This preliminary study found no significant differences in the effect of various combinations of beverages on hydration status of healthy adult males. Advising people to disregard caffeinated beverages as part of the daily fluid intake is not substantiated by the results of this study.

I used to drink a lot of Pepsi. I don't anymore. I stopped doing it to loose weight, although I've been drinking more cola in recent months because I seem to have lost energy since stopping smoking and I need the caffine fix more than I used to.

However, when I did drink a lot of Pepsi many of my friends used to say "Why do you do that? Don't you know that cola dehydrates you?" People are always so sure that random "facts" like this that they've picked up from who knows where are the absolute scientific truth.

This "fact" originally struck me as odd. I knew that if I was thirsty, and I drank a Pepsi, I wouldn't be thirsty anymore. So, drinking Pepsi seemed to serve it's purpose. I always drink cola with ice, preferably crushed ice, and I used to tell people who said this that the ice resulted in a net gain of hydration. The depth of their scientific knowledge of the effects of caffine on hydration was no match for this hypothesis and so it usually ended the discussion, but I always wondered about this.

I've googled around in the past for information clarifying the dehyrating effects of cafinated beverages to no avail, which increased my suspicion about the truth of this fact and my frustration with people who propagate it. I even thought about asking the myth busters. Today I managed to find a scientific study of the question. It's conclusion is that drinking a caffinated beverage does not result in a net decrease in hydration. So this "fact" is wrong. Drinking a Pepsi hydrates you.

Well, maybe. The study was funded by a grant from the Coca-Cola Company, who obviously have a business interest in combatting rumors like this that cause people to reduce their consumption. So perhaps the study is biased? Incomplete? Junk Science fueled by an evil corporate agenda?

I dunno. The next time someone tells me this "fact" I'm going to direct them at this study, which will hopefully top out a MemeStreams search for Pepsi once the indexer runs. I'm open to the idea that this study's conclusions might not be the final answer to this debate, but I think these results must be countered with another study and not simply with "well thats not what I heard..." or "the body building website I like says something different." If you've got a link proving that this study is wrong, biased, or incomplete, please let me know!

Does drinking cola dehydrate you?