Ask the Expert: Why should I drink water?

Q:  Why is drinking water so important? - And how much water should I be drinking throughout the day? 

A:  Of the 6 essential nutrients needed for life, carbohydrates, protein, fats, vitamins, minerals and water, water is the most overlooked.  You can survive for up to 6 weeks without food, but you wouldn’t last longer than a week without water. 

Water is the most abundant and important substance in the body making up 50-75% of our total body weight.  Every cell, tissue and organ in the body and almost all bodily functions require water.  Water regulates our temperature, transports nutrients and oxygen to your cells, and carries waste products away.  It moistens the tissues in the mouth, nose and eyes, and is the main component of every bodily fluid.

We are constantly losing fluid throughout the day through perspiration, urination, bowel movement and breathing.  To make sure you don’t get dehydrated, you need to make up for your fluid loss by replacing it throughout the day.  Even mild dehydration can give you headaches and reduce your physical performance; severe dehydration can lead to serious health problems.

Fortunately, according to the Institute of Medicine (IOM), a division of the National Academy of Science, the vast majority of healthy people meet their daily hydration needs by letting thirst guide their fluid consumption.  The thirst mechanism works well for most, but it is not foolproof, especially with the elderly children and those who are ill.  To be safe, they should drink enough to quench their thirst then a little more.  Exercisers and athletes need to pay more attention too.  Prior to starting an exercise session or an athletic event they should drink a cup (8 oz.) of water before they start, a cup for every half hour during the exercise session, and another cup when they are finished.  Ideally they should weight the same when they are finished as they did when they started the session or event.  One simple guideline is that if you are properly hydrated your urine will be pale, almost colorless.  Darker color urine is a sign of dehydration.

So how much water do you really need?  That varies based on a number of factors including body size, caloric expenditure, your environment, etc.  But according to the Institute of Medicine, women need about 8-9 cups of water per day; men need 10-12 cups.  Since water is the primary component of all beverages, all beverages can contribute to meeting your hydration needs.  Alcohol for obvious reasons should be consumed in moderation if not at all.  The other caution with some beverages is their caloric contribution.  We are now consuming on average more than 400 calories a day in caloric beverages.  Those are extra calories a weight conscious person cannot afford.  As you might remember hearing at the Institute, “you should eat your calories, not drink them.”  The majority of your fluid needs should be met with non caloric beverages with water being on the top of the list.  Another advantage of consuming a diet rich in fruits and vegetables is that they can contribute to your water intake as well.  Both bottled and tap water are for the most part safe, so let taste and convenience guide you.  If you are concerned about the safety of your tap water, take a sample to your local health department for an analysis.