Consumer group Which? found that a cappuccino at Costa Coffee delivers 325mg of caffeine, compared to 89mg for the same drink at Starbucks. The Costa serving contains roughly the same amount of caffeine as four cans of Red Bull, according to the report.
The study compared popular drinks across major coffee shop chains and found the differences extend well beyond cappuccinos. A single espresso at Pret a Manger contains 180mg of caffeine, which is nearly four times the 45mg found in a Starbucks espresso.
Caffeine levels vary sharply across matcha and espresso drinks
Matcha drinks showed a similar gap. A medium matcha latte from Costa serves 99mg of caffeine, while a Starbucks matcha green tea latte has 57mg and Pret’s version has 28mg. That means Costa’s matcha latte contains three-and-a-half times more caffeine than Pret’s, and it also exceeds the caffeine content of a Starbucks cappuccino, flat white, latte, and americano.
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The British Heart Foundation notes that the caffeine limit for most adults is generally considered to be up to 400mg per day. A single Costa cappuccino puts a customer at 81 percent of that daily ceiling.
Several factors explain why caffeine levels differ so much between chains. The type of coffee beans matters, as does the roast, the grind, the serving size, the brewing method, water temperature, and the length of extraction. Pret and Starbucks use arabica beans, while Costa and Greggs use a combination of arabica and robusta. Robusta beans contain around double the caffeine of arabica beans.
That partly explains the gap, but it doesn’t fully account for why a Pret espresso has four times the caffeine of a Starbucks one, since both chains rely on arabica. Serving size and brewing ratios likely play a larger role than the bean variety alone.
Watchdog urges customers to check what they order
Which? health and wellbeing expert Jessica Carson said caffeine content varies widely depending on where consumers shop. “If you drink multiple cups a day or need to cut back for health reasons, pay attention to where you shop and what you order to avoid any unwanted side effects,” she said.
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For people who are sensitive to caffeine or have heart conditions, the difference between chains could be meaningful. Someone who drinks two Costa cappuccinos would exceed the recommended daily limit, while two Starbucks cappuccinos would keep them well under it.
Pret and Caffè Nero declined to comment on the findings. Costa, Starbucks, and Greggs have been contacted for comment.
The report didn’t test every drink on every menu, and caffeine content can vary from store to store depending on how baristas measure shots and steam milk. But the scale of the differences suggests that customers who are watching their intake should treat menu labels as a rough guide rather than a guarantee.