Will Low Sugar Sports Drinks Make You Bonk?

Sports drink companies are cutting down on sugar. But is that good for endurance athletes?

In the past couple years, companies including nuun, GU, EnduroPacks and Gatorade started serving up less sugary sports drink options. They make sense for days off, but things get complicated if you’re exercising for more than two hours. Here’s what you need to know about the sweet stuff in your sports drink.

The original pitch for sugary sports drinks stems from research showing that faster-acting sugars like glucose, fructose and maltodextrin along with electrolytes can improve exercise performance. They help athletes keep up the pace by slowing down the drain of liver and muscle carbohydrate stores, the primary energy source for high-intensity exercise.

But recently, there’s been a shift in how society in general looks at sugar, with the casual use of traditional sports drinks playing a role in youth obesity. “That shift has had an impact on athletes as well,” says sports dietitian and Ironman competitor Marni Sumbal. “Consequently, many athletes are reconsidering how much sugar they want in their bottles believing less might be a healthier choice.”

Many traditional options, like Gatorade, provide about 21 grams of sugar (about 5 teaspoons) in a 12-ounce serving, along with roughly 150 milligrams of sodium and some potassium. But low-sugar options have a tiny fraction of that, if at all. A nuun Active tablet, for example, has just 1 gram of sugar and 10 calories. For a workout lasting less than 2 hours, low-sugar options should suffice, as long as you fuel properly before and after the workout, says Sumbal. But try to go any longer without some extra calories in the form of fast-acting sugars, and you’ll likely set yourself up for the dreaded bonk.

“Most research shows that athletes can benefit from 30 to 60 grams of carbohydrates for each hour of exercise,” says Sumbal. This equals about 16 to 32 ounces of a traditional sports drink per hour. Sumbal adds that less highly trained athletes may actually need more carbohydrate energy as their bodies aren’t as well adapted to the task at hand. So if you’re out for the long haul, you’ll have to get those carbs from somewhere else if your bottle is little more than flavor and electrolytes.

The health issues associated with high sugar intake, including metabolic conditions and weight gain, have not been shown to be of concern when you’re taking that sugar in during bouts of high volume training or sustained exercise. A 2016 review published in the International Journal of Sports Nutrition and Exercise Metabolism, for example, found that when higher sugar sports drinks are used to fuel exercise beyond 60 minutes in length they do not abolish the energy deficit created by working out. “Sugar is only a problem when you consume too much as part of your normal diet and not as part of a smart fueling strategy where it serves a specific function,” Sumbal says.

So when would you want a low-cal option? During periods of lower volume training when overall calorie and carbohydrate needs are less. There is also some evidence that sports drinks with a lower concentration of carbohydrates might be better for overall performance during bouts of high intensity training or race situations.

“This occurs because a more modest carbohydrate concentration can improve energy and fluid absorption rate resulting in better hydration status, improved delivery of their carbs to working muscles and less risk for digestive distress,” says Sumbal. Some sports nutrition researchers and athletes believe the concentration of carbohydrates (generally 6 to 8 percent) in traditional sports drinks is too high, thereby forcing your body to draw water from the blood into the gut to help with digestion—an outcome that can set the stage for digestive woes and, seemingly paradoxically, dehydration. So there is a push for drinks with a more modest carbohydrate concentration of 4 percent or less that also delivers some electrolytes. (If a sports drink contains 10 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, 10/240 x 100 = 4.2% carbohydrate). New Zealand researchers found that fluid absorption was fastest in cyclists who downed a 3.9 percent drink than when they used a product with a more-lofty 7.6 carb percentage. They also reported less GI discomfort with the former. When consuming lower sugar drinks, athletes will need to focus on meeting their calorie and carbohydrate needs during prolonged exercise from other sources such as gels, chews and bars. It’s important to consume these alternative energy sources with fluid to promote better digestion when on the move.

Still, lite sports drink products that use artificial sweeteners like sucralose or sugar alcohols such as sorbitol can cause tummy troubles. Some athletes may prefer products such as Bonk Breaker and nuun that glean their sweetness from less-engineered sources including dextrose, cane juice, stevia and monk fruit extract.

In the end, the only way to know if the low-sugar option is right for you is to test the drinks out. “The key is to experiment with a fueling and hydration regiment during training, Sumbal says, “to pinpoint what best keeps you energized with little risk for digestive problems.”