How many cups of green tea do you need per day?

Two to three cups of green (or other) tea per day appears to be the sweet spot. An umbrella analysis of 96 meta-analyses covering forty different health outcomes found the strongest association with lower risks of premature death, heart disease, stroke and type 2 diabetes at that amount. This is observational research: cause and effect have not been proven, but the pattern is remarkably consistent.

Every additional cup does help a little. A meta-analysis of 21 studies involving more than 1.3 million people showed that each cup per day lowers the risk of dying from cardiovascular disease by around 3%. At three cups, that amounts to a reduction of roughly 15%. Above five cups the benefit levels off and the additional gain barely increases. The authors themselves label the quality of evidence as 'low' (GRADE), so do not draw firm conclusions from it.

For people who specifically want to do something about their blood pressure: randomised trials in humans show that green tea lowers both systolic and diastolic blood pressure by just over 1 mmHg on average. That is modest. The effect appears somewhat larger in people who already have elevated blood pressure. Green tea works here as a supplementary measure, not as a replacement for blood-pressure-lowering medication.

Two cups per day already provides enough of the active plant compounds (flavonoids) to favourably influence blood pressure, LDL cholesterol and inflammatory markers, concluded an umbrella review of 23 systematic reviews. Normal consumption appears safe. Only at high doses as a supplement can you experience stomach complaints, and in rare cases liver damage has been reported.

One note about temperature: tea consumed at temperatures above roughly 55 to 60 degrees Celsius is associated with a higher risk of oesophageal and stomach cancer. So let your tea cool down a little before drinking.