Lion of the Blogosphere

Coffee doesn’t dehydrate you

For decades I have continually read that caffeinated beverages “dehydrate” you and therefore you shouldn’t drink them on hot days, etc.

Finally they did actual research with a proper caffeine vs. placebo study, and the discovery was that caffeine intake had no effect on urination at all.

A minor myth compared to the medical establishment hatred of cholesterol and salt, but yet another example of how the nutrition advice we get from the medical establishment is not based on valid scientific research.

Written by Lion of the Blogosphere

July 22, 2016 at 7:12 am

Posted in Politics

21 Responses

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  1. There’s a really fascinating mini documentary about alcohol where twin physicians, for a month, respectively had three drinks a night VS 21 drinks in one day once a week. This was to compare the effects of binge drinking vs moderate drinking.

    Anyway, on the day one twin drank 21 drinks vs his twin’s 3 (these are in british units so not as much as it would appear to americans, but still a lot) they had absolutely no difference in hydration or urine output despite drinking exactly the same amount of liquids (compensated for and beyond the alcohol).

    However the hungover twin said he FELT dehydrated, but apparently he wasn’t.

    In a different documentary, one twin ate an indigenous siberian diet of raw seal meat and whale fat, while the other twin ate a standard american diet. Guess which twin had better blood results by the end of it?

    slithy toves

    July 22, 2016 at 8:08 am

  2. Never heard of coffee dehydrating you, but what about coffee keeping you awake? Is this true? Also what about cold beer making you sweat on a hot day? I’ve heard that one, but my Tajik and me drink it on hot days and it doesn’t do that? Is it because a cold can sweats that the myth had originated? This is so stupid: a can sweats from the outside because it’s cold, you ain’t gonna get cold like that by drinking beer. It’s exactly the opposite process of a chap sweating, which is evaporative cooling – moisture to vapor. With a can of beer it’s condensation – vapor to moisture? So a chap gets cooled off, but a can gets warmed up. Gotta ask Carson, he might know.


    July 22, 2016 at 8:11 am

    • Alcohol lowers your core temperature, but raises the surface body temperature, where the capillaries are, making one feel hotter. Not sure how that affects sweat.

      Of course caffeine can keep you awake. It releases epinephrine, which is basically adrenaline. It has a half-life in the body of about six hours. Tolerance and exhaustion are also modifying factors.


      July 22, 2016 at 10:03 am

    • Caffeine definitely keeps me awake, although not really energetic or alert.

      Never heard the cold beer one, sounds like bs.


      July 22, 2016 at 10:14 am

  3. “but yet another example of how the nutrition advice we get from the medical establishment is not based on valid scientific research.”

    Of course not. It’s all bullshit – or to be charitable, 99.9% bullshit.

    Uncontrolled observational studies aren’t evidence.

    For that matter, even anatomical studies don’t prove as much as medical researchers think (because of individual variation and our poor understanding of biological processes). What goes on in the body is very much a black box, to an extent.


    July 22, 2016 at 8:18 am

  4. Is it the caffeine that is supposed to be dehydrating, or is it other ingredients in coffee/tea/sodas?

    Jose Habib

    July 22, 2016 at 8:19 am

  5. Regarding the supposed dangers of table salt, forty years ago my father, an eminent cardiologist, told me research showed that while a few people seemed sensitive to salt and did best to go easy on it, most people could eat as much as they liked without cause for concern: any amount in excess of what the body needed went out in the urine.


    July 22, 2016 at 8:25 am

    • Yup. A salty meal will temporarily elevate blood pressure and heart rate, but after a good piss, both BP and heart rate return to normal.


      July 22, 2016 at 6:07 pm

  6. isn’t based on good research *sometimes*. dont take scientific failures like this as an excuse to read alt diet blogs and believe whatever you want from them.

    james n.s.w

    July 22, 2016 at 8:31 am

  7. Caffeine is second only to alcohol as a gift of the gods. Both should be consumed in moderation, of course.

    Black Death

    July 22, 2016 at 8:55 am

  8. It’d be more convincing if they could incorporate the placebo effect into these things, like the wind chill factor in the weather. “It won’t, technically speaking, be real, but drinking coffee on a hot day will make you *feel* rotten.” Then people could make informed choices, and you might be able to start measuring cultural/racial differences.


    July 22, 2016 at 9:05 am

  9. I learned something useful about caffeine on talk radio recently, which is that you don’t get any energy kick from drinking it in the morning. But you do get a nice kick by taking it round 3 or 4 p.m., which tracks with my experience.


    July 22, 2016 at 11:25 am

  10. My Tajik makes iced green tea for us from the real stuff. Awesome! A pitty Trump is gonna deport him, but that life, I guess.


    July 22, 2016 at 12:31 pm

  11. It is water. Water in coffee makes you dehydrate.

    My Two Cents

    July 22, 2016 at 3:08 pm

  12. All the dietary guidelines from the 50s and 60s were bogus.

    Completely dictated by food corporation agendas and profits. Again and again, mainstream science is really an economic swindle or angle (ie global warming).


    July 22, 2016 at 3:35 pm

    • Not to mention the blank slate-ism science of human nature/genetics/races.

      To suggest that genes/biology plays a 50/50 role with environment is to risk being called a bigot.


      July 22, 2016 at 4:22 pm

    • AND all of Kinsey’s sex “research” was a blatant social engineering move by the plutocrats.

      We live in a world of lies.


      July 22, 2016 at 4:29 pm

    • All the dietary guidelines are still bogus.

      My Two Cents

      July 22, 2016 at 5:09 pm

  13. Coffee makes my mouth and tongue feel tacky, especially black coffee, so maybe that’s why people think it’s dehydrating. Also, coffee elevates blood pressure and heart rate, which also happen to be symptoms of dehydration as the blood thickens, forcing the heart to pump harder and more often to circulate the blood.


    July 22, 2016 at 6:10 pm

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