Popular wisdom says drink eight glasses of water a day for good health. But a new study has shown that those eight glasses might be unnecessary—or even harmful to your health.
Researchers at Monash University and the University of Melbourne found that determining the proper amount of water an individual needs to consume each day is as simple as listening to that body's unique cues. "If we do what our body demands us to we'll probably get it right—just drink according to thirst rather than an elaborate schedule," says Michael Farrell, an associate professor at the Monash Biomedicine Discovery Institute. The command center for this thirst, the researchers found, is a 'swallowing inhibition' that is activated by the brain after liquid has been consumed in excess of what the body requires.
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According to Science Daily, this built-in system is the body's natural tool for maintaining the ideal water volume. Therefore, the scientists found that consuming a perceived required amount of water per day—such as eight glasses—could lead to overconsumption of water, which in the most extreme cases could lead to water intoxication or hyponatremia, a dangerous lowering of sodium levels in the blood.
In order to test this hypothesis, the researchers asked study participants to rate the amount of effort it took to swallow water in two different scenarios. The first was directly following exercise, when thirst levels were high, and the second was when they were simply asked to drink a specific amount of water. Their conclusion showed that when water consumption was mandated, the participants found it three times more difficult to swallow.
"For the first time, we found effort-full swallowing after drinking excess water, which meant they were having to overcome some sort of resistance," says Farrell. "This was compatible with our notion that the swallowing reflex becomes inhibited once enough water has been drunk."
According to Farrell, the discovery of this bodily impulse suggests that consuming water beyond the point of natural thirst could be detrimental to one's well-being. One such fatal example of this is "when athletes in marathons were told to load up with water and died... because they slavishly followed these recommendations and drank far in excess of need," the professor says.
So when in doubt, let thirst be your guide.