The Best Energy Gel for Runners (2025): Why SFuels Zone-5 Might Beat the Rest

If you want a gel built for long events with surges (marathon, ultramarathon, Ironman) that prioritizes multiple fuel substrates, gut resilience, and a high-calorie, race-ready pouch, SFuels’ Zone-5 (and the SFuels system) deserve a close look. SFuels uses a patent-pending “Extended Substrate™” approach that combines medium-chain triglycerides (MCTs), targeted amino acids (L-glutamine) and engineered carbohydrates (maltodextrin / cyclic dextrin ± fructose) to: (1) supply fuel across intensities, (2) reduce GI distress, and (3) support fat-oxidation training when used as part of a “Right Fuel, Right Time” strategy. Company data, product formulations, and ingredient-level science all support the rationale — though large independent RCTs on SFuels’ finished products are still emerging. Endurance Sportswire+2FuelMe+2

Why Runner’s World picks (and how SFuels is different)

Runner’s World’s recent roundup of top gels highlights gels that excel at single things: Maurten for hydrogel + high-carb density, Huma (chia) for tummy-friendliness, UCAN for slow-release starch, etc. Their testing focuses on taste, digestibility and science behind single-ingredient technologies. Runner's World

SFuels takes a different, systems-level approach: instead of one dominant carb source, it intentionally blends multiple transportable substrates (fatty acids + amino acids + engineered carbs) so the fuel mix supports both steady-state and high-intensity outputs while supporting gut integrity — a strategy aimed at real race day variability. The company also positions fueling as a periodized system (“Right Fuel, Right Time”) with different products for Train / Zone-2, Zone-4, Zone-5 and recovery. SFuels Nutra LLC+1

What “makes” an energy gel actually work (brief science checklist)

Carbohydrate availability — more absorbable carbs = more exogenous fuel and better sustained power. Combining glucose + fructose increases total carb absorption because they use different intestinal transporters. PMC

Gastric emptying / low osmolality — engineered carbs like highly-branched cyclic dextrin (Cluster Dextrin / HBCD) empty faster and cause less GI upset than some sugars. journalofexerciseandnutrition.com+1

Multiple transportable substrates — delivering fat + carb + amino acids can smooth energy at mixed intensities and support cognition. MCTs (C8/C10) are rapidly metabolized and can supply quick ketone/fat fuel when combined properly. (Evidence is mixed; context matters.) PMC+1

Gut support — ingredients like L-glutamine have clinical evidence for supporting gut barrier integrity and reducing exercise-induced intestinal permeability. PMC+1

Any gel that ticks several of these boxes is attractive for long races where intensity and GI stress vary. SFuels intentionally engineers to meet these four. FuelMe+1

What’s in SFuels Zone-5 (and why each ingredient matters)

SFuels’ Zone-5 gel and the SFuels Extended-Substrate approach mix MCTs (C8/C10), L-glutamine, maltodextrin / cyclic dextrin, and (in some formulations) fructose — plus electrolytes and targeted amino acids — delivering ~300 calories per pouch in the Zone-5 race gel. That ingredient set is deliberate: FuelMe+1

• C8/C10 MCTs (caprylic/capric acids) — rapidly absorbed, quickly oxidized fats that can provide an alternate, fast lipid fuel and support cognition during long efforts; when combined with carbs, they can help stabilize energy supply. (Note: MCTs alone rarely improve endurance; benefits are typically context-dependent and often best when combined with carbs.) PMC+1

• L-Glutamine — an amino acid shown in multiple studies to reduce exercise-induced increases in intestinal permeability and support mucosal integrity — i.e., it helps protect the gut during long, hot, or high-stress efforts. This is a plausible mechanism for fewer GI issues in some athletes. PMC+1

• Maltodextrin / Cyclic (Cluster) Dextrin — engineered carbs (HBCD / cluster dextrin) offer fast absorption with lower osmolality and fewer GI complaints than some simple sugars, supporting high carb-delivery without the belly. journalofexerciseandnutrition.com+1

• Glucose + Fructose (when included) — co-ingestion increases total exogenous carbohydrate oxidation rates because they use separate transporters, letting athletes absorb more carbs per hour and sustain power longer. PMC

SFuels packages these deliberately into zone-specific products (Train / Zone-2 for fat-based endurance work; Zone-4 for threshold intensity; Zone-5 for high-intensity race surges), rather than a “one-gel-fits-all” approach. SFuels Nutra LLC+1

The Extended Substrate™ / patent-pending claim — what it means

SFuels markets an Extended Substrate™ (patent pending) technology that “combines fatty acids with amino acids to train your body to use fat as a primary fuel source” and to support gut resilience. That is their IP/engineering claim and is described in product and press materials; it’s patent-pending rather than a broad granted patent at time of writing. Endurance Sportswire+1

Important: “Patent-pending” describes a proprietary formula/approach — it does not, by itself, equal clinical proof of superiority. It does mean the product design is intentionally engineered, and SFuels has published company studies and athlete data supporting their Right-Fuel/Right-Time approach. SFuels Nutra LLC+1

What the peer-reviewed science says (honest summary)

• Glucose+fructose (multi-transport carbs) reliably increases exogenous carbohydrate oxidation and can boost performance in prolonged events — a well-established finding. That supports formulations that include dual carbs. PMC+1

