Here’s something to think about: more than half of your body is made up of water. Not fat, not muscle – H2O. So if you weigh, say, 70kg, about 40 of them come from the liquid stuff. In fact, every one of your cells is essentially a soggy bag of fluid, surrounded by more fluid. Without it, your cells – and you – would die. That’s why people can survive a long while without food but not without water, the single most vital substance for sustaining life. If this all seems dramatic, consider that ample water is key for keeping your digestion on track, your nasal passages moist and your kidneys content. And for enhancing pretty much all of your major organs, including your brain.
The Delivery System
You may now be picturing your insides as a bunch of parts just sloshing around in water. A more accurate picture involves some complex biology: every time you take a sip of H2O, it seeps through your intestines into your blood vessels and, like a bucket of water dumped into the ocean, becomes part of a larger mix of liquid and minerals – most notably, salt. This saline-type solution shuttles chemical signals back and forth between cell membranes, informing your every action. It also ferries around your body’s other must-haves (oxygen, glucose, hormones) via the blood, which is mostly made up of – you guessed it – water. How and when water exits your body depends on myriad factors, including humidity and temperature, your activity level and how much you sweat, says human biology expert Prof Lawrence Armstrong. What is clear is that if too much exits and not enough enters, your wellbeing can start to suffer.
Parched Health
Given all of the above, it may seem you have plenty of water to spare. But losing even a tiny amount can set off an alarm. Thirst – a dehydration warning sign, assuming you haven’t just had a salty snack – typically kicks in when you’ve lost a measly two percent of your water weight. At that point, you could become prone to muscle cramps and headaches. Your athletic abilities might falter. The resulting stress speeds up your heartbeat and can leave you fatigued, says Prof Lawrence Spriet, a biokinetics and nutrition expert and coauthor of Exercise Metabolism. In short, everything begins to feel like a slog. And if you rarely remember to sip water throughout the day, beware: long-term low liquid intake has been linked to problems such as kidney stones and urinary-tract infections, as well as prolonged labour if you’re pregnant.
An H2O deficiency can also affect the brain in surprising ways. Research suggests that mild dehydration – which may not even make you thirsty – can interfere with your ability to concentrate and can raise stress levels and increase anxiety. Scientists are still figuring out the particulars, but they suspect a lack of water adversely affects the nerve cells that control mood. Of course, being really dehydrated is very serious. If you lose five to six percent of your water weight at one time, you could suffer symptoms such as mental confusion or vomiting, says nutritional science expert Prof Stella Volpe. (This type of severe dehydration, which usually affects only athletes and those in extreme climates, should be considered an ER-worthy medical emergency.)
Smart Sipping
The tricky thing is, there are few set-in-stone guidelines. Turns out, the oft-heard “eight glasses a day” may be a health myth that won’t work for everyone; it all depends on individual biology and lifestyle. In general, experts recommend that the average woman get at least 11.4 cups of water a day, though that includes fluid you get from food (even cooked chicken, for example, is filled with water, making it likely you’ll eat around 20 percent of your daily H2O intake). The American College of Sports Medicine recommends pre-hydrating, or drinking about 500ml of water four hours before you exercise. Better yet, stay hydrated by sipping slowly throughout the day. Slurping down huge amounts right before hitting the gym – or, say, getting on a long flight – mostly just means extra trips to the loo, says personal trainer Hannah Davis.
When in doubt, stop and ask yourself, What activity am I doing, for how long and in what temperature? If you’re exercising for less than an hour in cool weather, you probably don’t need to drink water throughout your workout. If you’re getting in a fierce sweat session – say, a game of tennis or a longer run – pause for fluid breaks. If you’re at the office and just wondering about the sogginess of your cells, take a peek at your urine, says Volpe. If it’s pale yellow, you’re fine. Any darker means you need more water; consistently crystal clear urine means you’re trying too hard to hydrate. Above all, listen to what your body asks for. A recent article in the British Medical Journal suggests that while the sports-drink industry has raised loud alarms over dehydration, people should simply respond to their own symptoms. Therein lies the only hard rule of hydration: if you’re thirsty, drink. And if you’ve gone a few hours without sipping, down a glass of water.
Warning!
You can become overhydrated. Excess H2O means your cells can’t function properly, and your kidneys can’t work fast enough to get rid of the stuff. But water intoxication is very rare and is typically only a hazard for ultra marathoners and those who over-drink while exercising. (Everyone else can monitor their pee: if it’s always totally clear, cut back on your sipping).
