When you have a cold or flu, the doctor (or Dr. Mom) may tell you to drink lots of fluids. But did they ever explain why you need to guzzle all that water and juice? The extra fluid helps prevent dehydration, which can make you feel even worse, and make it harder to get well. If you have a runny nose, a feverish sweat, or vomiting and diarrhea, it may seem obvious why you’d need to drink more to replace those lost fluids. But these aren’t the only reasons the body needs extra fluid when you’re sick.

　　Increasing Metabolism

　　If you have a fever, that increase in body temperature increases your metabolism–in other words, all the biochemical reactions that keep you alive speed up. A fever of 101 degrees Fahrenheit increases your body’s metabolic rate by about 10%. What difference does that make?

　　Two key ingredients of metabolic reactions are water and oxygen. Increased metabolism uses more water and also makes you breathe faster, to supply the extra oxygen. And guess what? As you breathe faster, you breathe out more moisture, along with more carbon dioxide.

　　Dehydration

　　Even if you don’t have symptoms that cause obvious water loss–like a runny nose, sweating, vomiting or diarrhea–a cold or flu can dehydrate you in hidden ways. Just a slight rise in body temperature requires more water for metabolic reactions and breathing.

　　On top of all that, when you’re sick you just might not feel like eating or drinking as much as usual. That’s why Mom keeps reminding you to drink your fluids!

　　生病的时候为何会脱水？

　　当你不幸患了感冒或流感时，医生（或者妈妈）可能会叮嘱你要多喝液体，但他们是否曾解释过为什么你要狂喝水和饮料？额外的液体可以避免脱水，一旦脱水你会感觉更糟，也更难康复。如果你出现流鼻涕、发烧出汗、或者呕吐腹泻等症状，显然你需要多喝液体以弥补身体失去的水分。但这些并非你生病时身体需要多补水的全部原因。

　　加快新陈代谢

　　若你发烧，体温的升高将加快你的新陈代谢，换句话说，所有维持生命的生化反应将加速。101华氏度的高烧将使身体的代谢速率增加百分之十。这又有什么分别呢？

　　新陈代谢作用的两大主要成分是水和氧。新陈代谢加快需要更多的水，也使你呼吸加快以补充足够的氧。你猜接下来会怎么着？当你呼吸加快，你也将呼出更多的湿气和二氧化碳。

　　脱水

　　即便你没有会引起明显失水的症状，如流鼻涕、出汗、呕吐和腹泻等，感冒或流感却以隐蔽的方式导致你脱水。哪怕是体温一丁点的升高都需要更多的水以维持加快的新陈代谢作用和呼吸。

　　除此之外，你生病时食欲可能不如平常，这也是妈妈一直提醒你喝水的原因！