The Transport Ceiling Problem
Your gut cannot absorb unlimited carbohydrate per hour. Two separate protein transporters handle the job, and each has its own maximum throughput:
SGLT1 (Sodium-Glucose Linked Transporter 1) handles glucose and maltodextrin (which is broken down into glucose before absorption). SGLT1 saturates at roughly 60 g/hr of glucose equivalents. Feed it more than that and the excess stays in the intestinal lumen, drawing in water via osmosis. The result is gut cramps, bloating, and emergency pit stops.
GLUT5 (Glucose Transporter 5) handles fructose through an entirely separate pathway. It does not compete with SGLT1 and saturates at approximately 30–36 g/hr under typical exercise conditions, though gut training can push this higher.
The practical implication: if you combine glucose and fructose in the right ratio, you can run both transporters simultaneously and raise total carbohydrate delivery from ~60 g/hr to 90 g/hr in trained athletes. This is the entire physiological rationale behind multiple-transporter carbohydrate (MTC) formulations.
What limited early sports nutrition products was not the science (the concept of SGLT1 saturation was well understood) but a lack of controlled trials measuring what happened in exercising humans at high carbohydrate doses. That changed rapidly after 2004.
How the Ratios Evolved
The 2:1 Era (Mid-2000s to ~2018)
The 2:1 glucose:fructose ratio emerged from early research by Asker Jeukendrup and colleagues at the University of Birmingham. A landmark 2004 study (Jentjens et al.) showed that adding fructose to a glucose solution increased exogenous carbohydrate oxidation during exercise compared to glucose alone. Follow-up work by Currell and Jeukendrup in 2008 confirmed performance improvements with a glucose-fructose mixture at 1.8 g/min (equivalent to about 108 g/hr).
The 2:1 ratio (approximately 60 g glucose + 30 g fructose per hour) became the industry standard because it was the most-studied ratio that kept glucose below the SGLT1 ceiling and added meaningful fructose without exceeding GLUT5 capacity at moderate intake rates. GU Energy Labs, early SIS, TORQ, and many other brands built product lines around it.
The 2:1 also had a practical safety margin: athletes were typically advised to consume 60–80 g of carbohydrate per hour, well within the combined transporter capacity at that ratio.
The 1:0.8 Reformulation (2018–Present)
A 2015 meta-analysis by Rowlands et al. in Sports Medicine aggregated oxidation data across multiple ratio studies and found that ratios closer to 1:0.8 (less glucose-dominant, closer to equal parts) consistently produced higher oxidation rates than 2:1. The practical ceiling with a 1:0.8 ratio appears to be up to 90 g/hr for trained athletes with adapted guts.
Jeukendrup's updated guidance (2014, 2017) refined the recommendation: for athletes targeting above 80 g/hr, a ratio closer to 1:0.8 provides measurably better substrate delivery and lower gastrointestinal distress scores compared to 2:1 at equivalent total doses.
SIS Beta Fuel reformulated from 2:1 to 1:0.8 in 2021. Neversecond launched in 2021 natively at 1:0.8. Maurten, founded in 2015, launched with hydrogel technology and a 0.8:1 ratio (Maurten labels this as 0.8:1; equivalent to glucose:fructose 1:0.8 in independent research; the fructose-forward framing is a brand choice, not a different formulation). This convergence reflects manufacturer confidence that the higher-ratio formulation is the evidence-backed default for high-intake scenarios.
2:1 Ratio Brands
Products using the traditional 2:1 glucose:fructose ratio are well-suited for athletes consuming 60–80 g of carbohydrate per hour. At these intake rates, the SGLT1 pathway is not fully saturated and adding more fructose would provide minimal absorption benefit while increasing gut fructose load unnecessarily.
| Brand | Product | Carbs per Serving | Notes |
|---|---|---|---|
| GU Energy Labs | Energy Gel | 22 g | Classic 2:1; caffeine options available |
| GU Energy Labs | Roctane Energy Gel | 21 g | Higher amino acid content |
| 226ERS | High Energy Gel | 40 g | Large serving, 2:1 formulation |
| 226ERS | Sub9 Endurance Fuel | 48 g / serving | Powder drink, 2:1 |
| Näak | Ultra Energy Gel | 40 g | Cricket protein added |
| Näak | Ultra Energy Drink Mix | 30 g | 2:1 ratio |
| Styrkr | GEL 40 | 40 g | 2:1; MIX 90 also 2:1 |
| Styrkr | SF 90 Solid Fuel Bar | 90 g | Whole-food format |
| TORQ | TORQ Gel | 18 g | UK-based brand, 2:1 legacy |
| TORQ | TORQ Energy Drink | 43 g | Drink mix, 2:1 |
| Precision Fuel & Hydration | PF 30 Gel | 30 g | 2:1; PF 90 also 2:1 |
| Dextro Energy | Intra-Workout | 36 g | European brand, 2:1 |
Who should use 2:1 products: Beginners building carbohydrate tolerance, shorter events where total hourly intake stays below 70 g, athletes who have not yet completed systematic gut training, or anyone who finds 1:0.8 products harder on the stomach.
