WHAT TO EAT AND DRINK
WHEN THE RUN GETS LONG.
My first gel was at mile eighteen of a long run, warm and the texture of hair gel — I walked the last two miles feeling betrayed by the running community. Nobody had told me the actual rule: you practise fuelling in training, exactly as you practise running. Your gut is trainable, and race day is not the place to find out.
This page covers what to take, when, and — the part most sites skip — when you genuinely do not need any of it. For a lot of people reading this, that is most of the time.
How To Read This Page
Use it — bought with my own money and used on real runs. Including what I did not get on with.
Researched — not something I use. Based on independent testing, reviewer consensus and the research, and I would rather say so.
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WHAT DO YOU NEED?
Six sections. Start with the first one — it may save you money.
MOST RUNS NEED NOTHING AT ALL.
This is the section the nutrition industry would rather not open with. Your body stores enough carbohydrate for roughly 90 minutes of running. Below that, you are fuelling a tank that is already full — and a gel on a 5K does nothing except add calories and cost money.
So if your longest run is currently forty minutes, you can close this page and spend the money on socks. Come back when your long run passes an hour and a quarter — that is genuinely when this starts to matter.
The One Rule That Matters Most
Never use anything on race day that you have not used in training. Not a new gel, not a new flavour, not the free sachet in the goody bag. Your gut adapts to what you feed it, and a stomach that has never met maltodextrin at mile eighteen will let you know exactly how it feels about the introduction.
START WITH THE GENTLE ONES.
The main reason people give up on gels is not taste — it is that they picked a thick, concentrated one and needed half a bottle of water to get it down. Start with an isotonic gel, which is already diluted and can be taken without water. Learn the habit first, optimise later.
ISOTONIC ENERGY GEL
The one I put in a belt pocket and forget about. Isotonic means it goes down without water, which sounds minor until you are trying to open a sachet, drink from a bottle and keep running at the same time. Widely available, cheap, and forgiving on a stomach that is new to this.
ENERGY CHEWS
For everyone who tried a gel once and never again. Chews let you take fuel in small pieces rather than a single sweet hit, which suits people whose stomachs rebel at the texture or the concentration. Same carbohydrate, spread over several minutes.
60 GRAMS, 90 GRAMS, AND A TRAINABLE GUT.
This is where the science gets genuinely interesting, and where the numbers on the sachet start to mean something. There is a hard ceiling on how much carbohydrate you can absorb per hour — but you can raise it, and the mechanism is not what most people assume.
Why 60 Grams Was The Old Limit
Glucose crosses your intestinal wall through a transporter called SGLT1, and that transporter saturates at roughly 60g of glucose per hour. Take more and it simply sits in your gut, which is where the classic marathon stomach disaster comes from — not weak willpower, a queue at a biological door.
The breakthrough was that fructose uses a completely different transporter. Combine the two in roughly a 2:1 glucose-to-fructose ratio and you open a second lane — taking usable intake up to about 90g per hour. Early research found this raised carbohydrate oxidation by around 50% compared with glucose alone.
And your gut adapts. Repeated exposure to higher intakes during training increases the number of those transporters, speeds up stomach emptying and quietens the symptoms. Someone who can only handle 60g an hour can typically build to 90g, sometimes more, across 6 to 12 weeks of deliberate practice. This is called gut training and it is a real, boring, effective thing you do on your long runs.
HIGH-CARB DUAL-SOURCE GEL
What you graduate to when the long runs pass two hours. Around 30g of carbohydrate per sachet in the glucose-fructose blend the research points at — meaning three an hour gets you to 90g without carrying a pocketful. Reviewers consistently rate Torq, Precision Fuel and similar dual-source gels at the top for exactly this.
HYDROGEL — FOR BAD STOMACHS
If gels have historically ended your long runs early, this is the category worth trying. Hydrogel technology encapsulates the carbohydrate so it passes through the stomach more comfortably, and runners with a history of gut trouble consistently report fewer problems with it than anything else.
