We’re all familiar with the maxim that we need to drink eight eight-ounce glasses of water a day for optimal hydration and health. Not only do bottled water companies love to tout this, so does everyone from your doctor to your fitness instructor to your mom. One small study from the University of Connecticut revealed that drinking eight or more glasses of water a day promotes good mental health. Another from the University of East London revealed that it made participants up to 14% more more productive. Still other studies claim that proper hydration led to better overall cognitive function.
Of course, if you’re like me, you probably don’t drink eight glasses of water a day, and instead opt for sodas, coffee, sports drinks, or other beverages to quench your thirst. But if the studies (and bottled-water companies) are correct, could drinking eight or more glasses of water a day actually make you more productive? I swore off all beverages except water and drank up to 14 glasses a day to find out.
Spoiler alert: I did indeed observe improvements in my productivity when I upped my water intake to 14 glasses a day. Here’s what nutritionist and exercise physiologist Bill Sukala, PhD, had to say about my experience.
I frequently have trouble falling asleep at night. However, by my second day of drinking 14 glasses of water a day, my sleep improved greatly–-I fell asleep faster and woke up more refreshed. That’s proof that increasing water intake offered productivity benefits, right?
Perhaps not. "You have to wonder if this is cause and effect or coincidence," says Sukala. "If there was an expectation that 14 glasses of water per day were going to have a variety of benefits, then perhaps this contributed to your falling asleep quicker," he points out. In other words, this could have just been a placebo effect due to the studies and articles I’ve read that adequate water intake is important for good sleep. Alternately, the fact that I cut out other drinks such as stimulants like coffee and soda could have contributed to the better sleep I experienced, too.
I thought giving up caffeinated drinks would mean I had less energy, but by midweek, I found that I no longer suffered from the "afternoon slump" that features a decreased ability to focus at around 3 p.m. Avoiding the afternoon slump is a huge productivity boost, but Sukala says the benefit I experienced was probably not due to upping my water intake, but also due to eliminating stimulating beverages, which set your body up for a crash later in the day.
He says that coffee and soda pack a one-two punch of caffeine and sugar, adding extra calories without any real nutritive benefit. "As your body processes both the caffeine and refined sugar, that would cause a variety of hormonal changes that might account for your afternoon slump," Sukala explains. "If you replaced them with a healthier alternative (i.e., 14 glasses of water per day), then your body would not be subject to the same ‘metabolic groundhog day’ of doing the same thing over and over."
Again, I was surprised by how quickly this happened. By day three I realized just how much more alert and focused I was feeling–-a feeling that was sustained throughout the day.
Yet again, Sukala points out that just because I felt I had better concentration didn't mean that water intake led to it. After all, even though I don’t normally drink eight glasses of water a day, I’m never even mildly dehydrated. So the improvement I noted in my concentration could easily also be put down to a placebo effect.
In the end, "It’s hard to say for certain if this is a case of cause and effect or coincidence," Sukala says.
After my weeklong experiment, the only thing I can conclusively say is that I did experience productivity benefits—but it’s impossible to say if they were the direct result of my drinking more water. If I wasn’t even mildly dehydrated before my experiment, then just increasing my hydration was almost certain to have no mental or physical benefits.
Sukala explains that while a number of media outlets published articles on the effects of hydration on cognition and productivity, the studies they referenced included dehydrated teenagers, adults exercising after taking a diuretic medication, industrial workers performing their duties under extreme heat stress, or experiments conducted on mice. "The results of these studies are not directly applicable to your corporate executive," he says.
Sukala says that people with mild dehydration may indeed experience outward signs like a headache, mood change, or difficulty in concentrating, but he says it’s important to be aware that many of these symptoms have been only noted in people who were legitimately dehydrated and induced in a clinical research environment. "Realistically, the average person is unlikely to suffer any cognitive deficit or observable decreases in productivity while living and working in a region with an ambient climate with plenty of available fluid and food," says Sukala.
"Contrary to popular belief, our bodies absorb water not just from drinks but also from food," Sukala says. "Unless we are completely malnourished, are exercising for long periods at high intensities in extreme heat, or have some other underlying medical condition that alters the body’s fluid levels, I don’t think we can conclusively state people are chronically dehydrated."
As a matter of fact, he says we should probably forget the "drink eight glasses of water" maxim altogether. "It’s a myth," he says.
"I don’t think there’s anything wrong with eight glasses of water per day, but I think people need to use a bit of common sense as well and not obsess over it," Sukala continues. "If it’s a hot day, then you will probably need a little more water. If you’ve been exercising for three or more hours, then you’ll probably need more water." But, he adds, "if all you’ve done is gone to work and sat at a desk all day in an air conditioned office, then eight glasses of water is probably the least of your concerns."