by Gary2310 » Fri May 10, 2013 9:50 am
One of the reasons why you can feel sick (e.g., headache, fatigue, nausea, etc.) when the weather is really hot and you become dehydrated, even mildly dehydrated as Tom indicated, is because the body attempts to keep its core temp at a level to sustain life. If the body's core temp rose too high, which can easily happen if there were not physiological mechanisms at work keeping the core temp regulated, fragile enzymes needed to sustain the millions of chemical reactions that the body depends on in order to sustain life would become deactivated, meaning that they would not work as well and life would cease.
And so, one of the ways the body controls core temp when it's too hot is by sweating. Water evaporates off the skin and the net effect is cooling. In the process of sweating precious electrolytes like sodium and potassium are excreted through the skin, along with some waste products. If this excretion of electrolytes exceeds the intake of electrolytes through food and drink, the body can become quickly depleted of these important elements.
Consequently, this loss of water through sweating and the resulting chemical shift from excreted electrolytes causes blood volume to drop. This results in less oxygen perfusion to body and brain tissues. To compensate, heart rate increases and blood vessels in the brain dilate. The end result can be severe headaches, dizziness, fatigue, etc.
So, as many have said here already, drinking plenty of healthy fluids while out in hot weather is very important. Good quality plain water is good, but fresh fruit juices and vegetable juices are better...Water without electrolytes won't help all that much after a while. And so, bananas, watermelon, pineapple are all great fruits to have. And, as I've already said, the fresh juices are even better...Watermelon juice is really good!!
BTW, as a general rule, you should drink at least half your body weight, in ounces though, of good quality water per day. For example, if you weight 100 lbs., then you should drink at least 50 ounces of water per day, at minimum. And, during really hot weather, you should drink more than that. And, that is in addition to any other drinks you may have (e.g., soda, coffee, etc.). As it was already said, drinks that contain caffiene and alcohol should definitely be avoided, as they can easily make dehydration worse.