When it comes to post-exercise habits, sports nutrition is concerned with various things: glycogen replenishment, enhancing your body’s recovery and adaption to your training, and re-hydration. If you take a look at any supermarket shelf, you’ll see scores of energy drinks, recovery drinks, and sports drinks, each more fantastically colored then the next, and all of them promising to turn you into the next athletic superstar if you just drink them. Which is best? Is classic water better, or milk, or do Powerade and Gatorade really hold the secret to optimal re-hydration?

De-hydration is a simple process by which your body sweats out more fluid than you take in during exercise. Usually this isn’t a problem if you’re just going for a twenty minute run or lifting weights for half an hour, but for people who are doing intense endurance training or training repeatedly during the day, even a slight amount of de-hydration can negatively impact their next training session.

Is water the way to go? No. While on a basic, intuitive level, thinking that water is the best way to hydrate yourself makes sense, research has shown that including sodium and potassium in your drink helps you retain the water your drink. It’s not simply a case of pouring water down your throat, but also ensuring that that water stays in your body, and isn’t urinated out the next time you go to the bathroom.

Including sodium and potassium was what spurred the creation of sports drinks like Powerade and Gatorade. They also throw in some carbs to help glycogen replenishment, and that’s why they’re the leading kings when it comes to sports drinks. But are they the best?

A recent study took eleven healthy male volunteers and had them exercise in a warm, humid environment until they had each lost 1.7% of their starting weight. They were then given the 150% of the amount they had lost in water, milk, milk with added sodium, or Powerade over the course of four installments, monitored for the next four hours, and the amount they urinated gauged. What was discovered was that the people who drank the milk retained significant more fluid and reported less sensations of hunger. The researchers concluded that milk was superior to both water or Powerade at re-hydration.

This makes sense: milk already has high levels of potassium and sodium, and will be digested slower due to its protein content. Does this mean milk should be used instead of Powerade or Gatorade? Not necessarily; drinking large quantities of milk can be hard for most people, and one of the key components to a successful sports drink is the person’s willingness to drink it, hence how tasty Gatorade and Powerade can be.

So while on the track, while doing your actual Insanity Workout or lifting weights, a sports drink can be key. Says nutritionist Heidi Skolnik, M.S., CDN, FACSM, who advises both the New York Giants and the New York Knicks on healthy eating as well as drinking, “For training over an hour at medium to high intensity, look for a drink that provides between 13-19 grams of carbohydrate per 8 oz serving, and at least 80-110 mg sodium —and even more for longer duration training or those losing a lot of salt in their sweat.”

However, if you make recovery shakes after your workout? 2% milk is an awesome base to which to add your protein powder and fruit.