According to the U.S. Geological Survey, approximately 71 percent of the earth's surface is composed of water. Similarly, 60 to 70 percent of the average adult human body is composed of water. If you're a 120-pound female, you're made of at least 72 pounds, or 36 quarts, of water. If you're a 175-pound male, you're carrying around at least 105 pounds, or 52 to 53 quarts, of water. In either case, that's a lot of liquid. But that water isn't in your body for ballast. It's there for work. Water provides the medium in which all our physiological processes take place. In other words, water makes our lives possible.
This makes sense when we consider that the proportion of water on earth and in our bodies is approximately the same. Water is the conduit that makes things happen. From the perspective of complex biological organisms, without water there are no organs, no tissues, and no cells. And if there are no cells, there is no life.
Thus, water is essential to our survival. But our internal supply of water is dynamic. We use up more or less water depending on our activities. Of course, being more physically active causes more water to be consumed in metabolic processes such as releasing energy from ATP adenosine triphosphate) molecules.1 Rebuilding ATP supplies requires water as well. Additionally, your kidneys maintain dynamic control over the amount of water in your blood as one of the primary means of regulating blood pH, which must be in a very narrow range of 7.35 to 7.45. Even minor deviations from optimal pH levels can result in symptoms such as fatigue, headache, increased heart rate, muscle pain, and jaundice. Maintaining sufficient water intake is as important a requirement for good health as is regular exercise, a healthy diet, and obtaining necessary rest.
The question naturally arises, how much water should I drink each day? Drinking sufficient water takes a little bit of effort, but there is a big payoff. In fact, the recommendation to drink more water is possibly the most important nutritional advice one could receive. If one is not drinking enough water, any other nutritional improvements will have less of an impact. Specifically, the recommended daily intake for adults is 64 ounces of water each day. This amount is approximately two quarts or half a gallon of water daily.
Importantly, you can never really drink too much water, as your kidneys will immediately excrete the excess. But obtaining too little water is always a danger. Hikers and those living or working at altitude know that by the time you feel thirsty (or your mouth feels dry), it's too late.2,3 The solution is to make sure you're hydrated throughout the day. Such actions will help your metabolic processes and overall physiology maintain a steady state. The result will be increased energy levels all day long and improved long-term health and well-being.
1. Graham MJ, et al: Low-Volume Intense Exercise Elicits Post-exercise Hypotension and Subsequent Hypervolemia, Irrespective of Which Limbs Are Exercised. Front Physiol 2016 May 31. doi: 10.3389/fphys.2016.00199
2. Thornton SM: Increased Hydration Can Be Associated with Weight Loss. Front Nutr 2016 Jun 10. doi: 10.3389/fnut.2016.00018
3. Johnson EC: Hormonal and Thirst Modulated Maintenance of Fluid Balance in Young Women with Different Levels of Habitual Fluid Consumption. Nutrients 2016 May 18. doi: 10.3390/nu8050302