• Highly branched cyclic dextrin (HBCD / Cluster Dextrin) has multiple studies showing faster gastric emptying and less GI disturbance vs some other carbs — useful for race day. journalofexerciseandnutrition.com+1

• L-Glutamine has clinical evidence that it reduces exercise-induced intestinal permeability and supports mucosal immunity — a sensible gut-support ingredient. PMC+1

• MCTs: research is mixed. Some trials show no ergogenic benefit when MCTs are used alone; some show promise when combined with carbs or used chronically to shift substrate metabolism. So MCTs are plausible contributors but not a guaranteed magic bullet. SFuels’ approach relies on combining MCTs with carbs and amino acids to produce a net effect. PMC+1

In short: the ingredient science is solid for the mechanisms SFuels aims to exploit — increased carb absorption, lower GI distress, and gut barrier support. What’s still building: large, independent RCTs that test finished SFuels gels vs competitor gels in race conditions. SFuels has published internal/pilot work and athlete case data. SFuels Nutra LLC+1

Real-world strengths for runners (who should consider SFuels)

• Ultra and long-distance athletes who need a high-calorie, low-GI pouch (Zone-5 offers ~300 cals/pouch). SFuels Nutra LLC

• Runners prone to “runner’s gut” — the addition of L-glutamine + low-osmolality carbs may reduce permeability and GI distress. PMC+1

• Athletes using a fat-adaptation / Right Fuel Right Time strategy — SFuels explicitly structures products for training vs race day, enabling periodized fueling. endureiq.com+1

How SFuels stacks up vs Runner’s World picks (quick comparison)

• Maurten (hydrogel) — best for ultra-clean, high-carb density with hydrogel tech; SFuels offers higher calories per pouch and added gut-supporting amino acids. Runner's World+1

• UCAN — slow-release starch for steady energy (low GI); SFuels targets both fat and carb oxidation and presents a zone-based system. Runner's World+1

• Huma / Honey / Natural gels — easy on the stomach; SFuels aims to match or beat digestibility while delivering engineered substrates and higher calorie density. Runner's World+1

Practical fueling plan (race-safe recommendations)

• Train with SFuels — don’t debut in a race. Use Zone-2/Train products in base months and Zone-4/Zone-5 in harder sessions to test tolerance. SFuels recommends zone-specific stacking. SFuels Nutra LLC+1

• General gel math: start with ~30–60 g carbs per hour for long aerobic events; with glucose+fructose blends you can absorb more (up to ~90 g/hr for elite athletes). Always test in training. (Runner’s World recommends roughly one gel/hour as a basic guideline.) Gatorade Sports Science Institute+1

Caveats & transparency

• SFuels provides product-level engineering, athlete case data, and company studies (e.g., their Jan 2025 “Right Fuel Right Time” synthesis and pilot data). Those are promising but not the same as multiple large, independent RCTs comparing finished SFuels products head-to-head versus Maurten, GU, etc. I recommend treating SFuels as an evidence-informed, engineered option and verifying tolerance in training. SFuels Nutra LLC+1

Conclusion — Is SFuels the best energy gel for runners?

If your priority is a systematic, zone-based fueling system that blends engineered carbs, MCTs and glutamine to support both performance and gut resilience — especially for long races with variable intensity — SFuels offers a uniquely engineered option that merits testing. The company’s patent-pending Extended Substrate™ and zone products match a modern interpretation of performance nutrition: multi-substrate fueling + gut support + strategic periodization. The underlying ingredient science is strong; what’s needed next are independent, peer-reviewed trials of the finished product vs top competitors. Endurance Sportswire+2PMC+2

Short FAQ

Q: Does SFuels contain sugar?
Some SFuels race products include maltodextrin and sometimes fructose; their Train products are lower-carb/zero-sugar by design. Check the product label. SFuels Nutra LLC+1

Q: Is SFuels “doctor approved”?
SFuels lists Dr. Mikki Williden, PhD, as Director of Nutrition and uses clinician/research input in product design — that’s a credentialed endorsement within the company. It’s not the same as regulatory approval. mikkiwilliden.com+1

Q: Will it stop my runner’s gut?
Ingredients in SFuels (L-glutamine, HBCD, low-osmolality carbs) are shown in studies to help gut integrity and reduce GI issues in many athletes; individual responses vary, so test in training. PMC+1

Sources & further reading (key links used)

• SFuels product pages & Zone-5 product details. SFuels Nutra LLC+1

• SFuels blog on “Right Fuel Right Time” and Jan 2025 study notes. SFuels Nutra LLC

• SFuels announcement about patent-pending Extended Substrate™ and press. Endurance Sportswire+1

• Runner’s World “The 6 Best Energy Gels (2025)” (comparison benchmark). Runner's World

• Review on glucose+fructose co-ingestion and exogenous carbohydrate oxidation. PMC

• Reviews/studies on highly-branched cyclic dextrin (Cluster Dextrin / HBCD). journalofexerciseandnutrition.com+1

• Systematic reviews and papers on MCTs and athletic performance (mixed evidence). PMC+1

• Glutamine and intestinal permeability / gut integrity studies. PMC+1