Black tea may help reduce night-time fluctuations in blood pressure, according to an Australian study published in 2013 in the American Journal of Clinical Nutrition.
For six months, 111 people (ages 35 to 75) drank three cups a day of either black tea or a placebo beverage, which looked like tea and contained the same amount of caffeine. The tea drinkers experienced an immediate and sustained reduction in blood pressure variability at night, but not during the day.
Prior research has found that tea can lower blood pressure slightly. However, the decrease in variability seen in the new study was independent of any effect on blood pressure itself. There’s increasing evidence that variability in blood pressure is a risk factor for cardiovascular disease. The researchers attributed this benefit to flavonoids in the tea.