Above: Image © Staff Sgt. Brian Buckwalter, Wikimedia Commons

With summer weather fast approaching, you may often be told to “drink plenty of fluids” and to “keep hydrated”. We need water to survive and to maintain balance between the environment inside our cells and that on the outside, but is it possible to drink too much?

Maintaining Balance

Electrolytes, such as sodium, are necessary for the transmission of nerve signals and for muscle movement. When we exercise, we lose both sodium and water in our sweat. Individuals who replace only the lost water will have a low concentration of sodium in their blood stream. Think of it this way: if you have a container filled with a mixture of sodium and water and spill out half, the way you would if you were sweating, then replace the lost fluid with only water, the sodium concentration in the glass is less than it was before.

Did you know? One of the more widely-known health tips is to drink at least eight 8-ounce glasses of water per day. But according to Heinz Valtin, a kidney specialist and professor of physiology from Dartmouth Medical School, there is no supporting evidence to back this popular counsel.

The amount of electrolytes, like sodium, inside and outside our cells is tightly controlled by our body. If we only replace lost sweat with water, the sodium concentration outside our cells will be lower than the sodium concentration inside our cells. When we have too much sodium inside our cells, water will move into our cells to dilute the sodium within, through a process called osmosis. Our cells can stretch to accommodate this extra water, but if they stretch too far, they can swell.

Did you know? The balance our body seeks is called homeostasis, from the Greek word histemi meaning ”standing still”.

Can we over-hydrate?

Believe it or not, water, like any other substance, water can be a ”poison” if we have too much of it. The scientific term for water intoxication is called hyponatremia, which basically means the level of sodium in the body is dangerously low. This, in turn, causes the body’s cells (particularly those in the brain) to swell excessively.The occurrence of this condition is on the rise, as participation in sports increases and amateur athletes enter endurance events.

Did you know? Ironically, drinking too much water causes symptoms similar to dehydration, including nausea, vomiting, headaches and muscle cramps. In severe cases, sufferers may experience confusion and convulsions which could lead to coma or even death.

One of the most popular cases of hyponatremia happened in 2007 in California, when a radio station held a contest called “hold your wee for Wii”. Participants drank large amounts of water without the ability to use the bathroom in order to win a Nintendo Wii system. One of the participants, Jennifer Strange, died of water intoxication several hours after completing, but not winning, the competition.

This doesn't mean you should stop drinking water! It is a good habit to have a beverage with each meal and it is extremely important to drink fluids when you are thirsty. Keep in mind that the amount of water required to reach toxic levels is extreme. Our kidneys excrete one litre each hour, so as long as fluid intake does not severely exceed fluid excretion, and as long as we replenish lost sodium by drinking beverages containing the necessary electrolytes, the chances of hyponatremia are very low.

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References:

Justyna Kulpa

I am a PhD student at the University of Montreal studying estrogen receptors and their role in breast cancer.


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