WATER ALONE CAN ACTUALLY BE DANGEROUS.
This is the most serious thing on this page and it deserves your attention for two minutes. The instinct to drink as much as possible during a long race is not merely unnecessary — it has killed people.
Exercise-Associated Hyponatraemia
When you sweat you lose salt as well as water. Replace only the water and your blood sodium concentration falls — a condition called hyponatraemia, which causes the brain to swell and can lead to seizures, coma and death.
A study of runners in the Boston Marathon published in the New England Journal of Medicine found it occurred in a substantial fraction of the field. The single strongest predictor was not heat or pace — it was weight gain during the race, which is to say drinking more fluid than was lost. By 2000 there had been clusters of cases among marathon runners, with confirmed deaths.
The practical version is unglamorous: drink to thirst rather than to a schedule, and on anything long or hot, put sodium in what you drink. If you finish a race heavier than you started, you drank too much.
ELECTROLYTE TABLETS
A tablet in a water bottle, which is genuinely the whole product. Look at the sodium figure rather than the packaging — there is a real difference between brands, from around 100mg per serving at the light end to around 300mg for sport-focused ones. For summer long runs and hot races, the higher figure is the one you want.
HIGH-STRENGTH ELECTROLYTE MIX
For people who finish runs with salt crusted on their face — and if that is you, you know it. Sold in different sodium strengths so you can match the dose to how much you actually lose, which is a genuinely useful idea rather than marketing. Worth it for hot races and long efforts.
THE ONE THING THAT RELIABLY WORKS.
Of everything in a running nutrition aisle, caffeine has by some distance the strongest evidence behind it — and it is also the cheapest. You almost certainly already own the best delivery system, and it is a kettle.
What The Research Actually Says
The consistent finding across systematic reviews: 3 to 6mg of caffeine per kilogram of bodyweight, taken around 45 to 60 minutes before exercise, improves endurance performance by roughly 2 to 7% and lowers how hard the effort feels.
For a 65kg woman that is about 195–390mg — somewhere between a strong coffee and two. Notably, the lower end of that range delivers most of the mental benefit with fewer side effects, so more is genuinely not better. And it works whether it arrives as a gel, a tablet or a flat white.
CAFFEINE ENERGY GEL
The sensible use of these is not at the start — it is saving one for the point in a long race where everything gets mentally difficult, usually somewhere past two thirds. Carbohydrate and caffeine in one sachet, at the moment you need both.
CAFFEINE TABLETS
The unglamorous option that lets you actually control the dose. A 100 or 200mg tablet 45 minutes before a race is measurable in a way that “a coffee” never is — useful if you are trying to hit the researched range deliberately rather than approximately.
JELLY BABIES BEAT MOST OF THIS PAGE.
I want to be honest about something that costs me money to say. For a very large number of runs, a bag of jelly babies from a corner shop does the same job as an engineered gel for about a tenth of the price. They are sugar, they are easy to eat, and generations of runners got round marathons on them before the sports nutrition industry existed.
The genuine case for gels is not that they work better — it is portability, precision and the dual-carb ratio at high intake. If you are chasing 90g an hour in a marathon, engineered products make that possible. If you are doing a two-hour trail run for the pleasure of it, sweets are fine and always were.
CARB DRINK MIX
The option people forget. Carbohydrate and fluid in the same bottle means fewer sachets, less faff and a steadier intake than gulping a gel every forty minutes. Particularly good on trail, where you are carrying a vest anyway.
RECOVERY PROTEIN
What actually matters afterwards is getting protein and carbohydrate in within a couple of hours, and a shake is simply the most convenient version when you have a shift to get to. Not magic — a proper meal does the same job — but a proper meal is not always available at 7am.
