Coffee

What the evidence shows

A 2017 umbrella review (Poole et al.) of ~200 meta-analyses found moderate coffee intake (3–4 cups/day) associates with:

• ~17% lower all-cause mortality at the lowest-risk dose.
• ~19% lower cardiovascular mortality.
• Lower incidence of type-2 diabetes, Parkinson’s disease, several cancers (liver, endometrial), depression.

Caffeinated and decaffeinated coffee both contribute; many benefits are not pure caffeine effects.

Why coffee, not just caffeine

Coffee is a complex matrix — chlorogenic acids, diterpenes, polyphenols — in addition to caffeine. Decaffeinated coffee retains most polyphenols and shows many of the same associations, with smaller effects on cardiovascular and Parkinson’s outcomes.

Caveats

• Unfiltered coffee (French press, espresso) raises LDL via cafestol/kahweol; filtered (paper drip) does not.
• Pregnancy: high caffeine intake associates with low birth weight; most guidelines suggest <200 mg/day.
• Sleep: caffeine half-life is ~5–6 hours; consumption after early afternoon disrupts sleep architecture in many adults.
• Arrhythmia: contrary to old teaching, moderate coffee does not increase atrial fibrillation risk.
• Genetic variation in CYP1A2 affects caffeine metabolism; fast vs. slow metabolisers may respond differently.

Related entries

Type 2 diabetes, Parkinson's disease, Sleep optimization.