Health benefits of water.  According to Mayo and Cleveland Clinics
Water is your body's principal chemical component and makes up about 60 percent of your body weight. Your body depends on water to survive.
Every cell, tissue and organ in your body needs water to work properly. For example, water:
  • Gets rid of wastes through urination, perspiration and bowel movements
  • Keeps your temperature normal
  • Lubricates and cushions joints
  • Protects sensitive tissues
Lack of water can lead to dehydration — a condition that occurs when you don't have enough water in your body to carry out normal functions. Even mild dehydration can drain your energy and make you tired.
How much water do you need?
Every day you lose water through your breath, perspiration, urine and bowel movements. For your body to function properly, you must replenish its water supply by consuming beverages and foods that contain water.
So how much fluid does the average, healthy adult living in a temperate climate need? The National Academies of Sciences, Engineering, and Medicine determined that an adequate daily fluid intake is:
  • About 15.5 cups (3.7 liters) of fluids for men
  • About 11.5 cups (2.7 liters) of fluids a day for women
These recommendations cover fluids from water, other beverages and food. About 20 percent of daily fluid intake usually comes from food and the rest from drinks.
What about the advice to drink 8 glasses a day?
You've probably heard the advice, "Drink eight 8-ounce glasses of water a day." That's easy to remember, and it's a reasonable goal.
Most healthy people can stay hydrated by drinking water and other fluids whenever they feel thirsty. For some people, fewer than eight glasses a day might be enough. But other people might need more.
  • Activity level: If you work out a lot or are moving all day long, drink more water.
  • Location: If you find yourself in a warmer climate, you’ll probably want to increase your water intake.
  • Metabolism: If you consider yourself to have a faster metabolism, and your body seems to need more fuel to keep its engines revved — you may also notice that you need more water.
  • Size: The more you weigh, the more water your body tends to need.
  • Alcohol consumption: Before you decide on a second cocktail, drink a glass of water to rehydrate yourself and replace fluids caused by alcohol-mediated losses.
  • Health: “We really worry when people are sick and they’re not getting a sufficient amount of liquids, especially if they are also losing fluids due to vomiting or diarrhea” notes Dr. Sukol. If you have a fever, it’s a good idea to increase your daily quota of fluids by a few cups. Clear broth and gelatin also count as fluids.
  • Physical activity: Did you go for a sweat-inducing run or did you decide to snuggle up with a book? Again, the more active you are, the more water you’ll need.
  • Weather: You’ll definitely need more water during a heatwave than a blizzard. Use your common sense. If you live in a dry climate or a dry home, it won’t hurt to drink a little more than the daily recommendation.
water helps your:
  • Blood: Water ensures that your blood is just the right consistency to carry oxygen- and nutrient-rich blood to the areas that need it, including your brain, heart, kidneys and muscles.
  • Digestive system: “Dehydration is an easily reversible cause of constipation.”
  • Joints: Think of your joints like the gears of your car — they need to be well-lubricated to work and last.
  • Kidneys: Drinking adequate amounts of water can prevent kidney damage and disorders.
  • Skin: For clear, wrinkle-free skin, H2O can be just as effective as expensive anti-aging creams and lotions. It can also stave off certain skin disorders.
  • Teeth: Water keeps your mouth clean and lowers your risk for tooth decay.
There’s also research that water may:
  • Boost exercise performance.
  • Help with weight loss.
  • Reduce allergy and asthma symptoms.
  • How to tell if you’re drinking enough water
  • Even if you’re not thirsty, don’t assume you’re drinking enough water. Instead, take a peek at your urine. “If it’s almost the color of water, you’re right on track. But if your urine is bright yellow or has a strong odor, then you could probably use more fluids,” notes Dr. Sukol of the Cleveland Clinic