Coffee: benefits, limits and who should cut back
Nutrition
Key points
- 3 to 4 cups of coffee a day are linked to lower all-cause mortality.
- Coffee is more often linked to benefit than harm.
- During pregnancy, limit caffeine to 200 mg a day.
- Avoid coffee late in the day: it disrupts sleep.
What the research shows
Umbrella review. An analysis of 201 meta-analyses of observational studies and 17 of clinical trials found that coffee was more often linked to benefit than harm. The largest reduction in relative risk of death from any cause was seen at 3 to 4 cups a day, and coffee was also linked to lower risk of cardiovascular disease, several cancers and liver disease (Poole et al., 2017).
Safety. A systematic review of caffeine safety concluded that up to 400 mg a day is not linked to adverse effects in healthy adults, and up to 300 mg a day in healthy pregnant women (Wikoff et al., 2017). U.S. obstetricians (ACOG) advise staying under 200 mg a day during pregnancy.
Sleep. A meta-analysis found that caffeine shortened total sleep by about 45 minutes and lowered sleep efficiency. To avoid that effect, it recommended a cutoff about 8.8 hours before bedtime for a standard cup of coffee (Gardiner et al., 2023).
Who should cut back
- pregnant women;
- people with anxiety, insomnia or palpitations;
- women at higher risk of fractures;
- people with uncontrolled high blood pressure.
In practice
- Count all sources: coffee, tea, soda, energy drinks, pre-workout supplements.
- Have your last cup by early afternoon.
- Skip the syrups and whipped cream: a sweetened coffee drink can contain as much sugar as a can of soda.
Frequently asked questions
How much caffeine is in a cup of coffee?
An 8-ounce cup of brewed coffee has about 80 to 100 mg. Large coffee-shop drinks can contain 300 mg or more.
Does decaf have the same benefits?
Many studies found similar associations for decaf, suggesting that compounds other than caffeine play a role.
Sources
- Poole et al. (2017). Coffee consumption and health: umbrella review of meta-analyses of multiple health outcomes. BMJ :j5024. doi:10.1136/bmj.j5024
- Wikoff et al. (2017). Systematic review of the potential adverse effects of caffeine consumption in healthy adults, pregnant women, adolescents, and children. Food and Chemical Toxicology 109:585-648. doi:10.1016/j.fct.2017.04.002
- Gardiner et al. (2023). The effect of caffeine on subsequent sleep: A systematic review and meta-analysis. Sleep Medicine Reviews 69:101764. doi:10.1016/j.smrv.2023.101764
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A wallet or fridge card with % Daily Value rules and what to look for.