跑馬拉松的人 當心低鈉血癥
Question:
提問：
Is it possible to drink too much water?
人有可能會飲水過量嗎？
I typically drink far more than the recommended six to eight glasses per day, and feel dehydrated if I adhere to the guidelines. I have no underlying medical conditions, such as diabetes, that would lead to increased thirst.
據說每天的建議飲水量是六到八杯，但我通常喝水都遠多於此。如果要嚴格遵循上述指南飲水，我就感覺會脫水。補充一點，我並沒有糖尿病之類會讓人容易感覺口渴的病。
Answer:
回答：
Absolutely, and if you do, you can develop a dangerous condition called hyponatremia, or water intoxication.
人當然可以飲水過量，但這也可能會導致一種很危險的疾病：低鈉血癥，又稱水中毒。
Under normal conditions, the body beautifully maintains its fluid balance. Lose fluids through sweating, for instance, and your body responds with the feeling of thirst. You drink. If you swallow more liquid than needed just then, your body typically responds by excreting the excess through urination.
在正常情況下，人體都很完美地保持着體液平衡。例如，在因出汗而喪失體液時，身體會做出反應讓你感覺口渴，於是你就去喝水。如果攝入的液體量超過了所需，身體的反應通常是通過小便將多餘的水分排泄出去。
But should you consume so much fluid that your body can’t easily rid itself of the surplus, you dilute sodium levels in your blood. Osmosis then draws water from the blood into body cells to equalize sodium levels, and those cells swell. At that point, you have hyponatremia. If the cellular bloating occurs in the brain, it can be fatal.
但如果你補液過多，以致身體沒法一下子排出多餘的水分，血液中的鈉濃度就會下降。在滲透作用下，水從血液進入體細胞以平衡鈉水平，這就會引起體細胞膨脹，你就患上了低鈉血癥。要是細胞水腫發生在大腦還可能導致致命後果。
Until about 20 years ago, hyponatremia was extremely uncommon among healthy people. But then several marathon runners died from hyponatremia. In general, they had been middle- or back-of-the-pack, slower runners. They did not sweat much. But they drank plenty of water, trying to ensure that they would be well hydrated.
直到大約20年前，低鈉血癥在健康人羣中一直非常罕見。其後，有若干名馬拉松運動員因低鈉血癥死亡。這些人大多是跑在參賽者羣體的中後部、速度較慢的運動員。他們出汗不多，卻大量飲水，一心想着要確保水分充足。
Today, most knowledgeable coaches and exercise experts warn athletes not to overdrink. “You should drink only when you need to, when you are actually thirsty,” said Dr. James Winger, a professor of family medicine at Loyola University Medical Center, who has studied the hydration habits of athletes.
如今，最有見識的教練和運動專家都警告運動員不要過量飲水。詹姆斯·溫格(hydration habits)博士是洛約拉大學醫學中心(Loyola University Medical Center)的家庭醫學教授，一直在研究運動員的補水習慣。他說：“你應該只在需要時，也就是你確實渴了時再喝水。”
If you’re not sure whether you’re drinking too much or too little during exercise, try weighing yourself before and after a lengthy workout, experts advise. If you have lost more than about 3 or 4 percent of your body weight, you’re probably flirting with dehydration and might want to drink a bit more next time. But if you have gained weight or your fingers seem swollen and your rings tight, you’re most likely drinking too much and should moderate intake.
專家建議，要是你拿不準自己在鍛鍊時是否飲水過多或過少，可以試試在長時間運動前後分別稱一下體重。如果運動後你的體重減少了3%或4%以上，你很可能已經有輕度脫水，那麼下次可以酌情多喝點水。然而，如果你體重增加了，或是你的手指看起來有點腫，戒指也似乎變緊了，就可能是飲水過多了，以後要注意適量即可。
Most important, listen to your body’s signals, Dr. Winger said. “Thirst is a very reliable indicator,” he said, of whether and how much to drink.
溫格博士說，最重要的是要聽從身體給出的信號。要判斷自己是否需要喝水以及需要喝多少，“口渴都是很可靠的指標，”他說。
