Truth to tell, somDon't Let Yesterday Take Up Too Much Of Today-75etimes I don’t follow my own advice, and when I suffer the consequences, I rediscover why I offer it. I’ve long recommended drinking plenty of water, perhaps a glass with every meal and another glass or two between meals. If not plan water, which is best, then coffee or tea without sugar (but not alcoholic or sugary drinks) will do.

I dined out recently after an especially active day that included about 5 miles of walking, 40 minutes of lap swimming and a 90 minute museum visit. I drank only half a glass of water and no other beverage with my meal.

It did seem out that I had no need to use the facilities afterward, not even after a long trip home. But I didn’t focus on why until the next day when, after a fitful night, I awoke exhausted, did another long walk and swim, and cycled to an appointment four miles away. I arrived parched, begging for water. After downing about 12 ounces, I was a new person. I no longer felt like a lead balloon.

It seems mild dehydration was my problem, and the experience prompted me to take a closer look at the body’s need for water under a variety of circumstances.

Although millions of Americans carry water bottles wherever they go and beverage companies like Coke and Pepsi would have you believe that every life can be improved by the drinks they sell, the truth is serious dehydration is not common among ordinary healthy people. But there are exceptions, and they include people like me in the Medicare generation, athletes who participate in particularly challenging events like marathons, and infants and small children with serious diarrhea.

Let’s start with some facts. Water is the single most important substance we consume. You can survive for about 2 months without food, but you would die in about 7 days without water. Water makes up about 75% of an infant’s weight and 55% of an older person’s weight.

Good hydration definitely protects against kidney stones, and there is evidence that it counters constipation and exercise-induced asthma. It may also protect against vascular diseases, like stroke, an elevated heart rate or sudden drop in blood pressure and is especially important for people with diabetes.

Despite the vital importance of water, there are relatively few good studies of how much is needed, by whom and under what circumstances, according to Barry M. Popkin, a professor of nutrition at the University of North Carolina. “We do not truly understand how hydration affects health and well-being, even the impact of water intakes on chronic diseases,” he and his colleagues wrote in Nutrition Reviews.

“Nearly all funding of water research has been provided by industry,” Dr.Popkin said in an interview, referring to companies that sell all manner of beverages, including bottled water. “And most of the research on water has been organ-specific, done by people studying the kidneys or lungs. Whole body systems haven’t been well studied.

There are no formal guidelines on how much water people need each day. The amount is affected by what people eat, their weight and activity level and even the environment in which they live.

The institute stated that all kinds of liquids can contribute to a person’s total water needs, including beverages like tea, coffee, juices,

To be sure, it’s important for athletes to drink plenty of water, especially when high levels of activity, heat and humidity result in excessive sweating. But overdoing hydration has its own risks; marathon runners and other athletes have died after drinking more water than the kidneys are capable of processing in a timely manner, leading to swollen cells and dangerously low blood levels of sodium and other electrolytes.

At the same time, inadequate hydration can have debilitating effects. Studies by Lawrence B. Armstrong and colleagues at the University of Connecticut showed that dehydration can adversely affect vigilance, concentration, reaction time, learning, memory, mood, reasoning and can cause headaches, fatigue and anxiety.

 

Jane Brody

nytimeshealth.com

May 9, 2016

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