Caffeine

Psychoactive alkaloid in coffee (0.8-4% depending on species). Metabolic half-life 5-6 hours (variable CYP1A2 gene). EFSA recommended limit: 400mg/day for healthy adults, 200mg/day for pregnant women.

Background & Context

Caffeine (1,3,7-trimethylxanthine) is the world's most widely consumed psychoactive compound. In coffee, it serves the plant as a natural pesticide — its bitter taste deters insects from consuming unripe cherries. Caffeine content varies significantly by species: Arabica contains 0.8–1.4% caffeine by dry bean weight, while Robusta contains 1.7–4.0%, making Robusta roughly twice as caffeinated per gram. This difference is one reason Robusta is used in espresso blends — a small percentage adds significant caffeine kick. A standard 250ml cup of filter coffee contains approximately 80–120mg of caffeine; a single espresso shot (30ml) contains 60–90mg. Counter-intuitively, a large filter coffee contains more caffeine than a small espresso because of volume, despite the espresso's higher concentration per ml. Caffeine is relatively heat-stable and does not significantly degrade during roasting — the common belief that dark roast coffee is 'stronger' refers to flavour intensity, not caffeine content. EFSA (European Food Safety Authority) recommends a maximum of 400mg caffeine per day for healthy adults, and 200mg for pregnant women. Caffeine's psychoactive effect operates by blocking adenosine receptors in the brain, preventing the drowsiness signal that adenosine normally produces. The half-life in the body is approximately 5–6 hours, though CYP1A2 gene variants cause significant individual variation.

Practical Use

If you are sensitive to caffeine, choosing Arabica over Robusta (or any blend containing Robusta) makes a significant difference — up to 2× lower caffeine per gram. The timing of your last coffee of the day matters: a 3pm cup has half its caffeine still active at 8pm if your half-life is 5 hours. Decaffeinated coffee retains 1–3% of original caffeine, not zero — relevant for extreme sensitivity. Swiss Water Process decaf retains the least.

Related Terms

Related terms: Caffeine metabolism — CYP1A2 gene and individual variation. Robusta — higher caffeine than Arabica. Swiss Water Process — solvent-free decaffeination method. Bitterness — caffeine contributes 10–15% of perceived coffee bitterness.