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That myth about how Coke dehydrates you

logoYou know how whenever you’re thirsty and reach for an ice cold refreshing soft drink someone invariably tells you that soda will dehydrate you or only make you thirstier? Yeah, well it turns out that is total BS.

From the New York Times:

It was long thought that caffeinated beverages were diuretics, but studies reviewed last year found that people who consumed drinks with up to 550 milligrams of caffeine produced no more urine than when drinking fluids free of caffeine. Above 575 milligrams, the drug was a diuretic.

So even a Starbucks grande, with 330 milligrams of caffeine, will not send you to a bathroom any sooner than if you drank 16 ounces of pure water. Drinks containing usual doses of caffeine are hydrating and, like water, contribute to the body’s daily water needs.

A 12-oz can of Coke has 35mg of caffeine. So you’d need to drink 16 cans (1.5 gallons) in order to ingest enough caffeine for it to be the slightest bit dehydrating. Of course if you managed to drink that much Coke before any of the caffeine wore off you would be a champion–so you probably wouldn’t need to worry about little things like dehydration anyway.

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13 Comments

  1. Jack Whattam says:

    Soft drinks dehydrate you not because of the diuretic effect but because they are hypertonic, they have a higher concentration of solutes than what is in your body cells cytoplasm. This causes water to be drawn out of cells, dehydrating you.

    1. Adrian Devlin says:

      That’s not fully true Jack. Whilst you are correct in stating that the drinks in question are hypertonic: that will not have any dehydration effect upon the body due to the method in which the nutrients from the drink are absorbed. The balance between solutes and solvent creates a water potential that is only relevant when considering the administration of intra-venous fluids. Oral fluids, as I said, aren’t affected in such a way and can be drunk without regard to their concentrations.

      1. Adrian Devlin says:

        That is to say, not in the quantity contained in normal beverages. If you were to drink seawater, for example, which has a massive salt content than you’d still dehydrate.

  2. Andy says:

    Ahh… Lobby-biased research is the best, isn’t it?

    1. Andy says:

      I just want to say that in my education I’ve never learned that solvent/solute balance is only relevant when the fluid is shot straight into your veins. Just because in digestion the water is separated from the sugar, caramel, etc., doesn’t mean those substances don’t saturate your cells just the same. Sugar goes to your blood. Candy dehydrates you, Soda dehydrates you. PERHAPS diet soda might not dehydrate you, but I’m not certain if aspartime is a diuretic or not.

  3. Jonathan Santiago says:

    That’s great news. I get free soda at work, so my tendency is to consume a fairly good amount of Diet Coke each day.

    I can say one thing though, as much as I’d love to get all my liquid substance from the soda because it’s free and tastes so good, the soda does just not make my body feel hydrated.

    If I drink about 6 Diet Cokes between the hours of 9am and 5pm, come 5pm I feel tired and worn out, it’s harder for my eyes to focus, and when I go to the bathroom, (sorry) it looks like I haven’t drunken anything all day.

    I have to balance out each diet Coke with about a glass and a half of water to feel like I should. And I’m not overly sensitive to caffeine.

    I’m not sure what any of that means from a technical standpoint, but I know soda alone, does not cut it for me. My body gives me clear signs.

  4. Ryan33 says:

    Whether or not coke/coffee, in dosages above ~550+ are diuretic or not, and whether they dehydrate you or not, and whether they make one need to pee sooner or not, are not, as far as I know, terms defined well enough here to start making definitive meaningful statements, since there seems to be some circular reification problems. Firstly we would need to ensure the medical-scientific definition is consistent with the popular definition is, whatever that might be (urinate more? sooner [as the NYT author unreasonably assumes]? does ‘more’ really account for mineral-density/color? Is such a thing relevant? Is it possible that a drink can make you more hydrated at first, but less so in the long run?]. I think what we all want to know is – if you’re stuck on a boat with only a ton of caffeinated beverages to keep you from dying of dehydration, would it make sense to drink it? And could you live indefinitely on it, as a source of water? I suspect that at worse, it might be able to delay death by dehydration very substantially if not indefinitely, and thus only is unhealthy in that it might require a greater volume of liquid, compared to water alone, to get your daily required intake, since it might make you pass the water more quickly, with less time to be absorbed. Notable also is that soda is notoriously filling, so it would be harder to drink a lot of than of water. Water can be drank until one dies of water poisioning, of course, so that might be a factor. Maybe soda in the short term is hydrating, as our body would definitely have us believe. Maybe it’s a diuretic and hydrating, whereas beer might be a diuretic and dangerously dehdrating if drank as the sole source of satisfying thirst?
    tl;dr – one would need to read the studies, not a quote of an excerpt of an article that paraphrases what may or may not even be a metastudy conducted by what may or may not be a respected scientifically-literate individual or organization.
    P.S. I didn’t proofread

  5. Ryan33 says:

    Regarding the sugar-hypertonic-hypotonic-diet-aspartame-potential soda debacle, it should be noted that Diet doesn’t imply caffeine-free. Pepsi Max is zero calorie but has like 65 mg caffeine per 8 oz if memory serves.
    *sips from 16 oz Rockstar Mocha Doubleshot can*

  6. Steve says:

    Jonathan is a smart dude, would that more Americans would listen to their body – there would be a whole lot less Coke drunk.

    I find it interesting that Coca-Cola is shifting from the “refreshing soft-drink” business to the “hydration” business. Everything they put on their website is about “hydrating” – what a total joke. There is nothing better than drinking pure water (and eating enough vegetables and fruits) to “hydrate” someone in need.

    Sorry to be a hater on your major premise – that America can come up with something worthwhile that doesn’t lead to our demise.

    Maybe in this new millenium?

  7. Highway Monkey says:

    I drink diet soda drinks and one small can will leave me needing the toilet a few times during the day. I have to ration them to no more than 2 cans or else I feel dehydrated. Tea is the same for some reason.

  8. anthony says:

    So what company pays you to post this ? I have not had any soda in so long and I LOVE it. As a child all I would drink is soda and no water which was extremely unhealthy and contributed to many health problems/fatigue. Safe to say I can go on with my life never ever wanting to drink any soda ever again. There are absolutely NO health benefits in drinking your black colored sugar water.

  9. MeMyselfandI says:

    a$$hats, all of you

  10. [...] that your drink will shortly be returning to. I have however seen recently that the notion of caffeine being a diuretic might be [...]

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