Drinking three to four cups of coffee daily, without sugar or cream

Cost: Making coffee at home costs just one or two yuan per day. It takes only a few minutes to brew a cup, so it doesn’t take up much time at all.
In plain terms: People who drink three to four cups of coffee each day have a roughly 17% lower chance of dying during the same period compared to those who don’t drink coffee at all.
Benefit: One review combined results from 201 separate studies; all of these original studies simply recorded data without any subgroup analysis. The overall finding was that daily coffee drinkers (3–4 cups) faced a 17% lower risk of death than non-drinkers (relative risk 0.83, 95% CI 0.79–0.88 — this is a reliable range).
Evidence grade: A
Sources:Poole R, Kennedy OJ, Roderick P, et al. (2017). Coffee consumption and health: umbrella review of meta-analyses of multiple health outcomes. BMJ, 359, j5024. https://doi.org/10.1136/bmj.j5024
Notes: There is some debate here: the original authors pointed out that almost all evidence comes from observational tracking studies, and they also noted that “reliable randomized controlled trials are needed to confirm a causal link.” In other words, to prove causation, participants would need to be randomly assigned to either a coffee-drinking or non-drinking group. For this benefit to apply, coffee should be consumed black; adding sugar or cream negates these positive effects. This recommendation does not apply to pregnant women, or to people suffering from arrhythmia, anxiety, or insomnia.