What sports drink should I buy?

sports drinks are a $7.5 billion industry!

The goal of a sports drink is to keep athletes hydrated and fueled during games, training, or any physical activity.  These beverages are now formulated to be consumed before, during, and after physical exertion.  Because there are so many drinks available for purchase, it's hard to know which one to get, for what purpose, and when to drink them!! 

In general, a sports drink contains water, a source of electrolytes (salt, minerals, etc.) and a source of carbohydrates (sugar).  And, each drink has a special formula designed for a specific purpose- whether it's for hydration or recovery.  Originally, the ratio of the water:carbohydrates:electrolytes was supposed to be the same/similar to sweat, with the idea that as you drink your sports drink, you are consuming the same balance of electrolytes in your drink as those which leaving your system in sweat (perfect recovery- your body doesn't get dehydrated nor does it get hyponatremiac (meaning it has too little salt- also called "water intoxicated"). 

But- there are really 3 different types of sports drinks (isotonic, hypertonic, and hypotonic), and they each play a different role in the body's hydration and recovery process.

hypotonic sports drinks are helpful for hydration

A hypotonic sports drink is one that has less electrolytes than your own body fluids.  Water moves by osmosis and goes towards the area with more concentration (to keep your body in homeostasis or balanced).  So, when you drink something that is hypotonic (less concentrated) the water in the drink goes into your cells (which are more concentrated), and your body is most efficiently hydrated.  Essentially, hydration occurs almost simultaneously as you drink. Hypotonic drinks are best and most effective when consumed before an event.  The best example is water but watered-down sports drinks work, or anything "light" like Gatorade G2, Powerade Zero.

isotonic sports drinks are good to replenish and recover

An isotonic sports drink is one that contains fluid and up to 8% of carbs (ideally glucose) and electrolytes.  This is a similar concentration of water, sugar, and salt in your body which means that they replenish anything that was lost in sweat.  The water from the drinks is absorbed well, but when you drink these isotonic drinks you also provide important electrolytes (necessary for all body functions) and carbohydrates (an important source of energy) which help you maintain energy levels throughout the activity.  These are best to be used during and after an event.  Gatorade, Powerade, Accelerade, most commercially available sports drinks,  etc are examples 

hypertonic solutions

A hypertonic sports drink then is one that has more carbs and electrolytes than your body. The increased particle concentration is essential for athletes to replenish glycogen stores; however, they are absorbed the slowest (think- opposite of hypotonic). These are most often used as energy supplements after heavy and intense exercise.  Examples of these are the drinks that say high carb/high energy/high calorie, "endurance," "performance," or plain fruit juices, etc.

So why do I care what drink I drink and when?

• BEFORE you work out it is important to HYDRATE most efficiently to prepare your body for exercise (and prevent dehydration)
• DURING an event you want to HYDRATE and (depending on the length of exercise) maintain enough (REPLENISH) energy to continue by consuming carbohydrate and electrolytes
• AFTER an event the goal is to HYDRATE and REPLENISH the body for RECOVERY as quickly as possible. Many drinks formulated for this stage include protein (which I will talk about in a separate post!!)

marathoners have different electrolyte and glucose needs

In most cases- people who are exercising for less than an hour are fine drinking water (and saving money on expensive sports drinks).  The temporary electrolyte imbalance as a result of exercise will be normalized within a few hours or after consumption of some food.  It is when a person is heavily exercising or sweating that they need to be careful and look at what kind of drink they are consuming.

Cool facts about sports drinks:

• What makes sports drinks interesting is that their formulation encourages you to drink more.  The salt in the drinks prevents electrolyte imbalances, but also prevents dehydration because people consume more liquid.  (Studies have been done that show that people drink more volume of sports drinks than water because water quenches your "thirst" faster)! 
• Ingesting carbohydrates during prolonged strenuous exercise enhances performance compared to plain water (which is why you may want to opt for iso- or hypertonic sports drinks!)
• Sports drinks that contain vitamins to "boost your energy" or "improve performance" don't work.  Vitamins do NOT contribute to energy (they participate in reactions that encourage cell metabolism), but drinking a drink with B-vitamins will not immediately improve performance!!

Take-home message

• For most people who exercise moderately, there really isn't a need for sports drinks over plain water
• Remember- water is the most hydrating fluid!!
• Sports drinks provide electrolytes and carbohydrates necessary to replenish what was lost and recover quickly.
• If you are buying a drink and don't know when to drink it- look at the carbohydrate and electrolyte content.
• Look at the label.  An isotonic sports drinks is one with 110 - 220 mg sodium per 8 fl. oz AND/OR 14.2 - 18.9 grams carbohydrate per 8 oz
• Look at portions and serving sizes- some of these drinks have 200-300 calories per bottle (because there are multiple servings in the bottle) 
• Diet or lite sports drinks with artificial sweeteners do not contain the carbohydrates and cannot truly help with that recovery (some contain electrolytes which can help in recovery)
• Some drinks contain caffeine (which has been shown to enhance athletic performance) but it can also lead to dehydration!
• Try some "at home" recipes for sports drinks!  They taste great and cost much less than commercial ones.

Sources:

• Reents, Stan. "Sports Drinks and Recovery Drinks - A Review at AthleteInMe.com." Exercise, Fitness, Wellness Advice, and Fitness Gear Info at AthleteInMe.com. 24 Dec. 2011. Web. 24 Jan. 2012. http://www.athleteinme.com/ArticleView.aspx?id=358 .
• Murray R, Bartoli W, Stofan J, et al. A comparison of the gastric emptying characteristics of selected sports drinks. Int J Sports Nutr 1999;9:263-274  
• "What Is In Sport Drinks? | LIVESTRONG.COM." LIVESTRONG.COM - Lose Weight & Get Fit with Diet, Nutrition & Fitness Tools | LIVESTRONG.COM. Web. 24 Jan. 2012. http://www.livestrong.com/article/395288-what-is-in-sport-drinks/ .