I love my daily shot of caffeine, preferably in the form of a good espresso. Caffeine is a stimulant and vasoconstrictor. It can increase alertness, and will sometimes alleviate headaches (although a rebound effect means that withdrawal from caffeine may temporarily cause headaches). Alfréd Rényi famously said that “A mathematician is a device for turning coffee into theorems,” and that does seem to be true. In addition, moderate coffee intake seems to have minor health benefits, including a slight protective effect against some cancers.

There are, however, good reasons to limit caffeine intake to 400 mg day (and half that for pregnant women). That leads to the limits in the table below (data from here and here). I intend to keep on enjoying my coffee responsibly, within those limits!

Drink Volume Caffeine Max/day
Espresso 1 shot (30 ml) 60 mg 6
Brewed coffee 1 cup 200 mg 2
Starbucks coffee “venti” 400 mg 1
Black tea 1 cup 40–80 mg 5–10
Green tea 1 cup 30–60 mg 6–13
Coca-Cola 1 can 35 mg 11
Red Bull 1 can 80 mg 5

Good news for coffee-drinkers

A recent study in Nature Neuroscience reports that “post-study caffeine administration enhances memory consolidation in humans.” Apparently drinking coffee while – or just after – you study can help to store information in long-term memory. Two shots of espresso seem to be the optimal dose. See this New Scientist article for more details.

I’m off to make myself a double espresso.

Caffeine molecule