More than half of the human body is made up of water. We lose water when we breathe, sweat, and digest food. Water is needed for virtually everything the body does including getting rid of waste and maintaining the health of our organs and cells.
Water is obviously essential. How much should you drink?
Water needs vary from person to person, but as a baseline aim to consume about half as many ounces of water each day as pounds that you weigh. For a 150 pound person, this is about 75 ounces per day as a baseline. However, dependent on your activity and training level and the weather and how well acclimated you are, you could require additional intake.
When you exercise your muscles generate 20 times more heat than when they are at rest so your body cools itself by sweating. On days where you are sweating heavily due to exercise or exposure to hot weather you will obviously need to increase your intake or you risk becoming dehydrated. Dehydration stresses the body and makes exercise feel harder. Your heart rate increases, you burn more glycogen (the carbohydrate stores in your muscles), and you may experience a decrease in your ability to concentrate. Other symptoms of dehydration and heat exhaustion are heavy sweating, fatigue, muscle cramps, nausea, vomiting, headache, and dizziness. Left unchecked, extreme heat exhaustion can progress into heat stroke, which is a medical emergency that can result in death. Someone experiencing heat stroke may no longer be sweating and may experience confusion, disorientation, weakness, and rapid heart rate or breathing. If someone is experiencing signs of heat stroke, seek medical attention immediately. Get out of the heat, remove tight clothing, and place ice packs under the armpits and in the groin area to cool the person.
Water isn’t all you lose when you sweat, however. You also lose electrolytes: sodium, potassium, calcium, and magnesium. This loss of sodium, particularly, can be detrimental to athletic performance. Exercise lasting an hour or less doesn’t usually require that you replace lost electrolytes. Plain old water should do in most cases. For longer, more intense bouts of exercise or exercise in extreme heat, replacing sodium and potassium you’ve lost through sweating is important. Coconut water makes an excellent natural “sports drink” though most commercial sports drinks or coconut water don’t have enough sodium to replace what is lost due to prolonged heavy sweating. Consuming extra salt post exercise can enhance recovery and help you retain fluids or you can try electrolyte tablets added to your water while you exercise.
On the flip side of not drinking enough water, consuming too much water can actually be dangerous. If you’ve ever see stories in the news about high school football players who drink liters upon liters of water while practicing in the hot sun all day and later die, the culprit is often hyponatremia. Hyponatremia is caused by a sodium imbalance from overhydrating. Symptoms includesweeling of the hands and feet, bloating, nausea, headache, fatigue, and in extreme cases, disorientation, a decline in coordination, wheezy breathing, seizures, coma, and death. To avoid this dangerous condition, avoid water loading before an endurance event and consume salty foods and/or sports drinks with higher sodium amounts during an endurance event.
Berardi, J. and Andrews, R. (2015) The Essentials of Sport and Exercise Nutrition. Precision Nutrition.
Clark, N. (2014) Nancy Clark’s Sports Nutrition Guidebook. Newton, MA: Human K