Coffee. Some days your morning cup leaves you jittery and overly chatty, and other days you can barely lift your head off your keyboard. Turns out that coffee, like so many caffeinated items, is unpredictable and unregulated — the amount of caffeine in a cup of the same brand, made the same way, can vary wildly. Journalist Murray Carpenter has traveled to South America and China, interviewing consumers, scientists, regulators and industry representatives to get the full story on caffeine. He joins us to talk about his new book, “Caffeinated: How Our Daily Habit Helps, Hurts, and Hooks Us.”

Murray Carpenter, journalist and author of "Caffeinated: How Our Daily Habit Helps, Hurts, and Hooks Us"

  • Bob Fry

    Did the guest test the labs? That is, divide the same cup of joe into multiple samples, sending each to a different lab (or the same lab) to see variation and error in testing.

  • Fay Nissenbaum

    Timing of when I drink it affects me. I gave up drinking coffee in the morning b/c it makes me feel sleepy. So I switched to green tea in the morning and get a boost without the crash. However, if I drink coffee around 1pm in the afternoon, that crash does not happen. So how can caffeine in TEA work differently from caffeine in coffee?
    Great topic today,

  • Sadie McGarvey

    Something interesting to me about caffeine is that lack of it is often used as an acceptable excuse for not being kind or not being productive.

  • Sanjay Dhar
  • examineitmore

    What about ill effects of caffeine? If blood vessels to brain are constricted, less oxygen gets to the brain. Isn’t this bad?

  • David G

    I am skeptical of the report from the Florida scientist that Starbucks coffee varied so greatly in caffeine level. Was it reproduced? Reasons for skepticism: wasn’t it tied to litigation asserting that caffeine was deliberately added as a separate chemical to the coffee, given that arabica beans at Starbucks simply don’t yield so much caffeine in extraction? Wasn’t it a mixed drink, rather than a simple espresso or brewed coffee, that the scientist was measuring?

  • 510Jenn

    Does the combination of caffeine and taurine (as in Red Bull) vs plain caffeine make any difference?
    Separately, what do we need to know about caffeine’s impact on kids?

  • Dan

    Do people really like the taste of coffee or is it just the addiction to caffeine that makes us like the taste? Just like cigarretes and nicotine.

  • Laurie Mont

    Does mate (pronounced “ma-TAY”) tea have more or less caffeine than a cup of coffee?

    • mdcrumpler

      It’s the in between of coffee and tea. Coffee has the highest, followed by Mate (which also has other xanthines like the ones in chocolate!), then tea.

  • Joannefilm

    As a longtime decaf drinker, I am experiencing more and more that coffee shops don’t serve decaf. I am offered americanos – Yuck! – more and more. I really thought this would be going in the other direction in which decaf drinkers would have more choices, not fewer, or none at all. Philz is one place that serves a variety of decafs. Caffeine makes me unproductive and anxious, so decaf is the only choice for me, and I LOVE coffee!

    • Fay Nissenbaum

      I love DECAF if I dont know I’m drinking it!

    • Kenneth Hensel

      But Americanos are good! They’re like a really fresh cup of coffee. 🙂

  • david

    what about using cafe instead of Ritalin for children and adults with ADHD? It is a stimulant as it is ritalin.

  • fishbear

    Why do some people (myself, for example) receive little effect from caffeine, both in terms of stimulation and addictiveness?

    • Barry Spencer

      The reasons can be sorted into two general categories.

      One is variation in rate of caffeine metabolism. For example: different people inherit genes for different versions of CYP1A2, the main enzyme that dismantles caffeine molecules. (The gene is called CYP1A2; the enzyme is phenacetin O-deethylase. But the enzyme is often called CYP1A2.) Some people possess slow variants, some fast variants, and some intermediate variants of the enzyme. The more slowly a person metabolizes caffeine, the higher the peak body concentration following a dose of caffeine, and the longer caffeine remains intact in the body. So in slow metabolizers the “area under the curve” is greater, which means their nervous system is exposed to greater concentrations of caffeine for longer periods of time. That would tend to increase the effects of caffeine, and would also tend to provoke a greater degree of neurochemical adaptation to caffeine, which would tend to increase physical addiction.

      Conversely, the trait of rapidly metabolizing caffeine may prevent caffeine from having much of an effect on you.

      Female gender influences the rate of caffeine metabolism, because estrogen slows the rate at which the CYP1A2 enzyme dismantles caffeine molecules. Women, most of the time, metabolize caffeine more slowly than men do.

      And there are other factors, including environmental factors, that influence the rate of caffeine metabolism.

      The other category of variation that influences the effects of caffeine and addiction to caffeine is variation in neurochemistry.

      For example: caffeine works by blocking adenosine receptors and thereby blocking the effects of adenosine, a neurotransmitter chemical. Inherited variations in the adenosine system can therefore influence responses to caffeine.

  • Marie

    Just to point out the disambiguation that needs to be done in the statistics. Caffeine is a well-known appetite suppressant so it makes perfect sense that it might lower the incidence of type two diabetes. As to lung cancer, if in fact it’s true that smokers metabolize caffeine twice as fast as non-smokers then of course smokers are likely to be drinking more coffee and of course they’re more likely to get lung cancer.

  • Fay Nissenbaum

    No comments about the jitters??? The shakey feeling cannot be good for motor coordination, I wouldnt want a jittery surgeon. So caffeine stimulates but after a certain amount, the stimulation turns into nervousness and shakiness (for me). That’s gotta be a tight curve with a steep decent after peak blood level – what is going on??

  • HiloHattie

    Thanks, Sanjay, for your story. Your med creds helped validate your personal story and what the interviewed Carpenter was telling us but, the real life context made it hit home! Too bad you didn’t subtitle the web link so more of us late podcast listeners might click on it. Good luck on your continued caffeine sobriety. Increased sensory awareness… cool!

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