I recently acquired a new scale in my office to check patients' weights. The cool thing about this scale is that it not only detects percent of body fat, it also detects percent of body water (it also tells us how many pounds are bone mass, how many pounds are muscle mass, the caloric need to maintain that physiology and a few other tidbits).

For this article, the focus will be the body's water and hydration.

The admonition in Arizona is "don't get de-hydrated." But just like most things that are good for us, too much of a good thing, in this case water, could turn into a bad thing. Over-hydration is as potentially a life-threatening situation as under-hydration.

As always, a little bit of anatomy and physiology is necessary to better understand the topic at hand.

More than half of the human body is actually water. Women should be approximately 50 percent water and men should be approximately 60 percent. Too much water, however, could be considered a poison.

Three body systems (skin, lungs and kidneys) are responsible for contributing to the maintenance of the delicate balance necessary for optimum cellular functioning, called homeostasis.

Essentially, the skin maintains the temperature of this watery environment. We perspire when our insides get too hot and we shiver when our insides get too cold.

The lungs breathe in oxygen so the cells can metabolize energy and they breathe out carbon dioxide, a by-product of that metabolism.

Lastly, the kidneys are responsible for maintaining the body's electrolytes within certain ranges.

Electrolytes are minerals, most notably sodium, potassium and chloride. When there is too much water surrounding our body's cells, the level of sodium is diluted compared to the levels within the cells.

To maintain homeostasis water will flow into the cells actually causing them to swell. When the levels of any of these electrolytes move out of their normal ranges (either too much or too little) the body can experience a variety of symptoms that represent the effect that the imbalances have on other major body organs such as the heart and brain.

Adequate sodium balance is necessary for transmitting nerve impulses and proper muscle function, and a major deviation of this concentration can cause problems.

This is particularly evident by the earliest signs of water intoxication, which occur due to swelling of brain cells: Headache, personality or behavior changes, confusion, irritability or drowsiness.

Later symptoms of water intoxication include a heart rate that is too slow, muscle weakness, cramping, nausea and vomiting, and seizures. The body cannot function optimally when its water/electrolyte environment is disrupted. If not recognized and treated appropriately, death could ensue.

The American College of Sports Medicine recommends if you are exercising regularly, you will probably need between one half and one whole ounce of water (or other fluids) for each pound of body weight per day, or at least 1 to 2 liters depending upon one's body mass.

To determine your baseline range for water requirement, use the following formula:

• Low end of range = Body weight (pounds) x 0.5 = (ounces of fluid/day)

• High end of range = Body weight (pounds) x 1 = (ounces of fluid/day)

For example, if you weigh 150 pounds, your approximate water requirement will be between 75 and 150 ounces each day.

Thirst is an important indicator during and after physical activity, especially in hot environmental conditions.

However, the clear and important health message should be that thirst alone is not the best sign of dehydration or the body's fluid needs. Dehydration represents the opposite end of the spectrum from over-hydration and results from the failure to adequately replace lost fluids.

This can lead to elevated body core temperatures and increases strain on the cardiovascular system.

Dehydration is a potential threat to everyone, especially those who are not acclimated for strenuous activity in hot environments.

• Agnes Oblas is an adult nurse practitioner with a private practice and residence in Ahwatukee Foothills. For questions, or if there is a topic you would like her to address, call (602) 405-6320 or email aoblas@newpathshealth.com. Her website is www.newpathshealth.com.

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