Energy gels work. Let's start there. If you've ever bonked at mile 20 of a marathon, limped through the final 10K of a long training run, or watched your pace collapse in the second half of a race, you know what glycogen depletion feels like — and you know that a well-timed gel can pull you back from the brink. Gels deliver fast-acting carbohydrates when your muscles are screaming for fuel. They solve a real problem, and they solve it well.
But here's what most runners never think about: energy gels address what happens during a run. They don't address what happens between runs. And for runners training consistently — three, four, five times a week — it's what happens between sessions that determines whether you get fitter, stay healthy, and avoid the slow decline into overtraining, injury, and unexplained fatigue.
The uncomfortable truth is that most runners' nutrition strategy begins and ends with race-day fuelling. Gels, isotonic drinks, maybe some jelly babies at mile 16. That's fine for getting round a marathon. But it doesn't touch the five things that high-mileage running systematically strips from your body — things that no energy gel, electrolyte tab, or recovery shake was designed to replace.
What Energy Gels Actually Do (And Don't Do)
An energy gel is essentially a concentrated dose of simple carbohydrates — typically 20–25g of sugar in the form of maltodextrin, fructose, or a blend of both. Some include caffeine or electrolytes. They're designed to be absorbed quickly and converted into glucose, which your muscles can burn immediately. For runs over 60–90 minutes, where your glycogen stores start running low, they're genuinely useful. The research is clear on this.
But that's the full extent of what they do. Gels replace carbohydrate energy. That's it. They don't reduce inflammation. They don't replenish the iron your body loses through foot-strike haemolysis. They don't support the repair of damaged muscle fibres. They don't address Vitamin D insufficiency — something that affects the majority of UK runners, particularly during the six months of the year when you simply can't make enough from sunlight. And they certainly don't improve your body's ability to oxidise fat as fuel at endurance pace.
None of this is a criticism of gels. It's simply not their job. The problem is that most runners treat gel-and-drink fuelling as if it is their entire nutrition strategy — and wonder why they feel flat in training, pick up niggling injuries, or can't recover between sessions despite eating well and sleeping enough.
The Five Things Running Depletes That Gels Can't Fix
High-mileage running creates specific nutritional demands that are fundamentally different from the acute energy needs gels address. These are chronic, cumulative deficits that build over weeks and months of training — and they require a daily response, not a race-day one.
1. Iron — Lost Through Your Feet
Every time your foot strikes the ground, the impact destroys a small number of red blood cells in the capillaries of your feet. It's called foot-strike haemolysis, and it's a well-documented phenomenon in endurance athletes. Add to that iron lost through sweat — runners can lose 0.3–0.5mg of iron per litre of sweat — and the increased iron demands of high aerobic output, and you have a recipe for gradual depletion.
The symptoms are insidious: unexplained fatigue, breathlessness on hills you normally handle, a pace that's mysteriously slower than it should be, poor recovery between sessions. Many runners chalk this up to overtraining or poor fitness. Often, it's iron. Studies show that iron deficiency without anaemia — where your ferritin is low but your haemoglobin is still within range — affects up to 56% of female runners and 30% of male distance runners (Burden et al., 2015).
No energy gel contains iron. No electrolyte tablet does either. This is a daily nutritional issue that needs a daily solution. The form matters too — iron bisglycinate has roughly 90% bioavailability and is significantly gentler on the stomach than the ferrous sulfate tablets your GP might suggest.
2. Chronic Inflammation — The Silent Training Wrecker
Acute inflammation after a hard run is normal and even beneficial — it's part of the repair process. But runners who train frequently accumulate chronic, low-grade inflammation that doesn't fully resolve between sessions. This manifests as persistent muscle soreness, joint stiffness, slow recovery, and increased susceptibility to illness. Over time, it impairs adaptation — you're training hard but not getting fitter because your body is spending its recovery resources fighting inflammation instead of building fitness.
Curcumin — the active compound in turmeric — is one of the most studied natural anti-inflammatories. A meta-analysis by Nicol et al. (2015) found that curcumin supplementation significantly reduced delayed-onset muscle soreness (DOMS) and inflammatory markers in exercising individuals. But there's a catch: curcumin on its own has notoriously poor bioavailability. Your body barely absorbs it. That's why the form matters — patented Curcumin C3 Complex® combined with piperine (BioPerine®) increases absorption by up to 2,000% (Shoba et al., 1998).
Again: no gel, no isotonic drink, no protein shake addresses this. It's a daily demand that requires a daily approach.
3. Vitamin D — The UK Runner's Blind Spot
In the UK, we simply cannot produce adequate Vitamin D from sunlight between October and March. The sun sits too low in the sky for UVB rays to trigger synthesis in the skin. Yet this is precisely when marathon training ramps up — London Marathon entries are confirmed in October, training plans start in December or January. You're doing your highest-mileage, most physically demanding training at the time of year when your Vitamin D levels are at their lowest.
Vitamin D isn't just about bone health — though for runners, the link between Vitamin D deficiency and stress fractures is well established (Lappe et al., 2008). It's also critical for immune function, muscle repair, and reducing inflammation. A deficient runner is more likely to get injured, more likely to get ill during a training block, and slower to recover from hard sessions.
The NHS recommends all UK adults consider supplementing Vitamin D between October and March. For runners — with their higher physical demands and greater exposure to bone stress — this isn't optional. It's essential.
4. Fat Oxidation — The Endurance Edge Gels Can't Provide
Here's an irony: gels exist because your glycogen stores run out. But what if your body were better at burning fat for fuel in the first place? You'd need fewer gels, hit the wall later, and maintain your pace more consistently over long distances. That's not a hypothetical — it's what L-Carnitine does.