FUELLING RULES THAT ACTUALLY MATTER
NOTHING NEW ON RACE DAY
Not a gel, not a flavour, not the free sachet in the goody bag. Your gut adapts to what you have fed it, and race morning is the worst possible laboratory. Whatever you plan to use, use it on at least three long runs first.
UNDER 90 MINUTES, YOU ARE ALREADY FUELLED
Stored glycogen covers roughly an hour and a half of running. Below that, a gel adds calories and nothing else. Save the money and the stomach.
TRAIN THE GUT LIKE ANY OTHER SYSTEM
Tolerance is trainable. Repeated exposure across 6 to 12 weeks raises the number of intestinal transporters and speeds stomach emptying, taking most people from 60g an hour to 90g. Practise it on long runs, not in a race.
DRINK TO THIRST, AND ADD SODIUM
Overdrinking plain water is a genuine medical danger on long races, not a theoretical one. If you finish heavier than you started, you drank too much. Sodium in the bottle for anything long or hot.
QUICK ANSWERS
When do I need to start using energy gels?
When your runs pass roughly 90 minutes. Below that your stored glycogen covers the effort, and a gel adds calories without adding performance. Most people find gels genuinely useful from half marathon distance upward.
How many carbs per hour should I take when running?
Around 60g per hour for efforts of one to two and a half hours, and up to about 90g per hour beyond that. Getting above 60g requires a mix of glucose and fructose, because glucose alone saturates its intestinal transporter at roughly that point.
Why do energy gels upset my stomach?
Usually because the intake exceeded what your gut could absorb, leaving carbohydrate sitting in the intestine. It is rarely willpower or weakness. Build tolerance gradually across six to twelve weeks of long runs, and try an isotonic or hydrogel product if the problem persists.
Do I need electrolytes or is water enough?
For runs under an hour in mild weather, water is fine. Beyond that, and in heat, you lose sodium in sweat as well as water — and replacing only the water dilutes blood sodium, which in extreme cases causes hyponatraemia. Add sodium to what you drink on long or hot runs.
How much caffeine should I take before a race?
Research consistently supports 3 to 6mg per kilogram of bodyweight taken 45 to 60 minutes beforehand, improving endurance performance by around 2 to 7%. For most women that is roughly one to two strong coffees. More is not better.
Are jelly babies as good as energy gels?
For a lot of running, yes. They are simple sugar, easy to eat and far cheaper. Engineered gels win on portability, precision and the glucose-fructose ratio that lets you exceed 60g an hour — which matters in a marathon and matters very little on a Sunday trail run.
What should I eat before a long run?
Something carbohydrate-based and familiar, one to three hours beforehand — toast, porridge, a banana. The specific food matters far less than whether you have eaten it before a run before. Test it in training like everything else.
None of this is what makes a marathon go well. Sleep, consistent training and the long runs you actually did are what make a marathon go well.
Fuelling simply stops a good build being wasted in the last ten kilometres. Get the basics right — practised, boring, unglamorous — and then think about it as little as possible. The gel is not the plan. The gel just protects the plan.
Sources & Research
- Almond CSD et al. Hyponatremia among runners in the Boston Marathon. New England Journal of Medicine.
- Exercise-associated hyponatremia in marathon runners. PMC9699060 / Journal of Clinical Medicine.
- Increased exogenous carbohydrate oxidation with combined fructose-maltodextrin at differing ratios. PMC9560939.
- Effects of caffeine intake on endurance running performance and time to exhaustion: systematic review and meta-analysis. PMC9824573 / Nutrients.
- International Society of Sports Nutrition position stand: caffeine and exercise performance. PMC7777221.
- Contemporary perspectives on dietary carbohydrate and the endurance athlete. Gatorade Sports Science Institute.
Products marked USE IT are ones I buy and use. Those marked RESEARCHED are based on independent testing and reviewer consensus, not personal use. Educational content, not medical or dietary advice. If you are diabetic, pregnant, managing a health condition, or have any history of disordered eating, please speak to your GP or a registered dietitian before changing how you fuel.