There's no doubt that water is vital to any life.About 60 percent of the average adult human body is made of water. This includes most of your brain, heart, lungs, muscles and skin, and even about 30 percent of your bones. Yet there's little scientific agreement about the exact amount of the stuff an individual should consume each day. So how much water do you actually need to drink to be healthy?

    You may have heard that you should drink eight 8-ounce glasses of water a day. Yet, the downside of this rule, researchers say, is that drinking water by the glass is not the only way that humans take in it. The “8 X 8” rule essentially overlooks two big sources of daily water consumption. One such source is food. Everything you eat contains some water. Watermelons, for example, are more than 90 percent water by weight. Different diets naturally contain different amounts of waters, and the counts. The other key water sources are other beverages. Non-alcoholic drinks such as coffee, and tea, contain mostly water and all contribute to your hydration（水量）.

    So, between all the food, water and other fluids you consume in a day, how much water should you aim to take in?

    The National Academics of Sciences suggests that woman consume a total of approximately 2.7 liters (91 ounces) of warm from all beverages and foods each day and men 3.7 liters (125 ounces). But these are just general guidelines.

    The truth is, there is no magic standard for hydration—everyone's need vary depending on their age, weight, level of physical activity, general health and even the climate they live in. The more water you lose, the more water you'll need to replace with food and drink. If you are looking for concrete advice, though, the best place to look is within. Drink up when you're thirsty.