By Lisa Jahns

When was the last time you stopped to think about water?  Not that pesky leak in the kitchen sink, or the melting snow the dog tracked in.  But drinking water--it's easy to forget about at this time of year, isn't it?

Without the summer heat to work up a thirst, many of us may not drink as much water in the winter months as our bodies require.  Yet, cold weather can be as dry as desert heat.  This is because cold air cannot hold very much moisture.  Wind is also drying.  Indoor heating creates a very dry environment as well.  Even without sweating, our bodies lose moisture through the skin.  Much like houseplants, we need water year-round.

We are made of water.  Water is the largest component of our bodies.  The percent of our bodies that is made up of water however, depends upon several factors, such as our age, our gender, and our body fatness.  For instance, newborn babies have the most water.  They are born with about 75% water, which drops to around 65% in the first year. 

Muscle has higher water content than body fat. Therefore, because women naturally have more body fat than men, they are made up of slightly less water than men - about 55% compared to men at 60%. 

All of the organs of the body, such as lungs, heart, and muscles contain a great deal of water, and require water to stay healthy.  Most people, under the right circumstances could survive without food for weeks or even months, but no one could survive more than a few days without water.

Why is water good for us?  Blood is 83% water, which is used to transport oxygen and nutrients to our cells, remove waste products and regulate body temperature.  The liver and the kidneys, in particular, use water to help excrete toxins and harmful compounds that we consume or that our bodies produce as part of the daily business of keeping us alive and moving around.  Our bodies use water to help regulate blood pressure.  Most Americans consume too much sodium, and water is used to help remove sodium from the body.  Water helps to protect joints and keep them moving.  Water is essential to good health.

How much water do we need to drink every day?  Every day we lose water though breathing, perspiration, urine and bowel movements.  Therefore, we need a constant supply of water to maintain good health.  Too little water can lead to dehydration, which impairs normal functions. Even mild dehydration can drain your energy and make you tired (remember, the brain is 70% water).

We get water from many sources. U.S. survey data show that drinking water and other beverages provide about 81% of total water consumed by 19- to 30-year old men and women.  Food provides the remainder, about 20% of total water intake. The high water content of many fruits and vegetables gives yet another good reason to include them in our diets.  Tomatoes and watermelons, for example, are 90% or more water.  Remember, however, that fruit beverages and milk also contain calories, as do sugar-sweetened beverages.  Coffee, tea, and soda also contribute to total water intake, but also contain caffeine and can contain unwanted calories as well. 

The Institute of Medicine has recommended adequate intake (AI) values for total water at levels to prevent dehydration.   The AI for men aged 19+ is 3.7 liters each day, and 3 liters (13 cups) of which should be consumed as beverages. The AI for women aged 19+ is 2.7 liters about 2.2 liters (9 cups) of which should be consumed as beverages each day.