Primary sources from peer-reviewed studies show energy drinks often contain 80-300mg caffeine per serving plus high sugar (25-50g) and additives like taurine and guarana, linked to increased risks of cardiovascular issues, obesity, and dental erosion compared to black coffee's typical 80-100mg caffeine with negligible sugar and beneficial polyphenols. A Mayo Clinic review notes energy drinks' risks for arrhythmias and hypertension in youth due to synergism of stimulants, while coffee's risks are milder and offset by reduced diabetes and Parkinson's risks per meta-analyses. Government data from FDA adverse event reports (1998-2010) document 5,000+ energy drink-related ER visits vs fewer for coffee, but per capita coffee consumption is vastly higher, skewing raw numbers.

Cochrane reviews and NIH-funded studies indicate moderate coffee (3-4 cups/day) correlates with lower all-cause mortality (RR 0.83), whereas energy drinks show acute risks in RCTs, like elevated blood pressure (10-15mmHg systolic post-240ml). However, both can cause anxiety or insomnia at high doses; energy drinks' risks amplify in adolescents due to marketing and larger servings. No study declares one 'worse' outright—context like frequency, additives, and user age matters.

Official statements from EFSA and Health Canada set safe caffeine at 400mg/day for adults, achievable with 4 coffees but often exceeded in one energy drink (e.g., Monster 160mg + sugars). Longitudinal cohort studies (e.g., UK Biobank) favor coffee for metabolic health, but energy drink data is scarcer due to shorter market history.