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!
|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|