Humans aren’t like camels. We can’t store water. We need to replenish fluids daily.

How much do we need? The National Research Council recommends about a quart (4 cups) for every 1,000 calories expended. That’s about 12 cups for a man, 9 cups for a woman. You need more if you spend much time outside in the heat or are very active. Fiber also increases water needs.

It needn’t all come from drinking plain water. We also get water from fruit juice, milk, carbonated beverages and foods. A typical balanced diet of 2,000 calories contains 2-3 cups of water in the food. You’ll also get water in beverages that are caffeinated (coffee, tea, colas) or alcoholic (beer, wine), although you lose some, because alcohol and caffeine act as diuretics, increasing the body’s loss of water as urine.

For most people, thirst is the best way to know that you need to drink more fluids. But there are exceptions:
Glass of water
* Intense exercise, especially in hot weather. You may lose fluids so quickly that by the time your thirst mechanism kicks in, you may already be a little dehydrated. Drink 2 cups of water in the hours before exercise or so while you exercise.

* Age. The elderly have a blunted sense of thirst. In the Eating Lab, when young and elderly men consumed no fluids overnight, the next day the young men were very thirsty and rapidly drank enough water to restore fluid balance. but the elderly men experienced little thirst and drank so little water they remained dehydrated. Older readers should take care that they drink enough fluids when they are ill, exercising or overheated.

One indicator of the adequacy of fluid intake is the color of the urine. It should be pale yellow. if your urine is often very concentrated and dark yellow in color, try to drink more water.

Water and many beverages quench thirst but don’t satisfy hunger. Simply drinking water with a meal won’t help you eat less at the meal or at the next one, according to a controlled studies. But water will quench your thirst without calories and that can help you satisfy your need for liquid without adding calories to your diet.