Marks Daily Apple
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20 Feb

Dear Mark: Should I Consume Caffeine Before My Workout?

In today’s edition of Dear Mark, I cover a topic near and dear to many of your hearts: caffeine. But I don’t just cover caffeine; I explore whether caffeine truly does act as a diuretic, especially during exercise, and whether or not caffeine can actually be helpful to athletic performance. Should we all be downing mugs of joe or cups of tea before we hit the gym or head outdoors?

Let’s find out.

Dear Mark,

I’ve been told that drinking coffee prior to, or during workouts is a big no-no, because it’s a diuretic and will lead to dehydration, which is no good for performance (or health). But I love an iced coffee right before my workouts. I feel like it helps. It could just be placebo, but if it’s not hurting, I’m okay, right?

I wonder if you could give me the lowdown on what the literature says. Thanks!


First, let’s tackle the dehydration question. It has undoubtedly become “common knowledge” that coffee is a potent, perhaps the most potent, diuretic, that drinking it is like drinking negative water, and that if you’re stuck on a desert island you’d be better off drinking your own saliva than that steaming cup of joe from the Starbucks that inexplicably decided to set up shop on a desert island. Yeah, there are a lot of scary stories about coffee, but does it hold up to scrutiny?

No. A quick search on PubMed turns up a couple German-only studies with vociferously and unambiguously worded titles but no abstracts (“Coffee does not cause dehydration!” and “Coffee does not dehydrate. New studies of Germany’s favorite addiction: coffee.”), as well as some English ones with abstracts:

  • One from the University of Connecticut measured fluid, electrolyte, and renal indices of hydration over eleven days of caffeine consumption in human subjects. Doses of up to 6 mg caffeine per kilogram of body weight had no effect on body mass, urine osmolality (urine concentration), urine specific gravity (concentration of excreted materials in urine), urine color, urine volume, sodium excretion, potassium secretion, creatinine content, blood urea nitrogen (forms when protein breaks down), and serum levels of sodium and potassium, causing the researchers to conclude that caffeine does not cause dehydration.
  • Another compared hydration markers in patients who consumed either caffeinated beverages (coffee and cola), non-caffeinated beverages (coffee and other sodas), and/or water. The effect on hydration status was essentially uniform across all beverage categories, regardless of caffeine content.
  • And finally, a review from the American College of Sports Medicine found that not only does caffeine not reduce hydration nor induce electrolyte imbalances, it has no effect on heat tolerance during exercise.

I think that settles that. Caffeine does not dehydrate you or cause you to overheat. It’s “safe.” It’s not bad for the active athlete.

But is it actually good? Does it do anything except fail to dehydrate you?

Oh, yeah. Let’s dig into the literature to find out what it can do for your athletic performance.

Endurance Exercise

Most of exercise/caffeine literature centers on endurance training and performance. I remember back when I was running, the most oft-cited benefit to caffeine before a race or training was that it would increase the oxidation of fat, thus sparing muscle glycogen. That sounds nice and tidy, and it would be awesome if it were true, but the most recent evidence suggests that caffeine has little, if any, effect on fat or glycogen metabolism during endurance exercise. So what are we to make of the older evidence that does show a difference in fat oxidation after caffeine ingestion? Or the 1992 study that found caffeine reduced the tendency of muscle to burn glycogen early on during extended bouts of exercise, thus “sparing” it for later on?

It may be that caffeine simply makes exercise more tolerable, makes muscles work harder and better, and allows those exercising to do so harder. One study found that while pre-workout caffeine did not spare glycogen, it did boost the endorphin response to exercise. If endorphins are high, exercise is more tolerable, even enjoyable. If caffeine can increase the runner’s high, it’s also going to make exercise more effective and more self-perpetuating.

Whatever the case may be, the literature is pretty clear that caffeine improves endurance performance, perhaps by enhancing fuel partitioning or making exercise more tolerable and enjoyable.

Anaerobic Exercise

The extent of research into the effects of caffeine on anaerobic performance – think sprints, weight lifting, and interval training – is limited, but useful literature exists. One review, from 2009, noted that while caffeine appears beneficial to speed endurance training (in the realm of 60 to 180 seconds) and high intensity interval training (HIIT), it has limited use in power sports. It may help lower body muscle endurance, but it appears to have a minimal effect on the upper body. The authors propose a number of mechanisms for caffeine’s action, including enhanced calcium transport and the old fat utilization/glycogen sparing thing, but the most promising idea is that caffeine simply stimulates the central nervous system enough to blunt adenosine receptors, increase pain tolerance, and dampen perceived exertion.

What about resistance training? In one study, caffeine ingestion boosted trained women’s 1RM in the bench press (PDF). In another, caffeine seemed to have no effect. A review from 2010 determined that short-term, acute ingestion of caffeine is beneficial in team-based and power sports, but mostly in individuals who did not routinely ingest caffeine. Six of eleven resistance training studies reviewed in the study showed benefits to caffeine ingestion, so the evidence remains fairly equivocal.

Thus, when you drink coffee before lifting heavy things or sprinting, your performance will not suffer – and it may even improve.

It may even be a simpler, less exciting explanation than anything overtly physiological: that the “benefits” of caffeine to physical performance may actually be a cessation of the negative effects of caffeine withdrawal. As Sweat Science points out in a recent post, before double-blind trials on the effect of caffeine on performance, participants must abstain from caffeine for a day or two. If they’re habitual caffeine fiends (as many people are), by the time they begin the study they’re already suffering withdrawals. Studies on cognitive performance and caffeine have found that when you account for the withdrawal effect, caffeine has little to no benefit to performance. Researchers have yet to examine the withdrawal effect in studies on athletic performance, but it appears a likely candidate for at least some of the reported benefit to caffeine consumption.

