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Core verdict: For habitual ~2 cups/day in generally healthy adults, the best available evidence points to neutral-to-modest benefit; harms emerge mainly in specific subgroups (hypertensive individuals acutely, pregnancy, and possibly vulnerable populations). The 'contradictions' in the literature are largely explained by acute caffeine effects vs. habitual intake, residual confounding (especially smoking), population differences, and observational designs.

1. What large cohorts show at 2-3 cups/day

In the Multiethnic Cohort (185,000+ participants, 58,000+ deaths, 16.2-year follow-up), 2-3 cups/day was associated with lower all-cause mortality (HR 0.95, 0.93-0.98), while ≥4 cups/day showed higher mortality (HR 1.11, 1.07-1.16) — a J-curve that some interpret as true harm at high intake and others as confounding or reverse causation in this group Nonwhite population mortality HRs. In a Japanese cohort of 76,979 people, 1-2 cups/day of coffee was associated with lower CVD mortality in men (HR 0.67, 0.47-0.96), with a U-shaped caffeine-mortality relationship Japanese CVD mortality cohort. For coronary heart disease specifically, two large US cohorts (44,005 men; 84,488 women; 14-20 years) found no significant association at 2-3 cups/day (RR 0.97 men; 0.84 women) Harvard CHD cohort RRs.

2. Why studies appear contradictory

• Acute vs. habitual: 200-300 mg caffeine raises systolic BP ~8.1 mm Hg for up to 3 hours, yet long-term cohorts of hypertensive individuals show no elevated CVD risk — a genuine physiological time-window effect, not a contradiction Acute caffeine BP meta-analysis.
• Subpopulation context matters: In SLE patients (n=310, cross-sectional), coffee was associated with CVD (AOR 1.75, 1.01-3.04) — but causality cannot be inferred from this design and coffee is entangled with smoking SLE coffee-CVD cross-sectional study. Reviews conclude moderate intake may benefit healthy people while higher intake can aggravate pre-existing risk factors like hypertension and dyslipidemia Review of conflicting coffee-CVD effects.
• Umbrella review: Of 127 meta-analyses, probable decreased risk for several cancers, CVD, and type-2 diabetes; clear harms for caffeine during pregnancy; confounding by smoking and inconsistent dose definitions remain major blindspots Umbrella review of coffee health outcomes.

3. Confidence, blindspots, and what would change this

Confidence: moderate. All human data here are observational or acute-dose trials; no long-term randomized trial of coffee exists. Healthy-user bias (sick people abstain from coffee) plausibly inflates apparent benefits. The ≥4 cups/day mortality signal could be confounded by smoking, which many studies inadequately stratify. Self-reported intake misclassifies dose. If future adequately confounding-controlled cohorts or an RCT (e.g., NCT05757154 metabolite trial extended to outcomes) showed dose-dependent CVD harm at 2 cups/day, this conclusion would need revision.