1:0.8 Ratio Brands
Products at 1:0.8 are formulated to support 80–90 g of carbohydrate per hour in gut-trained athletes. Using both transporters at high volumes requires a conditioned gut — nausea and cramping are common when untrained athletes attempt high-dose protocols.
| Brand | Product | Carbs per Serving | Notes |
|---|---|---|---|
| Maurten | Drink Mix 320 | 80 g | Hydrogel matrix; listed as 0.8:1 (glucose:fructose 1:0.8) |
| Maurten | Drink Mix 160 | 39 g | Half-strength hydrogel option |
| Maurten | Gel 160 | 40 g | High-carb gel, hydrogel format |
| Maurten | Gel 100 | 25 g | Standard-size hydrogel gel |
| Maurten | Gel 100 Caf 100 | 25 g | Caffeinated variant |
| SIS (Science in Sport) | Beta Fuel Drink | 80 g | Reformulated 2021 from 2:1 to 1:0.8 |
| SIS (Science in Sport) | Beta Fuel Gel | 40 g | Reformulated 2021 |
| Neversecond | C30 Energy Gel | 30 g | Launched natively at 1:0.8 |
| Neversecond | C30+ Energy Gel | 30 g | With caffeine, same ratio |
| Neversecond | H30 Hydration Mix | 15 g | Lower-carb hydration option |
| Amacx | Carbs Drink | 90 g | High-volume drink mix |
| Amacx | Iso-Gel | 35 g | Isotonic gel format |
| 226ERS | Isotonic Drink | 49 g | Isotonic formulation, 1:0.8 |
Who should use 1:0.8 products: Competitive athletes targeting 80+ g/hr, those who have completed 4–6 weeks of systematic gut training at high carbohydrate doses, marathon and triathlon racers fueling above 80 g/hr, and athletes who have already confirmed individual tolerance.
Maltodextrin-Only Brands (Hammer Nutrition Philosophy)
Hammer Nutrition occupies a distinct corner of the market. Their flagship products (Hammer Gel, HEED, and Perpetuem) use maltodextrin as the primary carbohydrate source with no added fructose.
The Hammer rationale: fructose requires liver conversion to glucose before muscles can use it (hepatic glycogen synthesis), introducing a metabolic detour. Hammer argues this creates a lag in fuel availability and that fructose provides no direct muscular energy benefit. They also cite research showing that some athletes develop dose-dependent fructose malabsorption, leading to GI distress.
Hereditary fructose intolerance (HFI) is a medical diagnosis, not a self-reported sensitivity. Confirmed HFI patients must avoid fructose-containing sports products entirely and should not trial high-fructose formulations. If you suspect HFI, seek diagnosis before experimenting with 1:0.8 products.
The physiological trade-off is straightforward: without fructose, the GLUT5 pathway sits idle. The practical absorption ceiling is ~60 g/hr, significantly below what 1:0.8 products can deliver. For athletes whose target is 40–60 g/hr, maltodextrin-only products work cleanly and the ceiling never becomes a constraint. For athletes targeting 80+ g/hr, the absence of fructose is a genuine performance limiter.
Some athletes with sensitive guts do report better tolerance on maltodextrin-only products even at moderate doses, suggesting individual variation in intestinal fructose handling plays a real role in product selection.
Which Ratio for Your Needs
The choice is not about which ratio is universally superior. It is about matching the formulation to your target intake rate and gut capacity.
Choose 2:1 if:
- Your target is 60–80 g of carbohydrate per hour
- You are new to race-day fueling and still calibrating tolerance
- You have experienced GI issues with fructose-containing products in the past
- You are racing events under 90 minutes where total carbohydrate demand is moderate
Choose 1:0.8 if:
- You are targeting 80–90 g/hr in training or racing
- You have completed at least 4–6 weeks of systematic gut training at high carb doses
- You are racing a half-Ironman, Ironman, marathon, or multi-hour cycling event
- You want to maximize substrate delivery in the closing stages of long efforts
Choose maltodextrin-only if:
- You have a confirmed HFI diagnosis (a medical condition requiring complete fructose avoidance)
- Your intake target stays reliably below 60 g/hr
- You prefer simple, single-source carbohydrate fueling and find 1:0.8 products consistently cause GI problems
There is no ratio that eliminates GI problems if your gut is untrained. The ratio determines how high your theoretical ceiling is. Gut training determines whether you can actually reach it.
