by Jennifer Webster

Your body is more than half composed of water—not as in a glass half-empty, but as in a sponge half-way to capacity. Of that water, about two-thirds is inside your cells, and the other half is traveling around in the bloodstream and the tissue between cells. If you’ve ever worked in hydraulics, you’ll recognize there’s a possibility for pressure differentials across all those permeable membranes. And you know it’s important to keep the balance.

Each of your thousands of cells tries to maintain an appropriate water pressure, relying on dissolved salts to help keep that pressure up. Water in the body will pass through cell membranes in the direction of higher salt content. For instance, if you drink too much water or other liquids without consuming salt, water between the cells will have less salt (in comparison to the liquid in the cells), so it will flow into the cells, possibly overfilling and damaging them. This sometimes happens to endurance athletes who drink excessive amounts of water.

More commonly, though, people don’t get enough liquid. They may lose fluid via sweat and not replenish it. In these cases, there isn’t a lot of liquid between the cells or in the blood stream, so the cells release water outward through their membranes. The result is decreased cellular volume. What does that mean for you?

First, it affects your brain. As brain volume decreases, you may feel disoriented. Your memory and attention may be reduced. Your heart may beat faster to compensate for lower blood volume. And, as blood becomes more concentrated, your kidneys will try to prevent water loss through urination, meaning you’re retaining more toxins than usual in your body. You’ll be less able to regulate your body temperature. Add stress—such as exercise or simply spending too much time in the heat—on top, and you may experience heat exhaustion or heat stroke.

Luckily, the body knows how to rectify a lot of problems. For instance, if you don’t have enough fluids, you may become thirsty. Listen to that urge! Every day, you should be drinking a lot of water and other fluids—half a gallon or so, and more if you’re pregnant, exposed to hot conditions, physically active or taking medication that makes you lose fluid.

Remember, drink your water, juice or other fluids even if you don’t feel thirsty. People age 65 and older should pay extra attention to how much they’re drinking, as they may no longer feel thirsty when dehydrated. It may be easiest to keep that glass of iced tea at your elbow while doing housework, or a thermos of ginger beer nearby while mowing the grass, rather than having to remember to make “pit stops” for water.

If you don’t like water, there are plenty of low-calorie solutions for staying hydrated while enjoying a sweet taste, such as:

  • Add a floral, mint or fruit-flavored tea bag to your iced tea brew.
  • Dilute your favorite fruit juice with mineral water.
  • Fill a mason jar with half coffee, half ice-cold milk.
  • Slice a cucumber, lime or or fresh fruit, and add the slices to a pitcher of iced water.