Why Our Bodies Need Water

This is one in a series of stories; visit The Daily Meal Special Report: Water for more.

We've all heard that our bodies are mostly made up of water, and we understand that without water we can't survive a week. In fact, a mere two to five percent deficit in our body's water supply can trigger fatigue, headaches, a drop in blood pressure, fuzzy short-term memory, constipation, and other signs of first-stage dehydration. And we know that proper hydration is essential to good health — that it keeps our digestion working smoothly, our minds alert, our organs flushed from toxins, our skin dewy and blemish-free. But just why is water so important to our bellies, our brains, our pH balance, and the brightness of our complexions? How, exactly, does water work all these bodily wonders?

Water as cellular safeguard. "Hydration is really about making sure water goes where it needs to go — into the cell," says registered dietician Ashley Koff, a contributor to The Daily Meal who practices in both New York City and Washington, D.C. That's because all of our chemical reactions, which happen at the cellular level, require water. Cell function depends on a balance of potassium, an electrolyte that brings water in to cells, and sodium, which keeps water outside of cells, Koff explains. If we take in too much sodium and not enough water (as we often do after a salty meal or snack), potassium levels will suffer and so will our cellular function. If we're exercising vigorously and losing sodium through sweat, we may need to take in extra potassium in the form or bananas, avocadoes, or coconut water so that the optimal interior/exterior water balance can be maintained and our 200 different types of cells get on with the business of building and maintaining our body parts at the most basic level.

Water as transportation system. Another crucial function of hydration is transportation. "The body is like a vast system of canals," says Koff. "Water makes it possible for nutrients to get where they are supposed to go and do what they need to do in the body. If you don't have enough water, then your vehicular fleet—the bodily systems that carry those nutrients — won't be able to move much."

The vascular system, our vast network of arteries, veins, and capillaries through which blood flows, is a case in point. Blood volume — both how much we have and how fluid or viscous it is —i s a direct result of proper hydration. Without enough water in our system, our blood becomes sticky and flows less efficiently. If you've ever had blood drawn after a night of one too many drinks, you may have noticed that it takes an unpleasantly long time to fill a vial. The dehydrating property of alcohol is powerful! A well-hydrated person's blood should flow, well, like water. Because mostly that's what it is.

Since blood is the substance that ferries vital minerals, vitamins, glucose, and proteins, as well as oxygen, throughout the body, it follows that an adequate water supply is crucial to ensuring our systems can get what they need to do what they are supposed to do. In other words, you can eat all the kale in the farmers market, but if you're not getting enough water, the vegetable's abundance of antioxidant A, C, and K vitamins, carotenoids, flavonoids, and sulphur-containing phytonutrients won't do you much good.

Water as solvent. Another important way water works in the body is by dissolving chemicals and ridding our systems of toxins. Water breaks down waste products, including naturally occurring chemicals such as lactic acid or cortisol, and helps our organs, muscles, and tissues eliminate what's unnecessary in the form of pee, poop, and perspiration. Yes, sweating is the way the body's biggest organ — the skin — excretes unwanted elements. That's why clear skin depends on getting plenty of water. If you're not well hydrated, your sweat glands may deactivate, causing toxins to accumulate and get trapped.

Water as lubricant. Just as cars require gas and oil, so bodies need food and water. Without of the fluidity of water coursing through our systems, our body's gears, like those of any vehicle, will begin to grind and then to break down. The water in saliva lubricates the mouth, the throat, and the digestive system, making it easier to break food down, to swallow it, and to move it comfortably through the intestines. The water in your digestive system makes for smooth waste-elimination, which is one of the fundamental ways we rid the body of toxins. We're constantly hearing about the importance of eating lots of fiber for optimal digestive health. But without enough water, says Koff, "all that good fiber — which you're hopefully getting from whole food sources — won't move out of system and can be harmful or irritating."

The water in synovial fluid, the yolk-like substance in our joints, lubricates muscle and joint movements, providing for smooth, cramp-free motion and shock-protection. The water in our tears lubricates our eyes. Without it, teenagers would have a tougher time rolling their eyes and parents would have a tougher time blinking in disbelief. Of course, tears also keep eyes flushed from dust and debris. These lubricants and the countless others (think spinal fluid, mucous, the aqueous and vitreous humors, etc.), in our bodies require adequate water intake for proper functionality. Thirst, stiff joints, sluggishness, dry eyes, and sluggishness are all signs it's time to find a drinking fountain or to increase you consumption of water-rich foods.

Water as protective cushion. There is no better example of water as protective cushion than the amniotic sac. Yes, that soft bubble in which fragile embryos become babies sturdy enough to brave birth is essentially a big bag of water. It's strong enough to keep growing fetuses safe from bumps and jolts to a mother's belly, yet pliable enough to endure baby's kicks, punches, and lunges. It also regulates temperatures, keeping baby from experiencing whatever heat or cold its mother must endure. As most expecting mothers know, healthy amniotic fluid levels require healthy quantities of drinking water (no matter how often they may have to waddle to the ladies' room).

Similarly, cerebrospinal fluid (aka spine and brain fluid) serves as soft security for two of our most sensitive structures. Without the protective qualities of this liquid in our heads and around our spinal cords, our nerve sources would be extremely vulnerable. The fluid acts as shock absorbers, mitigating brain damage when there is a blow to the head or spinal damage in the case of a back injury by distributing the blow's impact and thereby dulling its force on any given spot.

How Can We Be Sure We're Getting Enough? With so many reasons to make sure you're well hydrated, the question becomes how much do we need on a daily basis. An easy way to estimate the quantity your body needs is to start with your weight in pounds, divide that number in half, and then convert it into ounces to be consumed. For example, a 150-pound person would need about 75 ounces of water per day. That's approximately nine eight-ounce glasses. Sound like a lot? Keep in mind that we lose water all the time—even through breathing and sleeping.[pullquote:right]

Also, "Water intake doesn't have to mean sitting down and gulping from a glass," says Koff. Drinking is important — and she recommends starting the day with a glass of water, preferably with a squeeze of lemon — but it's not the only factor. High-water-content foods can make a big impact in your hydration level. "If something drips with water when you bite into it, then it's got a high water content," says Koff, so you can factor it in to your personalized daily consumption plan. Pretty much any vegetable qualifies, she notes, as do most soups. Steaming, poaching, or cooking in broth are all good ways to increase the water content of your food.

Coffee and tea are essentially water and do count toward your daily intake. They can have a diuretic effect if they are caffeinated, but, unless consumed in excess, won't increase your risk of dehydration. Adding sweeteners to those beverages, however, or drinking lots of juice or soda, is not a great way to hydrate, as the body requires more water intake to flush out the deleterious effects of the sugars.

The bottom line is that along with a diet rich in high-water-content foods, we all should be drinking several glasses a day, preferably by sipping constantly, not guzzling a glass or two at a time. For people who just don't love the taste of water, click here for great ways to add healthy flavor using fruits and herbs.