In 30 seconds
- For sessions of less than an hour, water is enough. From an hour onwards, drink to thirst a drink with 400-1,100 mg of sodium per litre, and add 30-60 g of carbohydrates per hour if the pace is demanding.
- For a long race, start with a full tank: the ISSN suggests about 10 g of carbohydrates per kilo a day in the 48 hours beforehand.
- Afterwards, replace about 1.5 litres for every kilo lost and have 20-40 g of protein in the following 2 hours.
- Between 30% and 50% of athletes have stomach problems: test your food and drink plan in training, never on race day.
To run well you do not need a special diet, just to match what you eat and drink to how long each session lasts. Less than an hour: water. More than an hour: fluid with sodium and carbohydrates. When you finish: fluid, carbohydrates and protein. And on race day, nothing you have not tried before.
The essentials in 6 steps
- Eat the carbohydrates your training calls for: more kilometres, more carbohydrates 1.
- Arrive hydrated: 5-10 ml of fluid per kilo of body weight in the 2-4 hours beforehand 3.
- Less than an hour, water. More than an hour, a drink with sodium and carbohydrates 3.
- Drink to thirst and do not finish weighing more than when you started 6.
- When you finish, replace fluid and have carbohydrates and protein 2.
- Test everything in training. Your stomach can be trained too 1.
Your everyday diet: the fuel
The more you run, the more carbohydrates you need. The International Society of Sports Nutrition (ISSN) references for demanding training are these 1 2:
| Your training | Carbohydrates per day | If you weigh 70 kg |
|---|---|---|
| Intense, 2-3 hours a day, 5-6 days a week | 5-8 g per kilo | 350-560 g |
| With more kilometres or a faster pace | 7-10 g per kilo | 490-700 g |
| Very high volume | 8-12 g per kilo | 560-840 g |
Sources: Tiller et al., 2019 and Kerksick et al., 2017 (ISSN). These figures are for heavy training loads: if you run less, you need less.
These figures are designed for heavy training loads. If you run three or four days a week, you need considerably less. The practical approach is to increase carbohydrates on long-run or interval days, and not to cut them just when you are training most.
Protein counts too. To maintain lean mass and recover, the ISSN suggests about 1.6 g per kilo a day, and up to 2.5 g in the hardest training phases 1. Spread it over servings of 20-40 g every 3-4 hours 2. And if you are wondering whether creatine makes sense when you run, we cover it in creatine for runners.
Before running
The hours before an important session
Before running
Fluid. Drink 5-10 ml per kilo in the 2-4 hours beforehand: between 350 and 700 ml if you weigh 70 kg. That gives you time to pass any excess as urine. The sign that you are on track is pale yellow urine 3.
Food. For important sessions and races, choose something familiar and easy to digest, rich in carbohydrates and low in fat and fibre 1. Use that same 2-4 hour window to have breakfast without rushing.
Caffeine. It is one of the most studied aids for endurance. The dose that has consistently shown improvements is 3-6 mg per kilo, usually about 60 minutes beforehand: 210-420 mg if you weigh 70 kg. It can work even at 2 mg per kilo, and very high doses, such as 9 mg per kilo, cause more side effects without improving performance further 4. The response varies a great deal from one person to another, so try it in training 4. If you have high blood pressure or heart problems, or are pregnant, check with your doctor.
Carbohydrates per hour
How many carbohydrates to have while you run
During: depending on how long the session lasts
| Duration | Fluid | Sodium | Carbohydrates |
|---|---|---|---|
| Less than 1 hour | Water, if you are thirsty | Not needed | Not needed. In intense efforts of about 1 hour, a little sports drink or a mouth rinse may help |
| 1-2 hours | To thirst; as a guide, 0.4-0.8 L per hour | 400-1,100 mg per litre | 30-60 g per hour if the pace is demanding |
| 2-4 hours | To thirst, without exceeding 80% of what you sweat | 400-1,100 mg per litre; even more important if you sweat more than 1.2 L per hour | 30-60 g per hour; up to 90 g if you go beyond 2.5 hours, with blends of several carbohydrates |
| Ultra (more than 4-6 hours) | 450-750 ml per hour | 500-700 mg per litre; 300-600 mg per hour in the heat | 30-50 g per hour, with 150-400 kcal per hour in total |
Sources: Mosler et al., 2020; Burke et al., 2011; Kerksick et al., 2017; Tiller et al., 2019.
