How this is worked out, and its limits
EFSA 2015: up to 400 mg a day (200 mg at once) raises no safety concern in healthy adults; 200 mg a day in pregnancy and breastfeeding. Per-item values follow EFSA for coffee, cola, energy drinks and chocolate, with typical values for Indian chai. Leaf, brewing time and cup size change the real amount.
References: EFSA 2015, scientific opinion on caffeine
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