It’s also important not to lose sight of the fact that most of us are drinking coffee, not popping pure caffeine pills. Coffee contains tons of polyphenols, bioactive compounds that could have beneficial (or negative) effects on exercise performance. Most of the studies are looking at caffeine, so they have to isolate it. But if you’re drinking coffee, shouldn’t you look for studies that examine coffee? There’s a recent one that found ingesting coffee polyphenols increased fat oxidation (PDF). Of course, the caffeine, polyphenol, and other bioactive compound contents of coffee are not stable. Coffee is a food made up of hundreds of factors. It’s not just a source of caffeine. Based on soil conditions, climate, elevation, roast, and variety of bean, two cups of coffee can display remarkably different characteristics, and it’s likely that the effects of each on exercise performance will also differ.

Bottom line, though: if coffee makes you perform better, keep drinking it before, during, or after you workout. At least we can say for sure that it’s not dehydrating you.

How does coffee affect  your workouts? Better? Worse? No effect? Let me know in the comments!

You want comments? We got comments:

Imagine you’re George Clooney. Take a moment to admire your grooming and wit. Okay, now imagine someone walks up to you and asks, “What’s your name?” You say, “I’m George Clooney.” Or maybe you say, “I’m the Clooninator!” You don’t say “I’m George of George Clooney Sells Movies Blog” and you certainly don’t say, “I’m Clooney Weight Loss Plan”. So while spam is technically meat, it ain’t anywhere near Primal. Please nickname yourself something your friends would call you.

  1. THumbs Up! I love coffee,it boost my strenght during workouts and i can’t sleep like a baby without it period!!!

    sheryl wrote on March 5th, 2012
  2. Coffee is what keeps me alive in the afternoon between lunchtime and heading to the gym.

    onprcntr wrote on April 17th, 2012
  3. I absolutely love my coffee! I’m just wondering what your thoughts are on it causing the body to store fat? I keep hearing how I need to cut out coffee because it spikes your insulin causing you to store more body fat. Any thoughts? Thanks so much!

    Ashlie wrote on August 4th, 2012
  4. I’ve been drinking tea and coffee during workouts for years, and with positive results. No dehydration. Better performance.

    Vincent Porta wrote on January 1st, 2013
  5. In her book Primal Mind Primal Body, which, lets be honest is the best researched primal book there is (perhaps not the most livable) Nora D is emphatic that coffee is an all out poison. Adrenals suffer, pancreas suffers along with a whole host of other not nice stuff.
    I loved coffee for 4 years and then just started to feel it wasn’t doing me good. After the extraordinary detox headaches I’m free and all is good without.
    I think a combo of personal awareness, Norah’s book and the latte factor, ended my love affair with it.

    Al wrote on January 19th, 2013
  6. there is a ton of science on both sides. I think the key with this is the same with any substance that is potentially addictive and a stimulant.

    Pay attention to your body, recognize the things that historically have been negatively associated with Caffeine (high blood pressure/TC, jitters, sleeplesness, etc), and be willing to adjust our habits as necessary.

    I love coffee (live in Seattle AND worked for Starbucks in the early days when a barista really had to make the drink). but lately (especially after going Paleo), I’ve had to be more reserved about my consumption. After a week of almost no sleep, i started to cut back on the coffee…and my sleep improved dramatically.

    I think that we have to remind ourselves that we are a holistic creature…not a group of science articles all thrown together in a mess. we have to use science as what it is…a tool, and listen to what our bodies are telling us. My body told me that it was time to cut back :) not everyone will have to do that, but as long as your listening to yourself, you’ll probably be fine.

    Malachi wrote on January 29th, 2013
  7. For me, caffeine is dehydrating based on how diluted it is. I assume that’s fairly universal.

    Animanarchy wrote on February 19th, 2013
  8. I’m a 67 yr. old male, that has been drinking coffee most of my life,and I mean lots of coffee.I did suffer from High Blood Pressure & Border line Diabetes for over 20 yrs. This I and my doctors agree was hereditary.I was taking meds for the pressure problem and just monitoring my sugar,pricking my fingers 2 times a day”OUCH”. I’m 5’8″ and was about 20-30 Lbs.over weight.I lost the weight and started working out,eating semi-healthy,but still drinking lots off coffee. By loosing the weight,working out and getting my BMI (Body Mass Index) where it should be
    my doctors took me off the meds and I don’t prick my fingers anymore. Coffee has always given me a boost all day long. It gives me a boost in the morning when I’m at the gym and everybody is telling me that I shouldn’t be drinking it because I drink it at the gym. It has always worked for “Me”. Now all I take is my Vitamins, A baby aspirin and lots of coffee and I’m in tip-top shape. Thank you for Verifying Coffee is Good “FOR ME”

    bluangel47 wrote on May 15th, 2013
  9. I used to be a coffee addict. But over the years of working to improve my diet, I finally had to come to the conclusion that coffee was just too toxic and dehydrating. I mean, it’s a bean or seed, and nature puts all sorts of insecticides and toxic chemicals in it to protect the seed. I heard somewhere that a coffee bean has about a thousand toxic chemicals in it, naturally.

    Whether it actually does technically ‘dehydrate’ the body or not, I’ve found that its toxicity necessitates that I drink massive amounts of water to overcome its ill effects. If I have just one cup of coffee during the day, I can count on having to wake up every hour during the night to drink water, or else suffer from headache and relentless thirst.

    In my primal low-toxin diet, coffee just doesn’t fit, and nowadays I only indulge once every few months or so. And then predictably suffer all night because of it, not from the caffeine, but from the physical imperative to flush out all those astringent toxins with copious amounts of water.

    Ramana wrote on February 1st, 2014

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