A tablespoon of it will kill you, but most of us feel like death without it: we're talking about caffeine this episode. Inspired by a listener question — does green tea have more or less caffeine than black? and what about yerba mate? — Cynthia and Nicky explore the history and science of the world's most popular drug. Listen in as we discover the curious effect of birth control pills on how our bodies process it, calculate how much of an edge it gives athletes, and learn what dolphin dissection and the American Constitution have to do with each other, and with caffeine.

Caffeine is a miracle of plant chemistry—one that evolved on four separate continents, thought experts are not entirely sure why. The prevailing hypothesis has been that caffeine functions as a pesticide, but, on this episode, food science guru Harold McGee shares more recent science that seems to contradict that. In any case, humans quickly figured out that caffeine-rich plant products—cacao beans, coffee berries, tea leaves, kola nuts, and more—made them feel great: sharper, less tired, and even a little stronger. Murray Carpenter, author of Caffeinated: How Our Daily Habit Helps, Hurts, and Hooks Us, gives us the scoop on the science behind how caffeine affects our brains and bodies, while author Bennett Alan Weinberg demonstrates caffeine's impact by telling us the fascinating story of what happened when the stimulant finally arrived in Europe, a continent without a native source of its own.

And, finally, we answer our listener Erik's question, and not just by saying, "It's complicated"—although, of course, it is. All sorts of variables, from particle size to roast darkness to steeping time, affect how much caffeine is in your afternoon pick-me-up. And that's before we even get to variations in how different people metabolize caffeine—and how other drugs and foods can speed that process up or slow it down. Could that variation help explain the current "bulletproof coffee" craze, or is it all just the placebo effect? We talk to The New York Times Magazine's Jenna Wortham to find out what putting butter in your coffee does to your buzz. Listen in now—you'll never look at your espresso, English Breakfast, or energy drink the same way again.

Episode Notes

Murray Carpenter's Caffeinated

Journalist and caffeine fiend Murray Carpenter's book, Caffeinated: How Our Daily Habit Helps, Hurts, and Hooks Us, includes all sorts of fascinating snippets about the drug. For example, did you know that one of Monsanto's first products was caffeine? Or that synthetic caffeine and its natural counterpart are chemically identical, but can be differentiated using radiocarbon dating? (The carbon in synthetic caffeine comes from fossil fuels, so it's much older than the carbon in plants.) Check out Murray's book for all that and much more!

Harold McGee

Harold McGee writes about the chemistry of food and cooking, most famously in his book On Food and Cooking. He's starred on Gastropod before, trying to help Cynthia overcome her dislike of cilantro.

Bulletproof Coffee

In her article, "You, Only Better," Jenna Wortham meets the entrepreneur behind bulletproof coffee, Dave Asprey, as well as lots of other biohacking and self-optimization enthusiasts: read her story here, and follow Jenna on Twitter here.

The World of Caffeine

Bennett Alan Weinberg and Bonnie K. Bealer co-authored The World of Caffeine: The Science and Culture of the World's Most Popular Drug and maintain the World of Caffeine website.