How Much Water Do You Really Need To Drink?

"You are what you eat — but if you want to get literal about it, you are mostly what you drink. So, how much of that should be water?"

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. Besides being one of the main ingredients in the recipe for humankind, water helps us regulate our internal temperature, transports nutrients throughout our bodies, flushes waste, forms saliva, lubricates joints and even serves as a protective shock absorber for vital organs and growing fetuses.

Food and drink

One such source is food. Everything you eat contains some water. Raw fruits and vegetables have a lot; fruits such as watermelons and strawberries , for example, are more than 90 percent water by weight, according to the U.S. Department of Agriculture. Different diets naturally contain different amounts of water, but it adds up. According by the National Academies of Sciences, the average North American gets about 20 percent of his or her daily water intake through food, and that counts toward healthy hydration.

The other key water sources that the "8 x 8" rule overlooks are other beverages. Non-alcoholic drinks such as coffee, tea, milk, juice and soda contain mostly water , and all contribute to your hydration.

So, between all the food, water, and other fluids you consume in a day, how much water should you aim to imbibe? The National Academies of Sciences suggests that women consume a total of approximately 2.7 liters (91 ounces) of water from all beverages and foods each day and that men get approximately 3.7 liters (125 ounces) daily. But these are just general guidelines and are not supported by firm scientific studies.

The truth is, there is no magic formula for hydration — everyone's needs vary depending on their age, weight, level of physical activity, general health and even the climate they live in. The more water you lose to sweating, the more water you'll need to replace with food and drink.

So, naturally, a person doing strenuous physical work in a hot, tropical climate would need to drink more water than a person of identical weight and height who spent the day sitting in an air-conditioned office.