Adapted from the new book Fitter Faster , in which health journalist Robert J. Davis and celebrity fitness trainer Brad Kolowich, Jr., answer your burning fitness questions and show you how it’s possible to get in shape in just minutes a day.

We’re always hearing how important it is to drink enough water. Among other things, we’re told to down at least eight glasses of water per day and “to stay ahead of your thirst” before, during, and after exercise to avoid dehydration, which impairs performance and is harmful to your health. But it turns out, all this advice lacks sound scientific backing.

Research shows we usually get enough water through foods (which supply about 20 percent of our water) and beverages (including coffee, soda, and alcohol)—and that for most of us, thirst is a reliable indicator of when we need more fluid, even during exercise.

Dehydration isn’t always the threat it’s portrayed to be. According to a recent study (and contrary to popular belief), it’s generally not a cause of exercise-related muscle cramps or heat illness. And one study involving competitive cyclists found mild dehydration doesn’t impair exercise performance. In fact, drinking only when thirsty resulted in better performance than chugging constantly. Makes sense since we’re pretty sure no one loves the feeling of fluid sloshing around in their stomach mid-workout.

Though you want to make sure to consume enough water, especially if you’re older or exercising in the heat, a bigger problem may be drinking too much during exercise, according to some studies and this report authored by a panel of 17 experts.If you take in so much fluid your body can’t get rid of the excess through sweating or urination, sodium levels can become dangerously low. The resulting condition, known as hyponatremia or water intoxication, can cause headaches, vomiting, confusion, seizures, and, in some (extreme) cases, death. Not ideal. In the past, hyponatremia occurred mainly in slower marathon runners, but it’s also showing up in people who participate in activities such as hiking, half-marathons, and hot yoga.

One common method for determining your hydration status is to check the color of your urine. We often hear pee should ideally be pale yellow and that the darker it is, the more you’re dehydrated. But this advice, too, is misleading.

In a review of the evidence, researchers debunked the notion that urine color is an accurate marker of hydration. Part of the problem is that some foods (such as beets and carrots) can affect the color of urine, as can certain vitamins. The same goes for some medications and dietary supplements. You also need to consider the amount of water present in the toilet bowl, especially considering the water-saving options popular today. Besides, striving for pale pee could prompt you to drink too much, overhydrate, and develop hyponatremia.

The experts who authored the report on hyponatremia say the best way to ensure you’re properly hydrated before, during, and after exercise is to “drink palatable fluids when thirsty.” In other words, if you feel that sandpaper feeling in your mouth, just grab a drink.

If for you “palatable fluids” include plain water, that’s your best bet. If not, you can opt for flavor drops or powders. One downside is these options often contain artificial sweeteners and other additives. If you’re looking for something more natural, add slices of fruit such as lemon or orange, vegetables like cucumber, or sprigs of herb.

Sports beverages, which contain fluids, carbohydrates, and minerals known as electrolytes, can also be useful for athletes engaged in vigorous exercise for more than an hour, especially in hot weather. But for most of us, they offer no benefits over water and contain extra calories and sugar we don’t need.

Coconut water, which has definitely had its moment as the trendy drink of choice and is often touted as an alternative to sports drinks, is high in the electrolyte potassium. But coconut water typically contains less sodium than sports drinks, making it less effective for anyone doing prolonged, vigorous exercise. While some people prefer coconut water’s taste to that of regular water, coconut water also has more calories, and research shows it offers a minimal difference in hydration in humans.

Despite the hype surrounding other special waters storming the scene lately (alkaline, distilled, oxygenated, or vitamin-enhanced), there’s little evidence they’re more beneficial than regular water when it comes to hydration, athletic performance, recovery, or general health—for now.

The Bottom Line

Don’t overthink it. Staying hydrated isn’t rocket science. Listen to your body. If you feel thirsty, grab some water. One 20-ounce water bottle should do the trick for activities under 60 minutes. For longer efforts, shoot to sip seven to 10 ounces of fluid every 10 to 20 minutes to stay properly hydrated.Fluids and hydration in prolonged endurance performance. Von Duvillard SP, Braun WA, Markofski M. Nutrition (Burbank, Los Angeles County, Calif.), 2005, Mar.;20(7-8):0899-9007. If you do flavor your water for exercise, try fruits, vegetables, or herbs, or look for natural (and few) ingredients in electrolyte mixes. Most importantly, instead of stressing out over hydration, simply replace daily sugary drinks like soda with water.