How much caffeine is too much caffeine?

   Around 400mg of caffeine per day is commonly cited as a safe intake level for healthy adults. That's about 6-7 cups of black tea, 4-5 cups of home brew coffee, 2-3 Starbucks Grande Lattes, 8 cans of Diet Coke, or 5 cans of Red Bull. A typical serving or portion of caffeine is usually an 8 fl oz cup of home brewed coffee, a 20 fl oz diet cola, a 1.5 fl oz espresso shot and an 8.4 fl oz energy drink, all of which are about equal with a range of approximately 70-90mg.

  Caffeine is found in the seeds and leaves of more than 60 plants around the world. Coffee beans, tea leaves, cocoa beans, kola nuts, guarana plants, and yerba mate are just a few that contain caffeine.