Question: "Considering the amount of water in our food, how much water do I really need to drink? Should I ever be using sports drinks instead?"

Excellent question! Although it is a bit difficult to give a clean-cut answer. Water needs vary greatly based on your individual diet, environment, illness, age, fitness level and activity.

The traditional wisdom is that you should, on a normal day at a normal activity level, drink an 8 ounce glass of water 8 times a day for a total of 64 ounces. But those hydration recommendations are so 2001. A study in the 2002 American Journal of Physiology advocated a somewhat more liberal "drink when you're thirsty" view. In 2004 the Institute of Medicine agreed, removed the 64oz recommendations and replaced them with general fluid intake recommendations which include fluid derived from food. In addition to water, these guidelines include other fluids, even those containing caffeine. The IOM guidelines for healthy individuals not engaged in strenuous physical activity are now as follows (AI stands for adequate intake):

Life stage group	AI for Total Water, L/day
Infants 0–6 months	0.7
Infants 7–12 months	0.8
Children 1–3 years	1.3
Children 4–8 years	1.7
Boys 9–13 years	2.4
Girls 9–13 years	2.1
Boys 14–18 years	3.3
Girls 14–18 years	2.3
Men 19–70+ years	3.7
Women 19–70+ years	2.7

Again, these numbers represent the total fluid intake, which includes everything you eat and drink throughout the course of a day. So now we have to consider your diet. I'm going to give you the benefit of the doubt and assume that you eat a healthy diet full of fruits and vegetables. If you do, you probably get about 20% of your daily fluid needs from your food.

For example: Lettuce is around 95% water. So 1.5 cups of lettuce will give you 11.4 ounces of water. Even potatoes are 80% water! For more information about the water content of fruits and vegetables, click here.

So to finally answer your question, the revised fluid intake recommendation through beverages is 9 cups a day for women and 12.5 for men.

Now on to sports drinks. They're a "fluid" so you could toss them into the mix to meet your daily requirements too. But should you?

Probably not.

Sports drinks are based on the idea that your body needs carbohydrates to fuel activity. Carbohydrates are broken down and converted to glucose and then stored in the muscles as glycogen. During exercise that glycogen is the the first thing your body uses for energy. According to J. Anderson, L. Young and S. Prior of Colorado State University, those glycogen stores are enough to sustain you through 90 minutes of exercise and ingesting more carbohydrates won't help. Which means that sports drinks provide calories that will not be used during that activity. Water, on the other hand has no calories.

It is true that the sodium contained in sports drinks aids in hydration and would be helpful in very hot or humid environments. I've used this recipe (courtesy of the good doctors at Colorado State) before to make my own sports drink with limited calories, no artificial coloring or preservatives and enough sodium.

Add 6 tablespoons sugar and 1/3 teaspoon salt to each quart of water. Dissolve sugar and cool.

To review: Drink when you're thirsty, eat you're fill of fruits and vegetables and drink extra before and after any physical activity with small amounts during the exercise. Sports drinks are great for extended activity but the added calories may make it undesirable for the average person.