L-Carnitine plays a central role in transporting fatty acids into your mitochondria, where they're burned for energy. Research by Wall et al. (2011) demonstrated that L-Carnitine supplementation increased fat oxidation during exercise by 55% and spared muscle glycogen by 55% — effectively shifting your fuel mix towards fat at moderate intensities. This translates to better endurance, more consistent energy, and less reliance on frequent gel intake during long runs and races.
The branded form — Carnipure® L-Carnitine L-Tartrate — is the version used in most positive clinical trials, and it has an additional benefit: reduced markers of muscle damage and faster recovery after intense exercise (Volek et al., 2002). Not all L-Carnitine supplements are equivalent; the form and dose matter significantly.
5. Nutrient Absorption — The Multiplier Nobody Thinks About
You can take all the right nutrients and still get minimal benefit if your body can't absorb them properly. Piperine — the active compound in black pepper — is a bioavailability enhancer that increases the absorption of curcumin by up to 2,000% and other nutrients by 30% or more. It's not glamorous, but it's the difference between nutrients reaching your bloodstream and passing straight through.
This is why a well-formulated supplement includes an absorption enhancer, and why taking individual ingredients separately (a turmeric capsule here, an iron tablet there) often delivers less than the sum of its parts.
Race-Day Fuel vs Daily Foundation: Two Different Jobs
The simplest way to think about this is as two separate nutritional jobs — both necessary, neither replacing the other:
Race-day fuel manages acute energy demands during exercise. Gels, drinks, bars — carbohydrates and electrolytes delivered in real time. This is what SiS, Maurten, High5, and Precision Fuel & Hydration do brilliantly. Use them. They work.
Daily foundation nutrition addresses the chronic deficits that accumulate through consistent training. Iron for oxygen transport. Curcumin for inflammation. L-Carnitine for fat oxidation and recovery. Vitamin D for bone health, immunity, and muscle function. This isn't something you take on race day — it's something you take every day, with food, ideally after a run. The benefits build over weeks, not minutes.
Most runners have the first job sorted. Almost nobody has the second one covered — because until recently, no product was specifically designed to do it for runners. Generic multivitamins don't contain L-Carnitine. Iron supplements from Boots use ferrous sulfate, which is cheap but harsh on the stomach. Turmeric capsules from the health food shop don't include piperine for absorption. And none of them are formulated around the specific demands of running.
What Does a Complete Runner's Nutrition Plan Look Like?
Here's what a well-covered runner's nutrition stack actually includes — and where each piece fits:
Daily (every day, with food):
- A balanced diet rich in iron-containing foods, protein, complex carbohydrates, and vegetables
- A runner-specific daily supplement covering iron, anti-inflammatory support, Vitamin D, L-Carnitine, and an absorption enhancer
- Adequate hydration throughout the day
Around training (before, during, after):
- Pre-run: easily digestible carbohydrates 1–2 hours before
- During runs over 60–90 minutes: energy gels or drinks every 30–45 minutes
- Post-run: protein and carbohydrates within 30–60 minutes (recovery nutrition guide →)
Race day:
- Carb loading in the 2–3 days before
- Race fuelling strategy (gels, drinks, whatever you've trained with)
- Post-race recovery meal
Notice that the daily supplement and the race-day fuel are entirely separate. They address different problems on different timescales. One doesn't replace the other. A runner who takes gels but not a daily supplement is only covering half the picture. A runner who takes a daily supplement but doesn't fuel during a marathon is going to bonk at mile 18 regardless.
The Bottom Line
Energy gels aren't failing you. They're doing exactly what they're designed to do — keeping your muscles fuelled during a run. The problem is expecting them to do more than that. The fatigue you can't explain, the niggles that won't go away, the plateau you've hit despite training consistently — those are often symptoms of the five daily deficits that no gel, drink, or bar was ever meant to address.
Sorting your race-day fuel is step one. Sorting your daily foundation — iron, anti-inflammatory support, Vitamin D, L-Carnitine, and absorption — is step two. Most runners never take it. The ones who do notice the difference within four to eight weeks: better recovery, more consistent energy, fewer unexplained bad days.
Your gels handle the run. Your daily supplement handles everything between runs. Both matter. One without the other leaves a gap.
References
- Burden RJ, Morton K, Richards T, Whyte GP, Pedlar CR. (2015). Is iron treatment beneficial in iron-deficient but non-anaemic (IDNA) endurance athletes? A systematic review and meta-analysis. British Journal of Sports Medicine, 49(21), 1389–1397.
- Nicol LM, Rowlands DS, Fazakerly R, Kellett J. (2015). Curcumin supplementation likely attenuates delayed onset muscle soreness (DOMS). European Journal of Applied Physiology, 115(8), 1769–1777.
- Shoba G, Joy D, Joseph T, Majeed M, Rajendran R, Srinivas PS. (1998). Influence of piperine on the pharmacokinetics of curcumin in animals and human volunteers. Planta Medica, 64(4), 353–356.
- Volek JS, Kraemer WJ, Rubin MR, Gómez AL, Ratamess NA, Gaynor P. (2002). L-Carnitine L-tartrate supplementation favorably affects markers of recovery from exercise stress. Journal of Strength and Conditioning Research, 16(1), 76–83.
- Wall BT, Stephens FB, Constantin-Teodosiu D, Marimuthu K, Macdonald IA, Greenhaff PL. (2011). Chronic oral ingestion of L-carnitine and carbohydrate increases muscle carnitine content and alters muscle fuel metabolism during exercise in humans. Journal of Physiology, 589(4), 963–973.
- Lappe J, Cullen D, Haynatzki G, Recker R, Ahlf R, Thompson K. (2008). Calcium and vitamin D supplementation decreases incidence of stress fractures in female Navy recruits. Journal of Bone and Mineral Research, 23(5), 741–749.