In events lasting longer than about two hours, carbohydrate intake is one of the biggest levers you can pull. The challenge is that your gut has to be able to absorb it, and that's something you can train.
How much carbohydrate?
General sports nutrition guidance for long endurance events is:
- 30 to 60 g per hour for events of 1 to 2.5 hours
- Up to about 90 g per hour for events longer than about 2.5 hours
- Some well-trained athletes tolerate more, using a mix of glucose and fructose, after practising it in training
Your exact target depends on your event, body size, intensity and how well you tolerate it.
Why mix glucose and fructose?
Glucose and fructose are absorbed through different transporters in the gut. Combining them lets you absorb more carbohydrate per hour than glucose alone, with less chance of it sitting in your stomach. Many gels and drink mixes are built around this.
Training the gut
Your gut adapts to what you regularly give it. To build tolerance:
- Practise race fuelling in long sessions every week, not just before the race
- Start below your target and increase gradually over several weeks
- Use the same products you'll use on race day
- Practise at race intensity, not only at easy pace
- Log what you take and how your stomach responds
Common race-day problems
Stomach cramps, bloating and nausea are often caused by trying an intake you've never practised, by concentrated drinks taken without water, by heat and dehydration, or by high-fibre or high-fat foods close to the start.
Get personal advice
This is general guidance for healthy athletes. If you have a medical condition, or need a meal plan or weight-related advice, a registered dietitian is the right person to see.