Fluid. Drink to thirst and, in long sessions, do not replace more than 80% of what you sweat 3. You can find out how much you sweat by weighing yourself before and after a long run; the hydration calculator does the sums for you.
Sodium. From an hour onwards, your drink should contain 400-1,100 mg per litre. It is even more important if you sweat more than 1.2 litres per hour and the session lasts more than 2 hours 3.
Carbohydrates. In intense efforts of around an hour, small amounts are enough, and even rinsing your mouth can help. In longer sessions, the reference is 30-60 g per hour. If you go beyond 2.5 hours, up to 90 g, with blends of several types of carbohydrate so they are absorbed better 5. You will find the details of the studies in carbohydrates during exercise.
In practice, start early and drink in small, frequent sips, every 10-20 minutes 1 2. To keep track of your carbohydrates, add up what each item provides: a bottle of sports drink, a gel, a piece of fruit.
Be careful not to drink too much
Drinking more than you sweat can dilute the sodium in your blood and cause hyponatraemia. The international consensus puts it down mainly to overdrinking. The risk is higher in efforts of more than 4 hours, at slow paces and in people who gain weight during the event 6.
Drinks with sodium do not prevent it if you drink too much, because they contain much less sodium than your blood 6. The rule is still to drink to thirst. We explain it in drinking too much water during exercise.
If you run in the heat
In the heat, hydration matters even more. Three keys:
- Adapt gradually: acclimatisation shows within 1-2 weeks, and with it you sweat more and your sweat is less salty 7.
- Drink it cold: drinks below 22 °C taste better and make you drink more 7.
- Look after your stomach: in long events in very hot conditions, cutting down on foods rich in fermentable sugars (FODMAPs) in the previous 24 hours helps reduce discomfort 7.
You will find the full plan, including the signs that you should stop, in training in the heat. For the humid summer on the coast, read training in heat and humidity.
After running
What you eat and drink when you finish depends on when you will train again 2 3:
| Next session in less than 4 hours | No training in the next 24 hours | |
|---|---|---|
| Fluid | 1.5 litres for every kilo lost, spread over the following hours | Water and your meals, if you have lost less than 5% of your body weight |
| Carbohydrates | 1.2 g per kilo per hour, fast-absorbing | Those in your usual meals |
| Protein | 0.2-0.4 g per kilo per hour with 0.8 g of carbohydrates per kilo per hour, as an alternative | 20-40 g in the following 2 hours, then every 3-4 hours |
| Sodium | With your drink or food, to retain the fluid | The sodium in your meals |
Sources: Kerksick et al., 2017 (ISSN); Mosler et al., 2020; Evans et al., 2017.
Fluid. Drink more than you have lost, because you will carry on passing urine over the following hours. Water on its own is quickly passed; sodium, carbohydrates and protein help retain it 8. If you have lost less than 5% of your body weight and are not training in the next 24 hours, your meals and water are enough 3.
Carbohydrates. If you have two sessions in a day or less than 4 hours to recover, have 1.2 g of carbohydrates per kilo every hour, ideally fast-absorbing. Combining 0.8 g of carbohydrates with 0.2-0.4 g of protein per kilo per hour also works 2.
Protein. Having quality protein from straight after you finish up to 2 hours later stimulates muscle building. The reference is 20-40 g, about 0.25-0.40 g per kilo 2.
