Green tea vs coffee: caffeine, heart health and sleep compared

FDA's table of typical caffeine in 12-ounce drinks lists 37 mg for green tea, 71 mg for black tea and 113 to 247 mg for regular brewed coffee FDA. For most adults, FDA cites 400 mg a day, about two to three 12-ounce cups of coffee, as an amount not generally linked to negative effects, though people vary widely in sensitivity FDA. Strength varies with the leaf or bean, the cup size and how long it brews, so these are typical figures, not guarantees.

Caffeine is also why coffee has the better evidence for alertness. Low to moderate doses, from about 40 mg to 300 mg, improve alertness, vigilance, attention and reaction time Mclellan 2016. A cup of green tea sits at the low end of that range; a mug of coffee sits well into it.

Green tea. A meta-analysis of 14 trials (1,136 people) found green tea beverages or extracts lowered total cholesterol by 7.2 mg/dL and LDL by 2.2 mg/dL Zheng 2011. Pooling 13 trials (1,367 people), green tea lowered systolic and diastolic blood pressure by about 2 mmHg eachPeng 2014. NCCIH notes that most cholesterol trials tested extract supplements rather than the drink NCCIH, and a 2020 meta-analysis of 14 trials of green or black tea drinking for 4 to 24 weeks found no significant effect on blood pressure or blood lipids Igho 2020.

Coffee. An umbrella review of 201 meta-analyses of observational studies found coffee more often linked with benefit than harm. At three to four cups a day versus none, risks were lower for cardiovascular disease (15%), cardiovascular death (19%) and death from any cause (17%). The authors stressed that randomized trials are needed to know whether coffee causes any of this Poole 2017.

So neither drink earns more than a limited grade for the heart. Green tea's effects are measured but small; coffee's links are larger but come from studies that cannot rule out other differences between coffee drinkers and non-drinkers.

How you make coffee matters for cholesterol. A meta-analysis of 14 trials found unfiltered coffee, such as boiled coffee, raised total and LDL cholesterol, while filtered coffee caused very little increaseJee 2001.

In people with high blood pressure, 200 to 300 mg of caffeine raised blood pressure by about 8 mmHg systolic and 6 mmHg diastolic, starting within an hour and lasting at least three hours. In trials of two weeks of regular coffee, blood pressure did not rise compared with decaf or a caffeine-free diet, and cohort studies found no link between habitual coffee and heart disease in this group Mesas 2011. If you have high blood pressure, the heart health page covers what to discuss with your clinician.

In a controlled study, 400 mg of caffeine taken at bedtime, three hours before or six hours before all disturbed sleep compared with placebo, and the authors advised avoiding substantial caffeine for at least six hours before bed Drake 2013. That dose is about two to three 12-ounce cups of coffee FDA, but smaller amounts add up through the day. If sleep is a problem, switching an afternoon coffee to green tea, or to a caffeine-free herbal infusion, is an easy experiment; the sleep page has more.

Green tea. NCCIH reports no safety concerns for green tea as a drink for adults, apart from its caffeine. Extract supplements are different: they can cause nausea, constipation, stomach discomfort and raised blood pressure, and liver injury has been reported, mostly with extract tablets or capsulesNCCIH. Green tea also sharply lowered blood levels of the beta-blocker nadolol in a two-week study of 700 mL a day Misaka 2014; see green tea and nadolol.

Coffee. FDA lists a fast heart rate, palpitations, sleep problems, anxiety, jitters, upset stomach, nausea and headache as signs of too much caffeine FDA. In pregnancy, ACOG says moderate caffeine, under 200 mg a day, does not appear to be a major factor in miscarriage or preterm birth Acog 2010, and the coffee umbrella review linked high intake in pregnancy with low birth weight and pregnancy loss Poole 2017. Green tea's caffeine counts toward the same limit. If you take levothyroxine, see levothyroxine and coffee.

Both are in every supermarket. For a wider choice of loose-leaf or decaffeinated green teas, iHerb carries a broad range.