Did you know that most men and women can survive no more than 7 days without water (Williams 200S)? Because of its numerous and diverse functions in the body, water is often regarded as the most important nutrient.

Although there is rigorous proof of its benefits, scientists still have trouble objectively advising people how much they need to drink daily to maintain favorable health. Len Kravitz, PhD, program coordinator of exercise science and researcher at the University of New Mexico at Albuquerque, plunges in for a look at this mysterious nutrient called H20.

H20 is intricately involved in numerous functions of the body, including the transport of oxygen, nutrients and waste products into and out of the cells. Drinking water contains several electrolytes (substances in solution that conduct an electric current), including calcium, chloride, fluoride, magnesium, potassium and sodium. Water is necessary for all digestion and absorption functions.

H20 is the medium for most chemical reactions in the body, especially those metabolic reactions involved in energy production. The body uses water as a coolant, helping to regulate internal temperature during exercise, when fever is present and in hot environments. Water also serves as a cushioning component between joints, in the spinal cord and in the brain.

At different times in your life, you may need to pay special attention to water intake.

Seniors. With age, thirst becomes a less effective indicator of the body’s fluid needs, so older adults who rely solely on thirst signals increase their risk of be coming dehydrated. Seniors who relocate to places where the weather is warmer or dryer are also more susceptible to dehydration.

Pregnant women and those who are breast-feeding need additional fluids daily to stay hydrated. Women at risk of gaining weight are encouraged to consume more water (no calories) and limit their consumption of sweetened fluids (with calories).

In 1-hour of light exercise in a moderate environment, the amount of water you sweat out is easy to quickly replace. However, endurance exercise is different. The ACSM recently released its newest Position Stand on exercise and fluid replacement in an effort to guide exercisers toward safe and enjoyable participation in endurance exercise (Sawka et al. 2007).

Each person will have different and variable water losses, so one blanket recommendation is not possible. However, it discusses the importance of hydrating before, during and after your workout.

The Institute of Medicine explains that drinking fluids represents about 81% of total water intake, with 19% of water being provided by foods. So, the recommendation for actual fluid intake is 3.0 liters for men and 2.2 liters for women.