Gut Training Affects Both
The absorption capacities cited above (60 g/hr for glucose, 30+ g/hr for fructose) are not fixed biological constants. They describe untrained baseline values. Regular exposure to high carbohydrate doses during training upregulates SGLT1 transporter expression in the gut wall and improves overall GI tolerance to liquid carbohydrate ingestion.
Research by Jeukendrup and others shows that 4–8 weeks of consuming 60–90 g/hr of carbohydrate during long training sessions meaningfully reduces nausea, bloating, and side stitch incidence at those doses. Athletes who jump straight to 90 g/hr on race day without training their gut will frequently underperform the theoretical absorption advantage of a 1:0.8 product.
The practical protocol: start gut training at your current comfortable dose (typically 40–60 g/hr), add 10 g/hr every two weeks during long sessions, and stop increasing when discomfort appears. Target reaching your race-day dose in training at least 4 weeks before the event.
See the carbohydrate-per-hour reference guide for evidence-based intake targets by event distance and intensity. For how these ratios play out in specific product head-to-heads, see the Maurten vs SIS comparison.
Frequently Asked Questions
What is the best glucose-to-fructose ratio for endurance sports?
For athletes targeting above 80 g of carbohydrate per hour, current evidence supports 1:0.8 (glucose:fructose) as producing the highest oxidation rates and lowest GI distress. For 60–80 g/hr targets, 2:1 performs comparably and may be easier to tolerate. Neither ratio matters if the gut has not been trained to handle the volume.
What does the 1:0.8 ratio actually mean in grams?
In a 90 g/hr feeding, a 1:0.8 product delivers approximately 50 g of glucose (from glucose or maltodextrin) and 40 g of fructose. This saturates both the SGLT1 and GLUT5 transporters near their trained capacities simultaneously.
Is Maurten's ratio the same as SIS Beta Fuel?
Yes, functionally. Maurten labels their ratio as 0.8:1 (fructose:glucose); SIS labels theirs as 1:0.8 (glucose:fructose). Both ratios are mathematically equivalent: roughly equal parts glucose and fructose, slightly glucose-dominant.
Why did SIS reformulate from 2:1 to 1:0.8?
SIS updated Beta Fuel in 2021 based on the accumulated post-2015 literature showing higher oxidation rates with ratios closer to 1:0.8, particularly at doses above 80 g/hr. The reformulation also involved a switch to a mix of maltodextrin and fructose to improve palatability at high volumes.
Can I mix 2:1 and 1:0.8 products in the same race?
Yes. Many athletes use a lower-carb 2:1 gel in the early stages and switch to higher-volume 1:0.8 products when effort intensifies. Total hourly carbohydrate and the training status of your gut matter more than exact ratio consistency within a race.
Does ratio matter for events under 75 minutes?
No. Exercise lasting under 75 minutes does not meaningfully deplete muscle glycogen, and carbohydrate ingestion during the event does not improve performance through metabolic substrate supply (though mouth-rinsing with carbohydrate beverages has a neural effect). Ratio selection is irrelevant for short-duration events.
