 women over 70 years old. The average tea intake in these women was 525 milliliters (ml) or two cups daily.
In these women, the mean systolic blood pressure was 138 mmHg and diastolic blood pressure was 73.5 mmHg. The study shows that one cup of tea was linked to a 2.2-mmHg drop in systolic blood pressure and a 0.9-mmHg drop in diastolic blood pressure.
The effect of tea consumption on the risk of high blood pressure was studied in 1,507 subjects over age 20 without a history of high blood pressure. In this study, 39.8% of the subjects were habitual tea drinkers, namely drinking 120 ml (or half a cup) or more of tea per day.
When compared to non-habitual tea drinkers, the risk of developing high blood pressure dropped by 46% in those who consumed a half-cup to two cups a day. This risk was furthered reduced by 65% in those who drank more than two cups a day.
The effects of hibiscus tea on blood pressure were studied in 65 individuals with either pre- or stage-one high blood pressure who were not taking medication. They had either one cup a day of brewed hibiscus tea or a placebo for six weeks. Compared with placebo, hibiscus tea lowered systolic blood pressure by 7.2 mmHg. The change in diastolic blood pressure was not different from that of the placebo group.
Moreover, those with a higher systolic blood pressure at baseline showed a greater response to hibiscus’ effects. The authors speculated that the blood-pressure-lowering effect of hibiscus tea could be due to the flavonoid chemicals it contains. This herbal tea contains chemicals that have been shown in animal studies to dilate blood vessels, inhibit angiotensin converting enzyme (ACE), and increase sodium excretion by the kidneys.
Overall, it seems that regular tea consumption will likely help lead to a moderate drop in blood pressure.
Here are the previous parts of this blood pressure series:
What You Need to Understand About Blood Pressure
The Doctors’ Solution for Hypertension
DASH to Lower Your Blood Pressure
Four Minerals to Combat High Blood Pressure
The Protein to Lower Blood Pressure
Two Red Foods That Will Drop Blood Pressure
Can This Sweet Treat Drop Your Blood Pressure?