Dehydration
How do you know when you are dehydrated? Unfortunately, thirst may come too late. Therefore, when you sweat a lot or the humidity is low, you must drink a lot, even if you are not thirsty. When dehydrated, the urine has strong color and smell, since the kidneys retain more water and urine is more concentrated. Stronger symptoms are headache, fogginess, weakness, and finally, unconsciousness. Dehydration may also lead to renal failure and death. When you exercise vigorously, some muscle destruction always occurs. The muscle cells are lysed (broken up) and their contents (electrolytes, myoglobin, and enzymes) circulate in the bloodstream. The more dehydrated you are, the higher the concentration of these items. When a person has been exercising, it is normal to find a few red cells (blood) in urine. It is not normal to find”smoke" colored urine, which indicates either the breakdown of blood (hemoglobin) or muscle (myoglobin). The enzymes that are released with the breakdown of the muscle cells are the most destructive part and can damage the kidney to the point of failure. This is more likely to occur when the person is dehydrated. The kidney failure is usually temporary (1-7 days), some people die from it.
Avoiding dehydration is simple: drink frequently so the water can be gradually absorbed and used. Drink plenty of water before you exercise, and continue to drink during exercise (3-5 cups of water/hour for an average sized person). Electrolyte mixes (Gatorade, PowerAde, etc.) only have a marginal advantage over the best drink on the planet: water. As a rough gauge, water weighs about 8 pounds per gallon and there are 8 pints in a gallon, so, during and after working out, drink a pint of water for every pound you lose.
New Information
A recent report from the Institute of Medicine found that to be adequately hydrated, men need about 125 ounces, about 16 glasses, of water a day. Women need about 125 ounces, about 16 glasses. The water may come from many sources, such as colas, coffee, juice, milk, tea, fruit, vegetable, and other foods and beverages, except for alcohol, which increase the body’s water needs. Caffeine, although it is a diuretic and increases the excretion of urine, the effect is small and fleeting. Most people get adequate amount of water from normal drinking behavior and by letting their thirst guide them. You need more water if you exercise, perspire a lot, your skin shrivels, you get muscle cramps, or if you are chronically constipated. It is difficult to drink too much water but athletes who drink a lot of water should also replace the salt lost in sweat to prevent abnormal heart rhythms. Water may also be useful for weight control by drinking a glass before and during meals to fill you up and aid digestion. Recent studies have shown that merely drinking more water speeds metabolism.
Americans consume too much sodium chloride, or salt. The average man takes in 7.8 to 11.8 grams of salt each day. The average woman takes in 5.8 to 7.8 grams. These numbers are estimates since they only include prepared foods and do not include salt that people add at the table. The average person only requires about 3.8 grams of salt a day (about two-thirds of teaspoon, or 1500 milligrams of sodium) to replace that lost in sweat. The upper limit should only be 5.8 grams of salt a day (about a teaspoon).