You’ve heard it a thousand times: Drink eight glasses of water a day. Even though this is just an estimated amount for most people, you don’t do it. You’re drowning in excuses–you don’t like the taste, it’s not convenient, you never remember. No big deal, you think–it’s not affecting your health. To understand why water is so important, you have to know what it does for your body. So grab a tall glassful, and read on.

Waterlogged
Your body is one–half to four–fifths water, depending on how much body fat you have. Water makes up nearly 85 percent or your brain, about 80 percent of your blood and about 70 percent of your lean muscle. (because there are a lot of tissues that have less water, the average is about 50 percent.)
Every system in your body depends on water. Its roles are impressive. Water:

• regulates your body temperature.
• removes wastes.
• carries nutrients and oxygen to your cells.
• cushions your joints.
• helps prevent constipation.
• lessens the burden on your kidneys and liver by removing some of the toxins.
• helps dissolve vitamins, minerals and other nutrients to make them accessible to your body.

Lack of water can lead to dehydration. Even slight dehydration can sap your energy and make you feel lethargic. Dehydration poses a particular health risk for the very young and very old.

Prevention floats
Besides helping your body run smoothly, there’s some evidence that water helps prevent certain diseases. People who have had kidney stones can prevent further stones from forming by drinking lots of fluid. And in one study, women who drank more than five glasses of water a day had a risk of colon cancer that was 45 percent less than others in the study who drank two or fewer glasses a day.

Why water?
You lose about 10 cups of fluid a day through sweating, exhaling, urinating and bowel movements. Drinking water isn’t the only way to replace those fluids. You also get water from other beverages and even from foods. In an average diet, it’s estimated that solid foods provide between three and four cups of water a day. But because it’s difficult to estimate the amount of water solid foods contribute, it’s recommended that you only count fluids towards meeting your goal of eight glasses a day. But that’s only a ballpark estimate.

To better determine how much water you specifically need each day, divide your weight in half. Your answer is the approximate number of fluid ounces you should drink daily. Eight glasses is the average. Some people need more, while others can get by on less. Exercising or engaging in any activity that causes you to perspire and dehydrate increases your water requirement, as do hot, humid or cold weather and high altitudes. Keep in mind that sports drinks are better than water if you’re exerting yourself for 90 minutes or more at a time, 60 minutes if the activity is particularly intense or temperatures are very hot. Some beverages, such as those with caffeine and alcohol, are dehydrating, so if you drink them, you need even more water to compensate.

Water safety
Three out of four people are concerned about the safety of their tap water, which has led to a dramatic increase in sales of water filtration systems and bottled water. Is your water safe to drink? Be Hydrated! If you’re healthy and not in any dehydrating conditions, some experts say you can use your thirst as an indicator of when to drink. Others believe that if you’re thirsty, you’ve already started to dehydrate. Play it safe by making a conscious effort to keep yourself hydrated. Drink a glass of water when you get up and another when you go to bed. Keep a bottle with you during the day or take regular water breaks. Drink water with meals and avoid relying on soda to provide your fluid needs. Getting enough water just might buoy your health.