The ideal glucose: fructose ratio in sports nutrition
Introduction
Athletes and endurance sports enthusiasts constantly seek ways to optimise performance through nutrition. Some of the key components of sports nutrition are carbohydrate intake strategies, specifically the combination and ratio of different carbohydrate sources. The most commonly discussed combination is glucose and fructose, two sugars that use different intestinal transporters, enhancing absorption and oxidation rates when ingested together. This blog examines the evidence for the ideal glucose: fructose ratio. At truefuels, we have combined years of experience and scientific testing with the current academic literature and co-creator testing to develop a new type of gel. While there is plenty of debate about the ideal carbohydrate ratio in sports nutrition, we believe our 1:1 ratio is the most effective in maximising carbohydrate metabolism while minimising gastrointestinal (GI) distress.
The Science of Carbohydrate Absorption and Oxidation
Carbohydrates are a critical fuel source during endurance exercise, but their absorption in the intestine is rate-limited by transporter saturation. Glucose relies on the sodium-glucose co-transporter (SGLT1), fructose uses the GLUT5 transporter. When consumed together, glucose and fructose bypass the competition for the same transporter, allowing higher total carbohydrate uptake. Jeukendrup (2010) demonstrated that a combination of glucose and fructose can raise carbohydrate oxidation rates from 1 g/min (for glucose alone) to as much as 1.75 g/min [1]. This increase in oxidation is critical during prolonged endurance exercise, where energy demands are high. Importantly, the synergistic effect is only observed when both sugars are provided in substantial proportions. In this study, the participants were ingesting a total of 2.4g/min or 144g/hr of carbohydrate, giving an oxidative efficiency (oxidised divided by ingested carbohydrate) of 73%. It's thought that low oxidative efficiencies increase the risk of GI distress, which is why high ingestion rates are not recommended.
Optimal Ratio for Maximum Carbohydrate Oxidation
Research suggests that the optimal glucose: fructose ratio for maximal carbohydrate oxidation likely falls within the range of 1:0.7 to 1:1.1. Rowlands et al. (2015) found that ratio in this range yielded the highest exogenous carbohydrate oxidation rate compared to lower or higher fructose ratios [2]. Rowlands and colleagues observed that ratios with excess glucose (e.g., 2:1 glucose: fructose) did not produce the same metabolic benefits as the SGLT1 transporter became saturated. By contrast, a more even ratio ensured both transporters (SGLT1 and GLUT5) were maximally utilised.
Similarly, A study by Jentjens and Jeukendrup (2005) demonstrated that a 1:1 fructose-maltodextrin ratio produced an exogenous carbohydrate oxidation rate of 1.75 g/min, surpassing the oxidation rates of single-source carbohydrates like glucose or maltodextrin alone [7]. This aligns with other studies indicating that total carbohydrate oxidation is maximised when the intestinal transporters are not overwhelmed by one dominant sugar source.
To illustrate this, Figure 1 (adapted from O'Brien et al. 2013) demonstrates the relationship between glucose and fructose ingestion rates, oxidation rates, and oxidation efficiency across different ingestion ratios. It highlights that composite oxidation efficiency peaks when the fructose: glucose ratio falls around 0.8–1.1, aligning with the 1:1 target.
Reduced Risk of Gastrointestinal (GI) Distress
One of the most compelling reasons for a 1:1 glucose: fructose ratio is its impact on gut comfort. Gastrointestinal distress (e.g., cramping, bloating, and nausea) is a major issue for endurance athletes consuming large amounts of carbohydrates during exercise. The co-ingestion of glucose and fructose reduces the concentration gradient and osmotic pressure in the intestine, leading to faster fluid absorption and less GI distress.
O’Brien et al. (2011) investigated the effects of various glucose: fructose ratios on gut comfort during high-intensity cycling [4]. The 1:0.8 ratio produced lower GI distress compared to higher fructose or glucose-dominant ratios, suggesting that balancing the two sugars optimizes fluid absorption and minimizes gastrointestinal issues. By distributing the carbohydrate load across two separate transport pathways, athletes experience fewer symptoms of cramping and nausea, which can derail endurance performance.
The study by Podlogar and Wallis (2020) also highlighted how the ingestion of maltodextrin-fructose at a 1.5:1 ratio improved post-exercise carbohydrate oxidation without increasing GI distress [5]. While this ratio leaned toward more maltodextrin, the evidence supported the principle that combining fructose and glucose improves metabolic outcomes with less gastrointestinal burden.
Impact on Endurance Performance
Endurance performance is highly dependent on sustained energy availability. The capacity to maintain higher rates of carbohydrate oxidation is linked to improved time-trial performance. Several studies have shown that a 1:1 glucose: fructose ratio leads to performance benefits beyond those achieved with glucose alone.
