If you’re a runner, pour a spoonful of table sugar into your water bottle — it may be the simple trick you need to avoid hitting the so-called “wall.” Researchers from the University of Bath discovered this reliable new science-tested energy source after testing different types of sugary fuel on endurance athletes. Their results, published in the journal Endocrinology & Metabolism, may benefit marathoners, cyclists, and other long-distance athletes who exercise for more than three hours at a time.

“The carbohydrate stores in our liver are vitally important when it comes to endurance exercise as they help us to maintain a stable blood sugar level,” said the study’s lead researcher Dr. Javier Gonzalez, a human physiology professor, in a press release. “However, while we have a relatively good understanding of the changes in our muscle carbohydrate stores with exercise and nutrition, we know very little about optimizing liver carbohydrate stores during and after exercise.”

For their study, Gonzalez and his research team observed 14 long-distance cyclists as they completed two different workouts on a bike for three hours each. Participants consumed a sucrose-based drink during one cycling session, while for the other cycling session they consumed only glucose-based drinks. Four cyclists performed an additional third session where they only consumed water during the workout. Their liver and muscle glycogen levels were measured before and after both workouts.  

The researchers found cyclists who consumed glucose and sucrose prevented declining levels of glycogen in their livers, which is where extra carbohydrates are stored. Ultimately, this helped them avoid depleting the glycogen stored in their livers for energy and thus prevented fatigue. These athletes performed better than those who simply drank water. However, they also found glucose-only drinks tended to produce gut discomfort. Sucrose-only drinks proved to be more effective, and without side effects, the researchers said these drinks may benefit endurance athletes, such as cyclists and marathoners.

“We also found that the exercise felt easier, and the gut comfort of the cyclists was better, when they ingested sucrose compared to glucose,” Gonzalez said. “When your goal is to maximize carbohydrate availability, sucrose is probably a better source of carbohydrate to ingest than glucose.”

Sucrose and glucose are both simple sugars; however, sucrose (also known as table sugar) is made up of one glucose and one fructose molecule linked together. Glucose is the body’s preferred energy source because it circulates throughout the blood and provides energy, while fructose is the type of sugar found naturally in fruit. Researchers found when the two different sugar sources were combined, it increased how quickly the gut was able to absorb and process the sugar. This means table sugar mixed in water is a prime candidate for fulfilling the fast-energy needs of endurance athletes.

“Ingesting carbohydrates during exercise can prevent the depletion of carbohydrate stores in the liver but not in muscle,” Gonzalez said. “This may be one of the ways in which carbohydrate ingestion improves endurance performance.”

Source: Gonzalez JT, Fuchs CJ, and Smith FE, et al. Ingestion of Glucose or Sucrose Prevents Liver but not Muscle Glycogen Depletion During Prolonged Endurance-type Exercise in Trained Cyclists. Endocrinology and Metabolism. 2015.