Inside Sports Drinks (Just the Science)

Note: CTS has a partnership with Bonk Breaker and we recommend Bonk Breaker Real Hydration and provide it to our athletes at CTS Camps and events. That said, several brands – including Bonk Breaker – base their formulations off the science presented here, because… it’s good science.

A sports drink is essentially water with stuff dissolved in it. Some drinks have lots of different kinds of stuff dissolved in them, some of which just waste space. There is only so much room to dissolve solutes in a drink, and drinks with fewer ingredients can use more of that room for important things such as carbohydrate and sodium. The simplest drinks are the best because they are easiest on the gut and facilitate the transport of sugar and electrolyte across the semipermeable membrane of the intestinal wall better and faster.

The concentration of sports drinks is important. When you change the osmolality of the fluid (the total molecular concentration of everything in the drink—carbohydrate, electrolyte, flavoring, additives—per unit volume), it changes how the drink influences the overall mixture in your stomach, and hence how that mixture makes it into the intestine. Sports drinks are formulated to optimize the absorption of carbohydrate, fluid, and electrolyte. If the osmolality of the sports drink is too high because of a bunch of additives, it may contribute to slower gastric emptying. When the osmolality of sports drinks is lower, it is more likely to contribute to faster gastric emptying (depending on what else you’re eating and drinking), and if it’s being consumed on an empty stomach, it is formulated to get into the intestine quickly.

If you are designing a sports drink to have a relatively low osmolality but you want it to deliver moderate to high amounts of sodium and/or carbohydrate, you have to eliminate other stuff to make room. That’s a big part of the reason we’ve seen drink manufacturers shift to drinks with shorter ingredient lists.

The ingredients, primarily sugar, sodium, potassium, and flavoring, are in the drink for good reason. Putting electrolytes and flavoring into a fluid makes you want to drink more frequently and consume more fluid each time you drink. There’s actually a lot more to the way your sports drink tastes than marketing mumbo jumbo. A lightly flavored drink is preferable to a stronger one because when you consume half a bottle in one long slug, the stronger-tasting drink becomes overwhelming and you stop drinking. A drink that tastes almost watered down when you are at rest will taste just about right when you are exercising. This is why athletes have long diluted commercial sports drinks like original Gatorade, which these days are often flavored to appeal to convenience store customers instead of athletes.

Even taste components and mouth feel are important. A slightly tart drink will encourage you to drink more than an overly sweet one, and citrus flavors also increase the drive to drink. It should be no surprise, then, that almost every drink company has some version of lemon-lime and/or orange in its product line. In addition to the flavor, a sports drink needs to clear the mouth well. When a drink leaves a film in your mouth, as is often the case with overly sweet drinks, it’s not only unpleasant, but you’re not likely to drink again soon.

Rather than dilute sports drinks, it is better to find a drink with a lighter taste so you can comfortably consume it at full strength. The reason you don’t want to dilute heavily flavored commercial sports drinks isn’t really because doing so lowers the concentration of sugar in the drink but because it reduces the sodium concentration. Again, this is relative to all the other foods and fluids you are consuming, but if you are consuming a sports drink with the primary goal of staying hydrated—that is, maintaining proper fluid and electrolyte levels—then consuming a watered-down drink provides a lot of fluid and reduced sodium, which over time could contribute to inadequate sodium replenishment in relation to fluid intake.

What to Look For:

  • Multiple sources of carbohydrate: Different sugar molecules take different pathways through the intestinal wall. When you consume only one type of sugar you are only utilizing one set of “gates”. By consuming multiple types of sugar you can utilize more gates simultaneously, which means you will transport carbohydrate into your bloodstream more quickly.
  • Citrates: When you read the ingredient list, look for sodium citrate and potassium citrate rather than or in combination with sodium chloride and potassium chloride. Citrates are easier on the gut and help increase the absorption of fluid.
  • Sufficient electrolytes: While there are low-sodium versions of sports drink, if you’re consuming a sports drink with the intent of enhancing hydration status you want to consume 500-700mg of electrolytes per hour. That doesn’t all need to come from your sports drink (foods supply sodium, too), but low-sodium sports drinks make it less likely you will consume sufficient electrolytes.
  • Carbohydrate appropriate to your goals: There are high-carbohydrate (approx. 20+ grams/500ml bottle) and low-carbohydrate (approx. 20 grams or less/500ml bottle). The lower carbohydrate drinks are preferred if your primary goal is hydration. If you are participating in longer endurance events and want to consume a larger proportion of your carbohydrate energy via drinks, try the higher carbohydrate solutions. Be aware, however, that overconsumption of higher-carbohydrate drinks may increase your chances of gastric distress.  

Comments 5

  1. Could this not cause dehydration “if you are participating in longer endurance events and want to consume a larger proportion of your carbohydrate energy via drinks, try the higher carbohydrate solutions” – in that the water will be diverted away from say muscles via the veins into the gut to create the correct ph level (osmolality) for absorption? The goal I suppose is to ensure the drink remains isotonic.

  2. What about those who claim you should NEVER use simple sugars, even in sports drinks, only “complex carbs”? Any real rational to that?

  3. I always go with one plain water bottle and one with Nuun Performance when I am on bike rides over 2 hours/over 75 degrees. Otherwise just water. I ensure both are gone every 2 hours. The last hour/cooling down I had an extra tab to my water.

    I have no idea why I came up with this? However, I find it works and the extra sweet taste right at the end triggers something that makes me want to drink. When the water is plain, I find myself not drinking as much. Worse yet, probably moving towards the ole recovery beer at the finish line with others. Nuun seems to stave off the need for the recovery beer. Try it, perhaps it will work for you too!

  4. Many sports drinks are adding non nutritive sources of sweeteners, like Stevia. I had a “discussion” with HEED at Interbike. My feeling, based on the research, is that these actually make you crave sugar and may be associated with other rare side effects. Yet many are including them in their drinks and electrolyte supplements. Not Bonk Breaker! What are your feelings.

    1. just watch for Mag Citrate of longer events… unless want to clean out bowels. Too many companies use fructose which in long or hot events since hows its digested can cause GI issues in many not all. Most people add too much CHO per bottle so its good to see your rec on it. I go with 4-8% solution depending on temps. Also need to keep in mind starting and finishing temps

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