Health effects of tea

In clinical research conducted during the early 21st century, the health effects of tea has been widely studied.

Black tea is considered likely effective for improving alertness and possibly effective for certain conditions such as low blood pressure, but evidence does not support its effectiveness for preventing several types of cancer or diabetes; there is currently limited high-quality scientific evidence supporting most specific therapeutic uses of black tea. The United States Food and Drug Administration has approved a topical ointment formulated with a specific green tea extract for the treatment of external genital and perianal warts; although green tea and its extracts have been widely studied, the evidence remains inconclusive overall, with only modest or inconsistent benefits observed.

Two reviews of randomized controlled trials concluded that long-term consumption of black tea slightly lowers systolic and diastolic blood pressures (about 1–2 mmHg), a finding based on limited evidence. A 2013 Cochrane review found some evidence of benefit from tea consumption on cardiovascular markers (total and LDL cholesterol).

In regions without access to safe drinking water, boiling water is effective for reducing waterborne diseases by destroying pathogenic microorganisms, and this water can be used to make tea.