Expert Q&A

Sports drinks: Do you need them to rehydrate?

Do I need a sports drink when I work out? Why? What should I look for when I buy one?

Keeping cool means staying hydrated so that your body can perspire. The best way to do both is to consume plenty of water. During summer months, you may need 10-12 8-ounces glasses of caffeine-free fluids. Physical activity at any time of year increases your body’s fluid requirements, and with the heat of summer it needs even more. When you’re physically active, perspiration evaporates from your skin and thus increases your needs for fluids an additional 2-4 cups daily.

To keep hydrated, drink:

  • At least 2 cups of water, 2-2½ hours before your activity
  • 2 cups 15 minutes before your activity
  • ½ cup – 10 ounces every 15 minutes during the activity (depending on intensity)

When do you need to replace electrolytes with a sports drink?

After an intense workout that lasts more than one hour, or after you’ve exercised in extreme heat, you may need to replace electrolytes with a sports drink. Recommendations are 16 ounces for each pound lost post-exercise. The carbohydrate solution of a sports drink should be less than or equal to 6%. This prevents the bloating and discomfort that can be caused by some flavored beverages. A sports drink that is formulated as a 6% carbohydrate solution means that it contains 60 grams of carbohydrate per liter of water. This is the right amount of carbohydrates to enable your body to absorb the sports drink as fast as water, as well as quickly working muscles with needed electrolytes. Research shows that a carbohydrate solution that contains more than 6% is not better and won’t further improve your performance.¹

Calculating the carbohydrate percentage (%) in a sports drink

You can calculate the carbohydrate percentage of any beverage simply by knowing the total carbohydrate content (on the nutrition facts panel of the label) and the serving size in milliliters (also listed on the label). For example, if a sports drink contains 14 grams of carbohydrate for a 240 milliliters (8 ounces) serving, you would divide carbohydrate grams by serving size (in milliliters), then multiply that figure by 100.

So, 14/240 x 100 = 5.8% carbohydrate (under 6%). If you do choose a sports drink (not for regular exercise), look for one without caffeine and non-FDA approved herbs or additives that are touted as performance enhancers.


¹ Shi, X. et al. Med Sci Sports Exerc, 27: 1607–1615, 1995.

Michèle Turcotte, MS, RD/LDN
Contributing Expert

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