Brand-by-Brand Ratio Summary
| Brand | Product | Ratio | Carbs/Serving | Ratio Era |
|---|---|---|---|---|
| Maurten | Gel 100 | 0.8:1 (= 1:0.8 glucose:fructose) | 25 g | Modern |
| Maurten | Gel 160 | 0.8:1 (= 1:0.8 glucose:fructose) | 40 g | Modern |
| Maurten | Drink Mix 160 | 0.8:1 (= 1:0.8 glucose:fructose) | 39 g | Modern |
| Maurten | Drink Mix 320 | 0.8:1 (= 1:0.8 glucose:fructose) | 80 g | Modern |
| SIS Beta Fuel | Beta Fuel Gel | 1:0.8 | 40 g | Reformulated 2021 |
| SIS Beta Fuel | Beta Fuel Drink | 1:0.8 | 80 g | Reformulated 2021 |
| Neversecond | C30 Gel | 1:0.8 | 30 g | Modern |
| Neversecond | C30+ Gel | 1:0.8 | 30 g | Modern |
| Amacx | Iso-Gel | 1:0.8 | 35 g | Modern |
| Amacx | Carbs Drink | 1:0.8 | 90 g | Modern |
| 226ERS | Isotonic Drink | 1:0.8 | 49 g | Modern |
| GU Energy Labs | Energy Gel | 2:1 | 22 g | Classic |
| GU Energy Labs | Roctane Gel | 2:1 | 21 g | Classic |
| Näak | Ultra Energy Gel | 2:1 | 40 g | Classic |
| TORQ | TORQ Gel | 2:1 | 18 g | Classic |
| TORQ | TORQ Energy Drink | 2:1 | 43 g | Classic |
| Precision Fuel & Hydration | PF 30 Gel | 2:1 | 30 g | Classic |
| Precision Fuel & Hydration | PF 90 Gel | 2:1 | 90 g | Classic |
| Styrkr | GEL 40 | 2:1 | 40 g | Classic |
| Styrkr | MIX 90 | 2:1 | 90 g | Classic |
| Dextro Energy | Intra-Workout | 2:1 | 36 g | Classic |
| Hammer Nutrition | Hammer Gel | No fructose | 22 g | Maltodextrin-only |
| Hammer Nutrition | HEED | No fructose | 25 g | Maltodextrin-only |
| Hammer Nutrition | Perpetuem | No fructose | 27 g | Maltodextrin-only |
Real-World Form-Factor Considerations
The ratio that reaches your muscles is determined not just by what the label says but by whether you can physically consume enough of the product to make the transporter math work.
Pure 1:0.8 ratio gels (Maurten Gel 160 at 40 g, SIS Beta Fuel Gel at 40 g, Neversecond C30 at 30 g) are formulated for athletes targeting 80-90 g/hr. Hitting 90 g/hr from 30 g sachets means three Neversecond C30s per hour: logistically manageable but demanding across a multi-hour race. Larger gels like the Maurten Gel 160 or SIS Beta Fuel Gel cut the touchpoint count in half.
Classic 2:1 gels (GU Energy Gel at 22 g, TORQ Gel at 18 g, PF 30 Gel at 30 g) are appropriate at 60-75 g/hr targets and are often cheaper per gram. At these intake rates, the SGLT1 transporter is not fully saturated and adding a higher fructose ratio would provide minimal additional throughput. The 2:1 format is also more widely available at race aid stations, which has real value if your carry capacity is limited.
Mixed-strategy approach: many experienced athletes use a 1:0.8 gel alongside a 2:1 drink mix to manage the sweetness profile across a long event. A gel with high fructose content tastes markedly different from a glucose-forward drink; varying the flavor and texture source reduces palatability fatigue. The combined ratio across the hour falls somewhere between the two, still above 60 g/hr and sufficient for most trained guts.
Maltodextrin-only formulas (Hammer Gel, HEED) keep the ceiling at roughly 60 g/hr, because GLUT5 sits idle. Athletes who reach this ceiling often experience the gut backup and bloating that prompted the multi-transporter research in the first place. For GI-sensitive athletes who cannot tolerate fructose at any dose, staying at 45-60 g/hr with a clean single-source formula is the correct call, even if the theoretical ceiling is lower.
Drink mix versus gel at equivalent ratios: Maurten Drink Mix 320 delivers 80 g at 0.8:1 in a single liquid format. Many athletes report that the same 80 g in liquid is better tolerated than consuming the equivalent in four smaller gels, likely because the liquid distributes more evenly in the stomach rather than arriving as a concentrated bolus.
For practical insights on ratio and format combinations at age-grouper level, see Thomas Prommer's 120 g/hr protocol breakdown.
Key References
- Jeukendrup AE. (2010). Carbohydrate and exercise performance: the role of multiple transportable carbohydrates. Current Opinion in Clinical Nutrition & Metabolic Care, 13(4), 452–457.
- Currell K, Jeukendrup AE. (2008). Superior endurance performance with ingestion of multiple transportable carbohydrates. Medicine & Science in Sports & Exercise, 40(2), 275–281.
- Rowlands DS, et al. (2015). Fructose–Glucose Composite Carbohydrates and Endurance Performance: Critical Review and Future Perspectives. Sports Medicine, 45(11), 1561–1576.
- Jeukendrup AE. (2014). A step towards personalized sports nutrition: carbohydrate intake during exercise. Sports Medicine, 44(Suppl 1), 25–33.
- Jentjens RL, et al. (2004). Oxidation of combined ingestion of glucose and fructose during exercise. Journal of Applied Physiology, 96(4), 1277–1284.