Race day
| 10 km | Half marathon | Marathon | |
|---|---|---|---|
| Days before | Your usual diet | Your usual diet | More carbohydrates: about 10 g per kilo a day in the 48 hours beforehand |
| Breakfast | Familiar, rich in carbohydrates, low in fat and fibre | Familiar, rich in carbohydrates, low in fat and fibre | Familiar, rich in carbohydrates, low in fat and fibre |
| Fluid before | 5-10 ml per kilo in the 2-4 hours beforehand | 5-10 ml per kilo in the 2-4 hours beforehand | 5-10 ml per kilo in the 2-4 hours beforehand |
| Fluid during | Water if you are thirsty | To thirst | To thirst, without exceeding 80% of what you sweat |
| Carbohydrates during | Not needed; if you are racing hard for around an hour, a little sports drink may help | 30-60 g per hour from the first hour | 30-60 g per hour; up to 90 g if you go beyond 2.5 hours |
| Sodium during | Not needed | 400-1,100 mg per litre of drink | 400-1,100 mg per litre of drink |
Sources: Tiller et al., 2019; Mosler et al., 2020; Burke et al., 2011.
Days before. For the marathon and longer events, increase your carbohydrates so you start with a full tank. For ultra-distance events, the ISSN suggests about 10 g per kilo a day in the 48 hours beforehand 1. To fill your glycogen stores completely, 8-12 g per kilo a day 2.
Nothing new. Food, drink, gels and the timing of your intake should be rehearsed in training, well in advance 1. And look after the night before: here is how to sleep well before a race.
Anti-inflammatories, best avoided. The ISSN advises against taking ibuprofen or aspirin during ultra-distance events 1. If you need them for another reason, check with your doctor.
If you are preparing for a half or full marathon, you will find the step-by-step fuelling plan in what to eat and drink during a marathon. If you are running in Girona, see our plan for the Empúries Marathon.
Your stomach can be trained too
Digestive problems are very common
Train your stomach too
Between 30% and 50% of athletes have digestive problems during exercise, especially in endurance events 9. One of the main causes is that, during intense effort, less blood reaches the gut, particularly if you are dehydrated 9. In very long races it can be almost the norm: in a group of 100-mile runners, 96% had symptoms 1.
The good news is that the gut adapts. This is how you train it 1 9:
- Practise on your long runs exactly what you will take in the race.
- Increase gradually the amount of carbohydrates per hour until you reach your target.
- Choose your pre-run meal carefully: familiar, low in fat and low in fibre.
- Arrive well hydrated, so that more blood reaches your gut.
If you have a diagnosed digestive condition, talk to a professional before changing your diet.
A practical example
| When | What to do |
|---|---|
| 2-4 hours before | A familiar breakfast, rich in carbohydrates, and 350-700 ml of fluid |
| During | Drink to thirst, about 0.4-0.8 litres per hour, with sodium. Add 30-60 g of carbohydrates per hour from drinks, gels or fruit |
| When you finish | Weigh yourself: if you have lost 1 kg, drink 1.5 litres spread over the following hours |
| In the following 2 hours | A meal with carbohydrates and 20-40 g of protein |
Example for guidance, using the references in this guide. Adjust it to your sweat rate and what you tolerate.
Nitrus and the Hydration Pack
Nitrus Isotonic covers a good part of what you need in sessions of more than an hour. Each 25 g serving in 400-500 ml provides:
- 15 g of carbohydrates of three types: fructose, dextrose and maltodextrin.
- About 195 mg of sodium, with potassium, calcium, phosphorus and magnesium.
- All 13 vitamins at 100% of the NRV, 1 g of BCAAs 2:1:1, glutamine and 200 mg of taurine.
| Preparation | Sodium per serving | Sodium per litre | Carbohydrates per serving | Carbohydrates per litre |
|---|---|---|---|---|
| 25 g in 400 ml | 195 mg | 488 mg | 15.1 g | 37.8 g |
| 25 g in 500 ml | 195 mg | 390 mg | 15.1 g | 30.3 g |
Each 25 g serving contains 0.488 g of salt (about 195 mg of sodium), 148 mg of potassium and 15.13 g of carbohydrates.
