I'm no scientist, but I'm compelled to reply to this since I had a little experience in this subject area a couple of years ago.
I am one of those people that almost never gets thirsty. It just doesn't happen. I can eat an entire meal without even taking a sip of a beverage. I can go from the time I wake up to the time I go to bed on just one regular sized bottle of water/can of soda/glass of juice. I simply never was one to drink much of anything at all.
Then, two years ago (May 5, 2006), I came home from work and promptly fainted in the middle of my living room floor. I wasn't out for long, but I felt absolutely awful for the rest of the evening - cramping muscles, teeth-chattering chills, nausea, dizziness, lightheadedness, aches and pains, my whole body was tremoring. I finally gave up on trying to fight whatever it was that was wrong with me, and went to the emergency room in the middle of the night. Diagnosis? Dehydration. They put two bags of fluids into me, and I was as good as new. For about two days. And then the symptoms started all over again, and back to the emergency room I went. This happened *five times* (three trips to the emergency room, two to the doctor) within a one-month span, before I finally got the message.
The last doctor I saw didn't just pump three bags of fluid into me; she also advised me to up my liquid consumption. She said I should be taking in twelve to fourteen 8-ounce glasses of water a day. It didn't have to be strictly water, but anything caffeinated didn't count, nor did juice with pulp. Milk, pulp-free juice, water, and decaf teas/coffees/sodas were fine.
I started paying more attention to my beverage consumption. It was sheer torture for me those first couple of weeks, as I simply wasn't thirsty. I'd have to look at the bottle of water sitting on my desk and force myself to take a sip every few minutes. However, I did force it down, and I have to confess that I have never felt better. I have not had any more spells like I did during this period of dehydration. I used to have muscle aches and spasms that went away after I started hydrating. I was prone to getting severe headaches every single day that also vanished after I started drinking more water.
So, I am now one of those annoying women you see carrying a bottle of water with her everywhere, constantly sipping on it. The way I felt when I went through that whole dehydration ordeal was the most ill I have ever felt in my entire life. It scared me half to death. I was so afraid that something was desperately, terribly wrong with me. All it turned out to be was a lack of water! The most shocking thing I learned from this experience was that thirst is a last resort warning for your body. By the time your body registers the fact that you are thirsty, you are already starting to dehydrate. Since I never drank much at all, it's no wonder my body finally turned against me.
Even two years later, I still drink large quantities of water, although not quite as much as the doctor recommended. I drink 8 glasses a day, bare minimum, and on some days I drink up to 12 or 14. If it is hot, or I've been exercising/sweating, I'm flying, or I'm going to be doing anything else that dehydrates the body such as consuming alcohol, I make sure I drink extra water. I actually completely gave up caffeine after this ordeal. After the first two weeks, I don't even miss it anymore. Nor do I miss feeling groggy in the morning without my jump-start can of Dr. Pepper. When I wake up now, I'm awake.
You're right that every person is different - just because my body needs this much water doesn't mean that someone else's body will. Some people may need more water than me. And it doesn't have to be just plain water that you have to consume to maintain a state of hydration. I do stick strictly to water, aside from one glass of orange juice every morning. The added perk to this is that I don't drink my calories, I can actually eat them and enjoy them (important to me since I'm getting married in two months and am trying to keep my weight exactly the same as it is right now to be sure my gown still fits on the big day). I don't think that drinking lots of water is exceptionally "healthy" but it is certainly better than all of the sodas and energy drinks most people consume these days, and since you do have to drink *something* it may as well be water. As for flushing toxins out of your body? It probably does help the kidneys with this some, although I have no idea how much. I don't drink all of the water I drink to "purify" by body, but simply to remain hydrated.
When you consider how much of your body is made up of water, doesn’t it make sense to stay hydrated? The body needs it to function. I didn’t have enough water, and my body quit functioning. One of the times I went into the hospital, my dehydration was so bad that my heart started skipping beats. Of course, there are also dangers of over-hydrating. You have to learn what your body needs, and listen to it.
I’ll get off my soapbox now. I just wanted to give my perspective on this.
