Metabolism Myths: Thirst and Dehydration

You may have heard that by the time you are thirsty, it’s too late, and you’re probably already dehydrated.

To determine if there’s any truth to this, first you should know what goes on in your body when you’re thirsty.

Plasma osmolality is a measure of the concentration of substances such as sodium, chloride, potassium, urea, glucose, and other ions in blood. When you plasma osmolality increases, it means theses substances in the blood have become more concentrated. It also means that the amount of fluid or water in blood has decreased.

A rise of less than 2 percent in plasma osmolality will educe thirst. To indicate true dehydration, plasma osmolality should increase by 5 percent. This means that even if you eat a high-sodium meal and get yourself extremely thirsty, you could still be not dehydrated. According to Dr. Mark Dedomenico, “You can get significant increases in thirst without extreme concentration changes in your body fluid.”

However, instances when “thirsty” is “too late” do happen. These instances include water immersion and dehydration in the elderly. Water immersion is where you are plunged in cold water intermittently or for long periods of time at 60 F or lower.  Water immersion stems thirst response, so even though you maybe dehydrated, you won’t know it. as for dehydration in the elderly, aging is mostly to blame. As we get older, our thirst response to dehydration becomes less sensitive, thus many old people may not meet their fluid needs.

Now that you know how the body works when it’s thirsty, you can rest assured that you’re not dehydrated. It could be simply be your high-sodium lunch, or the bananas that you ate which spiked your potassium levels. Still you should aim for those 8 glasses of water a day, for optimum health.

Source: MSN Health

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