Rowlands et al. (2015) reported that glucose-fructose beverages provided endurance benefits of 1-9% in mean power output during cycling performance tests when compared to a glucose-only solution [2]. These performance improvements are attributed to higher exogenous carbohydrate oxidation rates and improved fluid absorption, both of which are crucial during long-duration endurance events.
O’Brien et al. (2013) found that a 0.8:1 ratio of fructose to glucose improved total exogenous carbohydrate oxidation compared to a 0.5:1 or 1.25:1 ratio [6]. While not perfectly aligned with the 1:1 ratio, these findings reinforce the idea that balanced glucose and fructose intake provides substantial metabolic and performance benefits.
Over the last 10 years, there has been a significant trend toward higher rates of carbohydrate ingestion during endurance training and competition. While the literature doesn’t seem to support exogenous carbohydrate oxidation rates >1.75g/min, anecdotal evidence suggests that higher oxidation rates are possible and beneficial for some athletes. It is possible that these extreme rates only occur when athletes can maintain a relatively high intensity over a long period of time and have adapted to high exogenous carbohydrate ingestion. In my experience, I would not be able to repeat a long-distance race effort in lab conditions.
The literature is consistent in that a maximum rate of exogenous glucose oxidation is around 1g/min [7], so it makes sense that high overall oxidation rates can only be achieved when the glucos-fructose ratio is close to or above 1.
Conclusion: Why 1:1 Is the Gold Standard
The available literature points to the optimum ratio between 1:0.7 and 1:1.2 glucose:fructose. We also have to accept there could be a great deal of individual variability in the ability to digest, absorb, and metabolise glucose and fructose. At truefuels, we exist to provide solutions to help maximize your health, fitness, and performance. Through rigorous testing, we have settled on the 1:1 ratio as the best approach.
The argument for a 1:1 glucose: fructose ratio in sports nutrition products is supported by clear evidence for improved carbohydrate metabolism, reduced gastrointestinal distress, and enhanced endurance performance. Studies consistently demonstrate that this ratio maximizes oxidation efficiency by engaging multiple transporters, reduces the likelihood of gastrointestinal discomfort, and enables sustained high-intensity performance.
While some formulations favour a 2:1 glucose: fructose ratio, the latest evidence suggests that a 1:1 ratio achieves the highest exogenous carbohydrate oxidation and best balances gut comfort. truefuels Performance Gel is the solution for you if you want a combination of scientific rigour, consumer testing, and high-quality ingredients with no additives or flavours.
Figure 1: (adapted from O’Brien et al. 2013)
Sources
-
[1] Jeukendrup, A.E. (2010). Carbohydrate and Exercise Performance: The Role of Multiple Transportable Carbohydrates. Current Opinion in Clinical Nutrition and Metabolic Care, 13(4), pp.452–457.
[2] Rowlands, D.S., Houltham, S., Musa-Veloso, K., et al. (2015). Fructose–Glucose Composite Carbohydrates and Endurance Performance: Critical Review and Future Perspectives. Sports Medicine, 45, pp.1561–1576.
[3] Rowlands, D.S., Thorburn, M.S., Thorp, R.M., et al. (2007). Effect of Graded Fructose Coingestion with Maltodextrin on Exogenous 14C-Fructose and 13C-Glucose Oxidation Efficiency and High-Intensity Cycling Performance. Journal of Applied Physiology, 104(6), pp.1709–1719.
[4] O’Brien, W.J. and Rowlands, D.S. (2011). Fructose–Maltodextrin Ratio in a Carbohydrate-Electrolyte Solution Differentially Affects Exogenous Carbohydrate Oxidation Rate, Gut Comfort, and Performance. American Journal of Physiology - Gastrointestinal and Liver Physiology, 300(2), pp.G181–G189.
[5] Podlogar, T. and Wallis, G.A. (2020). Impact of Post-Exercise Fructose–Maltodextrin Ingestion on Subsequent Endurance Performance. Frontiers in Nutrition, 7, 82.
[6] O’Brien, W.J., Stannard, S.R., Clarke, J.A. and Rowlands, D.S. (2013). Fructose–Maltodextrin Ratio Governs Exogenous and Other CHO Oxidation and Performance. Medicine & Science in Sports & Exercise, 45(9), pp.1814–1824.
[7] Jentjens, R.L. and Jeukendrup, A.E. (2005). High Rates of Exogenous Carbohydrate Oxidation from a Mixture of Glucose and Fructose Ingested During Prolonged Cycling Exercise. British Journal of Nutrition, 93(4), pp.485–492.