On runs of more than 90 minutes, top up your carbohydrates with gels or fruit until you reach your 30-60 g per hour. Riboflavin (vitamin B2), vitamins B6, B12 and C, niacin, pantothenic acid and folate contribute to the reduction of tiredness and fatigue. A varied and balanced diet and a healthy lifestyle are important.
If you run several times a week, the Hydration Pack brings together two tubs of Nitrus and BCAA 2:1:1 for €53.90, with free delivery.
Frequently asked questions
What should I eat before running?
Something familiar, rich in carbohydrates and low in fat and fibre, that does not sit heavily. Have it with 5-10 ml of fluid per kilo of body weight in the 2-4 hours beforehand: between 350 and 700 ml if you weigh 70 kg.
Do you need to drink during a 10 km race?
If you finish it in less than an hour, you usually need nothing more than water if you are thirsty. From an hour onwards, it is worth drinking during the race, ideally a drink with sodium.
How many carbohydrates should you have in a half marathon?
From the first hour onwards, 30-60 g per hour if you are running at a demanding pace, from drinks, gels or fruit. Try it first on your long runs to find out how much you tolerate.
What should I eat after running?
A meal with carbohydrates and 20-40 g of protein in the following 2 hours, and fluid with some sodium to replace what you have sweated: about 1.5 litres for every kilo of body weight lost.
Is it a good idea to have caffeine before running?
Caffeine is one of the most studied supplements for endurance: the usual dose is 3-6 mg per kilo of body weight, about 60 minutes beforehand. Very high doses, such as 9 mg per kilo, cause more side effects without improving performance further.
Sources
- Tiller NB, Roberts JD, Beasley L, et al. International Society of Sports Nutrition position stand: nutritional considerations for single-stage ultra-marathon training and racing. J Int Soc Sports Nutr. 2019;16(1):50. View publication
- Kerksick CM, Arent S, Schoenfeld BJ, et al. International Society of Sports Nutrition position stand: nutrient timing. J Int Soc Sports Nutr. 2017;14:33. View publication
- Mosler S, Braun H, Carlsohn A, et al. Position of the working group sports nutrition of the German Nutrition Society (DGE): fluid replacement in sports. Dtsch Z Sportmed. 2020;71(7-9):178-184. View publication
- Guest NS, VanDusseldorp TA, Nelson MT, et al. International Society of Sports Nutrition position stand: caffeine and exercise performance. J Int Soc Sports Nutr. 2021;18(1):1. View publication
- Burke LM, Hawley JA, Wong SH, Jeukendrup AE. Carbohydrates for training and competition. J Sports Sci. 2011;29(Suppl 1):S17-S27. View publication
- Hew-Butler T, Rosner MH, Fowkes-Godek S, et al. Statement of the 3rd International Exercise-Associated Hyponatremia Consensus Development Conference, Carlsbad, California, 2015. Br J Sports Med. 2015;49(22):1432-1446. View publication
- McCubbin AJ, Allanson BA, Caldwell Odgers JN, et al. Sports Dietitians Australia position statement: nutrition for exercise in hot environments. Int J Sport Nutr Exerc Metab. 2020;30(1):83-98. View publication
- Evans GH, James LJ, Shirreffs SM, Maughan RJ. Optimizing the restoration and maintenance of fluid balance after exercise-induced dehydration. J Appl Physiol. 2017;122(4):945-951. View publication
- de Oliveira EP, Burini RC, Jeukendrup A. Gastrointestinal complaints during exercise: prevalence, etiology, and nutritional recommendations. Sports Med. 2014;44(Suppl 1):S79-S85. View publication
Information based on published studies. It does not replace the advice of a doctor or registered dietitian. The results describe what was measured in each study, not the properties of any specific product.
